Tritium in the environment: Recommendations of the National Council on Radiation Protection and Measurements (NCRP report 62)

NCRP REPORT No. 62

TRITIUM IN THE ENVIRONMENT Recommendations of the NATIONAL COUNCIL O N RADIATION PROTECTION AND MEASUREMENTS

Issued March 9,1979 Second Reprinting May 15,1989 National Council on Radiation Protection and Measurements 7910 WOODMONT AVENUE / WASHINGTON, D.C. 20014

Copyright O National Council on Radiation Protection and Meaeurementa 1979

All rights resented. This publication is protected by copyright. No part of this publication may be reproduced in any form or by any means,including photocopying, or utilized by any information storage and retrieval system without written permission from We copyright owner, except for brief quotation in critical articles or reviewe. Library of Congress Catalog Card Number 79-63514 International Standard Book Number 0-913392-46-4

Preface Tritium, the heaviest and only radioactive isotope of hydrogen, is increasing in importance in energy and environmental considerations. This nuclide is widely distributed throughout man's environment because of its ubiquitous form as tritiated water and its persistence in the environment. This report considers and evaluates the available information on tritium in terms of its physical properties, production sources, physical transport, biological behavior, projected future production, waste management, and the long-term dose implications of tritium in the environment. The naturally occurring levels of this isotope of hydrogen, 3H, are the result of cosmic ray interactions in the atmosphere. Additional sources are from fallout from weapons testing and by-product waste of nuclear power reactors. Large quantities of tritium will be accumulated with concomitant fractional releases of significant quantities to the environment. The possible use of tritium as the fuel for fusion reactors in the next century may result in an additional source of tritium. Emission of tritium from the nuclear fuel cycle will increasinglybecome the d o - m t source of this nuclide and can become more important than the residue from weapons testing by 1985. Emissions from operating light-water reactors are, and will continue to be, insignificant as compared to the releaees from proposed fuel reprocessing. Projections of production and release of tritium are tied to economic growth and political decisions that are difficult to anticipate. Although the uncertainties of future development of nuclear energy are great, the inventories of tritium produced are certain to increase. In opposition to this increase will be certain improvement in the control of tritium release and containment. The Council has noted the adoption, by the 15th General Conference of Weights and Measures, of special names for some units of the Systkme International d'UniGs (SI) used in the field of ionizing radiation. The gray (symbol Gy) has been adopted as the special name for the SI unit of absorbed dose, absorbed dose index, kerma, and specific energy imparted. The becquerel (symbol Bq) has been adopted as the special name for the SI unit of activity (of a radionuclide). One gray equals one joule per kilogram, and one becquerel is equal to one second to the power of minus one. Since the transition from the special units currently employed-rad and curie-to the new special names is expected to take some time, the Council has determined to continue, for the time being, the use of rad and curie. To convert from one set of units to the other, the following relationships pertain: 1 rad = 0.01 J kg-' = 0.01 Gy 1 curie = 3.7 x 10lOs-'= 3.7 x 10" Bq (exactly). iii

iv

/

PREFACE

The present report was prepared by the Task Group on Tritium of Scientific Committee 38 on Waste Disposal. Serving on the Task Group during the preparation of this report were: Merril Eisenbud, Chairman Director, Laboratory for Environmental Studies Institute of Environmental Medicine New York University Medical Center Tuxedo, New York

Members Burton Bennett Division of Biomedical and Environmental Research U.S. Department of Energy New York, New York

John Koranda Bio-Medical Division Lawrence Livennore Laboratory University of California Livermore, California

Raymond Blanco Director, Regulatory Programs Chemical Technology Division Oak Ridge National Laboratory Oak Ridge, Tennessee

Alan Moghisei Office of Research and Development U.S. Environmental Protection Agency Washington, D.C.

Edgar Compere Chemical Technology Divisicn Oak Ridge National Laboratory Oak Ridge, Tennessee Edward Goldberg Scripps Oceanographic Institute . University of California La Jolla, California

John Ruet University of Chicago Department of Radiology Chicago, Illinois Joseph Soldat Radiological Health Research Battelle Pacific Northwest Laboratories Richland, Washington

Donald Jacobs Health Physics Division Oak Ridge National Laboratory Oak Ridge, Tennessee

Comu2tQnts John Crandell Director Division of Environmental Science Savannah River Laboratory Aiken, South Carolina

William Reinig Atomic Energy Division Savannah River Laboratory Aiken, South Carolina

W m e n Grimes Charles Bailey Chemical Technology Division Division of Environmental Science Oak Ridge National Laboratory Oak Ridge, Tennessee Savannah River Laboratory Aiken, South Carolina

NCRP Secretwiat, Thomas Fearon

The Council wishes to express its appreciation to the members and consultants of the Task Group for the time and effort devoted to the preparation of this report. Bethesda, Maryland Warren K. Sinclair November 15,1978 President, NCRP

Contents Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii 1 Introduction . . . . . . . . . . . . . . . . . . . . . . . ........ . ........ 1 2 Physical Properties of Tritium . . . . . . . . . . . . . . . . . . . . . . . . 3 2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2.2 Properties of Tritiated Water . . . . . . . . . . . . . . . . . . . . . . . . . 3 2.3 Isotopic Exchange in Water . . . . . . . . . . . . . . . . . . . . . . . . . . 4 2.4 Isotopic Exchange in Organic Molecules . . . . . . . . . . . . . . . 5 2.5 Isotope Effects in Tritium Reactions . . . . . . . . . . . . . . . . . . 7 8 3 Sources of Tritium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 3.2 Natural Tritium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 3.3 Tritium Production in Nuclear Reactors . . . . . . . . . . . . . . . 8 3.4 Tritium Releases from Production Plants . . . . . . . . . . . . . . 15 3.5 Tritium Releases from Fuel Reprocessing Plants . . . . . . . . 15 3.6 Tritium Production and Releases from Nuclear Detonations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.7 Tritium Production and Releases from Thermonuclear Reactors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.8 Summary of Tritium Sources . . . . . . . . . . . . . . . . . . . . . . . . . 4 Physical Traneport of Tritium . . . . . . . . . . . . . . . . . . . . . . . . . 4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2 Atmospheric Dispersion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3 Deposition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.4 Movement in Groundwater and Soil . . . . . . . . . . . . . . . . . . . 4.5 Behavior of Tritium in the Hydrosphere . . . . . . . . . . . . . . . 4.6 Release to Groundwater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.7 The Oceans . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Tritium Waste Management and Exposure to Populations Located Close to the Sources of Releases . 5.1 Some Dosimetric Considerations . . . . . . . . . . . . . . . . . . . . . . 5.2 Methods of Tritium Retention . . . . . . . . . . . . . . . . . . . . . . . . 5.3 Ultimate Disposal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Biology of Tritium Exposure8 . . . . . . . . . . . . . . . . . . . . . . . 6.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.2 Tritium Uptake and Retention . . . . . . . . . . . . . . . . . . . . . . . .

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vi

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6.3 Tritium Elimination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.4 DNA Incorporation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.5 The Relative Biological Effectiveness and Quality Factor

..

of Tntium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.6 Tritium in Ecological Systems . . . . . . . . . . . . . . . . . . . . . . . . 7 Projected Tritium Production and Releases . . . . . . . . . . . 7.1 Growth in Energy Demand . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.2 Expansion of Nuclear Power . . . . . . . . . . . . . . . . . . . . . . . . . . 7.3 Projected Sources of Tritium Release . . . . . . . . . . . . . . . . . . . . 7.4 Project~ons. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Long Term Dosimetric Considerations . . . . . . . . . . . . . . . . . 8.1 Dosimetry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.2 Environmental Modela . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.3 Doses from Tritium in the Environment . . . . . . . . . . . . . . . Appendix A Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Appendix B List of Acronyms . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The NCRP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . NCRP Publications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

.

.

47 50 51 52 59 59 60

62 66 67 67

71 78 84 88 89 108 114 123

1. Introduction Tritium, the heaviest and only radioactive isotope of hydrogen, has been a ubiquitous contaminant produced by atomic energy programs. The nuclide is produced copiously by the military nuclear program and tritium, in the form of water, was distributed worldwide by the nuclear weapons tests that took place in the open atmosphere, particularly during the period 1954 to 1962, The latter source has diminished substantially as a result of the limited nuclear test ban agreement among the major powers, but tritium production by nuclear power reactors is increasing rapidly and will in time become the dominant source. The world inventory of natural tritium due to cosmic ray interactions is estimated to be 70 MCi, corresponding to a production rate of 4 MCi y-'. The tritium inventory due to weapons testing reached a maximum of about 3100 MCi in 1963, an amount that will decay to the natural level of 70 MCi approximately by the year 2030. Tritium is formed in nuclear reactors by ternary fission and by activation of light elements such as boron, which is used for reactivity control in PWRs, and lithium, which is used to control corrosion. Estimates of the production rate by ternary fission range from below 12 to greater than 20 Ci per megawatts (thermal) per day (MWt d)-'. Light element activation contributes about 600-800 Ci y-' to the reactor coolant with an average annual release to the environment per 1000 megawatts (electric) (MWe) by light-water reactors of 63 Ci y-' for BWRs and 830 Ci y-' for PWRa. Barring a resumption of largescale atmospheric testing, emission of tritium from the nuclear fuel cycle will become more important than the residue from weapons testing by 1986. Emissions from operating light-water reactors are, and will continue to be, insignificant as compared to the releases from fuel reprocessing. Transfer of tritiated water from the atmosphere to the surface of the earth occurs mainly by precipitation, but also by vapor exchange. The mean residence time of tritiated water vapor in the troposphere ranges from 21-40 days. Deposition of atmospheric tritium is greatest in the latitudinal belt in which the tritium is released. If the atmospheric concentration of tritium is known, the average deposition rate can be estimated &om the deposition velocity which has been observed 1

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1.

INTRODUCTION

to be in the range of 0.4 to 0.8 cm s-'. The deposition rate is higher over the oceans than over land. Tritium in groundwater and soil exhibits the diffusion characteristics of water except for insignificant differences in vapor pressure. Absorption in soil is influenced by the state of the soil, soil structure, water content, and the amount of organic matter present. Tritium reaches surface water directly through precipitation, molecular exchange with water in the atmosphere, direct release of tritiated water from nuclear power or reprocessing plants to streams; and indirectly from runoff of groundwater into streams. Tritium in the oceans becomes rapidly distributed in the thin surface layer of relatively warm water, 50 to 100 m deep, known as the "mixed layer." Residence time in the mixed layer is of the order of 22 y at 75 m depth, but this varies with geographic location. In contrast to the oceans, most lakes are mixed vertically each year. When humans are exposed to tritium as tritiated water by inhalation, ingestion, or skin absorption, the tritium is rapidly distributed to intracellular and extracellular water. The kinetics of tritium movement throughout the body follow those of water. A small fraction of the intake becomes organically bound in two separate compartments. The effective half-life of the 'H in free water is 9.7 days compared to 30 days and 450 days from the two compartments into which the fraction is bound. Reported values of the relative biological effectiveness (RBE) of tritium range from less than 1.0 to greater than 2.0. This variation is due, in part, to the fact that the RBE is functionally dependent on the biological endpoint, and on the dose rate, as well as the reference radiation used, i.e., @%o gamma rays or 250 kV x rays. There are also uncertainties in dose estimation. Projections of production and release of tritium are tied to economic growth and political decisions that are difficult to anticipate. Although the uncertainties of future development of nuclear energy are great, the inventories of tritium produced are certain to increase. In opposition to this increase are probable future improvements in the control of tritium release and containment. This report assumes that installed worldwide nuclear capacity will reach 120 GWe by 1980 and 720 by 2000. The dose to humans residing in the northern hemisphere was calculated giving the following estimates: Natural Tritium

Fallout

Nuclear Power

Weapona Production

brad y-')

(mrad y - ' )

(mrad y-')

(mrad y-')

To* (nuad y ')

2. Physical Properties of Tritium 2.1

Introduction

Tritium, the heaviest and only radioactive isotope of hydrogen, was discovered in 1939 by Alvarez and Cornog (1939),and subsequent work established its physical half-life at 12.3 years. The nuclide, 'H or T, decays to form 3He by emission of a beta particle with a maximum energy of 18 keV and an average energy of 5.7 keV. Gaseous Tp at room temperature tends to form H T by reaction with gaseous hydrogen if present. A number of investigators have reported the critical point of T2 to be in the range of 40.000 K to 40.44 K and the triple point to be 20.62 K. Other measured and calculated thermodynamic constants are in good agreement (Jacobs, 1968).

2.2

Properties of Tritiated Water

The vapor, HTO, is formed readily and is the most commonly encountered form of tritium in the environment. Price (1958)determined that in the range of 25 to 80°C, the vapor pressure of HTO is less than that of Ha0 and that HTO has a higher boiling point than HpO. These general conclusions have been supported by more recent studies (Sepall and Mason, 1960;Smith and Fitch, 1965,Jones, 1963) in which the measured values of the vapor pressure and boiling point of tritiated water have been refined. Also, physical and chemical measurements have been made of isotope effects on vapor pressure; measurable parameters correlate with theoretical considerations (Jones, 1963; Bigeleisen, 1962).The properties of the oxides of the three hydrogen isotopes are listed in Table 2-1. Several groups of investigators (Wang et al., 1953;Cuddeback et al., 1953;McCall et al., 1959;Longsworth, 1960; Nakayarna and Jackson, 1963a; Mills, 1973; Woolf, 1975) have measured the diffusion coeffi3

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2. PHYSICAL PROPERTIES OF TRITlUM

TABLE 2-1-Thennodynamic properties of the orides of the Hyahgen isotopesa Prooertv

Boiling point, "C

Triple-point temperature, OC Triple-point prwjsure, mm Hg Heat of vaporization at the boiling point, kcal mole-' Entropy at 298.16 K eub

HTO

HLJ

IM)

100.76

100.00

101.42

101.51

T.0

Ibfrmnw

2.25

0.010

3.82

4.49

4.73

4.58

6.02

4.87

9.91

9.72

9.9

10.1

Smith and Fitch (1%) Smith and Fitch (1%) Smith and Fitch (1965) Jones (1963)

17.88

16.75

18.9

19.0

Jones (1963)

'From Jacobs (1968). I, Entropy unit (eu) is a thermodynamic unit equal to one calorie per degree centigrade.

cients of various deuteriated and tritiated forms of water in natural water. Wang et al. (1953) measured the diffusion coefficient of HTO in natural water a t 25OC and obtained a value of 2.44 f 0.057 x lo-' cm2 s-'. Other measurements at ambient pressures and 25°C ranged from 2.2 to 2.64 x cm2 s-'. Nakayama and Jackson (1963a) made measurements in dilute agar gel concentrations and obtained a value of 2.41 0.055 x lo-' cm2 s-' by extrapolation to zero concentration of gel at 25OC. On the basis of measured values, Mills (1973) calculated self-diffusion coefficients for Hz0 in Hz0 of 2.299 x 10-%m2 s-' and for D20 in DzO of 1.872 x cm2 s-I.

*

2.3

Isotopic Exchange in Water

Tritium follows closely the reactions of orhydrogen, but the relatively large mass differences make isotopic effects easily discernible. Because of the importance of water in the life processes, its isotopic exchange with tritium is of special concern. Libby (1943, 1947) calculated theoretical equilibrium constants for a number of reactions involving the isotopic variants of hydrogen gases and their oxides. Black and Taylor (1943) experimentally determined the equilibrium constants for the reaction H T + H20 = Hz

+ HTO

over the temperature range 16 to 303OC and observed that they compared quite well with the theoretically derived values of Libby. The experimental values were consistently higher, but they were within the estimated limits of accuracy of the theoretical values. The mass action equilibrium coefficient for the above reaction is approximately 6 at 25OC, thereby favoring the formation of tritiated water.

2.4

ISOTOPIC EXCHANGE IN ORGANIC MOLECULES

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5

Roesch (1950) estimated that tritium gas would be easily converted to tritiated water in the atmosphere in the presence of a suitable catalyst. Ionizing radiation increases the rate of exchange of hydrogen isotopes between their gases and water (Thompson and Schaeffer, 1955; Yang and Gevantman, 1960; Casaletto et al., 1962; Yang and Gevantman, 1964; Dorfman and Hemmer, 1954). Dorfman and Hemmer (1954) showed that the beta radiation from tritium decay is sufficient to initiate a reaction between tritium and oxygen to form tritiated water, but Yang and Gevantman (1960) suggest that the conversion of tritium to tritiated water in the atmosphere by this process would be less than 1 percent per day. Harteck (1954) discussed the relative abundance of H T and HTO in the atmosphere on the basis of several reactions. When tritium atoms are formed by cosmic radiation, they initially have a high kinetic energy. The most probable initial reaction for tritium a t pressures below atmospheric is a three-body collision with oxygen to form the stable compound TO2. Subsequent reactions of the TO2 would be expected to yield HTO, but not HT, in the atmosphere. Repeated photochemical decomposition of TOz and reactions with ozone are necessary to account for the relative abundances of HT and HTO. A second possible initial reaction is the collision of tritium with an Hz molecule resulting in isotopic exchange. Altitude has a pronounced influence on the reactions that occur in the atmosphere. Below 5 km, TOz will be transformed to HTO. In the region from 10 to 40 krn, HT is the predominant form, and above 40 km the concentrations are so small that the fraction of HT relative to total tritium is negligible. The tritium concentration in atmospheric hydrogen is stable (Harteck, 1954), but is variable in rainwater, depending on the source of the moisture from which the rain is formed (Libby, 1953).

2.4

Isotopic Exchange in Organic Molecules

The exchange between deuterium gas and the hydrogen of methanol or water is catalyzed by platinum and proceeds a t a conveniently measurable rate a t room temperature (Swain and Kresge, 1958). The reaction is limited to the exchange of hydroxyl hydrogen. Eastham and Raaen (1959)observed an exchange between tritiated isopropyl alcohol and the active hydrogens of organic compounds, and found the exchange to proceed at the expected rate. Lang and Mason (1960) used tritium exchange between the hydroxyl hydrogen of cellulose and water vapor to study accessibility. The incomplete reversibility indi-

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2.

PHYSICAL PROPERTIES OF TRITIUM

cated that changes in accessibility occurred during wetting and drying. For amylopectin, an apparent accessibility of 123 percent of the hydroxyl hydrogen was obtained, a result indicating that isotopic effects are operative. Two isotopic effects were considered to be responsible-one in the exchange reaction and the second in the recovery of tritiated water. Leach and Springell (1962) used tritiated water to study the exchangeable hydrogen atoms in proteins. They considered that carbon tritiation in proteins is unlikely, but it might occur along with racemization at asymmetric centers or when specific activities due to tritiation at nitrogen and oxygen centers are so high that self-radiation induces labeling of adjacent carbon sites. When radioactive decay of tritium occurs, the emission of the beta particle gives the resulting species a recoil momentum that is very large in chemical terms. The recoil tritium (so-called "hot atoms") can be used for labeling organic compounds (Wolfgang et al., 1955).In this case, tritium labeling is not restricted to the replacement of active hydrogens; the recoil momentum of the (3HeT)+formed by beta decay is sufficient to break C-H bonds and allow substitution of tritium at any position occupied by a hydrogen atom. The proposed technique is limited in use because it will not permit production of high specific activities nor the labeling of specific positions obtainable by chemical synthesis. Wilzbach (1957) developed the recoil technique and determined that exposure of organic compounds to tritium gas yields products of high activity without extensive radiation damage. Tritium is distributed throughout the product, but the distribution is not completely random. In addition to recoil labeling, organic compounds can be labeled by beta labeling (Soklowska, 1965; Lee et al., 1965; Nash, 1965; Wexler, 1963) and by beta radiolysis of Tp(Yang and Gant, 1962).Beta labeling is the term applied when the labeling reaction is initiated by electrons (Yang and Gant, 1962; Dorfman and Mattraw, 1953). The electrons can be supplied internally by the beta decay of the tritium, or they can be added from an external source. Formation of tritiated ethylene involves both recoil labeling and beta labeling (Yang and Gant, 1962). Tritiated ethane, propane, and n-butane are formed exclusively by beta labeling. The labeling yield per beta decay for tritiated methane, ethane, and propane increases linearly with tritium concentration (Yang and Gant, 1962). Yields decrease when T p is replaced by HT, but irradiation with an external gamma source increases yield. Lee et al., (1964) substituted recoil tritium atoms on the carbon skeleton of numerous saturated hydrocarbons and halocarbons and observed that significant yields of variously labeled olefins were pro-

2.5

ISOTOPE EFFECTS IN TRITIUM REACTIONS

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7

duced, perhaps as the result of the replacement of a single group in the primary energetic process followed by the elimination of a small molecule from the excited labeled product. Shores and Moser (1961) observed that reacting tritium atoms of intermediate energy with unsaturated hydrocarbons resulted in both addition and substitution. With saturated hydrocarbons, substitution was the principal reaction.

2.6

Isotope Effects in Tritium Reactions

Bigeleisen (1962) developed the theory of relative tritium-hydrogen and deuterium-hydrogen isotope effects for both kinetic and equilibrium processes. The ratio log a ~ - ~ / l ~oDg. Hshould be in the range 1.33 to 1.55. S m d effects occur in systems where there is no significant change in the chemical bonding of the labeled hydrogen atom in the net reaction. The largest kinetic and equilibrium effects arise when the labeled hydrogen is strongly bonded in the reactant and is loosely bonded in either the product or in a transition state. Abnormal ratios of tritium-to-deuterium isotope effects provide evidence of such phenomena as tunneling. Bigeleisen (1964) also found that kinetic isotope calculations yield the same results as calculations of equilibrium isotope effects and that they are the same as those obtained from collision theory. The preexponential, or temperature independent, factor is the ratio of the square roots of the molecular weights of the reactants and the transition states. At high temperatures this ratio is exactly cancelled by the Boltzmann excitation terms. Kinetic studies of the base-catalyzed exchange of acetone, deuterated acetone, and tritiated acetone indicate secondary isotope effects to the extent of 5 to 10 percent (Jones, 1965). For the limited data, the values of the ratio of log(kH/kT)/log(k~/k~) seem to be about 1.44, which are to be compared with Bigeleisen's (1964) limits of 1.33 and 1.55. However, the experimental values of k ~ / k were ~ considerably higher than theoretically predicted values of Swain and Schaad (1958). Varshavskii (1962) calculated the distribution coefficient of tritium between various hydrogenous substances on the basis of statistical mechanics and estimated that values as high as 20 can be obtained for the .hydrides of alkali metals. Kandel (1964) measured the rates of the forward and reverse reactions of CHI with Tg to give successively C&T, CHaT2, CHT.1, and CT,. Equilibrium constants calculated from the steady-state concentrations were close to the classical values.

3. Sources of Tritium 3.1 Introduction Tritium is produced both by ternary fission and by neutron reactions with light elements such as boron in control rods or dissolved as "burnable poisons" in the coolant of pressurized water reactors. Most of the fission product tritium produced is retained within the fuel and only a minor fraction passes to the coolant or is released with gases or liquids to the environs of the reactor. In the preparation of this section, considerable dependence was placed on the earlier survey by Jacobs (1968) and the proceedings of the 1971 Tritium Symposium in Las Vegas (Moghissi and Carter, 1973). The excellent reviews by Burger (1972), USERDA (1976), Brown (1976),Burger and Trevorrow (1976),and Steindler and Kullen (1976) were also of value. 3.2

Natural Tritium

The production of tritium by natural processes was discovered by Libby (1946) and has been reviewed more recently by Nir et al. (1966). Cosmic ray production has been calculated to occur at a global average rate of 0.16 to 0.20 triton per square centimeter of the earth's surface per second (~m-~s-'). A value of 0.19 triton ~ m - ~ s would -' result in a steady state global inventory of 26 megacuries (MCi). Based on excess tritium measured in the casing of the Discoverer 17 satellite during the major solar flare of November 12, 1960 (Fireman et aL, 1961), Flamm et aL (1962) estimated that such phenomena could account for an additional 0.4 triton ~ m - ~ s - ' or , more than twice the normal production rate.

3.3 3.3.1

Tritium Production in Nuclear Reactors

Introduction

Tritium was first identified as a fission product by Albenesius (1959). The fission yields, as determined directly by various investigators, 8

3.3

TRITIUM PRODUCTION IN NUCLEAR REACTORS

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9

have been summarized by Dudey (1968), Horrocks and White (1970), Horrocks (1971). Fluss et al. (1972), and Erdman and Reynolds (1975), to 1.75 and are listed in Table 3-1. The yields range from 0.68 x x depending on the nuclide and neutron energy. In addition to the directly determined yields of tritium, values can be calculated from experimental spectrometric measurement. The data obtained in this way are shown in Table 3-2. Erdman and Reynolds (1975) estimate a tritium yield from thermal neutron fission of W 9 Pas~2.0 x NOdata have been published for the fast fission of 233U or mPu, or for the fission of 24'Pu. The fission yield of tritium from the fission of 235U is a function of the energy of the neutrons causing fission. This situation is presumably also true for other fmile nuclides (Dudey, 1968) and should be taken into account in estimating the tritium yields of reactor fuels. The neutron spectrum characteristic of the reactor type must be considered as well as all fissile nuclides. The data library of the ORIGEN code (Bell, 1973). frequently used for long-term fuel cycle projections, currently assigns the following TABLE3-1-Tritium fissionyields

*

nuehde

Neutron energy

mu

Thermal

Fission yield'

Invesligator

0.95 x lo-'

Albenesius and Ondrejcin

0.80 x 0.99 x 0.85 x 2.0 x

Sloth et al. (1962) Marshall and Scobie (1966) Fluas et al. (1972) Fluss et al. (1972) Dudey et al. (1972);Fluas and Dudey (1971) Horrocks and White (1970) Horrocks and White (1970)

(1960)

160-600 keV 2WWW) keV

lo-' lo4 lo4 lo4 2.2 x lo-'

mu

Thermal 0.91 x lo-' Thermal (1.8 x lo-' ' The percentage of fissions leading to a particular nuclide.

q u

TABLE3-2-Relative and derived tritium fission yields in thermal reactors F+

nuclide

Obsvved T/a

Derived W n yields

lnvasligator

Dakowski et al. (1967) Vorobiev et al. (1969a) Vorobiev et aL (1972) Cambiaghi et al. (1972) Krogulski et aL (1969) Cavallari d al. (1969) Cambiaghi et aL (1972) Vorobiev et al. (1974) CambLaghi et aL (1969) Vorobiev et al. (1969b)

'Derived by use of Noble's (1962)values of fission per long range particle.

10

/

3. SOURCES OF TRITIUM

values for tritium fission yields per nuclide in the neutron spectrum of light-water reactors with uranium or mixed oxide fuels respectively: 23'2Th,(2.0 X

2.0 x

233U,(1.35 X

1.55 X

235U,(1.08 X

1.24 x

238U,(2.3 X

2.3 X

%lPu (1.68 X

1.8 X

'-Pu,

(1.64 X

1.75 X

A fission yield of 1 x lo4corresponds to a tritium production rate of 0.0130 Ci d-I MWt-' (MWt: Megawatts thermal). Tritium is also produced by thermal or fast neutron reactions with various light elements found in reactors (summarized in Table 3-3). Tritium formed in this way can be more readily delivered to the coolant, from which transfer to the environment is facilitated. 3.3.2

Light Water Reactors

For the next several decades in the United States and many other countries most nuclear power will be generated in reactors with lightwater coolants, i.e., boiling water reactors (BWR) and pressurized water reactors (PWR). The light-water systems have a thermodynamic efficiency of a little more than 30 percent, so that approximately 3200 MW of thermal energy (MWt) is required to produce 1000 MW electrical energy (MWe).Summaries of tritium behavior in light-water cooled reactors include those by Ray (1968), Jacobs (1968), Kouts and Long (1971),Smith and Gilbert (1971),Locante and Malinowski (1971), USAEC (1973a), USAEC (1973c), Eisenbud (1973b),and Trevorrow et al. (1974). In addition, important parameters and relationships are given in the Standard Safety Analysis Reports for BWR (e.g., General TABLE3-3--Effective cross sections for neutron reactionsproducing tritium or ~recursom~ Reaction

(I O " * ~ ~ J )

2H (n,y) T 'He (n,p) T % (n,a) T 'Li (n,na) T %e (n,a) 'Li '"I3 (n,a) 'Li '"I3 (n,2a) T "C (n,a) 'Be "N fn.t) I2C

'Bell (1973)ORIGEN Data Library.

HWR, CANDU, (BWR) HTGR PWR, HTGR, LMFBR, MSBR PWR, MSBR, (HTGR, LMFBR) MSBR Control rods, burnout poison, shim Control rods, burnout poison, etc. HTGR SEFOR, Atmosphere

3.3

TRITIUM PRODUCTION IN NUCLEAR REACTORS

/

11

Electric, 1975), and PWR (Westinghouse Electric, 1974a),safety analysis reports for specifiic reactors, and USAEC (1973b). The annual production of fission product tritium by a 1000 MWe LWR will be in the range of 15,000 to 25,000 Ci. This estimate takes into account the production and fissioning of plutonium, which has a tritium yield twice that of uranium. Plutonium fission accounts for about one-third of the reactor power during core life (USAEC, 1973a). and operated at an For a PWR fueled with UOe (3.3 percent average specific power of 30 MW t-', fuel removed following a burnup of 33,000 MWd t-' will contain 540 Ci tritium per metric ton according to present estimates that use the ORIGEN code (Bell, 1973).Zirconium alloy cladding, currently used in both BWRs and PWRs, has been shown to combine with tritium to form zirconium hydride (tritide). This results in retention in stable form of tritium released from the oxide fuel pellets. The tritium content of samples of commercial PWR fuel irradiated to -40,000 MWd t-I has been determined. About 13 percent of the total tritium was found in the cladding and about 87 percent in the fuel pellets. However, the accuracy of the material balance calculations (regarding the total amount of tritium expected to be present) was limited because the irradiation history was not known precisely. However, the data indicated that little, if any, tritium was lost to the coolant (Goode and Vaughen, 1970). Thus, it appears that tritium is released only through defects in zirconium alloy clad fueLs. Defects in zirconium alloy cladding are infrequent (Williamson and Ditmore, 1970), and the release of fission product tritium by operating PWRs using zirconium alloy clad fuel is limited to 0.1 to 1 percent of that produced (General Electric, 1975; Smith and Gilbert, 1971). The use of stainless steel cladding in PWRs built before 1968 resulted in release to the coolant of most tritium formed in fuel. Prior to 1971, control rods of boron carbide encased in stainless steel were used in BWRs (Smith and Gilbert, 1971). After 15 years of operation, it has been estimated that the tritium content of such rods, due to neutron reactions with the boron, could be 90,000 Ci for a 1000 MWe reactor. In addition, during the initial year of operation, boron carbide "curtains" can be installed to control excess reactivity. This may result in production of an additional 10,000 Ci of tritium annually. There is no evidence of tritium release by boron carbide (General Electric, 1975). Since 1971, gadolinium oxide, which does not produce tritium, bas been incorprated in BWR fuel to control excess reactivity. This has made the use of B4Ccurtains unnecessary. The control rods used in recent PWRs utilize an alloy of silver,

w)

12

/

3. SOURCES OF TRITIUM

indium, and cadmium, which does not result in production of tritium. However, because dissolved boric acid is used to control excess reactivity, about 700 Ci of tritium per year will be produced from this source in a 1000 MWe PWR (Westinghouse Electric, 1974a). In addition, the maintenance ("feed and bleed") of 2 ppm lithium hydroxide for pH control (Locante and Malinowski, 1971) results in the formation of about 18 Ci y-L. Tritium appearing in the primary coolant of most light-water-cooled reactors currently in operation has been released to the environment in gaseous or liquid waste streams. Reported releases in liquid waste streams of 9 BWRs and 9 PWRs over the three-year period, 1972-1974 (NRC, 1975) are summarized in Table 3-4. For a 1000 MWe BWR at full power, the leakage from fuel elements averages 63 Ci y-'. For the PWRs, the leakage rate was probably of similar magnitude, but is overshadowed by tritium produced by neutron interactions with boric acid. The average annual release per 1000 MWe was 830 Ci (Westinghouse Electric, 1974b). The release of tritium from a pressurized water reactor of earlier design was studied by Kahn et al. (1974) at the Haddam Neck (Connecticut Yankee) electric generating station, a 590-MWe PWR with stainless steel clad fuel. During 1973, when 13.8 x lo6 MWt-h of power was produced, about 6000 Ci tritium was released in liquid effluents, and about 170 Ci in airborne effluents. This is equivalent to an annual rate of about 12.000 Ci for a 1000 MWe reactor.

3.3.3

Heavy Water Reactors

Heavy water moderated reactors include the CANDU and SGHWR power reactors, various research reactors, and production reactors (IAEA, 1967). The use of heavy water as moderator permits greater burnup of natural uranium oxide fuel, but results in the production of tritium by neutron activation of the deuterium to a degree far in excess of that produced in the fuel. Kouts and Long (1971) estimated that annual production of tritium in the fuel of a 1000 MWe plant could be about 15,000 Ci, compared to 600,000 Ci in the heavy water moderator. Lewis and Foster (1970) noted that both the necessity to recover expensive heavy water and the hazard from release of the tritium require that the system be effectively sealed to prevent escape of heavy water. The anticipated levels of tritium in the heavy water after several years' operation exceed 5 Ci I-'.

3.3

TRITIUM RELEASES FROM PRODUCTION PLANTS

/

13

TABLB3-&-Reported b-ilium release rates (1972-1974) for light-water-cooled reactors with zirconiwn alloy-clad fuel REACTOR PARAMETERS

Number of reactors Total power, MW Total nuclear thermal output (full power MWt

BWR

9

17,000 36,000

PWR

9

~.000 =,000

years)

Tritium released (all reactore, 3 years) Gaseous, Ci Liquid, Ci Total, Ci Specific release rate ratio, Ci MWt-' y-I Average release per GWe (full power), Ci y-'

210' 490 700 0.02 63

240

6600 6800 026 830

'May not include HT and possibly other tritiated nonaqueous compounds appearing from time to time in the steam condeneer air ejector release gas-.

3.3.4

Advanced Reactors

The liquid metal fast breeder reactor (LMFBR),the high-temperature gas-cooled reactor (HTGR), and the molten salt breeder reactor (MSBR) are concepts that have characteristics in common with respect to tritium behavior but differ markedly from light-water-cooled reactors. Since these reactors will operate at higher temperatures, they are more efficient, and less fission energy is required per unit of electric power. In addition, because the primary coolant is nonaqueous, the tritium exists in the form of molecular hydrogen rather than water. Tritium, like hydrogen, can diffuse through metals at high temperatures, and various schemes for trapping the tritium to reduce reIease from the primary circuit appear both necessary and practical.

Liquid Metal Fast Breeder Reactor (LMFBR)

5 is the dominant fissile nuclide in liquid metal fast breeder reactors. Trevomw et al. (1974) estimated the fast fission yield of to 3.5 x lo-'. The yield of 2. x lo-' assigned tritium to be 1.5 X by Erdman and Reynolds (1975) corresponds to a tritium production rate of 24,000 Ci GWe-Iy-'. Tritium release from the stainless steel clad EBR-I1 (second Experimental Breeder Reactor) fuel of 70-75 percent was reported by Ebersole et al. (1971). Trevomow et a1. (1974) indicate that, at the higher LMFBR temperatures, essentially no tritium will be retained by the fuel elements. The use of boron carbide (B4C)control rods will result in tritium production by the reactions 1°B(n,2a)Tand "%(n,a)'Li(n,a)T. Seghal

14

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3.

SOURCES OF TRITIUM

and Rempert (1971) estimate the tritium production by this process to be 2.4 to 2.7 times the amount produced by fission, or an annual rate of about 60,000 Ci for a 1000 MWe reactor. Tritium was retained in B4C control rods by EBR-11, according to Miles et al. (1974), but considerable release occurs above 700°C. Release under LMFBR conditions has not been established. The use of tantalum for control and shim elements will remove this source. Boron and lithium impurities in the fuel and blanket materials could contribute up to 2000 Ci y-' in a 1000 MWe LMFBR according to Trevorrow et al. (1974),while similar impurities in the primary sodium coolant could generate an additional 150 Ci y-'. The LMFBR Program Environmental Statement (USAEC, 1974b) estimated that about 33,000 Ci GWe-' y-' of tritium would be generated. All of this tritium is expected to enter the sodium coolant. Tritium behavior in liquid metal coolants has been discussed on a theoretical basis by Taylor and Peters (1972), Kabele (1972, 1974), Kumar (1974), Trevorrow et al. (1974), LMFBR Program Environmental Statement (1974), and Erdman et al. (1975). The experience with EBR-I1 was discussed by Ebersole et al. (1971). The important phenomena are tritium removal by cold trapping, a characteristic of LMFBRs, and permeation of the system and heat exchanger metal walls. With sufficient natural hydrogen to serve as a carrier, it appears that the major fraction of the tritium can be accumulated in cold traps. Methods for management of the cold trap residues have not been described other than to indicate they could be converted into solids prior to storage (USAEC, 1974b). The distribution of tritium in EBR-11, as reported by Ebersole et al. (1971), was as follows:

Fuel Primary sodium Secondary sodium Primary cold traps Water system Shield cooling air

30 percent 3.5 percent 0.8 percent 65 percent

0.25 to 0.5 percent 0.5 to 0.8 percent

The high retention in the metallic fuel was attributed to the formation of uranium hydride.

3.4

TRITIUM RELEASES FROM PRODUCTION PLANTS

3.4 3.4.1

/

15

Tritium Releases from Production Plants

Tritium Production at the Savannah River Plant (SRP)

The Savannah River Plant, Aiken, South Carolina, has been the primary production source of tritium in the United States. Tritium releases from the production reactor processes result almost entirely from the discharge of tritiated D20 either as a liquid or vapor. Liquid releases originate primarily from the storage basins for the spent fuel and target assemblies. The water in these basins becomes contaminated with tritium from the tritiated D20 adhering to the irradiated fuel and target assemblies at the time they are discharged from the reactors. The average amount of tritium released annually to the environment by these mechanisms is 35 kilocuries. Releases of tritiated water vapor from the reactors occur during unloading and loading operations and from evaporation of minor spills, storage basin water, etc. This tritium is discharged through the 61 m high reactor building exhaust stacks and averaged 230 kilocuries per year during the period 1971 to 1974. Tritium is also released from a rework facility in which degraded heavy water is restored to reactor grade (>99.7 percent D2O). About 6 kilocuries are discharged to plant streams each year as a result of this process. When irradiated reactor fuel is reprocessed, a small fraction of the fission product tritium is released to the atmosphere in the dissolver off-gases. However, most is converted to HTO and released to a seepage basin with the waste water. The lithium-aluminum tritium production targets and the irradiated reactor fuel are processed separately. Annual releases from the separations facilities average about 357 kilocuries to the atmosphere, 22 kilocuries to seepage basins, and 9 kilocuries to effluent streams (1971-1974). Approximately 2.7 MCi of tritium is stored as solid waste in the SRP Burial Grounds. Waste material is in the form of (1) spent lithiumaluminum furnace melts; (2) contaminated equipment; (3) vacuum pump oil; (4) housekeeping scrap from routine operations; and (5) miscellaneous scrap and solidified waste from offsite operation. Significantly smaller quantities (<5 x lo4 Ci) of tritium are retained in the liquid waste storage tanks.

3.5

W t i u m Releases from Fuel Reprocessing Plants

Reprocessing facilities that are currently in operation in the U.S. handle primarily spent fuels from military operations. The processes

16

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3.

SOURCES OF TRITIUM

used are variants of the Purex process (Irish, 1959) in which the fuel is dissolved in a nitric acid solution, and extracted by a solution of tributyl-phosphate in kerosene. Essentially all of the tritium accompanying the dissolved fuel is released in the form of tritiated water. Some tritium may also be released as gas or removed with solid wastes. The reprocessing of reactor fuels and the fate of accompanying tritium have been reviewed recently by a number of authors, including Eisenbud (1973a), EPA (1973), b e y et al. (1975), Kullen et al. (1975), ORNL (1970), Rhinehammer and Lamberger (1973), USAEC (1972a), Yarbro et al. (1974), and Blomeke et al. (1974b, 1975). Factors related to the distribution of tritium within the reprocessing plant and waste storage areas were considered by Blomeke et al. (1974%1974b, 1975).

3.5.1

Tritium Content of Fuel

The tritium inventory in irradiated fuel will depend on the type of fissile material, the irradiation history, and the cooling time. Yarbro (1974),using the ORIGEN (Bell, 1973) code, estimated that light-water reactor fuel with an exposure of 33,000 MWd MTU-' (megawatt day per metric tonne of uranium) during a 3-year irradiation life, followed by 160 days cooling, would have a tritium content of 690 Ci MTU-' (currently revised to 526 Ci MTU-')I. Runion (1970) indicated that, for typical BWR and PWR spent fuels a t 30,000 MWd MTU-', 150 days cooling, a tritium content of about 375 Ci M T V ' was anticipated. The differences largely reflect the computer codes and yield data used to calculate reactor production rates. Anticipated values for LWR (both PWR and BWR) and LMFBR fuels are shown in Table 3.5 TABLE3-&Tritium content of irradiated reactor fuels Fuel Cladding Average burnup', MWtd MTU-' Average specific power. MWMTU-' Refueling period Fraction replaced Cooline period, days Annual fuel dischargea,t GWe-I Tritium inventow, Ci MTU-' % in fuel matrix % in clndding % to reactor coolant

LWR

LMFBR

UOz Zirconium alloy 33,000 30-38 l year 1/3 160 27-30 526 90 1W tl

(U.h)02 Stainless steel -40,000~

-52 -W 1/3 30 18 1070 0-5 -0 -100

* Blomeke et al. (1974a);Kee (1976). Average for core and blanket. 'Goode and Cox (1970);Melehan (1970);Grorrsman and Hegland (1971).

' MTU: metric tonne of uranium, in the SI system one metric tonne is denoted as t.

(Kullen et al., 1975; Blomeke et al., 1974a). Other values, not cited here, are generally in the given range. For Zirconium alloy-clad fuels, such as are currently used in lightwater reactors, a fraction of the tritium will become fixed in the cladding as zirconium tritide, depending on the power level a t which the core was operated (Goode and Cox, 1970;Melehan, 1970; Grossman and Hegland, 1971). Thus, for linear power ratings of 1.5 to 2 kW m-' (presently anticipated for Light-water reactors), 5 to 15 percent of the tritium will be contained in the cladding. At higher ratings, the amount entering the Zirconium alloy cladding becomes much greater (Grossman and Hegland, 1971) (i.e., 75 percent at 50 kW m-' and about 96 percent at about 100 kW m-I). Stainless steel cladding was used on PWR fuel elements prior to 1968 and, as mentioned in a preceding section, a large fraction of the tritium formed in the fuel readily diffused through the cladding. This increased the tritium released by the reactor, but decreased the quantity that reached the reprocessing facility. Stainless steel cladding will also be used on LMFBR fuel elements. At the higher LMFBR temperatures, practically all fission product tritium will be released to the sodium coolant during reactor operation, from which it may largely be removed in the form of sodium tritide by cold trapping. Thus, only small quantities are expected to be transferred with the fuel to the reprocessing plant. Tritium recovery from the zirconium alloy-clad fuel of heavy water reactors (e.g., CANDU) would be similar to that for light-water reactors, although the necessity for reprocessing the natural uranium fuel is not great. The larger quantity of tritium produced by irradiation of the heavy water is not presently processed. 3.5.2

Commercial Fuel Reprocessing Plants

Three commercial fuel reprocessing plants have been constructed in the U.S. to process fuel from light-water reactors. None are operating at the present time. The Nuclear Fuel Services, West Valley (N.Y.) plant was the finst U.S. commercial fuel reprocessing plant. It operated for a number of years, processing a variety of types of fuel (Runion, 1970; Nuclear Fuel Services, 1962; North and Booth, 1973; Kullen et ah, 1975). The plant ceased operation in 1971 and alterations to permit operation at 750 MTU y-' were initiated. These alterations have been stopped and no further processing will be attempted, but the predicted behavior of tritium in the proposed plant will be of interest. A fraction C1&16 percent) of the tritium was expected to be retained in the zirconium

18

/

3.

SOU~CESOF TRITIUM

alloy hulls, which would be stored as solid waste. Of the tritium accompanying the dissolved fuel, it was estimated that about 1percent might be utilized, 7 percent would be stored with high-level waste, and about 92 percent would be released to a storage pond from which it would eventually pass to the watershed. It was estimated that this plant would release about 470,000 Ci y-' as liquid release. The Midwest Fuel Recovery Plant has never operated and is not expected to do so. The Allied-Gulf Nuclear Services, Barnwell (S.C.) Nuclear Fuel Plant (GulfNuclear Services, 1973; Murbach et al., 1974; Rhinehammer et al., 1973; Kullen et ab, 1975) is designed to process 5 MTU d-'. Of the tritium accompanying the dissolved fuel after the chop-leach procedure, 4 percent will be retained with high-level waste and 96 percent will be evaporated and released to the atmosphere through a 61 m stack. There are no designed liquid releases. Thus, the full capacity annual release of tritium to the atmosphere by this plant is estimated as about 7 x 1@Ci y-l.

3.5.3

Government Plants

Government plants for the reprocessing of various types of reactor fuels are located a t the Department of Energy facilities at Hanford (Wash.), Idaho, and Savannah River (S.C.)(Rhinehammer and Lamberger, 1973; USAEC, 1973c; Kullen et al., 1975).These plants process a variety of fuels irradiated to quite different extents. They all dissolve the fuel by various processes. Dissolution of metal fuels causes an appreciable fraction of the tritium to be released as H T gas. After dissolution of the fuel, the Purex process is generally used. At the Hanford plant, the processing of zirconium alloy clad fuel (Jeppson, 1973; Kullen et al., 1975) releases about 5-9 percent of the dissolved tritium to the atmosphere, less than 1 percent to recovered fuel, 5-16 percent to waste storage, and 73-90 percent to ponds. The capacity of this operation is about 3600 MTU y-'. At the Idaho Chemical Processing Plant (Cole et aL, 1973; Kullen et al., 1975), the dissolution of aluminum-clad metallic fuels with HNO, resulted in the release of 45 percent of the tritium to off-gas as HT, while with zirconium-clad fuels, dissolution with HF resulted in 90 percent of the tritium going to off-gas. Liquid wastes from these processes were either evaporated to the atmosphere or pumped into the plant injection well. The capacity of this plant has not been published. The Savannah River Plant was discussed in an earlier section (see also Sykes et al., 1973; Kullen et al., 1975).

3.6

3.5.4

TRITIUM FROM NUCLEAR DETONATIONS

/

19

Plants Outside the United States

Kullen et al. (1975) list 9 foreign fuel reprocessing plants with a combined capacity of about 340 MTU y-I that were operable before 1975. In addition, they list 16 plants, with a capacity of 9100 MTU y-', to be operable during the period 1975-1980. The tritium content of the fuel to be processed in these plants was estimated to be 4 x 10%Ci per year by 1980, and was reported to be about lo5 Ci y-' by the end of 1974. The list does not include the plants operating in Communist-bloc countries.

3.6

Tritium Production a n d Releases from Nuclear Detonations

The production of tritium by nuclear and thermonuclear explosions depends on the spectrum of fission and fusion energy yields, the type of explosive, and the characteristics of the explosion site. Based on a fission tritium yield of 1 x and an explosive yield to 1.4 x fissions/megaton (MT), Miskel (1971) estimated a tritium yield of 700 Ci MT-' of fission. This yield would be augmented by various (n,t) reactions. A tritium yield of 0.02 MCi MT-' for fission explosions is quoted by Terpilak et al. (1971). The tritium yield from thermonuclear weapons is enormously greater than for fission weapons. Leipunskii (1957) estimated the tritium released by pure "hydrogen" bombs to be about 6.7 MCi MT-'. Eriksson (1965) indicated a direct yield of 4 MCi MT-' and an additional indirect yield of 1.5 MCi MT-' for a total of 5.5 MCi MT-I. Miskel (1964) suggested that variations in design, performance, and location could cause the tritium yield to range from 7 to 50 MCi MT-I, and suggested (Miskel, 1971) that an average value of 20 MCi MT-' be used. Begemann and Libby (1957) estimated a northern hemisphere deposition of about 250 MCi after the 22 MT Castle tests in 1954, a value indicating a yield of 11 MCi MT-l. The fission and total energy yields of nuclear weapons tests conducted in the atmosphere by all nations were summarized in Federal Radiation Council Report No. 4 (FRC, 1963) and are given in Table 36, together with estimates of the quantities of tritium produced, based on yields cited above. The Begemann-Libby yield implies that the 1963 inventory of tritium from fusion explosions was about 3100 MCi (Grathwohl, 1972). The additional input from fission explosions is estimated to be about 300 MCi. Estimates by others give 1963 global

20

/

3.

SOURCES OF TRITIUM

TABLE 3-&Energy yield and estimated tritiwn yields of atmospheric nuclear weapons tests, 194.5-1962 Inclusive years

1945-51 1952-54 1955-56 1957-58 1959-60 1961 1962

Fission enMl"

.71 38. 13.1 40. 0. 25. 76.

Fupion ansrgy

MY

Tritium MCi"

.05 22. 14.9 45. 0.' 95. 141.

.55 242. 163.9 495. 0. 1045. 1551.

' Federal Radiation Council Report No. 4 (FRC, 1963). Bnaed on 11 MCi M Y ' fusion (Begemann and Libby, 1.957). ' Does not include 3 MT French detonations noted by Roulin (1864) and Crathwohl (1972).

tritium inventory estimates ranging from 1700 MCi (Eriksson, 1965) to 8000 MCi (Miskel,l971; Schell and Sauzay, 1973). Underground tests of thermonuclear devices have been conducted on a wide scale by the major nuclear powers since the Test Ban Treaty agreement was signed in 1963. This has not added significantly to the inventory of tritium in the atmosphere and surface waters, but an inventory of uncertain magnitude exists underground at the test sites. The extent to which this inventory will contribute to human exposure will depend on the extent of its hydrological isolation. This is not evaluated in this report. 3.7

Tritium Production and Releases from Thermonuclear Reactors

An assessment of thermonuclear energy by the Division of Controlled Thermonuclear Research of the U.S.Atomic Energy Commission (USAEC, 1973d) contains the statement: "Present eetimatea indicate that an orderly aggressive program might provide commercial fusion power about the year 2000, so that fusion could then have a significant impact on electrical power production by the year 2020."

Large-scale use of thermonuclear reactors for heat or power generation, therefore, seems quite unlikely in the next 25 years. However, if thermonuclear reactors come into use, they will contain substantial inventories of tritium and will pose considerable tritium-management problems. Controlled Thermonuclear Reactors will not be discussed further in this report.

3.8

3.8

SUMMARY OF TRITIUM SOURCES

/

21

Summary of Tritium Sources

The world inventory of natural tritium may reasonably be taken as 70 MCi, corresponding to a world production rate of 4 MCi y-'. The inventory assignable to weapons tests was (within a factor of 2) about 3100 MCi in 1963. By decay, such an amount will be greater than the natural level of 70 MCi until about 2030. Tritium is formed in reactors by ternary fission at a rate of about tritium atoms per fission. The yield from 2 3 9 Pis~ perhaps twice that from 23SU and =U. Furthermore, the yield is greater a t neutron energies in the resonance (and presumably fast) regions. Estimates of the production rate by ternary fission have ranged from less than 12 to more than 20 Ci MWt-' d-' depending on the fissile mix and exposure and the yields assumed. Tritium can also be formed in reactors by activation of light elements, particularly outside the fuel. In general, less than 1percent of the tritium formed in fuel is released by Zirconium alloy-clad elements of light-water reactors (LWR). Thus, a 1000 MWe BWR (thermal efficiency= 0.32) might produce tritium a t a rate of 15,000 to 25,000 Ci y-', but would release less than 1 percent to the environment. Pressurized water reactors use boric acid and traces of lithium-7 hydroxide for reactivity and corrosion control and these sources contribute about 600 to 800 Ci y-' to the reactor coolant. Studies of several commercial nuclear power plants have shown that the average annual release to the environment by a 1000 MWe reactor was about 60 Ci y-' for BWR, and 830 Ci y-' for PWR. Early model PWRs using stainless steel clad fuel elements released greater amounts of fission tritium to the coolant and thence to the environment. In heavy water reactors, tritium formed by neutron activation of deuterium is estimated to accumulate a t rates up to 600,000 Ci y-' in a 1000 MWe reactor. In liquid-metal fast breeder reactors, tritium formed at relatively high rates from plutonium permeates the stainless steel cladding to enter the liquid sodium coolant. It then permeates system walls. Control by trapping appears feasible, but may require coprecipitation with hydrogen. No commercial facilities for the reprocessing of fuel discharged from light-water reactors are operating as of this writing, although two operable plants exist. The tritium content of fuel a t the start of reprocessing is estimated to be as high as 526 Ci MTU-', of which perhaps 10 percent (depending on the fuel linear power density) will remain with the undissolved zirconium alloy cladding. If placed in operation, the 1500 MTU y-' Barnwell, S.C. plant could release up to nearly 700,000 Ci y-' of tritium to the atmosphere.

22

/

3.

SOUfiCEs OF TRITIUM

Government facilities at Hanford (Washington), Idaho, and Savannah River (S.C.) have the capability of reprocessing substantial quantities of a variety of fuels; small quantities of tritium are released in all cases. The reprocessing capability of Western foreign nations is estimated to be about 340 MTU y-'. Before 1980, sixteen additional plants with a capacity of about 9000 MTU y-' are scheduled for operation. The tritium releases per MTU are estimated to be similar to that of U.S. plants. Controlled thermonuclear reactors of the future are expected to operate with the D-T-Li cycle. The form of lithium blanket and the method of recovering tritium from it have not been defined.

4. Physical Transport of Tritium 4.1

Introduction

Releases of tritium to the environment can take place under a wide variety of physical conditions. In general, the risk from tritium exposure to persons located close to the point of release can be evaluated by use of conventional methods of environmental impact analysis. The factors involved in such analyses will be discussed in Sections 5 and 8. This section will review the broader geophysical and ecological factors that affect populations located at considerable distances from the source, i.e., greater than 100 krn.

4.2 Atmospheric Dispersion The transformation of tritium released to the atmosphere into tritiated water vapor is a complex process, with the rate of oxidation depending upon the presence of catalysts as well as the concentrations of HT and HTO. The rate of transformation is initially less than 1 percent of the tritium released (Burger, 1976). The diffusion of the plume containing HTO may be described by various models, such as those discussed in Meteorology and Atomic Energy, 1968 (Slade, 1968). For shortrange estimates of atmospheric concentrations, a modification of the gaussian bivariate equation is usually used, along with statistics of windspeed and direction frequency for various stability classes. For distances greater than approximately 80 km from the source, trajectory methods can be used to estimate air concentrations. See, for example, Machta et aL., 1973. Assessment of the impact of aqueous tritium releases on the world population assumes that the annual release is uniformly distributed in the mixed layer of the oceans of the world or northern hemisphere (EPA, 1974). The food and water consumed by the world population is assumed to contain this same tritium concentration. Other assess-

24

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4.

PHYSICAL TRANSPORT OF TRITIUM

ments have used a dynamic model consisting of three compartments. atmosphere, oceans and seae, and surface water (Eckerman and Congel, 1974); or seven compartments (Easterly and Jacobs, 1975). A more recent model is essentially a "box model" in which HTO is assumed to follow the hydrologic cycle (Renne et al., 1975). The atmospheric and surface water HTO concentrations are estimated for each latitude belt, and mass balance equations are written for the atmosphere and surface water that include all fluxes of HTO that enter and exit a particular latitudinal band. Solutions are obtained only after some simplifying assumptions are made: Surface runoff plus evaporation = runoff plus precipitation - Outflux of vapor across latitudinal boundary plus precipitation = influx of vapor across boundary plus evaporation No HTO releases occur directly to groundwater Depth of precipitation is much less than the depth of surface water.

-

Table 4-1 shows the results of using the box model to estimate HTO concentrations in air and water for land and ocean environments at eight latitudinal belts. Note that the concentrations were calculated to be greatest in the 3 0 ° 4 0 0 belt, which, of course, is where the release was assumed to take place.

Deposition

4.3

Estimates of the mean residence time of tritiated water in the troposphere range from 21 to 40 days (Libby, 1958, Barrett and TABLE 4-1-Average groundleuel, atmospheric, and surface water concentrations by lcrtitude belt for land masses and awurs assuming 1 Ci y-' ahnospheric relocure in Latitude 300-ww kad"

Ltitnde

oceamc

Air

ION)

Water (pCi I-')

(pCi m-'1

0-10 10-20 20-30 30-50

60-60 60-70 70-80 80-90

4.0 X lo-' 4.2 14.0 35.0 15.0 5.9 1.9 0.8

'From Renne et aL, 1976 Assumed depth

0.5 m

'Assumed depth = 76 m

0

171. x lo-' 224.0 287.0 64.0 180 83 0

Air (pCi m-')

0.13 X lo-' 0.3 2.8 15.3 3.8 0.6 0.1 0.03

Water (pCi 1-9

0 0.15 X lo-' 2.0 25.8 0.5 4.9 X lo-"' 3.4 X lo-'* 0

Huebner, 1961; Begemann and Libby, 1957; Walton et al., 1962;Barrett and Huebner, 1960, Brown and Grummitt, 1956; Bolin, 1964). From this, and if the tropopause is assumed to be at a height of 12 to 15 km (Harteck, 1954, the deposition velocity of tritiated water can be estimated to be between 0.4 and 0.8 cm s-'. Considering diffusion only, the deposition velocity can be calculated to be less than 0.4 cm s-', but the value depends almost entirely on other factors such as air motions and precipitation (Engelke and Bemis, 1962). Eriksson (1965) estimated the eddy diffusion velocity of tritiated water over ocean areas to be about 1 cm s-I, on the basis of the rate of evaporation and the relative humidity of the air. Another estimate of the deposition velocity for tritiated water can be made from the concentration and deposition rate of natural tritium. Harteck (1954) estimated the amount of natural tritium to be 0.6 mole in the world's atmosphere, and gave a value for a molar ratio of tritium to hydrogen in water of 3.5 f 0.7 x lo-''. Verniani (1966) estimated the average water-vapor content of the atmosphere to be 9.4 X 1017 moles. Another 3.3 moles of tritium is present in the atmosphere as HTO. If tritium is distributed similarly to the rest of the mass of the atmosphere (Lange and Forker, 1961), the ground level concentration ~. (1963a) gave an of tritium would be about 0.48 atom ~ m - Bainbridge average of 0.39 k 0.15 atom cm-2 s-' for the deposition rate of natural tritium integrated for all latitudes, a rate that yields a mean deposition velocity of 0.8 cm s-', in close agreement with the values estimated in other ways. Bolin (1961) suggests that in light rains the tritium concentration is representative of that in the moisture at lower levels, whereas in moderate or heavy rains the exchange at lower levels is insignificant. Chamberlain and Eggleton (1964) considered the exchange of tritium between rain drops and water vapor on the basis of a film-diffusioncontrolled process. Theu findings that the specific activity of drops reaching the ground after passage through a plume contaminated with tritium is very dependent on drop size support Bolin's suggestions. Chamberlain and Eggleton further estimate that the washout coefficient for the plume of tritiated water vapor should be on the order of

lo-'

S-I.

When the atmospheric concentration of tritium is uniform, the concentration of tritium in rainfall over continental area9 will be higher than in rainfall over the oceans (Eriksson, 1965; Israel et al., 1963; Brown, 1964b). Because precipitation falling on land is unlikely to be diluted, water re-evaporated from land has nearly the same tritium content as the original precipitation. Conversely, precipitation falling on the ocean and other deep bodies of water is rapidly mixed to a

depth of about 75 m, and the concentration of tritium in evaporated water is therefore likely to be lower than in precipitation (Bainbridge, 1963a). Brown (1964b) tried to correlate temporal fluctuations of tritium concentration in Canadian precipitation with meteorological factors, such as type of storm, height of precipitation formation, rainfall duration and intensity, and type and origin of the associated air mass. Only air-mass considerations led to any significant correlation; the deeper the air mass traversed by precipitation, the higher the tritium concentration. Also, air-mass trajectories from the north and west yielded precipitation of high tritium concentration, but those originating in the south and east resulted in low tritium concentration. This phenomenon was probably due to differences in transfer from the stratosphere. Even when tritium is uniformly distributed throughout the stratosphere of the northern hemisphere, it is preferentially deposited in the mid-latitudes (Libby, 1963; Eriksson, 1965) because of higher rates of stratospheric-tropospheric transfer. This zone includes some of the most highly populated parts of the world, including most of the United States and Europe. When the releases of tritium are restricted to the troposphere, there is much less chance for lateral mixing, and deposition is limited to the general latitude of the release (Libby, 1958). In addition to latitudinal variations, deposition of tritium over continental areas differs markedly from deposition over the oceans (Eriksson, 1965). The annual precipitation over the oceans is greater than over the continents (Gorczymski, 1945; Eriksson, 1965), and this situation also suggests that deposition of tritium over the oceans is relatively greater due to direct exchange of water vapor between air and seawater. Eriksson (1965) estimates that transfer of tritium by vapor exchange over the oceans may account for about two-thirds of the tritium removal. This may explain the discrepancy between Libby's (1963) estimate of rainfall of 2.5 m y-' over oceans and measured values of about 0.9 to 1.1m Y-' (Wust, 1954; Gorczymski, 1953). Practically all of the continental deposition of tritium occurs from precipitation (Libby, 1958). However, when tritium is released through a stack, the downward diffusion of the plume w i l l probably cause it to reach the ground surface before washout by rain occurs (Chamberlain and Eggleton, 1964). Once deposited, the tritium can undergo one of several fates (Baver, 1956). The tritium can transfer by surface runoff during and immediately following a rain, and by direct evaporation from the surfaces of vegetation, standing pools of water, and the soil surface. Water that infiltrates the soil is cycled more slowly. Movement in soil may occur

both laterally and vertically with losses due to transpiration, evaporation, recharge of surface streams, and direct groundwater flow into oceans. Some of the water that recharges the groundwater moves so slowly that the tritium associated with this fraction of the precipitation is effectively lost from circulation. The annual rainfall over continental areas of the world is about 0.66 m y-' (Rankama and Sahama, 1949). Of this amount, about 0.25 m y-I, or 37 percent, is lost by runoff and underground flow. The remaining 63 percent returns to the atmosphere by evaporation and transpiration (CarLston, 1964). For the continental United States, the annual rainfall is about 0.76 m, of which about 28 percent is lost by runoff and underground flow, with the remainder lost by evapo-transpiration (Griffiths, 1966).In the Clinch River watershed, the runoff and underground flow amount to about 40 percent of the rainfall (Morton, 1961). Begemann and Libby (1957) summarized in detail the water balance in the Mississippi River valley following the U.S. Pacific weapons tests in the spring of 1954. Precipitation in that area is about 0.77 m y-', of which about two-thirds is water evaporated from the ocean and about one-third is re-evaporated groundwater. The Mississippi River annually returns about 0.28 m of water to the ocean by runoff; the remaining 0.49 m y-' is evaporated, with about 0.24 m y-' of the evaporated water being returned to the ocean. They estimated that about 8 m of groundwater is available for mixing and that this groundwater has a storage time of about 10years. They estimated that tritium deposited on the North American continent has an effective residence time of 5.7 years. In the Ottawa River drainage basin of 24,000 square miles, the mean residence time for tritium has been estimated to be 3.7 years, and the reservoir is estimated to have an effective depth of 2.1 m (Brown, 1961).About 55 f 10 percent of the re-evaporated water is made up of fresh precipitation. There is a fast-drainage component that cannot be adequately accounted for by a simple one-compartment model. This assumes complete mixing with a single turnover time (Brown, 1964a). Eriksson (1963) made a detailed analysis of Brown's (1964a) data, along with later data, and determined the runoff of water as a function of storage time. The results are in good agreement with the physiography and geology of the basin. An amount of tritium approximately equivalent to that deposited by two years of precipitation stays in the basin less than eight years. Runoff is maximum relative to the volume stored at about three years, with an indication of an earlier peak occurring after about one year. Eriksson (1963) suggested that the early peak is due to surface runoff and near-surface groundwater flow

28

/

4.

PHYSICAL TRANSPORT OF TRITIUM

into streams and rivers that discharge directly into the Ottawa River. The second peak he attributed to holdup in the system of lakes in the upper Ottawa River valley.

4.4

Movement in Groundwater and Soil

It is generally assumed that tritiated groundwater will behave in a similar manner as ordinary water, except for the slight difference in vapor pressure. Tritiated water depositing on soil from the atmosphere will diffuse into soil and mix with the soil particles, with some of it eventually reaching the groundwater. Infiltration of tritiated water vapor will depend upon a variety of factors such as: a. state of the soil (cultivated or fallow) b. type of soil (clay, loam, or sand) c. water content d. organic matter. Recently cultivated agricultural soil was exposed to tritiated water vapor in an experiment described by Koranda and Martin (1973). Tritium was infiltrated into the soil to a depth of 15 cm but was rapidly evaporated from the surface stratum (0-2.5 cm). Tritium that diffused deeper into the soil was not subject to the same loss mechanisms that took place near the surface. The depth profiles of tritium in the exposed soil were integrated at each sampling time, and the integral soil concentration was plotted against time to obtain a half-life of tritium in the profile. A very short initial half-life of 16 minutes was present with a longer component of 123 hours that accounted for most of the distribution of tritium below 2.5 cm. Tritiated water begins to move downward as a layer that gradually becomes less distinct because of variable dispersion rates and vertical molecular diffusion. Lateral molecular diffusion also occurs (Zirnmerman et al., 1967) and tends to level out the velocity dispersion diierences of the individual molecules. In general, the more water that is already present in the soil, the more slowly the labeled water will move. The water associated with minerals in the ground may have various degrees of mobility, depending on the nature of the association. In a water-saturated formation, the bulk of the water will be in the aqueous form. This water may be considered to be mobile, although its velocity of movement will vary, depending on the interstitial pore size. In addition to this water, loosely bound water of hydration is attached to the mineral surfaces. Joergensen and Rosenqvist (1963) studied the

4.4

MOVEMENT IN GROUNDWATER AND SOIL

/

29

bonding of hydrogen in micas and found that a t room temperature, the water of hydration reaches equilibrium with its environment after a very short time. A second phase of adsorbed water requires much longer for equilibration and is vaponied in the 200 to 500°C temperature range. Finally, a thud phase requires very long times or hydrothermal alterations for exchange. This water can be removed in the 500 to 1150°C temperature range. This phase is thought to consist primarily of structural hydroxyl groups. The impact of these adsorbed phases of water on tritium behavior in the ground is dependent primarily on two factors: (1)the relative amounts of these phases compared with the free water in the interstitial macropores and (2) the conditions under which the adsorption and desorption reactions occur. Tritiated water would be expected to move more slowly through a very dry soil than through a moist soil. If the tritiated water is produced at very high temperatures, i.e.. in the hightemperature region of a nuclear explosion,exchange with the structural hydroxyl groups may occur. Since an activation energy must be exceeded to initiate the exchange reaction, the subsequent replacement of this fraction of the tritium would be very slow. Koranda (1965) observed that in the Pacific Proving Ground the mineral-bound water of the soil is high in tritium. The "soil" consists almost entirely of CaC03 and Ca(OH)2. The free water in the soil had a concentration of 60 tritium units?-,compared to the bound water, which had a concentration of 3.7 x 10' tritium units. In a saturated formation, nearly all of the tritiated water will be in the interstitial macropores, and i t . velocity of movement will vary depending on the dispersive characteristics of the formation (Nir, 1964). Nakayama and Jackson (196313) reported that the apparent diffusion coefficient for tritiated water in soils was nearly constant for volumetric water contents between 10 and 40 percent. Below 10 percent the apparent diffusion coefficient increased rapidly, with a maximum at 4 percent water content, beyond which the diffusion coefficient decreased rapidly, suggesting an influence of absorbed phases. Jordan et al. (1974) found that, in unsaturated soils, mass flow of tritiated water occurred through a network of large soil pores that permitted rapid downward movement of the labeled water. These large pores or channels were conjectured to be the result of clay shrinkage, tillage, roots, and the activity of ants and earthworms. Lang and Mason (1960) reported that the exchange of tritium between cellulose and water vapor is not completely reversible. Bolin (1961) suggested that the history of tritium concentration in the 'The term "tritium unit" (TU) has been commonly used to denote the number of tritium atoms per 10'"aetoms of hydrogen. One TUJ is equivalent to 3.231 pCi 1-'HB.

groundwater could be reconstructed by analyzing the specific activity of the cellulose in tree rings. Workers in Japan presented data on the tritium content of tree rings to estimate the tritium content of rainwater (Kigoshi, 1961; Kigoahi and Tornikura, 1961). This technique has also been extensively developed in Canada (Brown, 1964c),where no exchange has been shown between ambient tritiated water and the C-H bonds of cellulose within a five-year period. Woods and O'Neal (1965)showed that most of the water withdrawn by small trees comes from the first 0.3 m of the soil. 4.6

Behavior of Tritium in t h e Hydrosphere

Tritium can reach surface waters by a variety of pathways: directly through precipitation, through molecular exchange with the atmosphere, by direct release of tritiated water from nuclear plants to streams, and indirectly from runoff of groundwater into streams. 4.6.1

Behavior of Tritium in Rivers

Water in stream channels moves at various rates into oceans and seas. In Tennessee's Clinch River the measured flow velocities range from about 0.06 to 0.7 m s-', depending on the discharge (Morton, 1962;Parker, 1964);the mean velocity is about 0.21 m s-' (Morton, 1963) compared with a geometric mean wind speed of about 2.2 m s-' (Chamberlain and Eggleton, 1964).In other streams the flow velocity may differ considerably, the variation reflecting the hydraulics of the system (Kato et al., 1963;Clayton and Smith,1963). With a slug discharge of tritium, the duration and intensity of the tritium peak reaching downstream users would depend on the diffusion encountered in the river, the flow velocity, and the discharge (Parker et al., 1966). Downstream concentrations of tritium can be predicted if the dispersion characteristics of the stream are known (Parker et al., 1966),

4.6

Release to Groundwater

At present a large fraction of the tritium produced on the North American continent is released into the ground (Haney et al., 1962; Horton, 1963; Parsons, 1963; Hawkins and Schmaltz, 1965). These releases of tritium have been used as bacers to predict the migration

4.5

BEHAVIOR OF TRITIUM IN THE HYDROSPHERE

/

31

of other radionuclides. At Hanford, Washington, approximately onehalf to two-thirds of the tritium produced by fission has been released to the ground (Haney et al., 1962). The tritium content of the groundwater shows preferential directional movement toward the Columbia River a t a rate that is in agreement with the movement expected on the basis of the hydrology and geology of the site. At Savannah River, nearly all of the tritiated water from the aqueous stream used in fuel reprocessing is discharged to open seepage pits, and most of this tritium enters the ground (Horton, 1963).The tritium must move a distance ranging from 150 to 600 m before entering surface waterways (Reichert, 1962). Movement of the groundwater is irregular; most of the movement has been through sandy strata or sand-filled intrusions (Reichert, 1962; Horton and Ross, 1960). Approximately 18,000 Ci of tritium were released to the ground a t the National Reactor Testing Station in Idaho (Hawkinsand Schmaltz, 1965) between 1953 and 1965. Tritium has been detected in groundwater over an area of about 195 krn2downgrade from the disposal well. An attempt was made to detennine longitudinal and lateral dispersion coefficients, but the direction of flow could not be adequately described to provide an adequate fit of the limited amount of data to a theoretical dispersion equation. Tritium was also released to waste seepage pits a t the Oak Ridge National Laboratory during the period 1952 to March 1966, but only cursory results on movement have been obtained (de Laguna, 1964). Tracer studies (Lomenick et al., 1967) with injections of tritiated water in the seepage-pit area indicate that the median groundwater velocity in this area is about 0.15 m d-'. Tritium is released directly to the ground by the underground detonation of nuclear devices, especially fusion devices (Stead, 1963; Culler et al., 1962). Essentially all of the released tritium is assumed to form water, either by oxidation or exchange (Stead, 1963). If the exchange of tritium between the tritiated water and the rock matrix is negligible, it is estimated that the tritium concentration would be about 3 pCi ml-' in the crushed zone; outside of this zone the concentration of tritium could be reduced only by dilution and dispersion in nearby groundwaters. The actual tritium concentrations that would be attained would, of course, be dependent on the extent of the crushed zone, the water content of the formation, and the amount of venting of tritium that occurred. In addition, any high-temperature reaction between tritium and the minerals of the formation would be expected to reduce the quantity of tritium available for contamination of the groundwater. In general, the velocity of groundwater flow ranges from about 1.5

32

/

4.

PHYSICAL TRANSPORT OF TRITIUM

m y-' to about 1.5 m d-', although in highly permeable aquifers the velocity may be several hundred feet per day (Galley, 1962; Clebsch and Lieberman, 1962; von Buttlar, 1958; Menitt, 1962; Blavoux, 1964). In deep subsurface strata, flow velocities may be on the order of 6 cm per year (Galley, 1962) and the storage time in deep formations may be on the order of tens of thousands of years (Carlston, 1964; Vogel and Ehhalt, 1963). The age or storage time of groundwater cannot be determined exactly by assuming simple exponential decay of tritium from its time of entry into the ground because the mixing from hydrodynamic dispersion and diffusion influences the concentration (Koranda, 1965). The magnitude of this dispersion under field conditions is much greater than that measured in the laboratory and could result in sigmficant spreading of a contaminant (Theis, 1962, 1963). A wide range of permeabilities approximately exponential in character exists in any suite of sedimentary beds. Part of these effects is reflected in a more or less statistical variation of flow velocities over a wide range, but some variations may be due to the presence of lenses that are so extensive that they cannot be treated statistically. Thus, the magnitude of spreading that is likely to occur in a formation due to dispersive phenomena cannot be predicted a priori. The geology and general hydrology of an area should be well defined before tracer tests are interpreted for determining the rates of movement and the degree of dispersion. Where tritiated water is released to the ground near the surface, hydrologic studies must be undertaken to determine the transit times to surface waters. Tracer studies could be employed to estimate the magnitude of the dispersion that would likely occur. This information could then be used to estimate the loss of tritium by radioactive decay during its movement from the point of injection to its entry into surface water. However, to achieve any significant advantage over direct release to surface streams, storage time would need to be at least a few decades. Storage times of this magnitude, and longer, would be much easier to attain if deep permeable formations were used for disposal. Tritium could then be isolated until it had decayed to a predetermined level (Galley, 1962; American Association of Petroleum Geologists, 1964).

4.7

The Oceans

Tritium in the ocean becomes rapidly distributed in the thin surface layer of relatively warm water 50 to 100 meters deep known as the

4.7

0-?

Tritium Units 1-1 10

5

and 'C

15

(...-I

20

OCEANS

-

/

33

25

.-c f

=

My. 1986

"

i -B

19.28'N. 116'02W

. ;I Salinity (----I

Fig. 4.1 Protile in the Pacific Ocean (1g028'N and 116"0!2'W) taken in May 1965, showing the manner in which fallout tritium is retained above thermocline (after Suess, 1969).

"mixed layer." Immediately below thislayer the temperature decreases quite rapidly with depth (a stratum called the thermocline). Below this thermocline the temperature decreases more slowly (see Figure 4.1) (Suess, 1969). The thermocline prevents water from the mixed layer from intermingling extensively with that of deeper levels, so that for mid-latitude regions, mixing of the surface waters with deep waters is slow. Figure 4.1 shows a profile of tritium concentration at one location in the Pacific Ocean with a maximum above 50 meters and a rapid decrease a t depths below 100 meters.

5. Tritium Waste Management and Exposure to Populations Located Close to the Sources of Releases The global concentrations of tritium dominated at present by "weapons" tritium should continue to decline for several more years, even if releases from nuclear power installations are unrestricted. However, the quantities and concentrations to be coped with locally vary widely, and correspondingly varied methods of control are practiced. Many available control techniques have been cited in recent bibliographies, including those by Dixon et al. (1975), Rhinehammer and Lamberger (1973), ORNL (1973), and Hannahs and Kershner (1972).Surveys of the general aspects of management of tritium wastes have recently been made by Rhinehammer and Lamberger (19731, Bixel et al. (1976), Schnez et al. (1974), Musgrave (1974), Burger (1972),Burger and Ryan (1974),Arnold et al. (1973),Eisenbud (1973c), Brown (1976),Burger and Trevorrow (1976), and Steindler and Kullen (1976).

5.1 Some Dosimetric Considerations 5.1.1

Release to the Atmosphere

The effects of atmospheric release are indicated by the following calculation: if the average annual concentration in air per unit of s m-3 at 1krn from a ground source tritium released (X/Q) is 2 x (Bryant, 1964a, 1964b),annual release of 16,000 Ci of tritium will result in an average atmospheric concentration of 1000 pCi m-3 at that location; such an average concentration was estimated (Anspaugh et 34

5.1

SOME DOSIMETFUC CONSIDERATIONS

/

35

al., 1973) to result in a dose of 1.6 mrem y-' by inhalation and skin absorption, with additional possible dose increments of 1.6 mrem y-' from vegetable consumption, 0.6 rnrem y-' from milk, and 0.7 mrem y-' from meat. At 5 km, the average ground level air concentration and associated dose would be about a factor of 20 lower. The product of average dispersion and distance from source is approximately constant out to at least 100 km. Finney et al. (1975) indicate that, with a 100-meter stack, the highest average annual X / Q would be within about a factor of two of 3 x lo-' s m-3, at distances between about 1 km and 4 km, and would subsequently decrease in inverse proportion to distance.

5.1.2

Release to Liquid Streams

Liquid releases may be estimated in a manner similar to that used for atmospheric release. Smith and Gilbert (1971) estimated that the condenser coolant required for once-through operation of a 1000-MWe reactor should amount to about 50 m3 s-I. The release of 16,000 Ci y-' (0.5 mCi s-') into a condenser flow of 50 m3 s-' would result in water that would have a tritium concentration of 10 pCi ml-'. The daily ingestion of food and drink containing 2000 ml of such water would result in a dose of 0.8 mrem y-'. The use of cooling tower evaporation will somewhat increase the concentration in the cooling tower discharge but will sharply reduce the volume of liquid release. The larger amounts of tritium present in the low level aqueous waste of fuel reprocessing plants require that large volumes of water, approaching the flow of fair-sized rivers, be available (Schwibach, 1969). Similarly, far removed site boundaries are needed for dispersion into the atmosphere. As an example, to obtain an air concentration of 1000 pCi m-3 (as above) with release of 800,000 Ci y-' requires an average s m-3. The ground-level release value cited dispersion of about 4 x above, 1 x lo-' a t 5 krn, would indicate that this could be achieved with a boundary about 12 km from the point of release; with a 100meter stack such a dispersion value could be expected within about 5 km according to Finney et al. (1975). The average dispersion from a stack depends on stack height (and plume rise), distance to the receiver, frequency and quality of meteorological conditions, and on local terrain (Slade, 1968). The cost of evaporation of tritiated water for stack dispersal was estimated by Arnold et al. (1973) as $0.003 per liter for fuel plus $0.007 per liter for capital charges. Thus,costs increase with dilution prior to evaporation.

36

5.1.3

/

5. TRITIUM WASTE MANAGEMENT

Ponds

Tritiated water may also be evaporated from ponds. Ideally, ponds should be sealed to prevent seepage into the ground and to avoid surface inflow, and fenced to prevent cattle and wildlife from drinking the water. Individuals working near the ponds would require protection to minimize radiation exposure. Site boundaries should be at sufficient distances to provide the desired meteorological dispersion. Ponds should be of sufficient area to accommodate the tritiated water and precipitation a t the prevailing evaporation rate. For example, Arnold et aL (1973) described a proposed 100-acre pond capable of accommodating an annual flow of 3 x lo8 1 of tritiated water in addition to annual precipitation of 0.55 m per year. The cost was estimated to be $0.05 per liter. Doses to particular locations could be higher than by stack release because of lower dispersion of a ground source, and because of the variation of evaporation rate and meteorological dispersion conditions with time of day, as pointed out by Horton et al. (1971). The relative net flux of HTO from pond water into air of greater than 8 percent humidity is greater than that of H20, as a result of mass transfer effecta. 5.1.4

Release to Earth

The release of low-level aqueous wastes or tritiated water to the earth occurs from disposal wells at the Idaho site, from buried dispersal "cribs" a t Hanford, and by seepage from ponds at Savannah River (Rhineharnmer et al., 1973; USAEC, 1973c; Ashley and Ziegler, 1975; USERDA, 1975). Such releases, because of slow movement in soil, become useful combinations of the delay and decay, and dilute and disperse approaches. Robertson (1974) and C&EN (1973) showed that the tritium dispersion from wells and ponds at the National Reactor Testing Station, Idaho could be satisfactorily modeled by coupling hydraulic equations of groundwater motion with mass transport expressions. Transverse hydraulic dispersion was important. It was indicated that, if operations were continued, detectable concentrations of tritium (-2 pCi ml-') would be found in groundwater by the year 2000 as much as 24 krn down gradient from the original discharge. The average annual discharge of the Idaho Chemical Processing Plant has been 1.1 x lo6 m3, containing about 400 pCi m l - I tritium, discharged into a 183-m well extending about 45 m below the water table. At a separate point, the average discharge into waste ponds from the Test Reactor Area

5.1

SOME DOSIMETRIC CONSIDERATIONS

/

37

amounted to about 7.6 x lo5 m3 y-' containing 600 pCi ml-' tritium. (The combined seepage plumes are indicated to hold about 31,000 Ci.) Accumulated (30-year) tritium released from underground "cribs" at the Hanford reservation to the unconfined aquifer was indicated (USERDA, 1975) to amount to 3.5 x 10' Ci; only very near the point of release did the concentration in groundwater rise as high as the radiation concentration guide limit for drinking water (3000 pCi ml-', ERDAM, 1975). Tritium concentration attributable to these sources in groundwater bordering the Columbia River was in the range 1-30 pCi ml-' or lower. Release of substantial quantities of tritiated water or other wastes into the earth is essentially irreversible except for radioactive decay; and adequate area, suitable and known hydrology, and appropriate monitoring, including surveillance wells, are indicated.

5.1.6 Deep Wells The disposal of tritiated water into geological structures sealed below useful aquifers was discussed by de Laguna (1968), Treqorrow and Warner (1975), Trevorrow et al. (1977), Arnold et al. (1973), Schnez et al. (1974),and Schwibach (1969). It has also been proposed that chimneys of underground nuclear explosions could be used, or dome space in abandoned oil fields. A particular problem for such deep, confined regions of storage would be to establish that the desired capacity is available, at injection pressures that would not result in water breakout into the biosphere. Hydrofracturing, a variation on deep well disposal, has been successfulIy established, largely for other radioactive isotopes in aqueous effluents. Hydrofracturing consists of pumping liquids into a well penetrating a deep layered rock structure at pressures (2000 psi) such as to develop sheetlike horizontal ruptures. Aqueous wastes are incorporated into a cement grout that is injected into these cracks. This method may be limited by transportation costs for large volumes (de Laguna et al., 1971). However, a total of 2.04 X 10' 1 of waste have been hydrofractured a t Oak Ridge National Laboratory over the period of 1966 to 1970, in batches of 9 x lo4 to 6 x Id liters.

6.1.6 Other Methods of Disposal The disposal of large volumes of tritiated water into deep ocean or onto ice packs was mentioned by Rhinehammer and Lamberger (1973).

38

/

5. TRITIUM WASTE MANAGEMENT

These are subject to high transportation costs as well as a present lack of international agreement on appropriate regulations, and do not justify further discussion here.

5.2

Methods of Tritium Retention

6.2.1 Reactors

The alternative to release is retention, generally to be followed by fixation for permanent isolation; in some cases the recovery of tritium in useful form may be possible. Zirconium alloy cladding on fuel elements for light-water reactors retains practically all fission-product tritium within the fuel elements. Less than 1percent of the fission product tritium leaks into the reactor cooling water from failed fuel. Thus, approximately 99 percent of the fission product tritium will reach the fuel reprocessing plant. (As discussed in Section 3, tritium is also produced in the reactor primary coolant by neutron activation processes.) Recently, the recycling of all reactor plant water has been proposed in order to minimize radioactivity release (Wilson et d.,1970). As a result of the evaporation, recovery, and recycling of all liquid radiation waste, tritium can build up over the plant lifetime (Locante and Malinowski, 1971). While resulting in lower offsite releases, employee exposure could be increased by this practice. It is necessary ultimately to remove some water for disposal or storage, but the mode of final disposition of such plant water has not been established. Operation with "no planned releases of radioactive water" is in progress a t the Rancho Seco PWR (Rancho Seco PSAR, 1971), as well as being proposed for the SKAGIT nuclear power project (BWR) (SKAGIT Nuclear Power Project, 1975). During the first 119 effective full power days operation of the 2772 MWt, 913 MWe Rancho Seco PWR, 0.5 Ci tritium was released in gaseous effluents, and 0.045 Ci tritium in liquid effluents, while 267 Ci of tritium (897 Ci GWe-' y-') accumulated in the primary coolant. 6.2.2

Advanced Reactors

Sources of tritium waste in liquid-metal fast-breeder reactors were indicated in Section 3 to include cold trap solids,waste sodium, system metals, inerted containment atmospheres, and steam generator water

5.2

METHODS OF TRITIUM RETENTION

/

39

in addition to that remaining in the fuel elements transferred to reprocessing. Except for steam generator tritium, and that in fuel elements, this tritium will be unoxidized (HT), and consequently will require methods of management different from those appropriate for light-water reactors. Most of the tritium from LMFBRs will presumably be removed in cold traps or retained in sodium. Disposal methods have not yet been established. 6.2.3

Control Elements

Little information is available in the literature concerning the control of tritium waste from reactor control elements. In many cases these will consist of boron carbide in stainless steel. Some tritium will be retained in the B4C lattice. It would be possible to store the control rods as a form of solid waste. 6.2.4

Fuel Reprocessing Plants

Options for the management of tritium waste in reprocessing plants have been discussed in ORNL (1970), by Yarbro et al. (1974), North and Booth (1973), Murbach et al. (1974), Finney et al. (1975), and Kullen et al. (1975), among others. For light-water reactor fuel, a fraction of the tritium is found in zirconium alloy cladding hulls, which could be separated.and stored as solid waste. Other options include (Yarbro et al., 1974; Finney et al., 1975): a. Immediate dissolution, with release or disposal of tritium-bearing aqueous waste to the atmosphere as at the Barnwell plant, or to the local watershed by seepage, etc., as at the West Valley plant. b. Similar prompt dissolution, with total water containment. Total water containment is indicated to be effective, but high in cost (Yarbro et al., 1974). c. The voloxidation process (Goode et al., 1973), developed for LMFBR elements, should be readily adaptable to LWR elements, with due consideration of risks of zirconium alloy fires. In this process, the sheared fuel is heated in a rotary calciner under an oxygen atmosphere to volatilize tritium and large fractions of the iodine and noble gases. It is estimated that volatilization of approximately 99 percent of the tritium is possible. The volatilized HTO can then be condensed and only unevaporated traces (approximately 1percent) need subsequently appear in the process water.

40

/

5. TRITIUM WASTE MANAGEMENT

d. Combination of voloxidation and total water containment should result in a retention factor for tritium of about 99 percent (Finney et al., 1975). Adoption of the voloxidation process to reduce atmospheric tritium emissions projected for the Barnwell plant by a factor of 100 was estimated by Murbach et al. (1974) to cost about $35,000,000. Adoption of the voloxidation process to reduce tritium release (largely in liquid effluents) at the West Valley plant by a factor of 100 was projected by North and Booth (1973) to cost about $10,000,000. 5.2.5

Removal from Gas

Tritium can be removed from various atmospheres by several methods. Generally, HT may be oxidized to water using CuO/MnO2 at 600°C (Pelto et al., 1975), or with air over platinum alumina catalyst (Bixel and Kershner, 1974). These methods also oxidize volatile tritiated organic compounds and yield tritiated water. Tritiated water may be removed from the atmosphere by condensation (Pelto et al., 1975),condensation on molecular sieves (Bixel and Kershner, 1974), or other absorbents. Aune et al. (1973) showed that moderate amounts of tritiated water could be removed by passing the air through a bed of moistened silica gel. 5.2.6

Isotope Separation

The possibility of concentrating the tritium in aqueous wastes to be stored in larger depleted streams that could be released has been surveyed by a number of authors. However, the application of this method is limited by the projected costs for achieving the removal of tritium from large volumes of water. Large scale operations generally emphasize the energy cost of separation, efficiency of operation, and control of losses, while small scale operations are likely to be concerned with effectiveness of separation and cost of equipment. Methods for the concentration of tritium are much the same as those considered for deuterium (Maloney et al., 1955; Bebbington and Thayer, 1959; Barn and Drews, 1960) except that deuterium is much more concentrated in natural water than tritium is likely to be in reactor or r e p r o c e m plant wastes. Methods suitable for stripping tritium from large volumes include fractional distillation, HT-HTO exchange and HZS-H~Oexchange (Bebbington and Thayer, 1959; Lin, 1972; Leonard and Kueck, 1972;

5.3

ULTIMATE DISPOSAL

/

41

Brown, 1976), and possibly some form of laser excitation (Goodman and Thiele, 1972; Jensen and Lyman, 1974; Jensen, 1975; Whittaker et al., 1975). If recycling of industrial plant waters is practiced (Ribnikar and Pupezin, 1974; Schnez et al., 1974; Brown, 1976), a semi-concentrate should become available which might, in addition to the methods listed above, be concentrated by reversible electrolysis (McLaren, 1952; Drazic et al., 1975), cryogenic distillation of molecular hydrogen isotopes (Leger et al., 1970), or extractive distillation. The depleted product might be sufficiently diluted to permit direct release or addition to other plant streams to achieve necessary dilution for release. The concentrate could either be solidified (see fixation, Section 5.3.4) for final storage, or subjected to further concentration. If special plant methods are used, which keep tritium from dngling with plant waters to an appreciable extent, then a relatively concentrated tritium-bearing stream may be available. In addition to the methods of enrichment mentioned above, electrolysis, palladium chromatography, or thermal diffusion may be used to produce a highly tritiated product. As tritium concentration becomes high, consideration must be given to its separation from deuterium as well as the normally more abundant protium ('H).

5.3 Ultimate Disposal 5.3.1 Disposal a s Liquid The storage or disposal of relatively concentrated tritium in aqueous (or other liquid) form includes storage in tanks or cylinders, deep well disposal, deep ocean dumping of cylinders, and open ocean release of tritiated water. Long-term retention of tritiated water in steel tanks is technically feasible according to Arnold et al. (1973) who estimate the cost of insulated heated carbon steel tankage at $0.013 per liter. The gross cost, including surveillance, replacement, etc., was estimated as about $0.026 per liter. The possible disposal of tritium-bearing aqueous waste in deep wells has been examined by Trevorrow et al. (1977) who concluded that suitable sites were abundant in the U.S. The technology is in hand and costs would be low. Legal and regulatory constraints not yet in place will be the most important determinants of feasibility.

42

/

5. TRITIUM WASTE MANAGEMENT

The possibility of disposal in deep ocean was considered by Olivier (1976) who noted that the 1972 London Convention placed a limit for tritium of lo6 Ci per ton of waste, and noted that the limiting capacity of the North Atlantic area considered for dumping would be about 1015 Ci y-I for tritium. It is evident that a major constraint on dumping into the ocean will be economic and philosophical. Slow release of tritiated water ((2Ci 1-I) into a ship's wake should also prove acceptable (Schnez et al., 1974).

5.3.2

Disposal as Solids

The disposal of tritium-containing waste in a solid form can be as packages in which liquid forms have been taken up by various absorbents, or forms in which tritium fixation has been brought about (Rhinehammer and Lamberger, 1973). Final disposal of tritium-containing waste by burial in an approved repository is an option, provided tritium can be suitably contained. This will require adequate packaging of tritium wastes, or the fixation of tritium in solids such that release to the biosphere does not occur to an appreciable extent. For economic reasons, incorporation into solids may not be appropriate for high volumes of tritiated water. The methods of preparation of tritium waste for burial used at various imtallations were discussed by Rhinehammer and Lamberger (1973).

5.3.3

Packaging

Methods of packaging and containing tritiated wastes at various installations were reviewed by Rhinehammer et al. (1973). In one example (Rhinehammer and Mershad, 1974) tritiated solids are introduced into a thick-walled 103 1polyethylene drum which is sealed and placed in a sealed asphalt-lined, 114 1, stainless-steel drum, and this in turn is contained in a sealed asphalt-lined, 209 1, stainless-steel drum. These operations may be carried out in contained systems, and are thus suitable for high-level waste. The drum is then transported to a federal repository for burial. Mershad (1975) used laboratory determinations of the water permeability of polyethylene to estimate that tritiated water fured in cement-plaster and contained in the 103 1 polyethylene drum described above would be released at a rate of per month. The decay of tritium produces 3He, and may also produce combustible radiolytic gases. Burger and Ryan (1974) and Colombo et al.

6.3

ULTIMATE DISPOSAL

43

/

(1975a) point out that, except at very high tritium concentrations, this phenomenon will be quite minor and can be ignored.

Many of the options involved in the fixation of tritium in solid form suitable for permanent isolation have been examined by Burger and Ryan (1974) and summarized by Bixel et al. (1975), USERDA (1976), and Brown (1976). The incorporation of tritiated water into cement provides one way of preparing tritium for permanent disposal with readily available and inexpensive materials and equipment, Solids, such as silica gel, molecular sieves, clays, etc., carrying additional tritiated water, can be incorporated. Part of the water in cement may be free, depending on the mix and cure times, and therefore somewhat mobile. Leaching results in release of tritium from the cement. Asphalt coating and polymer impregnation of cement bodies have shown some promise of reducing the rate at which tritium is leached from cement. The scaling up of leach test data to permit estimates of release under practical disposal conditions is generally based on diffusion and mass transport models (Godbee et al., 1969; Godbee and Joy, 1974). The fractional release is usually proportional to the surface/volume of the solid, and frequently varies with the square root of time (diffusion controlling), or linearly with time (surface effects controlling). Leach test data reported for tritiated cementa by Emelity et al. (1973) and by Colombo et al. (197413, 1975a. 197513) are given in Table 5-1. These data indicate that the use of coatings or impregnation resulte in considerable improvement in reducing the leach rate of tritium. The larger cement volumes to be used in disposal operations should greatly increase the time required to release a given fraction. The effect of various factors of mix, cure, and treatment requires additional study. TABLE 5-1-Leach test data for tritiated cementa Po& 1' Water/cmmnt bLment

.4

-

Surfam/vohrm* cm-' 14 d.y LU) dayw 31

Port. 1'

Port. 1'

Port. Illh

Lumniteh

4 Asphalt

.4

.18

.I8

.18

-

Styrene

Styrene Rooilns wh.lt polymer 1.1 1.1 1.1 .7 h t h d mkaw in Lcorar kach t~& ,012 .26-.32 .08 .a3 ,028 .*.a .20 .09

-

-

-

-

Lumnite"

polymer .7

.7

.a

,007

.62

,013

-

-

' Emelity el d (1973). Portland Cement 1. "Colombo ei d (1974b, 1976% 1975b). P o N u d Cement 111 and h i t e cement impregnated with styrene monomer,polymerid by heating at 50-60°C.

44

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5. TRITIUM WASTE MANAGEMENT

Recent lysometer studies by Colombo et al. (1976) indicate that release of tritium to earth from buried polymer impregnated tritiated concrete solids is considerably slower than the direct leaching by sustained water immersion. Rates are slow enough that this form should meet retention requirements for final isolation. Costs, depending on type and proportion of mix and any further treatment, will amount up to one dollar per liter of water. Consequently, the use of cement may not be attractive for low concentrations of tritiated water. The carbon-hydrogen bond is less subject to exchange than other bonds involving hydrogen in organic compounds (Brown, 1976). Tritiated water can be reacted with calcium carbide to produce acetylene, which can be converted to a solid polymeric hydrocarbon (Colombo et aL, 1974a, 1974b). However, the tritiated calcium hydroxide coproduct must be reprocessed. Other organic forms that have been examined involve formation of acetaldehyde by reaction of acetylene with tritiated water, and subsequent polymerization with phenol or resorcinol to a bakelite-type solid (Burger and Ryan, 1974). The partial hydrogenation of various polyrnerizable aromatics to yield cyclohexane structures has been suggested, and the formation of tritiated ureaformaldehyde polymers appears to be of interest.

6. Biology of Tritium Exposures 6.1

Introduction

Tritium is readily assimilated by the body following ingestion of HTO or by passage through skin or inhalation either as liquid HTO or in a gaseous form. Distribution to extracellular and intracellular water is quite rapid. The kinetics of tritium oxide through the body follows that of body water, except that a small portion of the intake becomes organically bound in tissue and is retained for somewhat longer times. There have been many studies of the metabolism of tritium in animals and humans with somewhat less attention given to radiation effects. The animal studies of Thompson (1952,1953) contributed early information on tritium metabolism. Several useful reviews of the biological aspects of tritium in man include Pinson and Langham (1957), Siri and Evers (1962), Butler and LeRoy (1965), Woodard (1970). Osborne (1972), and Silini et al. (1973).

6.2

Tritium Uptake and Retention

Several routes are available by which tritium as a gas or as tritiated water can reach the body tissues of man. It can be absorbed in either form by way of the skin or the lungs, or it can be ingested in the water of food or as drinking water. A special case is the organically bound tritium consumed in food. When humans inhale gaseous tritium, a very small fraction of the tritium is converted to HTO (about 0.004percent) and retained as free water (Pinson, 1951). A small fraction of the tritium atoms from tritiated water is incorporated into organically bound moieties but most is turned over from the free water pool rather rapidly. The uptake by way of inhalation of tritiated water vapor is quite efficient, i.e., 99 percent of that inhaled is taken into the body water within seconds (Hutchins and Vaughn, 1965). Skin uptake of tritiated water is correlated with the skin temperature (in the range of 30'45

46

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6. BIOLOGY OF TRITIUM EXPOSURES

34°C) and in general is about equal to the intake by inhalation (Osborne, 1966).Ingested tritiated water is almost completely absorbed from the gastrointestinal tract and quickly appears in the venous blood (Pinson and Langham, 1957). Within minutes it can be found in varying concentrations in the various organs, fluids, and tissues of the body (Pinson, 1951; Thompson, 1952; Mewissen et al., 1975). When there is a protracted exposure to relatively stable levels of tritiated water, as when thermonuclear bombs were being detonated in the atmosphere, the body water and tissues of humans adjusted to the prevailing tritium ratios with a variable lag-time. Following pulsed exposures to HTO, tritium blood levels increase rapidly, then decrease at a somewhat slower rate. Organic compounds of tritium, particularly tritiated thymidine, are used for labeling in biological studies. The public would not normally be exposed to these compounds. Kirchmann et al. (1971) found that tritium bound to the organic fractions of cows' milk, largely in the milk fat, was 10 times higher in cows fed grass with organically bound tritium than in those given equal amounts in their drinking water. It is uncertain to what extent these labeled organic compounds may be transferred directly to organically bound compounds in man. In general, however, the tritium catabolized to water in the ingestion process is a greater contributor to the dose. Only one-eighth of ingested thymidine survives catabolism and crosses the gut as thymidine (Vennart, 1968). The transfer of tritium to organic compounds following intake of tritiated water occurs largely by exchange of tritium from body water with the labile hydrogen of organic fractions. Carbon bound hydrogen is very stable and without some enzymatic assistance there is normally little exchange with hydrogen of free body water (Smith and Taylor, 1969). In a study with mice given daily injections of tritiated water for 14 days, 1 percent of the injected activity was found in organically bound form whereas a total of 12 percent was retrieved in all of the body, mostly as free water. Except for blood, where tritium was largely in the form of free water, all tissues incorporated only a small amount of tritium in the organic form (Thompson, 1952; 1953). In rats and mice exposed to tritiated water for extended periods, the highest relative concentrations were in the brain lipids (Thompson and Ballou, 1954); followed by the skin and muscle (Pinson and Langham, 1957). It has been observed with pulsed exposures that the brain of the mouse is somewhat slower to accept free water tritium into the organic fraction than are other tissues, except for body lipids and the lung, but that the half-life within those tissues is markedly longer than the average for the entire mouse (Mewissen et al., 1975). This supports

6.3

TRITIUMELIMINATION

/

47

the general conclusion that slow uptake is logically associated with long retention. It has been observed by some investigators that liver and fat attain the lowest concentrations after extended exposures (Pinson and Langham, 1957). Following a brief exposure to HTO, the ratio of organically bound tritium to free water tritium, as observed within a 4 week period, was found to be dependent on the age of mice, with adults having 2-3 times as much in the organic fraction as did the juvenile and newborn (Mewissen et al., 1977). The organically-bound tritium provides the tritium that remains in the animal body for the longest time and was found to have a half-life of 3.5 to 8 days in the mouse (Mewissen et al., 1977). It is known that there are additional pools of organically-bound tritium with half-lives that extend beyond the life of the animal.

6.3 Tritium Elimination The rate at which tritium is eliminated from the body, either from the free water or organically bound pools, is an important influence on the radiation dose following exposure to tritium in any chemical form. The biological half-times are known to vary with animal species. As noted in Mewissen et al. (1977) the half-times also vary with the pool under consideration, the age of the animal, and the tissue or organ under consideration. The question that is most pertinent is the amount of tritium that becomes incorporated into DNA. In one study with mice and rats administered tritiated water for 41-147 days, the nonexchangeable organically bound tissue hydrogen was 25-40 percent of the tissue free water hydrogen. The mouse liver DNA non-exchangeable organically bound tritium was 12 percent of that of the tissue water. All DNA bases were labeled with tritium in various amounts. One in four of the hydrogens, and presumably tritium, in DNA is exchangeable (Hatch and Mazrimas, 1972). In one study (Mewissen and Rust, 1975) incorporation of tritium into RNA was five-fold greater than in DNA. Some representative biological half-life values are of interest. The vertebrates with the shortest half-life for free water tritium probably are fresh water fish with a two component half-time of 0.2 hours (96 percent) and 0.9 hours (4 percent) and for organically bound tritium 8.7 days (except for a small residue). The concentration factor, i.e., the relative specific activity of body water over environmental water, as an estimate of discrimination against tritium incorporation, is less than 1 (Elwood, 1971a). In marine animals, vertebrate and non-vertebrate, the loss of organically bound tritium from chronically exposed animals

48

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6. BIOJBGY OF TRITIUM EXPOSLIRES

ranged from 110 to 290 days. The maximum specific activity, as an estimate of discrimination, was less than 50 percent of that of the sea water in which they were exposed (Hanison et al., 1971). Retention time of tritium in mice given a pdse of tritiated water varies according to age and tissue (Mewissen et al., 1977); the free body water half-life being about 2% days and the organically bound half-life ranging from about 3% to 8% days (Mewissen et al., 1975). Other investigators have found different half-life values (for example, Thompson 1952, 1953). The data for human beings are more directly important. In 310 individuals who had been chronically exposed hnd whose urine contained more than 20 pCi of tritium per liter, the biological half-life was determined. Among these subjects, the half-life of the rapidly eliiinated pool ranged from 4 to 18 days with an average value of 9.5 4.1 days (p = 0.1). There was no correlation between the amount of tritium assimilated and the biological half-life. The half-life correlated inversely with age (Butler and LeRoy, 1964). In another report of protracted exposures in which two individuals were in daily contact with tritiated luminous paint, the effective half-lives of the two pools were determined to be 26 and 550 days in one case and 21 and 280 days in the other. For a third exposed individual only the long component (330 days) was reported. All were females. In one subject there was seasonal variation in both body burden and urinary output related to increased water intake in the summer. However, the results for the second subject did not fluctuate (Moghissi et al., 1971). In another study, in which the individuals were chronically exposed to luminous paint containing tritium, excretion studies of two females indicated 12.1 day and 13.4 day half-lives (Jones and Lambert, 1964). One of the most important cases was that of a man repeatedly exposed for long periods to high concentrations of tritium gas, with fatal consequences (Minder, 1969). Studies of the tritium content of the urine during the 16 months after cessation of exposure gave evidence of at least two components to the excretion regression curve. One component, from an organically bound pool, had a half-life of about 30 days (90 percent) and another a half-life of about 230 days (5 percent). The half-life of the free body water was not reported. The acute exposure is of interest since it gives the best estimate of the short-term half-life values in body water. It is not complicated by the heavily loaded organically bound pools developed in protracted exposed individuals which may release tritium to the free water pool from the less tightly bound organic pools. In a study of a worker who was exposed, probably by acute inhalation of tritium gas, the urinary excretion was followed for 415 days. Three exponential components

+

6.3

TRITIUM ELIMINATION

/

49

were observed, having half-lives of 6:1, 23, and 342 days (Reinig and Sanders, 1967). In another acute inhalation exposure, half-lives of 9 days (98 percent) and 34 days (about 2 percent) were estimated (Snyder et al.,1968). Another report is concerned with three workers who were acutely exposed, one externally to tritiated water and two to tritium gas by inhalation and skin exposure. The worker with the tritiated water exposure had a half-life for his urinary tritium of 13.2 days. The workers exposed to gaseous tritium excreted the nuclide from two compartments, with half-lives of 11.9 and 6.99 days (Biro and Cziblog, 1966). Six individuals, all males, exposed acutely to tritium gas, excreted the nuclide with a half-life of 8.5 days with a range of 6.4 +- 0.4 days to 12.1 f 0.7 days (Wylie et al., 1963). Finally, in a study of 17 subjects who were exposed to tritiated water vapors, either by skin alone or by skin and inhalation, the effective half-life ranged from 6.4 to 14.4 days irrespective of the mode of exposure (Osborne, 1966). It seems reasonable to conclude that one pool of tritium in exposed individuals is in the form of free body water. It has a half-life between 6 and 18 days. The retention curves suggest the existence of two additional pools that range from 21 to 30 days and 250 to 550 days. One of these reflects the existence of a labile organic pool and the other a more tightly bound organic pool. The ICRP method of computing the m h u m permissible concentrations in air and water utilizes only the free water pool, which ICRP assumes to have a halflife of 10 days (ICRP, 1969).Earlier, the National Council on Radiation Protection (1959) and the ICRP (1959) chose 12 days. These are both quite reasonable selections and represent a useful estimate of the rate of elimination. One investigator who compared the one exponent model and a three exponent model concluded that, for a person consuming 3 pCi per milliliter of tritiated water for 111 days, the calculated exposure to the testes a t 254 days from the first model would be 51 rads compared to 53 rads from the second. This illustrates the relatively small contribution of organically bound tritium (Patzer, 1968). Hatch and Mazrimas (1972) advocated an additional safety factor based on the fact that the body water tritium is about Y3 to M of that of the imbibed water tritium in the steady state. There is no evidence for a significant concentration process for tritium in either plants or animals. There are, of cows&,some differences in the residual specific activity of the various organs and tissues, particularly the brain and body fat, but it is always weU below (10-40 percent) the specific activity of the tritiated water from which it was derived (Thompson, 1971). In the case mentioned earlier (Kirchmann et ad., 1971), in which organically bound tritium in grass produced

50

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6. BIOLOGY O F TRITIUM EXPOSURES

higher than expected levels in the milk fats of cows, the specific activity of the milk fat was below that observed in the grass. However, there may be an apparent discrimination factor when measurements are made under non-equilibrium conditions.

6.4

DNA Incorporation

One major concern is that incorporation of tritium into DNA may result in undesirable genetic or somatic effects (NCRP, 1978). Assumh g that plants and food animals synthesize some DNA that contains tritium, an assessment can be made of the tritium content of the pyrimidine and purine bases that will reach newly forming DNA. This would be most important to the fetus and newborn. The equilibrium level of non-exchangeable hydrogen relative to body water hydrogen in meat is about 27 percent (Hatch and Mamimas, 1972). Assuming that all bases act as thymidine in the mouse, then about 2 percent of the hydrogen reaches the bloodstream intact and 98 percent is metabolized to water. Of this 2 percent, 10 percent, i.e., 0.2 percent, will be incorporated into DNA directly and 50 percent of the remainder will be incorporated into other organic fractions or metabolized into the tritiated water labile component and the majority into P-hydroxyamino-isobutyric acid (non-labile component or stabile) and both excreted by way of the urine (Rubini et al., 1961; 1960). The radioactive decay of a tritium atom located in a DNA molecule can result in a breakdown or rearrangement of the DNA molecule. The biological effect of such an event is small in relation to the associated beta ray ionization (Bond and Feinendegen, 1966; Burki and Okada, 1970). One study reported that cytosine labeled in the 5 position was about 25 percent more radiotoxic for bacteria and Drosophila than pyrimidine rings labeled in other locations (Funk and Person, 1969; Kieft, 1968). Such an effect could not be found in other precursors of DNA or RNA. It is not known whether this effect can be detected in mammals. Its practical consequences, however, are minimal in the extreme, since such a unique localization would not occur. The possible effects of tritiated water exposures to embryos and fetuses have been examined in detail (Cahill and Yuille, 1969; Bond, 1971). The radiotoxic effects are consistent with those expected from an equivalent absorbed dose from external irradiation. There is evidence that pregnant female rats exposed to tritiated thymidine by continuous infusion (an artificial mode) throughout pregnancy deliv-

6.4

DNAMCORPORATION

/

51

ered offspring with labeled DNA in every cell (Fleidner et al., 1968; 1969).There was no increase in chromosome anomalies in the newborn. With large doses, i.e., 1.6 pCi, histopathologic changes were observed in the ovaries of the newborn (Bond, 1971). Pertinent to this was the observation that newborn mice exposed to tritiated thymidine kept 0.025 to 6 percent of the administered dose of tritiated thymidine in their DNA for 1000 days, effectively their entire life (Mewissen et al., 1972). Newborn mice exposed to tritiated thymidine developed more tumors than did control mice, mice exposed to tritiated water, or mice exposed in early maturity (Baserga et al., 1966, Mewissen and Rust, 1973; Johnson and Cronkite, 1966). These observations suggest that the most hazardous time for mammals exposed to tritium as thymidine, and possibly other DNA precursors as well, would be in utero or as neonatah. No effects following exposure of adult mice were demonstrable in these experiments.

6.6 The Relative Biological Mectiveness and Quality Factor of Tritium

In general, the radiation effect is governed by the conditions under which the radiation is imposed, the magnitude and biological nature of the specific effect studied, as well as the physical nature of the types of ionizing radiations under consideration. The relative biological effectiveness (RBE) of two types of radiation is defined as the inverse ratio of the different doses that produce an equal biological effect. The standard reference radiation is 250 kV x rays or sOCogamma rays. The basis for the dose comparison is the energy absorbed per unit mass of tissue exposed (absorbed dose). Numerous factors other than absorbed dose influence the RBE. The major factors include: linear energy transfer (LET), dose rate, fractionation, distribution, oxygenation of the exposed tissue. The biological effect used as an endpoint may a h influence the RBE. For low LET ionizing radiations, i.e., x rays and rays, the RBE value is approximately one. For high LET radiations, i-e., particles, protons, and neutrons, RBE values may be quite large. At very low doses or low dose rates, the effectiveness per rad of x rays is greater than gamma rays by a factor of two or more based on microdosimetric and theoretical considerations which support radiobiological observations (Bond et al., 1977). Theoretical estimates of the RBE for tritium /3 rays (average LET over the entire range of the particle estimated as 5.5 keV p-') a t low doses may well differ by a factor of two or more (Ellett and Braby,

52

/

6.

BIOLOGY OF TRITIUM EXPOSURES

1972) over the range of LET (3.5 keV pm-') designated as "low LET" radiation (NCRP, 1954). This variation depends not only on the dose rate-dose magnitude used, but also on the precise reference radiation used for comparison (Bond et al., 1978). Experimental quantitative assessment of the RBE of tritium /3 rays is confounded by the following difficulties: a) the metabolic and physiologic processes controlling the distribution and, therefore, the dose due to tritium, are poorly known. (This is especially important in extended exposure situations); b) tritium incorporation into organic molecules and structures as well as the differential distribution of tritiated water result in inhomogeneous dose distributions; c) dose estimates are based on secondary measurements; d) disruption of tissue structures by the initial dose fraction of a total dose delivered over an extended time period will result in a nonhomogeneous dose distribution; and e) the reproducibility of low dose experiments relative to high dose experiments is low (Berry et al., 1973). Some reviews of experimental determinations of the RBE of tritium betas a t high doses and dose rates have concluded that the RBE does not differ (within experimental error) significantly from 1.0 (Bond and Feinendegen, 1966; Vennart, 1969). However, values in the range of 2.0 or more have been determined (Dobson, 1976; Ellett and Braby, 1972). The quality factor, Q, of tritium beta rays was assigned a value of 1.7 by ICRP in 1966(ICRP, 1966). Following several reviews in the 1960s, indicating that the RBE could not be shown to be different from unity, a value of 1.0 was recommended for Q for use in radiation protection (ICRP, 1969). This value currently remains in effect (NCRP, 1971). [For a more extensive review of the RBE for tritium, see NCRP, 1979.1 6.6

Tritium in Ecological Systems

The release of tritium can result in human exposure on either a local or global scale. Local exposure will depend on how closely the local population is coupled to the environment in the immediate vicinity of the releases. Such exposure could be especially important in agricultural areas. 6.6.1

Absorption by Plants

Absorption by Lower (Non-Flowering)Plunts. Absorption of tritiated water by lower plants such as mosses, fungi, and lichens occurs a t a rapid rate because these plants freely exchange tissue-water with the

6.6

TRITIUM IN ECOLOGICAL SYSTEMS

/

53

atmosphere. Some water uptake from the substratum may occur through root-like organs called rhizoids. Although it is well known that poikilohydric plants absorb surface-deposited elements, such as radioactive and chemical fallout, no specific data for tritiated water uptake are known. Absorption by Vascular Plants. The exchange and absorption of HTO vapor by plant leaves apparently occur rapidly in spite of the fact that during daylight the plant is releasing a considerable amount of water from the leaves in transpiration. The primary absorption route for HTO vapor is the same as the release of transpirational water: the water enters through the stomata and transfers to the mesophyll cells within the leaf where it takes part in photosynthetic reactions. The hydration state of the plant affects the stomatal aperture, which controls HTO uptake. Soil water potentials will likewise condition the uptake relationship in their effects upon plant water potential and stomatal mechanism. Plant uptake factors (leaf tissuewater concentrations/air concentrations during exposure) were given by Koranda and Martin (1973) for eight species that were growing in the field at the time of exposure (Table 6-1). There is a general correlation between the water physiology of the plant and its HTO absorption. The number and distribution of stomata as well as other epidermal characteristics affect uptake. Species that transpire at high rates have a higher uptake factor than xeric plants, such as the black pine. The species listed in Table 6-1 include several representatives of agricultural vegetation typical of m a l areas, and

TABLE 6-1-Plant uptake factors for eight plant species' Time of

Species

e

~

bin)

m

2e;t*

Black pine (Pinus thbergiana) Oats (Avena sativa) Burclover (Medicago hispida) Corn (Zea mays) Cranebill (Erodium moschatwn) Barley (Hordeum vulgare) Fiddleneck (Amsinckia) Sunflower (Helianthus annua) ' From Koranda and Martin (1973) pCi ml-' tritium htissue-water of plant at to Uptake Coefficient pCi ml-' tritium in vapor of exposure chamber

-

54

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6. BIOLOGY OF TRITIUM EXPOSURES

may be used to calculate potential uptake by forage in the absence of more specific information. When the atmosphere is the primary source of tritium exposure of vascular plants, it is apparent that the tritium ratio in the plant can never exceed that of the atmospheric moisture. This upper limit is based on the assumption that all of the tissue-water of the plant had equilibrated with the moisture in the air. This is an unreasonable assumption because the plant is probably transporting uncontarninated water to the leaves via the transpiration stream. Uptake coefficients determined from data obtained immediately after exposure ceased would also suggest that the maximum possible concentration of HTO achievable in leaves is approximately 50 percent of the air concentration in succulent plants and somewhat less in other plants. When the stem-water of a tree is labeled with HTO,the leaves never equilibrate with the water of the transpirational stream, but usually reach only between .60 and .70 of that concentration. This indicates that between 30 and 40 percent of leaf water under typical conditions may be atmospheric in origin. The average uptake factor given in Table 6-1 is 0.31. Anspaugh et al., (1973) assumed an uptake factor of 0.5 which would be sufficiently conservative to allow for variation due to species, stage of development, and season. These factors have measurable effects on tritium uptake. The tritium absorbed by the vascular plant is eliminated with a short initial half-life, usually less than one day, but somewhat longer in coniferous and deciduous trees (Anspaugh et al., 1973). Generally, the decay is biphasic, and if measurements are continued, a third longlived component is seen which is most likely related to soil-water contamination. Tritium in air transfers to soil water, even when the land is completely vegetated. Koranda and Martin (1973) described an experiment in which a field of California native vegetation was exposed to tritiated water vapor for one hour. Tritium was detectable in the foliage (primarily burclover-Medicago hispida) for 50 days after exposure, exhibiting a three-component elimination pattern. Forty days postexposure, the peak soil-water concentrations of tritium were at a depth of 7.5 cm to 15 cm, and were approximately of the initial value in the vegetation. Soil water and plant leaf water were in approximate equilibrium at this time, suggesting that plant tritium may be derived primarily from the soil rather than any internal pool within the plant at long times post-exposure. The decay of tritium in an ecosystem exhibits different characteristics from the decay of any of its component trophic levels. This was demonstrated in studies of the Puerto Rican rainforest by Jordan et al. (1970) and Martin et al. (1970). Data

6.6

TRITIUM LN ECOLOGICAL SYSTEMS

/

55

obtained at Sedan Crater in the Nevada desert indicated that the halflife of tritium in the body-water of resident populations of small mammals was controlled by the half-life of tritium in the general environment (Koranda and Martin, 1969). 6.6.2

Tritiated Water in Aquatic Ecosystems

In addition to airborne release, tritiated water may also be released into surface waters and coastal marine environments. When tritium is introduced into an aquatic environment, the tissue-water of all invertebrate and most vertebrate organisms resident in that body of water will approach equilibrium with the tritium concentration in the water after a period of several weeks. Planktonic algae and macro-algae, such as the kelps, will equilibrate with tritium within a few days and, being autotrophic, will form tritiated organic compounds as soon as exposure begins. These organic compounds, especially those in planktonic unicellular algae, enter the food chain rapidly. The significance of organically synthesized tritium to other organisms is seen in a study by Patzer et al. (1974). Fishes (mosquito fish and top-minnows) raised in tritiated water exhibited tissue-bound tritium concentrations which were from 0.31 to 0.56 of that in the water. The tissue-bound tritium concentrations in fishes fed brine shrimp (Artemicr) also reared in tritiated water were 0.73 of that in the medium (Hanison et al., 1971). 6.6.3

Enrichment Effects in Ecosystems

No apparent enrichment or concentration effect for tritium has been found in aquatic or terrestrial food chains. In fact, dilution in larger hydrogen or organic pools is the general rule, as tritium moves through trophic levels from autotrophic organisms to consumer populations. Isotope mass effects should be apparent in ecosystems, especially where phase changes occur, such as in transpiration from plant leaves and evaporation from soil surfaces. However, this mass effect is apparently lost in the host of other physical and biological interactions that occur in an open, natural system. The possibility of enrichment of tritium in animal and plant tissues has been reviewed by Bruner (1973). By enrichment is meant that a higher concentration (T/H atoms) of tritium is present in the solid organic phase of the organism than is present in the tissue or bodywater of the same organism. As Bruner noted, few plants or animals attain concentrations in their body or tissue-water which exactly

56

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6. BIOLOGY OF TRITIUM EXPOSURES

match concentrations in the medium, whether on an acute or chronic exposure basis. The tissue-water of plants grown from seed in tritiated water under open atmospheric conditions did not equilibrate a t maturity (Chorney and Scully, 1965). The exchange of unlabeled water from the atmosphere into the leaves was the obvious source of diluting hydrogen in this case. Mammals, when exposed chronically to tritium in their drinking water, do not equilibrate with this source because the liquid water contribution to the body water pool may be as low as 33 percent. Humans are estimated to derive from W to Yz of their body water from liquid water intake. Inhalation and free air oxidation water of foods are other sources which are not labeled in a drinking water uptake experiment. Certain species of kangaroo rat (Dipodomys) are able to maintain a positive water balance on the water of oxidation when respirational losses are low. When mammals are fed tritiated food in addition to tritiated drinking water, the level of equilibration in the body water increases, and the level of saturation of labile hydrogen compartments increases. It is apparent from the multi-phasic rates of elimination of tritium from the body-water or tissue-water of organisms exposed to tritium that very likely two and probably three compartments are involved. The body-or tissue-water is obviously the primary kinetic pool. Labile hydrogen in communication with the body-water pool is a logical candidate for the second and longer-lived compartment. This second compartment has been estimated to be about 30 percent of the hydrogen in organic compounds (Martin and Koranda, 1972).This is seen in the body-water of man and in the tissue-water of plants. Structural hydrogen would comprise a third tritium and hydrogen compartment with a much longer half-time. Martin and Koranda (1972) in Lifetime studies of kangaroo rats exposed to tritium in food, water, and air demonstrated that the tissue concentrations of tritium would exceed body-water concentrations as the general body burden of tritium was reduced after removal of the animals from the contaminated environment. The potential for differential rates of elimination of tritium in labeled organic and environmental compartments exists throughout natural ecosystems and may lead to the erroneous assumption of an enrichment effect. Because a wide span of temporal data on tritium concentrations in the appropriate compartments is often not available, and when the complete exposure history of the organism and the ecosystem has not been documented, a single measurement of tritium concentrations in the organic and aqueous phases of the organism or the ecosystem will provide only one point on a rather complex exposure history. It is for

6.6

TRITIUM IN ECOLOGICAL SYSTEMS

/

57

this reason that it is often not possible to know the state of equilibrium from only a few analyses. Observed apparent enrichments may be due to the fact that equilibrium has not been achieved. The variations in the ratio of body-water tritium to organic tritium, such as those reported by Evans (1969) and others, which are generally within a factor of two of each other, may be explained by variations in the exposure history of the animals. If the ratio is greater than 1.0, the animal is very likely equilibrating with a new, and lower, environmental concentration which affects its body-water concentration much more rapidly than its tissue-bound tritium levels. This would be especially true of highly mobile and territorial animals living in an heterogeneous exposure field. Kangaroo rats, living at Sedan Crater at the Nevada Test Site at the time of capture (Martin and Koranda, 1972), had ratios that were on the average 1.40 k .14. The mean residence time of tritium in the Sedan environment was shown (Martin and Koranda, 1971) to have a mean of 13.2 z t 1.7 months and the body-water of the kangaroo rat population was also demonstrated to be in equilibrium with this general environmental elimination rate (13.2 1.3 months). Bennett (1973) predicted a maximum aqueous to non-aqueous tritium ratio of 1.32 for man as the tritium concentrations resulting from releases during weapons tests were reduced more rapidly in the environment (and in the body-water of man) than in the tissues of man. Ratios of less than one are seen as the organism is equilibrating with a new, higher concentration of tritium. The value of the ratio (1.4) observed at Sedan Crater would seem to indicate a level of environmental tritium that was decreasing with time and not an enrichment factor. The history of the site and the measurements of the tritium inventory in the soil (Martin and Koranda, 1971) and in the populations of small rodents in residence at the site indicate that this assumption is a valid one. The possibility of enrichment or concentration of tritium in ecological or biological systems may be resolved when sufficient kinetic and temporal data are obtained. Hatch and Mazrimas (1972) showed that tritium concentrations in nucleoproteins, lipids, and proteins extracted from the Sedan kangaroo rats had ratios of bound-to-loose tritium as high as 4. These ratios would seem to be greater than could be explained by the effects of different rates of elimination, but we do not know the range of this effect and have very few examples such as the Sedan rodents in which generations of exposure have been delivered in a natural open ecosystem. The ratio of tissue-bound to tissue-water tritium in plants will exceed unity, as demonstrated by Koranda and Martin (1973), at times very

*

58

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6.

BIOLOGY OF TRITIUM EXPOSURES

soon after exposure. This is due to the slower elimination of photosynthetically fixed tritium in the metabolism of the plant, and the rapid turnover of a large fraction of the water content of the plant in the transpiration stream. Leaf tissues under typical radiation loads and wind diffiivities may transpire several times their dry weight in a few hours. Thus,ratios greater than one are probably the rule in vascular plants, and are the result of differential turnover rates rather than any enrichment mechanism. Some enrichment in photosynthetic products has been observed in studies involving unicellular algae (Kanazawa et al., 1972). This appears to occur in the same general class of compounds in which long tenn retention occurs in mammals, namely the lipids.

7. Projected Tritium Production and Releases 7.1

Growth in Energy Demand

The demand for all forms of energy has been growing since the turn of the century. From 1950 to 1970 total world energy consumption increased a t a rate of 5.2 percent per year overall and 3.3 percent per year on a per capita basis (Krymm, 1973). It is anticipated that between 1970 and 2000 the world will consume as much energy as it has in the past 20 centuries. The rates of growth of energy consumption in industrial countries may decrease, particularly as conservation strategies are initiated. In 1974 the total consumption of energy in the U.S. decreased by 2.2 percent from 1973,after two decades of steady increase. Several factors contributed to that particular decrease: the Arab oil embargo, higher energy prices, the economic slowdown, implementation of conservation efforts, and a relatively mild winter. The relative contributions of these factors are uncertain as are the effect on future consumption of energy due to higher prices and conservation measures. It is considered that, in the U.S., it would be possible to reduce the previously projected energy consumption for 1985 by 10 to 20 percent by institution of conservation measures alone (Ford Foundation, 1974;Executive Office of the President, 1977). However, any decreases in the growth of energy consumption are likely to be more than offset by a substantial acceleration of energy consumption in developing countries. Economic progress is associated closely with energy availability, and there is a high degree of correlation between a nation's per capita energy consumption and its per capita gross national product. In 1971 the per capita consumption of electricity in the U.S. was about 8000 kwh (ANL, 1973).Norway had a per capita consumption almost twice that of the U.S., but the world average is about '/s that of the United States. Improvements in the economic conditions and standard of living in developing countries, coupled with increases in world populations, are likely to lead to continuing increases in world energy consumption. Projections of world population and the total energy consumption needed to provide for 59

60

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7 . PROJECTED TRITIUM PRODUCTION AND RELEASES

modest per capita increases in gross national product indicate a possible four-fold increase in energy demand from 1970 to UK)O (Krymm, 1973). A part of the tremendous increase in energy use in the two decades between 1950 and 1970 can be attributed to the availability of large, low-cost reserves of petroleum from the Middle East and North Africa. Also, technological improvements in conversion of thermal energy into electricity, combined with economic advantages of large central power generating stations, led to decreases in the cost of electric power, contributing to marked increases in its use.

7.2

Expansion of Nuclear Po-wer

The period since the 1973 Mid-East war has been characterized by both uncertainty in U.S. energy policy and the role of nuclear power. Moreover, beginning in 1977, the President of the United States

TABLE 7-1-Projected production and release of tritium in the U.S. from nuclear power Year

W e d Nuclppr Ca city ,&B)

Amount of Tritium

Production (MCi)

Atmospheric Release IMCi)

Liquid Relsnse (MCi)

7.2

EXPANSION OF NUCLEAR POWER

61

/

announced that spent fuel reprocessing would be discouraged to reduce the risk of nuclear weapons proliferation. However, other countries are placing increased reliance on nuclear fuels. The projections made in this report are based on the best information at the time of writing (mid-1978). Any changes in the tritium production rates wiU result in proportional changes in the environmental concentrations. The latest projections of the Energy Information Administration of the Department of Energy with respect to installed nuclear capacity in the U.S. and abroad in non-communistcountries are given in Tables 7-1 and 7-2 (DOE, 1978). These projections are extended to the year 2000 and, to account for nuclear power in communist bloc countries, it was assumed that total capacity worldwide would be double that of the U.S. The mix of reactors in each case was assumed to be similar to those made in USAEC (1974a), except that fast breeder reactors are not assumed to penetrate the commercial market prior to the year 2000. These projections are somewhat lower than those used by NCRP Report No. 44 on krypton-86 (NCRP, 1976). TABLE7-2-Projected production and rekase of tritium outside the U.S.from Installed Year

N U ~ W

Ca city

(&el

ArWmt of ~riti~m hduction (MCi)

A-heric

Release (MCi)

muid ~ ~ (MCi)

1 -

62

/

7. PROJECTED TRITIUM PRODUCTION AND RELEASES

There has been a slight slowing of the rate of increase in energy consumption in the U.S., and it is likely that neither total energy consumption nor electricity consumption will continue to increase as rapidly as in the past. However, nuclear power is projected to play a major role in generation of electricity in the future.

7.3

Projected Sources of Tritium Release

Estimates of total tritium production were made based on the latest projections of the Department of Energy. Past experience was used to project gaseous and liquid releases at the power station and during fuel reprocessing for those types of reactors currently being operated. Estimates of release for advanced reactor concepts were based on probable effluent control technologies. In the U.S. it was assumed that fuel would not be processed until 1990 and at that time, two years accumulation of fuel would be processed each year until the backlog was reduced. In other countries it was assumed that spent fuel would be processed as removed from the reactor. Tritium contained in liquid high level wastes from processing of spent reactor fuel was assumed to be released to the atmosphere during waste solidification 5 years after processing of the fuel. Projections also include continued release of tritium from nuclear research centers, such as the Department of Energy facilities in the U.S. 7.3.1 Reactors

Boiling Water Reactors As previously discussed, the major production of tritium in BWRs is by ternary fission, which yields a generation rate of about 20,000 Ci GWe-' y-', and by neutron activation of boron in control rods, of deuterium in the primary coolant, and of lithium and boron impurities in structural materials (Trevorrow et al., 1974; Kouts and Long, 1971). Activation of boron in control rods was estimated to result in a production rate of about 10,000 Ci GWe-' y-', but the other sources are of minor importance. Given a 70 percent capacity factor, total tritium production in BWRs would be about 21,000 Ci y-' for each GWe installed capacity. Tritium that appears in the primary coolant from activation of deuterium and escape from fuel rods and control rods will eventually

7.3

PROJECTED SOURCES OF TFtITXUM RELEASE

/

63

reach effluent waste streams. If 1 percent of the fuel cladding is defective, there would be about 200 Ci of tritium released per GWe-y; this value is slightly higher than rates of releases experienced in BWRs in the U.S. in 1972-74 of liquid-releases of 45 Ci and atmospheric releases of 20 Ci GWe-' y-I (NRC, 1975). The remaining fission product tritium was assumed to remain in the spent fuel until it is reprocessed.

Pressurized Water Reactors The primary source of tritium production in PWRs is also ternary fission. However, boron activation reactions are important since reactivity control in PWRs has usually been accomplished by regulating the concentration of soluble boron in the primary coolant. With this additional source, appreciably more tritium appears in liquid effluent waste streams of PWRs than of BWRs (NRC, 1975). Thus, it is assumed that 20,000 Ci will be produced per GWe-' y-', to which, in the case of the PWR, releases amounted to 800 Ci GWe-' y-' in liquid effluents and 35 Ci GWe-' y-' in gaseous effluents are projected for zirconium alloy clad fuel.

Heavy Water Reactors Heavy water reactors (HWRs) are used extensively in Canada and also in India, Pakistan, and Argentina. They are currently not planned

but are projected to constitute about 6.5 percent of for use in the U.S., the world's nuclear installed capacity in the year 2000. The tritium releases from HWRs are substantially larger than from LWRs. It was assumed that liquid and atmospheric releases would be 50,000 and 5,000 Ci y-' per GWe installed capacity, respectively. It was also assumed that the fuel would not be processed and that the bulk of the tritium produced by activation of heavy water would not be released.

Fast Breeder Reactors (FBRs) Fast breeder reactors are still in the development stage, but it is projected that they will constitute about 17-18 percent of the world total installed nuclear capacity in the year 2000. It was assumed that the production rate of f k i o n product tritium will be 30,000 Ci GWe-' y-'. The other significant source of tritium will be from activation of

64

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7.

PROJECTED TRITIUM PRODUCTION AND RELEASES

B4C control rods which will give an assumed production rate of 66,000 Ci GWe-' y-' (Trevorrow et al., 1974). Other processes were assumed to produce tritium a t a rate of about 2150 Ci GWe-' y-I. The tritium produced in the B4Ccontrol rods was assumed to be retained. Use of tantalum for control and shim elements would eliminate this source of tritium. Ninety percent of the h i o n product tritium was assumed to permeate the steel fuel cladding and be retained in the coolant as sodium tritide, with 10 percent remaining in the fuel until fuel reprocessing. Atmospheric and liquid releases of tritium at the reactor were estimated to be 60 Ci y-I, each, for an installed capacity of 1 GWe (USAEC, 1974b).

Other Reactors Advanced thermal reactors are expected to be introduced, and may constitute about 12 percent of the world's nuclear capacity in the year 2000 (USAEC, 1974a).Such reactors will use natural uranium and selfgenerated plutonium for fuel. It was assumed that the production and release of tritium would be the same as the weighted average of the year 2000 for LMFBRs, PWRs, and BWRs. 7.3.2

Fuel Reprocessing

Reprocessing will give rise to the largest releases of tritium in the nuclear fuel cycle. During reprocessing of LWR spent fuel, it is projected that about 16 percent of the tritium will be stored with hulls (fuel cladding), 7.6 percent will be stored with high level radioactive wastes, 63 percent will be released to the atmosphere, and 13.5 percent will be released in aqueous waste streams (Kullen et ad., 1975). At the Barnwell, S.C. plant, it is anticipated that all tritium will be discharged to the atmosphere by evaporation. As much as 30 to 60 percent of the tritium may remain with zirconium alloy hulls. AU of the fission product tritium remaining in LMFBR fuel, 10 percent of that produced in the reactor, is assumed to be released to the atmosphere during reprocessing. Heavy water reactor fuels are assumed not to be reprocessed while reprocessing of HTGR fuel is assumed to release 1 percent of the fission product tritium to the atmosphere; the remaining tritium is assumed to be collected on zeolite beds and retained. The tritium distribution from processing of fuels from advanced thermal reactors is projected to be the same as the weighted average for LMFBRs, PWRs, BWRs, and HTGRs.

7.3

PROJECTED SOURCES OF TRITIUM RELEASE

/

65

Tritium retained with high level liquid waste is projected to be released to the atmosphere during waste solidification after a five year storage period. 7.3.3

Other Sources of Tritium

Based on the data given in Section 3.6, it can be calculated that about 550 MCi of tritium was produced during the atmospheric testing of weapons in the period 1945-58 and another 2250 MCi in the period 1959-62. The amount remaining in the environment after radioactive decay should have been about 1250 MCi in 1975. This report assumes that open air testing will, in the future, not be a significant source of tritium. Information on tritium releases compiled h m environmenta1 monitoring reports from major USERDA contractor sites indicated that, TABLE7-%Total projected release and accumuldwn of tritium from all sources

(MCd Annual Release

Year

Tritium Amumulated in the Envimnment Atmospheric

Natural

'Ititiul? -uctmn

Nuclaar

Power

0thActivities

Total

66

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7.

PROJECTED TRITIUM PRODUCTION AND RELEASES

in 1973, atmospheric releases amounted to 580,000 Ci and liquid releases 87,000 Ci; respective releases during 1974 were approximately 930,000 and 70,000 Ci, including an accidental release of about 480,000 Ci of H T to the atmosphere at the Savannah River Plant. For the purposes of projections in this report, it was assumed that world-wide atmospheric releases from nuclear research and weapons installations would be 1.5 MCi and liquid releases 0.15 MCi y-'. Natural tritium production was assumed to be 4 MCi y-'.

7.4

Projections

On the basis of the above assumptions, projections were made of the ranges of yearly tritium production and release. These projections are summarized in Tables 7-1, 7-2, and 7-3.

8. Long Term Dosimetric Implications The dose to humans from environmental tritium depends on the physical dispersion and ecological behavior of the tritium following release to the environment as well as the metabolism of tritium in the body. Tritium released to the environment enters the hydrological cycle. Transfer to man is by inhalation, passage through skin, and by ingestion in food and drinking water. The metabolic considerations include water balance in the body and the amounts of hydrogen (tritium) in free water and in organic bound form in tissue. The previous sections have provided the required basic information. We must now make specific choices of parameters and models to obtain general indications of the dose consequences of releasing tritium into the environment.

8.1

Dosimetry

The average dose rate from a tissue in which tritium is uniformly distributed is a function of the concentration of tritium and the mean disintegration energy. Thus, for 1 pCi kg-', the absorbed dose rate, assuming total absorption of the disintegration energy within the substance, is

D = (3.7 x 10% ss-'pCi-') (0.001 $3 g-') (0.0057 MeV dis-'1 (1.6 X 104 erg MeV-') (0.01 rad erg-lg-') (3600s h-') = 12.1 p a d h-' = 106 mrad y-'.

Another useful expression of this relationship is 290 mad-' for a 1 mCi kg-' exposure. For chronic intake of tritiated water (from all sources including food and air) a t a concentration of 1pCi 1-', the equilibrium absorbed dose rate to body water is 106 mrad y-'. The dose rate to tissue containing 75 percent water is 106 x .75 = 80 mrad y-', if the dose due to tritium combined in tiasue solids is neglected. When nonaqueous tritium is 67

68

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8. LONG

TERM DOSIMETRIC IMPLICATIONS

included, the dose rate to actively metabolizing tissue is 1.2 times the dose rate due to HTO in tissue, or about 95 mrad y-' (Bennett, 1973). The dose model upon which this estimate is derived assumes a water balance of 3.0 1 d-' and retention half-time components of 9.6,30, and 450 days for tritium in the body. The three component model of hydrogen in the body is illustrated in Figure 8.1, in which tritium is assumed to follow hydrogen without discrimination. Body water (42 kg), compartment A, is assumed to be 60 percent of body mass (70 kg) (ICRP, 1975). An estimated 10 kg of actively metabolizing tissue solids are in the body (i.e., 70 kg:42 kg water-13 kg fat-5 kg mineral bone) (Woodard, 1970). The dry tissue solids contain 7 to 8 percent hydrogen (7.2 percent assumed here), and this amount of organically bound hydrogen is distributed between compartments B and C. The division was selected to give good fits to long-term tritium retention measurements in several human cases (Bennett, 1973; Sanders and Reinig, 1967).There is no physiological significance to the bound tritium compartments that would identify them with specific tissues or organs. They reflect, rather, the daerences in chemical bonding of hydrogen in tissue. The water balance assumed in the above model gives a half-time of water in the body of 9.7 days:

Accounting for transfer to the bound compartments reduces the retention half-time of the body-water compartment to 9.6 days. The annual dose to body water from an intake of 1mCi, with the assumption of a 3 1 d-' water balance, is 106 mrad y-' .001 mCi 1-I

X

.33 1-' d x l y x 365d

-

97 mrad mCi-'

If the fractional amount of water in wet tissue (.75) and the contribution to tissue dose from combined tritium in tissue (1.2) are considered, A

Intake

330gH d" 13.01H20 d.0

-

4687gH

-

2.77gH d-I

120 &i

142 1 H201 0.924gHf11

- ,

C

BOO l H

Fig. 8.1 Three compartment model of hydrogen in the body.

the absorbed dose after an intake of 1 mCi is 90 percent of the water dose or 87 mrad. This result is also obtained directly h m the three compartment model calculations (Bennett, 1973). For tritium intake mixed with the daily water intake (3.0 1 d-I), the dose rate factor for tissue is 0.095 p a d (p Ci y I-')-' intake. This is the committed dose (pad) per integrated intake or the equilibrium dose rate b a d y-') per constant intake concentration (pCi I-'). The dose to tissue is due 84 percent to unbound tritium and 16 percent to organically bound tritium. After an acute intake, 50 percent of the t k u e dose is delivered within 11days and 90 percent within 200 days of the intake. The water content of tissues varies slightly, and thus it may be desirable to make adjustments in the generalized dose estimate given above. The water content of muscle is approximately 75 percent. For most organs the water content varies from 70 to 80 percent. Outside of this range are red marrow, 40 percent, and yellow marrow, 15 percent. The dose to fat cells and to mineral bone, if required, would call for separate analysis of the hydrogen content and retention characteristics. The water balance in individuals and even in the same individual at different times varies widely and thus also alters the dose estimates. A 9.7 day retention half-time for body water was derived above h m the reference man water volume and water balance. A reasonable range of 8.5 to 11 days might be expected under usual conditions, as suggested from the listing in Table 8-1 (Bennett, 1973). The 310 cases reported by Butler and LeRoy (1966) with 4 to 18 day retention half-times give a range that includes values reported by all other investigators. The TABLE 8-1-Tritium retention half-timesin man" InveafigaLol

Pinson and Lngham (1957) Fallor d a/.(1857) Foy and Sfhniedsn (1960) Richmond rl aL ( 1962)

wye Bntlsr and Lsmy (1965) h b o m e (1988)

Casee

9

20 10 6 7 310

30

Snyder d a/. (1868) S a n k and R e i (196e)

1

MinLr (1969) L n m h t et d.(1971)

1

Moghid el d.(1972)

No-

Studied

1

nnge 9.3-13 mngebll high ambient temp.

T?

Ta

34 23

244

11.3

8.6 7.6

9.5 ranee 6 1 2

range 4-18 -6.4-l4A

diurecicused

8.5 9.5 10.5 8.7 6.1

9.1

1 3

Ream~bleFIang~: Assvmed Average: 'From Beonett (1973)

TI

8.6-11 9

1030 36 21-26 2036

30

139-m ZW-SW zOW5cX 4W

70

/

8. LONG

TERM DOSIMETRIC IMPLICATIONS

difference in retention times is caused by variability due to metabolism, age, water intake, ambient temperature, and treatment procedures. There are very little data with which to estimate retention times or the potential variability of bound tritium in tissue. The tissue dose commitment per unit intake (mrad mCi-') is approximately 9.3 times the retention half-time (days) of tritium in body-water. The relationship was determined from the three compartment model calculations with the body-water retention half-time varying from 6 to 12 days and with 30- and 450-day components for bound tritium. The water balance assumed for reference man, 3.0 1 d-', consists of intakes listed in Table 8-2. The food water intake, based on analysis of food items of a standard diet, including 0.6 1 d-' milk and 0.03 1 d-' fruit juice, was found to be 1.27 1d-' loose water and 0.29 1 d-' oxidation water (Bogen, 1973). Water vapor in air can vary considerably, but we will assume an intake based on an absolute humidity of 6 ml m-3 air, corresponding to a reported Northern Hemisphere midlatitude mean value of water vapor in surface air (NOAA, 1976). The average adult breathing rate is 22 m3 of air per day (ICRP, 1975). Passage of tritium through skin is estimated to be 10 pCi r n i n - I per pCi 1-' in air (Osborne, 1972), equivalent to absorption of 10 liters of air per minute or 14.4 m3 of air per day. This amount about equals the resting inhalation rate but is somewhat less than the average daily inhalation rate. The drinking water intake makes up the remainder of the assumed 3.0 1 d-' total water intake. The dose from tritium intake by the various pathways is dependent on the relative contributions to total water intake. For an equilibrium situation, the tissue dose rate ( p a d Y-I) is equal to the effective concentration of the tritium intake times the dose rate factor (absorbed TABLE 8-2- W a r intake bv man Source lntake

(Id-')

Drinking water Food, milk, juice" Inhalation Passage through skin Total

" in food oxidation of food in milk oxidation of milk in juice oxidation in juice

.72 1 d-' .25 .53 .04

.02 .002

1.22 1.56 0.13 0.09 3.0 1 d-'

dose rate per unit concentration):

x 0.095 p a d (pCi y 1-')-I where the concentrations (pCi 1-I) are for drinking water C,, loose water in food C,,,oxidation water of food Cr,, and air C,. If concentrations are known only in surface waters and air, it may be sufficient to assume that the tritium concentrations in food are approximately equally due to tritium in air and in surface water. To determine the doses following releases of tritium to the environment, the integral concentrations of tritium in water from the various pathways are required. For estimates of these quantities, we must consider the regional and global dispersion of tritium and its entry into the hydrological cycle. 8.2

Environmental Models

For general considerations of the dose due to release of tritium to the environment, including estimation of the global buildup in tritium activity, it is necessary to formulate a model for the hydrological cycle. The simplest approximation would be to recognize a single compartment that would reflect the circulating waters and in which tritium releases would be considered instantaneously mixed. It would seem prudent to limit the amount of water involved to that in the hemisphere or latitudinal band of the release. A step closer to reality is achieved by considering separately the water circulation between the atmosphere, ocean surface, and surface waters of land. This three compartment model can be extended somewhat, based on estimated water volumes in surface soil, streams and lakes, and inland seas and including transfer to deep groundwater and to deep ocean. Such a model with seven compartments should provide the best estimates of environmental concentrations that result from specified releases. The underlying basis for the models of tritium cycling in the environment is the data on component volumes of the world water supply and the estimates of annual evaporation and precipitation. These data are presented in Table 8-3 (U.S. Geological Survey, 1970). It is useful to subdivide the ocean into the deep ocean and the mare rapidly mixing and cycling surface region. The area of the ocean surface is 361 x 1012m2 (Sverdrup et al., 1942). Thus, the surface ocean (to a depth

72

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8. LONG TERM DOSIMETRIC IMPLICATIONS

TABLE%3- WorM water supply and evaporation-precipitation balancea Volume Atmosphere Surface Soil Water Rivers (average instantaneous vol.) Fresh Water Lakes Saline Lakes and Inland Seas Deep Ground Water Ocean Icecaps and Glaciers Annual Evaporation From World Ocean From Land Areas Annual Precipitation On World Ocean On Land Areas

10" ma 0.13 0.67 0.0126 1.26 1.04 83.6 13200. 292. ma y-' loB4 3.6 0.7

1.0

" From the U.S. Geological Survey (1970).

of 75 m) contains 270 x 1014 m3. The waters locked in icecaps and glaciers are not considered in the tritium cycling. Narrower limits of extent of water volumes are estimated from the useful latitudinal breakdown of Sverdrup et ad. (1942). For example, the Northern Hemisphere contains 67.4 percent of the world's land area and presumably that fraction of the surface soil water and deep groundwater. The water area in the Northern Hemisphere is 42.8 percent of the total. In the 30-50°N Latitude Band, the land area is 21.5 percent and the water area 9.9 percent of the total land or water suiface areas of the world. The distribution of water volumes in fresh and saline lakes is based on the location and areal extent of the major lakes of the world. 8.2.1

One Compartment Model

An initial approach to model environmental tritium behavior is to consider a single compartment consisting of the circulating waters of the world with which man maintains equilibrium. The deep groundwater and deep ocean are excluded. The surface ocean water volume provides the dominant contribution to the compartment size. Activity is considered to be removed from the compartment only by radioactive decay. A release of tritium to the environment is thus assumed to be rapidly diluted in a large water volume. Table 8-4 lists the integral water concentrations (pCi y 1-') from a single release (MCi). T h m values are also the equilibrium concentrations (pCi 1-') for a constant

8.2

ENVIRONMENTAL MODELS

/

73

release rate (MCi y-I). The tissue dose rate is detennined directly by using the dose rate factor, 0.095 p a d (pCi y 1-I)-'. 8.2.2

Three Compartment Model

A natural division of the waters of the world consists of atmosphere, land waters, and ocean. Limiting the consideration to the more rapidly circulating waters again excludes deep groundwater and the deep ocean. The three compartment model is shown in Figure 8.2. The mean residence times of water in the compartments (volume divided by the rate into or out of the compartment) are 11 days in the atmosphere, 3 years in land surface waters, and 77 years in the ocean. Transfer coefficients for specific pathways (rate out of a compartment divided by the size of that compartment) describe the fractional compartmental transfers per unit time. Tritium released into one of the three compartments is considered instantaneously mixed. A series of differential equations describes the subsequent cycling. A practical method of solution, particularly with larger numbers of compartments, is a computer chain calculation with simultaneous transfers, based on the transfer coefficients, in steps TABLE+One

compartment model N.Hemisphere

WorM

Water volume' (10" m3) Integral concentration per 1 MCi releaseh (pCi y I-') Tissue dose in man per 1 MCi release' b a d )

273 0.66

118 1.5

0.062

0.14

30aO0NLat.

28.5

6.2 0.59

' Circulating waters (excludingdeep ocean and deep groundwater) Activity released per unit water volume times radioactive mean life of tritium (1.44

x 12.3~)

'By using the dose rate factor of 0.095 p a d (pCi y I-')-'

Land Surf=

Wmrs

3.0.1014 m3

0 . 3 ~ 1 0 1m3 ~ y.1 2.7.1016

mJ

Fig.8.2 Three compartment model of world water cycle.

74

/

8. LONG TERM DOSIMETRIC IMPLICATIONS

small compared to the compartment residence times. Radioactive decay is included, and the calculation is continued for as many iterations as may be required. The results of the three compartment model calculations are listed in Table 8-5. The integral concentrations per unit release (or equilibrium concentrations per unit release rate) are given for release into any of the three compartments. Relatively uniform mixing in the atmosphere within a latitude band may be obtained from a single release point, but the other release situations require rather widespread sources for the results to be applicable. The integral concentrations in air, land water, and ocean can be combined in various ways to give the integral concentrations in man. The values shown assume water intake of 3.0 1 d-' with tritium in the atmosphere contributing to inhalation and passage through skin (water intake = 0.22 1 d-') and to one-half of concentrations in food (0.77 1 d-I). The land waters contribute the other half of concentrations in food and drinking water C(0.77 + 1.22) 1 d-'I. The concentrations in the ocean contribute a small intake through fish (0.02 1d-I). Thus, the integral concentration, in man I,,,,is: TABLE 8-&Three comartment model World

N. Hemisphere

Water volumes (10" m3) Atmosphere 0.13 Land Waters 3.0 Ocean (Upper Layer) 270. Integral concentrationsper I MCi release @Ci y t') Release to Atmosphere Atmosphere 3.4 Land Waters 2.9 Ocean Surface 0.6 3.0 Man Release to Land Waters Atmosphere 2.2 Land Waters 10.4 Ocean Surface 0.5 Man 7.6 Release to Ocean Surface Atmosphere 0.6 Land Waters 0.5 Ocean Surfaces 0.7 Man 0.6 Tissue dose in man per I MCi rekcrse (pad) Release to Atmosphere 0.29 Release to Land Water 0.73 Releaee to Ocean Surface 0.05

3050°N. Lat.

8.2

75

/

ENVIRONMENTAL MODELS

The tissue dose is the integral concentration times the dose rate factor. The tritium concentrations in man are due primarily to the land water pathway, particularly for the world and Northern Hemisphere release situations. The initial concentrations in air following an atmospheric or oceanic release to the 30-50°N. latitude band make the air pathway most important.

Seven Compartment Model

8.2.3

The three compartment model can be usefully extended by considering tritium cycling to the deep ocean and to deep groundwater. The land waters can be differentiated into surface soil water, streams and freshwater lakes, and saline lakes and inland seas. The streams and freshwater lakes are interconnected and may as well be considered a single compartment. Additional transfer coefficients are needed. Some of these were derived by Easterly and Jacobs (1975) who utilized a similar model. Including man as a separate compartment is feasible. However, since the compartment volume and the amounts transferred are much less than the other compartments, this compartment plays an insignificant role in the hydrologic cycle. The model is shown in Figure 8.3. The mean residence times of water in the compartments (volume divided by the rate into or out of the compartment) are 11 days in the atmosphere, 200 days in surface soil, 4.1 years in freshwater lakes, 13.8 years in the surface ocean, 210 years in saline lakes, 330 years in the deep ground, and 810 years in the deep ocean. I

I

1

g . 9 3 ~1013 m3 y.1

3.2

1014 m3y-I

6 . 8 5 ~1013 m3 y.1

1 Surface Soil Wmar

1.94 x 1013 m3

3.6~10~~ m3y.l

f S u r t m Sv.aml& Fresh Water L & n

S d ~ n eLsksr &Inland Sea

Oasn

Surtaa

1 . ~ ~ m3 1 0 ~ ~

2 . 7 ~ 1 m3 0 ~ ~

t 30

1013m~v.l

1 4 ~ 1 0 ~1 ~ .0~10~~ ,"3 " - 1

)

Deep Orran

1 . 2 9 ~ 1 m3 0~~

8 . 3 5 ~ 1 0 m3 '~

Fig. 8.3 Seven compartment model of world water cycle.

76

/

8.

LONG TERM DOSIMETRIC IMPLICATIONS

The results of the seven compartment model calculations are listed in Table 8-6. Releases to atmosphere, streams, and ocean surface are illustrated. Again, except for atmospheric release within a latitude band, the other situations require rather widespread releases to be strictly applicable. TABLE 8-&Seven compartment model World

Water uolumes (10" m3) 0.13 Atmosphere Surface soil water 0.67 1.26 Streams & freshwater lakes Saline lake8 & inland seas 1.04 Deep groundwater 83.5 Ocean surface 270. Deep ocean 12930. Integral concentratwm per I MCi release @Ci y f ') Release to Atmosphere 3O . Atmosphere 2.4 Surface soil water Stream & freshwater lakes 1.9 Saline lakes & inland seee 0.06 Deep groundwater 0.1 Ocean surface 0.3 Deep ocean 0.006 Man 2.2 Release to Streams 0.3 Atmosphere Surface soil water 0.3 Streams & freshwater lakes 26.4 Saline lakes & inland seas 0.006 Deep groundwater 0.01 Ocean surface 0.3 Deep ocean 0.006 Man 8.8 Release to Ocean Surface Atmosphere 0.3 Surface soil water 0.2 Streams & h h w a t e r lakes 0.2 Saline lakes & inland seae 0.006 Deep groundwater 0.01 Ocean surface 0.3 Deep ocean 0.007 Man 0.23 Tissue dose in man per I MCi release (pad) Release to Atmosphere 021 Release to Streams 0.83 Releaee to Ocean Surface 0.02

N. Hemisphere 0.065 0.45 0.95 1.0 66.3 116. 5534.

6.0 3.5 2.5 0.06 0.2 0.7 0.01 3.7 0.6 0.4 35.1 0.006 0.02 0.6 0.01 11.8 0.6 0.4 0.3 0.008 0.02 0.7 0.02 0.38 0.36 1.1 0.04

8.2

ENVIRONMENTAL MODEIS

/

77

The integral concentrationsin man have been derived with assumptions similar to the previous example, except that drinking water is assumed to be obtained 80 percent from streams and freshwater lakes and 20 percent from deep groundwater. The tissue dose in man is highest for release to streams. If the release is to streams with no further drinking water intake occurring downstream from the discharge point, the tissue doses are comparable to doses following release directly to the ocean. Figure 8.4 illustrates the changes in concentrations in the various compartmenb following a single 1MCi atmospheric release to the 3050"N.latitude band. Initial high concentrations in air and surface soil water decrease rapidly, passing below the concentration in surface

T C n A h m h n )

Fig. 8.4 Concentratione multing h m a aingle atmospheric release of tritium (1MCi) to tbe 3040°N. latitude band.

78

/

8. LONG TERM DOSIMETRIC IMPLICATIONS

ocean in 3 years. Thereafter, the decline in concentration of the atmosphere, and, in turn, of surface soil water, is governed by the decrease in surface ocean (effective Tllz -6.2 years). Decreases in streams and freshwater lakes (initial Tl/z -2.6 years) gradually match the loss rate from surface soil water. The concentration in man is intermediate between that in streams, atmosphere, and surface soil water until about 20 years after the release. Subsequent tritium concentrations in man are about the same as in surface soil water.

8.3 8.3.1

Doses from Tritium in the Environment

Natural

The average concentration of tritium in environmental waters due to natural tritium production in the atmosphere by cosmic rays is 3.2 to 16 pCi I-'. The production rate is estimated to be 4 to 5.5 MCi y-'. The larger estimate, with the seven compartment model (release to world atmosphere) gives an equilibrium tritium concentration of 16.6 pCi 1-' in air, 10.4 pCi 1-' in streams, 1.6 pCi 1-' in surface ocean, and 12.3 pCi 1-' in man. The absorbed dose rate in tissue in man is 1.2 x mrad y-', a rather small component of the total natural background radiation dose rate of about 100 mrad y-'.

8.3.2

Fallout

Atmospheric weapons testing resulted in marked increases in tritium concentrations in environmental waters. Average concentrations in surface streams in the United States reached about 4000 pCi 1-' in 1963. Bennett has reconstructed the history of fallout tritium concentrations, based primarily on data from the U.S. Geological Survey's program of analyzing river water for tritium content (Bennett, 1973). Figure 8.5 shows the average concentrations for 20 streams throughout the U.S. from 1961-68 and for 15 streams in 1969-70. Less complete data, gathered from the literature, were used to estimate the concentrations in other periods. The average U.S. river tritium concentrations declined with a half-time of 3.2 years from 1963 until 1969. Tapwater samples from New York indicate that more recent atmospheric testing may be delaying slightly further declines in tritium concentrations in surface streams. Most recent data show tritium levels of about 150 pCi 1-' in surface waters.

8.3

DOSES FROM TRITIUM IN THE ENVIRONMENT

/

79

Year

Ng. 8.5

Environmental tritium in surface waters. (From Bennett, 1973)

The amount of tritium released to the atmosphere during weapons testing has been estimated by Eriksson to be 1900 MCi, produced from 1952 through 1962 (Eriksson, 1965). More recently, Michel (1976) estimated that about 5300 f 1500 MCi were produced based on measurements of the tritium inventories in the ocean. From estimated weapons yields, Miskel(1971) obtains an even higher figure, 8000 MCi. The data on maximurn and current levels of tritium in streams in the U.S. are matched most closely with the seven compartment model by assuming 7000 MCi of tritium were injected into the atmosphere in 1962 and 90 percent of this amount, or 6300 MCi, was deposited in the Northern Hemisphere. This is probably an overestimate since the levels in the mid-latitude region are enhanced by the general fallout deposition pattern. To account for this effect, a smaller injected amount leading to lower overall hemispheric average concentrations can be assumed. The model calculation provides a convenient means of extrapolating the environmental levels of tritium. Figure 8.6 shows the contribution of weapons produced tritium to the concentrations in streams and freshwater lakes. If one can assume no further significant axr~ountsof atmospheric weapons testing, the concentration due to fallout tritium should decrease below the level due to natural tritium just beyond the year 1990. The tissue dose in man from fallout tritium is estimated to have been about 0.2 m a d y-' a t maximum in 1963 and is currently about 0.01 m a d y-'. The dose commitment, which quantifies the past and future individual dose, can be estimated by comparing the total amount

80

/

8.

LONG TERM DOSIMETRIC IMPLICATIONS

released with the natural tritium production and dose rate. Using estimates previously discussed, the dose commitment for the Northern Hemisphere is .0012 m a d y-' X 6300 MCi = 2.7 mrad 2.75 MCi y-' For the Southern Hemisphere the estimate is 0.3 mrad.

8.3.3 Nuclear Industry Evaluation of the dose after release of tritium in airborne or liquid effluents from a nuclear facility requires consideration of the local and regional dispersion with eventual entry into the global or hemispheric water cycle. The concentrations and doses a short distance from the point of release could be quite variable depending on the specific local conditions. The operators of the nuclear installation will be required to evaluate this situation and insure that doses do not exceed imposed limits. A generalized approximation of the dose to the local population can be obtained by comparing the tritium concentration in air with the concentration and equilibrium dose rate from natural tritium. The natural tritium dose rate to tissue is 1.2 p a d y-'. Average water vapor content of air (6 ml m-3) at the background concentration level (16 pCi 1-') gives .096 pCi per m3 of air. Since it is not possible that the entire water intake be in equilibrium with the concentration of tritium in air at any specific location in the dispersion path, we will consider the components directly related to the air concentrations (inhalation and passage through skin, 0.22 1 d-', and one-half of the food intake, 0.77 1d-I). An average dispersion factor at 1km h m a nuclear facility can be taken to be 5 x s m4 (UNSCEAR, 1977).A release rate of 1Ci y-' can therefore be expected to lead to a dose rate at 1km on the order of 1Ci y-'

5x 3.15

lo-' X

s m-3 1.2 x 10" rad y-' 0.99 1 d-' lo7 s y-' .096 x 10-l2 Ci m3 3.0 1 d-' = 7 x 10" rad y-'.

At greater distances dispersion reduces the concentration approximately as the -1.5 power of the distance (UNSCEAR, 1977).Thus, at 100 km the tissue dose rate would be 7 x lo-'' rad y-' and at 1000 km 2 x 10-l2 rad y-'. The average dose rate in the region 1to 100 krn from the release point per Ci released, obtained by integrating the dose rate with distance, is 2 x lo-'' rad y-', on the assumption that the

8.3

DOSES FROM TRITIUM IN THE ENVIRONMENT

/

81

population density is uniform in the region. In the region from 100 to 1000 km,the average dose rate is 6 x 10-12rad y-'. For a large reactor (1000 MWe) producing 20 Ci of tritium per MWe y and releasing the entire amount at either the reactor or reprocessing plant site, the rad y-' and average dose rate in the local region (1-100 krn) is 4 X in the more distant region (100-1000 km)it is lo-' mrad y-'. If the entire water intake is assumed to have the same concentration as tritium in water vapor in air, the dose rate estimates would be higher by a factor of 3. Subsequent dispersion of the tritium throughout the hemisphere has been considered by Renne et al. (1975). Weighting each latitude band by the population indicates that the collective dose distribution

Ymr

Fig. 8.6 Contributions to the concentration of tritium in streams and freshwater b m a l l sources.

82

/

8. LONG TERM DOSIMETRIC IMPLICATIONS

is due 60 percent to the 30-50°N. latitude band, which was the assumed latitude of release. No significant contribution was outside of the region from 10' to 60°N. latitude. The seven compartment model provides an overall estimate for the average dose for an atmospheric release to the 30-50°N. latitude band (Table 8-5). The result is lo-'" rad per Ci released or lo-" rad y-' per release rate of 1 Ci y-'. The dose or dose rate applies to a population of 1.7 x 10' in this region. The model can be used to determine the concentrations in the environment and the dose rate to man from releases of tritium from nuclear industry. The estimates of the previous and projected releases are those that were given in Section 7. The liquid releases of tritium from nuclear power production are assumed to be one-half to streams and one-half to coastal bays or to the ocean. The results are shown in

Fig. 8.7

Projected tissue dose rate in man.

8.3

DOSES FROM TRITIUM IN THE ENVIRONMENT

/

83

Figures 8-6 and 8-7. Also shown are the contributions from natural tritium in the environment, weapons production, and fallout. The contributions to the concentration of tritium in streams and freshwater lakes from all sources are shown in Figure 8-6. By accounting for these levels and also the tritium concentrations in air, surface soil, deep groundwater, and the ocean, the projected tissue dose rate in man is shown in Figure 8-7. Tritium released by projected nuclear power production becomes the dominant contributor to the tissue dose in 1988. The total dose rate from all sources reaches a minimum of about 0.007 mrad y-' in 1987 and then increases by a factor of 2 by the year 2000. Projections of releases beyond the year 2000 have not been made. However, the model indicates that continuing releases at the year 2000 rate will result in an equilibrium dose rate that is just slightly less than in the year 2000 (-0.013 mrad y-I). Curtailing releases causes immediate reductions in concentrations and dose rate, similar to the decline projected for fallout tritium. By a l l contemporary criteria, the dose from tritium will be insignificant for the foreseeable future. However, as is true of all estimates based on calculations such as those presented in this report, there are many uncertainties. The source terms,the transport models, and our knowledge of the biological effects of tritium will be on a firmer basis in future years, and it will be desirable to reevaluate this report in another 10 years.

Appendix A

GLOSSARY absorbed dose: The energy imparted to matter by ionizing radiation per unit mass of irradiated material at the place of interest. The special unit of absorbed dose is the rad. One rad equals 0.01 joules per kilogram. aqueous tritium: That tritium associated with water molecules. biological half-life: The time required for the body to eliminate onehalf of an administered dosage of any substance by regular processes of elimination. boiling water reactor (BWR):A nuclear reactor in which water used for coolant is allowed to boil. breeder reactor: A nuclear reactor that produces more fissile material than it consumes. burnable poison: Bomn or other light elements having high neutron capture cross sections that are added in dissolved form to PWR coolant to reduce reactivity early in core life. The amount added is adjusted so that the high cross section nuclides disappear, "burn", as the reactor core ages. X : Concentration of radionuclide in the atmosphere at a downwind point given in units of Ci m". X/Q: Concentration to source strength ratio (s m-3). chop leach process: In nuclear fuel reprocessing individual fuel rods are sheared into short (approximately 5 cm) lengths to expose the fuel. The fuel is then leached with nitric acid. cladding: An external layer of material applied directly to nuclear fuel to provide protection from a chemically reactive environment, to provide containment of radioactive products produced during the irradiation of the composite, or to provide structural support. cold trapping: A method of removal of gaseoua materials by means of deposition of the material, as a solid, on a surface cold enough to convert the material from a gas to a solid. coolant: A substance, usually a liquid or gas, used for cooling any part of a reactor in which heat is generated. Such parts include not only the core but also the reflector, shield, and other elements that may be heated by absorption of radiation. 84

critical point: The temperature a t which a substance displays the properties both of a liquid and a saturated vapor. cross section, nuclear:.The probability that a certain reaction between a nucleus and an incident particle or photon will occur. It is expressed as the effective "area" the nucleus presents for the reaction. "Macroscopic cross section" refers to the cross section per unit volume or per unit maes. "Microscopic cross section" is the cross section of one atom or molecule. dose equivalent 0: The product of the absorbed dose in rads, the quality factor, and any other modifying factors. Dose equivalent is expressed in rems and is considered to be related to the radiation risk. effective half-life: Time required for a radioactive element in an animal body to be diminished 50 percent as a result of the combined action of radioactive decay and biological elimination. effective half-life =

biological half-life x radioactive half-life biological half-life radioactive half-life

+

fast reactor: A nuclear reactor in which most of the fissions are produced by fast neutrons, with little or no moderator to slow down the neutrons. Aesion yield: The percentage of fissions leading to a particular nuclide. flux density (fluence rate): The number of particles that, per unit time, enter a sphere per unit of cross sectional area of that sphere. In the case of neutrons it is usually expressed in cm-* s-'. heavy water reactor (HWR):A nuclear reactor in which heavy water serves as moderator and sometimes also as coolant. high temperature gas cooled reactor (HTGR):A prototype gas cooled reactor in which the-coolant is pr-urhd helium gas; the fuel consists of fully enriched uranium and thorium. isotope effect: The effect of difference of mass between isotopes of the same element on non-nuclear physical and chemical properties, such as the rate of reaction or position of equilibrium of chemical reactions involving the isotopes. kerma: The total kinetic energy of directly ionizing particles ejected by the action of indirectly ionizing radiation per unit mass of specified material. h e a r energy transfer 0 : The average energy lost by a directly ionizing particle per unit distance of its travel in a medium. As here employed, the term is to denote L,, i.e., the entire energy lost by charged particles per uiit distance with inclusion of all energy

carried by charged particles (e.g., delta rays) that are not considered separately. Liquid metal fast breeder reactor (LMFBR): A type of fast reactor using highly enriched fuel in the core, fertile material in the blanket, and a liquid-metal coolant such as sodium; high energy neutrons fission the he1 in the compact core, and the excess neutrons convert fertile material to fissionable nuclides. maximum permissible concentration (MPC): The maximum quantity per unit volume of radioactive material in air, water, and foodstuff that is not considered an undue risk to human health. mean residence time: The average time that a given compound will remain in a specified state. Mean residence time, T , is related to the residence half-life, T, as: megaton 0: A unit of explosive energy equivalent to that released upon detonation of lo6tons of TNT. moderator: Material used to moderate or slow down neutrons from the high energies a t which they are released. molten salt breeder reactor (MSBR): see liquid metal fast breeder reactor. MTU: Metric tons of uranium. MWe: Megawatts electrical. MWt: Megawatts thermal. nuclear reactor: An apparatus in which nuclear fiasion may be sustained as a self sustaining chain reaction. nuclear transformation: Interaction between two or more particles including at least one nucleus and leading to the emission of different particles. organic tritium: That tritium associated with organic molecules. ORIGEN: The ORNL Isotope Generation and Depletion Code - a computer code that solves equationsof radioactive growth and decay for large numbers of isotopes. The code is used to compute compositions, inventories, and radiation levels of fission products, cladding material, and fuel elements in LWRs, LMFBRs, MSBRs, and HTGRs. power: The time rate of doing work; the unit of power is the watt. pressurized w a t e r reactor (PWR): A nuclear reactor in which water is circulated under enough pressure to prevent it from boiling, while serving as moderator and coolant for the uranium he]; the heated water is then used to produce steam for a power plant. quality factor (Q): A multiplying factor used with absorbed dose to express its effectiveness in causing detrimental biological effects.

GLOSSARY

/

87

The numerical values of the quality factor are given as a function of the stopping power in water for the radiation producing the absorbed dose (see dose equivalent). radioactive half-life: Time required for a radioactive nuclide to lose 50 percent of its activity by decay. radioactive recoil: The acceleration of the residual nucleus upon emission of particular radiation from the parent radionuclide. relative biological effectiveness (RBE): Biological potency of one radiation as compared with another. The RBE of radiation A with respect to the reference radiation, B, is defined in terms of the that produce equal biological effect. It absorbed doses, D A and W , is equal, therefore, to &/DA. The standard of reference used in this report is moderately hltered 250 kVp x radiation. The use of this term is to be restricted to radiobiology and it should be distinguished from the quality factor that is employed in radiation protection. source strength (Q): The number of curies of a radionuclide released per unit time to the atmosphere (Ci y-I) (see X/Q). specific activity: Total activity of a given nuclide per gram of a compound, element, or radioactive nuclide. ternary fission: A fission in which two nonnal-range fission products and a high-energy light nuclide, most frequently an alpha particle, are given off. In 235U this occurs in about 1out of 300 events. triple point: The temperature and pressure a t which all three phases (solid, liquid, or gas) of a compound coexist at equilibrium. triton: The nucleus of tritium as a product of a nuclear reaction. tropopause: The boundary between the thermal atmospheric region (troposphere) characterized by decreasing temperature with height and the region of fairly constant temperature with height (stratosphere). tropopause gap: The region where exchange of air takes place between the stratosphere and troposphere, usually in the latitudes of the jet stream, 30-50°N. and 30-50's.

Appendix B

List of Acronyms BWR CANDU EBR I1 HTGR

HWR ICRP LET LMFBR MSBR ORIGEN

PWR RBE SEFOR SGHWR SRP

- Boiling Water Reactor

- Canadian Deuterium Uranium Reactor

- Second Experimental Breeder Reactor - High Temperature Gas Cooled Reactor

- Heavy Water Reactor - International Comminsion on Radiological Pmtection - Linear Energy Transfer - Liquid Metal Fast Breeder Reactor - Molten Salt Breeder Reactor - ORNL Isotope Generation and Depletion Code - Pressurized Water Reactor - Relative Biological Effectiveness - Southwest Experimental Fa& Oxide Reactor - Steam Generating Heavy Water Reactor - Savannah River Plant

References ALBEN~IUS, E. L. (1959). "Tritium ss a product of fission," Phys. Rev. Lett. 3, No. 6, 274. ~ B E N E B I U ~E. . L AND O N D R E J ~ R, S. (1960). "Nuclear fission product tritium," Nucleonics 18,No. 9, 100. ALVAREZ,L. W. AND CORNW,R (1939). "Helium and hydrogen of mas6 3," Phys. Rev. 66, No. 2,613. AMERICAN ABSOCIATION OF PETROLEUM G E O ~ C I S (1964). I~ Radioactive Waste-Disposal Potentials in Selected Geologic Basins-A Reconnaissance Study, USAEC Report No. SAN-413-2 (US. Atomic Energy Commission, Waehington). ANL (1973). Aqonne National Laboratory, Social Costs for Alternote Means of Electrical Power Generation fur 1980 and 1990, USAEC Report No. ANG89Q3 (Argonne National Laboratory, Argonne, Illinois). ANSPAUGH, L. R., KORANDA, J. J., ROBESON,W. L. AND MARTIN,J. R. (1973). 'The dose to man via food-chain transfer resulting from exposure to tritiated water vapor," page 406 in Tritium, Moghiesi A. A. and Carter, M. W., Eds. (Messenger Graphics, Phoenix, Arizona). ARNOLD,W. D., LIN, K. H., SALMON,R. AND DE LACUNA,W. (1973). Preliminary Evaluation of Methoda for the Disposal of Tritiated Water from Nuelearly Stimulated Natural Gas We& Report No. ORNLTM-4024 (OakRidge National Laboratory, Oak Ridge, T e n n e e ) . ASHLEY,C. AND ZEIGLER,C. C. (1975). Environmental Monitoring a t the Savannah River P l a a , Report No. DPSPU-75-302 (DuPont de Nemoura (E.I.) and Co., Savannah River, Aiken, South Carolina). AIJNE,R. G., CANTELOW, H. P. AND BOLTIN,R L. (1973). "Practical contml of tritiated water vapor by silica gel and of tritium gas by use of a purging device," page 749 in Tritium, Moghiasi, A. A. and Carter, M. W., Eds. (Messenger Graphics, Phoenix,

Arizona). BAINBRIDGE,A. E. (1963). "Tritium in d a c e waters of the North Pacific," page 129 in Nuclear Geophysics (National Academy of Sciences, National Research Council. Washington). BARR, F.T. AND DBEWB,W. P. (1960). "The future for cheap heavy water," Chem. Eng. Prog. W,49. BARRETC,E. W. AND HUEBNER,L. (1960). Atmospheric Tritium Analysis, Technical Progress Report No. 2, USAEC Report No. AECU-4739 (University of Chicago, Chicago, Illinois). BABREIT, E. W. AND HUEBNER,L. (1961). Atmospheric Tritium Analysis, Technical Progress Report No. 3, USAEC Report No. TID-14425(University of Chicago, C h w o . Illinois). BAEEROA,R,Lwco, H. AND KISELESKI, W. E. (1966). 'Tumor induction in mice by radioactive thymidine," Radiat. Res. 29,583. BAVER,L D. (1966). Soil Physics (John Wiey & Sons, Inc., New York). BEBEINGTON, W. P. AND TIIAYER,V. R (1969). "Production of heavy water," Chem. Eng. Prog. 56,70. BEGEMANN, F. AND LIBBY, W. F. (1957). "Continental water balance, ground water 89

inventory and storage times, surface ocean mixing rates and worldwide water circulation patterns from cosmic-ray and bomb tritium," Geochim. Cosmochim. Acta 12, 277. BELL, M. J. (1973). ORIGEN-The ORNL Isotope Generation and Depletion Code, Report No. ORNL-4628 (Oak Ridge National Laboratory, Oak Ridge, Tennessee). BENNETT,B. C. (1973). "Environmental tritium and the dose to man," page 1047 in Proceedings of the Third International Congress of the International Radiation Protection Association, Washington, D. C. September, 1973, Report No. CONF730907-P2 (National Technical Information Service, Springfield, Virginia). BERRY,R. J., CAVENAGH, J., OLIVIER,R. AND WINSTON,B. M. (1973). "Variation in relative biological effectiveness with dose rate for different radiation qualities," Health Phys. 24,369. BIGELEISEN,J . (1962). "Correlation of tritium and deuterium isotope effects," page 161 in Tritium in the Physical and Biological Sciences, Vol. I, IAEA Report No. STI/PUB/39 (International Atomic Energy Agency, Vienna). BIGELEISEN, J. (1964). "Correlation of kinetic isotope effects with chemical bonding in three-centre reactions," Pure AppL Chem. 8, 217. BIRO,T. A N D CZIBOLG,C. (1966). "Determination of internal radiation doses from tritium intake," page 93 in Proceedings of the Second Symposium on Health Physics, Vol. 1, Report No. CONF-660948 (National Technical Information Service, Springfield, Virginia). BIXEL,J. C. A N D KERSHNER,C. J. (1974). "A study of catalytic oxidation and oxide adsorption for removal of tritium from air," page 261 in Proceedings of the 2nd AEC Environmental Protection Conference, Albuquerque, New Mexico, April 16-19,1974, Report No. CONF-740406, WASH-1332(74) (National Technical Information Service, Springfield, Virginia). T . B. (1975). Monsanto/Mount BIXEL,J. C., KERSHNER,C. J . A N D RHINEHAMMER, Laboratory Tritium Waste Control Development Program, Report No. MIM-2262 (Mount Laboratory, Miamisburg, Ohio). BIXEL,J. C., HARTZELL, B. W. AND PARK,W. K. (1976). Experimental Determination of Reaction Rates of W a r . Hydrogen Exchange of Tritium and Hydrophobic Catalysts, Report No. CONF-760822-10 (National Technical Information Service, Springfield, Virginia). BLACK,J. F. AND TAYLOR,H. S. (1943). "Equilibrium in hydrogen-water systems containing tritium," J . Chem. Phys. 11. No. 9,395. BLAVOUX, B. (1964). "Hydrodynamics and content of tritium in the waters of the Evian Basin (France)," Compt. Rend. 259,4323. BLOMEKE,J. O., KEE, C. W. AND NICHOLS,J. P. (1974a). Projections of Radioactive Wastes to be Generated by the U.S. Nuclear Power Industry, Report No. ORNLTM-3965 (Oak Ridge National Laboratory, Oak Ridge, Tennessee). BLOMEKE, J . O., KEE, C. W. AND SALMON, R. (1974b). Projected Shipments of Special Nuclear Material and Wastes by the Nuclear Power Industry, Report No. O R N L TM-4631 (Oak Ridge National Laboratory, Oak Ridge, Tennessee). R. (1975). "Shipments in the nuclear fuel BWMEKE,J. 0.. KEE. C. W. AND SALMON, cycle projected to the year 2000," Nucl. News, June 1975,62. BOGEN,D. C., HENKEL,C. A., WHITE,G. C. C. AND WELFORD,G. A. (1973). "Tritium intake in New York City," page 639 in Tritium, Moghissi, A. A. and Carter, M. W., Eds. (Messenger Graphics, Phoenix, Arizona). BOLIN,B. (1961). An Investigation of Tritium in Atmospheric Moisture, Rainwater, and the Sea in the European Area, USAEC Report No. TID-13376 (National Technical Information Service, Springfield, Virginii).

REFERENCES

/

91

BOLIN,B. (1964). Research in Geophysics, Vol. 2, page 479 (The M.I.T. Press, Cambridge, Massachusetts). BOND,V. P. (1971). "Evaluation of potential hazards from tritiated water," page 287 in Environmental Aspects of Nuclear Power Stations, IAEA Report No. STI/PUB/261 (International Atomic Energy Agency, Vienna). L E. (1966). "Intranuclear 'H-thymidine: Dosimetric BOND,V. P. A N D FEMENDEGEN, radiological and radiation protection aspects," Health Phys. 12, 1007. BOND,V. P., MELNHOLD, C. B. AND Rossr, H. H. (1978). "Low-doae RBE and Q for xray compared to gamma-ray radiations," Health Phys. 34,433. BROWN. R. M. (1961). "Hydrology of tritium in the Ottawa Valley," Geochim. Cosmochim. Acta 21,199. BROWN, R. M. (1964a). "Tritium in the Ottawa River," page 18 in Progress Report, Biology and Health Physics Division, October I to December 31, 1964, Canadian Report No. PR-B-64 (Atomic Energy of Canada, Ltd., Chalk River, Ontario). BROWN, R. M. (196413). "Tritium in precipitation at Canadian sites, 1953-1963," page 71 in Tritiwn and Other Environmental Isotopes in the Hydrological Cycle, Technical Report Series No. 73, STI/DOC/10/73 (International Atomic Energy Agency, Vienna). BROWN, R. M. (1964~).Actiuities of AECL in the Fields of Biology, Health Physics, and Medicine. Canadian Report No. AECL-2107 (Atomic Energy of Canada, Ltd., Chalk River, Ontario). W. E. (1956). ''The d e t e n r a t i o n of tritium in natural BROWN, R. M. AND GRUMMITT, waters," Can.J. Chem. 34,220. BRUNER, H. D. (1973). "Distribution of tritium between the hydrosphere and invertebrates," page 303 in Tdium, Moghissii A. A. and Carter, M. W., Eds. (Messenger Graphic., Phoenix, Arizona). BRYANT,P. M. (1964a). Methods of Estimation of the Dispersion of Windblown Material and Data to Aesist in Their Application, Report No. AHSB(RP)R-42 (United Kingdom Atomic Energy Authority, Harwell, Berks, England). BRYANT, P. M. (1964b). "Derivation of working Limits for continuous release rates of iodine-131 to atmosphere in a milk producing area," Health Phys. 10,249. L.L (1972). The Separation and ConLrol of Tritium State of the Art Study, BURGER, Report No. PB-244928 (Battelle Pacilic Northwest Laboratories, Richland, Washington). BURGER,L. L (1976). The Conversion of Tritiated Hydrogen to Water in the Atmosphere, Report No. BNWL-2113 (Battelle Pacific Northwest Laboratories, Richland, Washington). BURGER,L L. AND RYAN,J. L. (1974). The Technology of Tritiwn Fixation and Storage, Report No. BNWL-1807 (Battelle Pacific Northwest Laboratories, Richland, Washington). BURGER,L. L. AND .I~EVORROW, L. E. (1976). Release of Tritium from f i e 1 and CoUectMn for Storage, Report No. BNWL-SA-5778 (Battelle Pacific Northwest Laboratories, Richland, Washington). BURKI,H. S. AND OI~ADA, S. (1970). "Killmg of cultured mammalian cells by radioactive decay of tritiated thymidiie at -196OC," Radiat. Res. 41,409. BUTLER,H. L.AND LEROY,J. H.(1964). "Observations of biological half life of tritium" (presented at the Health Physics Society Meeting, Cincinnati, Ohio, June, 1964). BUTLER,H. L. AND LEROY,J . H. (1965). "Observation of biological half-life of tritium," Health Phys. 11.283. CAHIU,D. P.AND YUILLE,C. L. (1969). "Some effects of tritiated water on mammalian fetal development," page 283 in Proceedings of a Symposium on Radiation Biology

of the Fetal and Juvenile Mammal, Richland. Washington, Report No. CONF690501 (National Technical Information Service, Springfield, Virginia). CAMBIAGF~, M.,F O ~ ~ A T F.IAND , WELLI, T.(1969). "hng-range alpha particles and light charged nuclei in the neutron-induced f i o n of NUOVO Cimento JJX B, No. 2, 236. CAMBIACHI, M.. CAVALLARI, F., FWATI, F., JAPPELLI,F., PETRONIO, C. AND PINELLI, T. (1972). "Experimental results concerning long-range light particles and fragments in the ternary fission of "U, '%I, and ='Cf," NUOVO Cimento 11A, No. 3,716. CARLSTON, C. W. (1964). "Use of tritium in hydrologic research-prob1en:n ar~dlimitations," Bull. Int. Assoc. Sci. Hydrology 3, 38. CASALETTO, G. J., GEVANTMAN, L. H. AND NASH, J. B. (1962). The Self-Radiation Oxidation of Tritium in Oxygen and Air, Report No. USNRDL-TR-565 (Naval Radiological Defense Laboratory, San Francisco, California). M., FOSSATI,F. AND PINELLI,T. (1969). "Emission of light CAVALLARI, F., CAMBIACHI, charged nuclei in the n-thermal fiasion of q u , " pago 891 in Proceedings of the 2nd IAEA Symposiwn on Physics and Chemistry of Fission, Vienna (International Atomic Energy Agency, Vienna). C&EN STAPF. (1973). Chemical and Engineering News, "Underground movement of waste clarified," Chem. Eng. News 1 5 (October 15,1973). CFR (1976). Code of Federal Regulations. Title 10. Appendix B. "Part 20-Concentrations in Air and Water Above Natural Background" (Superintendent of Documents, U.S. Government Printing Office, Washington). CHAMBERLAIN, A. C. AND EGGLETON, A. E. J . (1964). "Washout of tritiated water vapour by rain," Int. J. Air Water Pollut. 8, 136. CHORNEY,W. AND &ULLY, N. J. (1965). "Radiation effects of 14-C and tritium on g~owthof soybean," Radiat. Bot. 5,257. CLAYTON. C. G. AND SMITH,D. B. (1963)."A comparison of radioisotope methods for river flow measurements," page 1 in Proceedings of a Symposium on Radioisotopes in Hydrology, IAEA Report No. STI/PUB/71 (International Atomic Energy Agency, Vienna). CLEBSCH,A., JR., AND LIEBERMAN, J. A. (1962). "The possibility of groundwater contamination by fallout," page 306 in Radioactive Fallout from Nuclear Weapons Tests, Proceedings of a Conference Held in Gennantown, Mwykznd, Report No. TID-7632 (National Technical Information Service, Springfield, Virginia). COLE,H. S., HENRY,R. N., KELLER,J. H., OLEHY,D. A. AND ROHDE,K. L. (1973). "Distribution of tritium in the Idaho Chemical Processing Plant," page 417 in Tritium Control Technology, Rhinehammer, T. B. and Lamberger, P. H., Eds., Report No. WASH-1269 (U.S. Atomic Energy Commission, Washington). COLOMBO, P., BEcKER, W..NEILBON.R. AND PRUZANSKY,J. (19741). Tridium S t 0 r a ~ e Development, Progress Report NO. I, July-September, 1974,Report No. ~ ~ 1 9 4 0 8 (Brookhaven National Laboratory. Uvton.. Long Island. New York). COLOMBO, P., BECXER,W., ~mmN; R AND PRUZAN~KY,J. (1974b). Tritium Storage Development, Progress Report No. 2, October-December, 1974, Report No. BNL19688 (Brookhaven National Laboratory, Upton, Long Island, New York). CoLoMBo. P., BECKER. W.. NELISON.R. AND PRUZANSKY. J. (19'75a). Tritium S t o r a ~ e Development, progress Report NO: 3. January-March, 1975,Report No. BNL-19981 (Brookhaven National Laboratory. Uoton.. Low Ialand. New York). COLOMBO, P., BECIKER, W., NEILsON; R AND pRuzANsxY, J. (1975b). Tritium Storage Development, Progress Report No. 4, ApriCJune, 1975, Report No. BNL20Q21 (Brookhaven National Laboratory, Upton, Long Island, New York). COLOMBO, P., NIELBON,R. JR., BECKER,W. AND DIVIIS. E. (1976). Tritium Storage

-

-

REFERENCES

/

93

Development, Progress Report No. 8, ApridJune, 1976. Report No. BNL-50583 (Brookhaven National Laboratory, Upton, Long Island. New York). CUDDEBACK, R. B., KOELLER, R. C. AND DRICKAMER,H. G. (1963). "The effect of pressure on diffusior. in water and in sulfate solutions," J . Chem. P h y . 21,No. 4,589. CULLER,F. L. et al. (1962). "Cane program," page 207 in Chemical Technology Division Annual Progress Report for Period Ending June 30, 1962, USAEC Report No. ORNL-3314 (Oak Ridge National Laboratory, Oak Ridge, Tennessee). DAKOWSXI, M., CHWAZC~WSKA, J., KROGUMKI,T., PIASECKI,E. AND SOWINSKI,M. (1967). "Energy spectra of long range particles from the thennal neutron fission of =U," P h y . Lett. B 26. No. 3, 213. DE LACUNA, W. (1964). Oak Ridge National Laboratory, unpublished, July 31, 1964. DE LACUNA, W. (1968). "Importance of deep permeable dispwal formations in location of a large nuclear fuel repmce&ng plant," page 21 in Subsurface Disposal in Geologic Basins-A Study of Reservoir Strata, Galley, J. E., Ed., AAPG Memoranda 10 (American Association of Petroleum Geologists, Inc., Tulsa,Oklahoma). DE LACUNA, W., WEEREN.H. 0.. BINFORD,F. T., WITIKOWSKI, E. J. AND S T R U X N E ~ , E. G. (1971). Safety Analyses of Waste Disposal by Hydraulic Fracturing at Oak Ridge. Report No. ORNL-4665 (Oak Ridge National Laboratory, Oak Ridge, Tennessee). DIXON,M. N.. HOMWAY.C. F., HOUBER,B. L. AND JACOBS,D. G. (1975). Indexed Bibliography on Tritiwn, Its Sources a n d Projections, Behavior Mearruremenl and Monitoring Technques, Health Physics Aspects, and Waste Management, Report No. ORNL-5057 (Oak Ridge National Laboratory, Oak Ridge, Tennessee). DOBSON,R. L.,ARRINGTON, J. H. AND KWAN, T. C. (1976). Tritium Toxicity: Increased Relative Biological Effectiveness of 'HOH with Protraction of Exposure, Proceedings of the Fourth National Symposium on Radioecology, Report No. CONF-7505031 (National Technical Information Service, Springfield, Virginia). DOE (1978). Department of Energy, Energy Information Admkkdration Annual Report to Congress, Pmjection of en erg^ Supply and Demand and Their Impacts, Report No. DOE/EIA-003612 (Department of Energy, Washington). DORFMAN, L. M. AND HEMMER,B. A. (1954). "Ion pair yield of the tritium-oxygen reaction," J. Chem. Phys. 22,No. 9, 1555. DORFMAN, L.M.AND MATTRAW, H. C. (1963). "The exchange reaction of hydrogen and tritium," J. Phys. Chem. 57,723. M. (1975). Yugoslav Patent AppL DRAZIC,D. M., VORKOPIC, L. Z. AND ATANAIKOVIC, No. 331/74 (Faculty of Technology. Belgrade University). DUDEY,N. D. (1968). Review of Low-Mass Atom Production in Fast Reactors, Report No. ANL7434 ( A r g 0 ~ National e Laboratory, Lemont, Illinois). R L. AND RYMM,S. J. (1972). "Tritium yields from fast DUDEY,N. D., MALEWICKI, neutron fission of (200-800 keV)," Trans. Am. NucL Soc. 16, No. 1,483. EASTERLY,C. E. AND JACOBS,D.G. (1975).Radiation Effects and Tritium Technology for Fusion Reactors, Report No. COW-750989 (National Technical Infonuation Service, Springfield, Viqinia). EASTHAM, J . J . AND RAAEN,V. F. (1959). "Determination of active hydrogen in organic compounds by exchange with tritiated isopropyl alcohol," Anal. Chem. 81.No. 4,556. W. R. A N D KRSUL,J. R. (1971). "Tritium in the EBR-TI ~ E R S O L EE., R., VROMAN. Reactor Complex," Trans. Am. NucL Soc. 14, No. 1,321. ECKERMAN, K. F. AND CONCEL,F. J. (1974). Suppkmental Testimony Regarding Doses to the World Population from the Normal Operational Tritium and Krypton Releases of the Barnwell Nuckar Fuel Plant, Report No. Docket No. 50-332 (Allied General Nuclear Services, Barnwell Nuclear Fuel Plant, Barnwell, North Carolina).

94

/

REFERENCES

EISENBUD,M. (1973a). "Fuel reprocessing," chapter 11, page 290 in Environmental Radioactivity, 2nd ed. (Academic Preaq New York). EISENBUD,M. (1973b). "Reactors," chapter 9, page 216 in Environmental Radioactivh, 2nd ed. (Academic Preea, New York). "Management of radioactive wastes," page 299 in Environmental EISENBUD,M. ( 1973~). Radioactivity, 2nd ed. (Academic Press, New York). ELLETT,W. AND BRABY,L. (1972). "The microdosimetry of 250 kVp and 65 kVp xr a y ~ , ~ Cgamma o rays and tritium beta particles," Radiat. h. 51,229. ELWOOD, J. W. (1971). Tritium Behavior in Fish from a Chronically Contaminated Lake, Proceedings of the 3rd National Symposium on Radioecology, Report No. CONF-710501-45 (National Technical Information Service, Springfield, Virginia). EMELITY,L. A.. CRRISTENSON, C. W. A N D WANNER,J. J. (1973). 'Tritium loss from coated cement paste blocks," page 776 in Tritium, Moghissi, A. A. and Carter, M. W., Eds. (Messenger Graphics, Phoenix, Arizona). ENGELKE, M. J. AND BEMIS,E. A., JR. (1962). A Study of the Diffusion and Mixing of Tritium Gas in Air, USAEC Report No. LA-2671 (Lo8 Alamos Scientific Laboratory, h s Alamos, New Mexico). EPA (1973). U.S. Environmental Protection Agency, Environmental Analysis of the Uranium Fuel Cyck, Part ZZI. Nuclear Fuel Reprocessing, Report No. PB-235806, EPA-520/9-73-003D (Office of Radiation Programs, U.S.Environmental Protection Agency, Was-n). EPA (1974). U.S. Environmental Protection Agency, Environmental Radiation Dose Commitment: An Application to the Nuclear Power Zndusby, Report No. EPA520/4-72-002 (Office of Radiation Programs, U.S. Environmental Protection Agency, Washington). ERDAM (1975). Standards for Radiation Protection, Report No. ERDAM-0524 (U.S. Energy Research and Development Administration, Washington). ERDMAN. C. A. AND REYNOLDS,A. B. (1975). "Radionuclide behavior during normal operation of liquid-metal-cooled fast breeder reactors, part 1. production," Nucl. Saf. 16, No. 1,43. ERDMAN, C. A., KELLY,J. L. AND REYNOLDS, A. B. (1975). "Radionuclide behavior during normal operation of liquid-metal-cooled fast breeder reactors, part 2. transport," Nucl. Saf. 16, No. 3, 318. ERIKSSON,E. (1963). "Atmospheric tritium as a tool for the study of certain hydrologic aspects of river basins," TeZlus 15,303. ERIKSSON,E. (1965). "An account of the major pulses of tritium and their effects in the atmosphere," Tellus 17, No. 1, 118. EVANS,A. C. (1969). "New dose estimates from chronic tritium exposures," Health Phys. 16, 57. EXECUTIVEOFFICE OF THE PRESIDENT(1977). A National Energy Plan (Executive OfFice of the President, Washington). FINNEY,B. C., BLANCO,R. E.. DAALMAN. R. C., KITTS,F. G. AND WITHERSPOON, J. P. (1975). Correlation of Radioactive Waste Treabnent Costs and the Environmental Impact of Waste Effluents in the Nuckar Fuel Cycle for Use in Establishing "As Low As Practicable" Guides-Nuckar F k l Reprocessing, Report No. ORNL-TM4901 (Oak Ridge National Laboratory, Oak Ridge, Tennessee). FIREMAN,E. L., DE FELICE,J. AND RLLES,D. (1961). "Solar flare tritium in a recovered satefite," Phys. Rev. 123, 1935. FLAMM,E., LINGENFELTER, R. E., MACDONALD, J. F.AND LIBBY,W. F.(1962). "Tritium and helium-3 solar flares and loss of helium from the earth's atmosphere," Science 138,48.

~EIDNER, T. M.. HAAS,R. J., STEALE,H. AND ADAMS, A. (1968). "Complete labelling of all cell nuclei in newborn rats with %-thymidine," Lab. Invest 18,249. ~EIDNER, T. M., HAAS, R J., BORNE,F. AND HAiUUSS, E. B. (1969). "Rsdiation effects produced in pregnant rats and their o&pring by continuous infuaion of hitiated thymidine," page 263 in Proceedings of the Symposium on Radiation Biology of the Fetal and Juvenile Mammal, Richland, Washington, Report No. CONF-690501 (National Technical Information Service, Springfield,Virginia). buss, M. J. AND DIJDEY. N. D. (1971). "Tritium and helium yields in fast fission of Trans. Am. Nucl. Soc. 14. No. 2,809. buss, M. J., DUDEY,N. D. AND MALEWICKI, R L. (1972). 'Tritium and alpha-particles yields in fast and thermal fission of =U," P h y ~ Rev. C 6, No. 6,2252. ~ O R DFOUNDATION (1974). Exploring Energy Choices: A PreReport (The Ford Foundation Energy Policy Project. Washington). FRC (1963). Federal Radiation Council, Estimates Md Evaluation of Fallout in the United States from Nuckar Weapons Testing Conduc&d Through 1962, FRC Report No. 4 (Federal Radiation Council, Washington). ~JNK, F. AND PERBON,S. (1969). ''Cybaim to thymine transitions from decay of cyto&e-6-% in bacteriophage S-13," Science 166,1629. page 347 ALLEY, J. E. (1962). "Geologic basim studies as related to deep-well in Second Ground Disposal of Radioactive Wastes Conference, Held at Atomic Energy of Canada Limiied, Chalk Riuer. Canada, September 26-29, 1961, USAEC Report No. TID-7628 (National Technical Information Service, Springfield, Virginia). ~ENERALDYNAMICS CORPORATION (1975). General Atomics Standard Sdety Analysis Report, Report No. GA-A-13200 (General Atomic Division, General Dynarniw Cop., Snn Diego, California). ;ENERAL ELECTRIC COMPANY (1975). General Eketric StMdards Safety Analysis Report, Report No. BWR-6, Docket-STN-50447-46 (General Electric Company. Atomic Power Equipment Department, San Jose, California). ~DBEE H., W. AND JOY,D. S. (1974). Assessment of the Loss of Radioactive Isdopes from Waste Solids to the Enuironment. Part I : Background and Theory, Report No. ORNL-TM-4333 (Oak Ridge National Laboratory, Oak Ridge, Tennessee). J. 0. AND BLANCO,R. E. (1969). ~ D B E EH. , W., FITZGERALD,C. L., BLOMEKE, "Diffusion of radioisotopes through waste solids," Tnuls. Am. Nucl. SocL 12, No. 2, 450.

~OODE, J. H.AND COX, C. M. (1970). The Distribution of Fission Product Tritium in a Zircaby-Clad U02 Blanket Rod from PWR-1, Report No. ORNLTM-2994 (Oak Ridge National Laboratory, Oak Ridge, Tennessee). V. C. A. (1970). ORNL Experiments on the Behwwr of ;OODE,J. H. AND VAUCHEN, Tritium During Head-End Processing of Irradiated Reactor Fuels, Report NO. ORNLTM-2793 (Oak Ridge National Laboratory, Oak Ridge, Tennessee). D, h o e , J. H., BAYBARZ, R D., CLINTON,S. D., FARRAR,L G., F ~ ~ E R ~C.L L.. HAIRE, R G., ' ~ N N E R Y V., J., VAUCKEN.V. C. A. AND WATBON, C. D. (1973). Voloxidation-Removal of Volatile Fission Products from Spent LMFBR Fuels, Report No. ORNLTM-3723 (Oak Ridge National Laboratory, Oak Ridge, Tennessee). ~DMAN M., F. AND THIELE,E. (1972). "Laser-induced rate processes in gases: Dynamics, unimolecular decay, and scattered field," Phys. Rev. A 5,1355. ;ORCZYMSKI, W. (1953). Comparison of Climate of US and Europe (Polish Institute of Arts and Science in America, New York, 1945); also referenced as Fireman, E. L. (1953). "Measurement of the (n,HS)cross section in nitrogen and its relationship to the tritium produced in the atmosphere," Phys. Rev. 91, No. 4,922

96

/

REFERENCES

GRATHWOHL, G. (1972). Erzeugungund Freisetzung uon 7Yitiu.m durch Reactoren und Wiederaufbereitungsan~enund die wraussiehliche Belastung der Hydrosphare bis r u m J a h r 2WO. Report No. ND-19896 (Diplomarbeit, Institut fur Physikalsche (hundlagen der Reaktortechnik.University of Karlsruhe, Karlaruhe, West Germany). GRIFFITHS, J. P. (1966). Applied Climalologv, page 99 (Oxford University Press, Amer. House. London). GROSSMAN, L. N. AND HEGLAND.J. W. (1971). Tritium Disb-ibution in High Power Zucaloy Fwd Elements,Report No. GEAP-12205 (General Electric Cdmpany, &henectady, New York). GULPNUCLEAR SERVICES (1973). BarnweU Nuclear Fuel PLant Sqfety Analysis Report, Allied Gulf Nuclear Services, Report No. Docket-50-332 (National Technical Information Semce, Springfield, Virginia). HANEY,W. A., BROWN,D. J. AND R E ~ N A U E R A., E. (1962). FisBion Product 7Yitium in Separations Wasles and in the Groundwater, USAEC Report No. HW-74536 (Henford Atomic Producta Operation, Richland, Washington). HANNAHB, B. J. AND KERSHNER.C. J. (1972). Bibliography on Handling, Control and Monitoring of Tritium, Report No. MLM-1946 (Mound Laboratory, Miamisburg, Ohio). HARRISON,F. L.,KORANDA, J. J. AND TUCKER, J. S. (1971). ltitMtwn of Aquatic Animale in an Experintental Marine POOL,Report No. UCRL731 (Rev. 1)(Lawrence Radiation Laboratory, Livermore, California). HARTECK,P. (1954). 'The relative abundance of HT and HTO in the atmosphere," J. Chem. Phya 22, No. 10,1746. HATCH, F. T. AND MAZRIMAS, J. A. (1972). '%tiation of animals from tritiated water," Radiat. Res. 60,339. H ~ w s m s ,D. B. AND SCHMALTZ,B. L. (1965). Environment Tritiwn Studies a t the National Reactor Testing Station, USAEC Report No. IDO-12613 (Idaho Operations Office, Idaho Falls, Idaho). D. L (1971). 'Yielde of bitium during the fission@ of nuclides of interest HORROCKB, in the operation of nuclear power reactore" (Lae Vegee Tritium Symposium. September, 1971). page 30 in ZWiwn, Moghissi A. A. and Carter, M. W., Eds. (Messenger Graphics, Phoenix, Arizona). HORROCKB, D. L. AND WHITE, E. B. (1970). "Tritiiun yield in the thermal neutron fission of Nucl. Phys. A 151,66. HORTON, J. H. (1963).Fission Product Tritium at the Savannah Riwr PlanL, USAEC Report No. DPSPU-63-30-38B (Savannah River Laboratory, Aiken, South Carolina). HORTON, J. H. AND Ross, D. I. (1960). "Use of tritium from spent uranium fuel elements as a groundwater tracer," Soil Sci. 90, No. 5, 267. J. H., COREY,J. C. AND WALLACE, R. M. (1971). "Tritium loss from water HORTON, exposed to the atmosphere," Environ, Sci. Technol. 5, No. 14,338. Humnms, M.E. AND VAUGHN, B. E. (1965). "Skin contact transfer of tritium from brass," Health Phys. 11, 1047. IAEA (1967). International Atomic Energy Agency. Tritium and Other Environmental ~sotOpe8in the Hydrological Cycle, Technical Report Series No. 73-STI/DOC/10/73 (International Atomic Energy Agency, Vienna). ICRP (1959). International Commission on Radiological Protection, Recommendations of the International Commission on Radiological Protection, ICRP Publication 2 (Pergamon Prese, New York). ICRP (1969). International Commission on Radiological Protection, "News and comment," (Progress Report of the ICRP, Dunster, H. J., Ed.) Health Phyg 17,389. ICRP (1975). International Commission on Radiological Protection, Report of the Task

w,"

REFERENCES

/

97

Croup on Reference Man. ICRP Publication 23 (Pergamon Press, New York). IRISH,E. R. (1959). Description of Purez Plant Process, USAEC Report No. HW-60116 (Hanford Atomic Products Operation, Richland, Washington). ISRAEL,G. ET AL. (1963). "Seasonal variations of bomb-produced tritium in rain," J. Geophys. Res. 68,3771. JACOBS,D. G. (1968). Sources of Tritium and Its B e h i o r Upon Release to the Enuironment, Report No. TID-24635 (U.S. Atomic Energy Commission, Washington). JENSEN, R. J. (1975). Hydrogen Isotope Separation from Water (U.S. Patent office, Washington). JENSEN, R. J. AND LYMAN,J. L. (1974). Laser Induced Recovery of Deuterium o r Tritium from Water, Report No. LA-UR-74-429 ( h Alamos Scientific Laboratory, Los Alamos, New Mexico). JEPPSON,D. W. (1973). "Tritium effluentr, during zirconium alloy-clad fuel promasing," page 412 in Trihiun Control Technology, Report No. WASH-1269, Rhinehammer, T. B. and h b e r g e r , P. H., Eds. (U.S. Atomic Energy Commission, Washington). I. (1963). "Replacement and bonding conditions for JOERCENSEN, P. AND ROBENQV~~T, alkali ions and hydrogen in dioctahedral and trioctahedral micas," Norak Geol. Tidsskr. 41,497. E.P. (1966). "Effecta of tritiated thymidine on mortdity JOHNSON, H. A. AND CRONHITE, and tumor incidence in mice," Radiat. Res. 27,560. JONES, H. G. AND LAMBERT,B. E. (1964). Radiation Hazard to Workers Using Tritiated Luminous Compounds, Report No. CONF-448-16 (National Technical Information Service, Springfield, Virginia). JONES, J. R. (1965). "Rates of abstraction of hydrogen, deuterium, ahd tritium from acetone in alkaline media," T r a n s Faraday Soc. 61.95. JONES, W. M. (1963). Vapor Pressures of Tritium Oxide and Deuterium Oxide, Interpretation of the Isotope Effect, USAEC Report No. LADC-5905 (hAlamos Scientific Laboratory, L m Alamos,New Mexico). JORDAN,C. F., KORANDA, J . J., KLINE, J. R AND MARTIN,J . R. (1970). "Tritium movement in a tropical ecosystem," Bioscience 20,807. JORDAN, C. F., STEWART, M. L.AND KLINE,J. R. (1974). "Tritium movement in soils. The importance of exchange and high initial dispersion," Health Phys. 27,37. KABELE,T. J. (1972). "Tritium distribution in the FFTF," Trans. Am. Nucl. Soc. 15, No. 1, 79. KABELE,T. J. (1974). Parametric Study of the Tritium Distribution in the FFTF. Report No. H E D L T M E 76-6 (Hanford Engineering Development Laboratory, Richland, Washington). KAHN,B., BLANCHARD, R. L., BRINCK,W. L., KRIECER,H. L., KOLDE,H. E., AVERETT, W. J., GOLD,S., MARTIN,A. AND GELS,G. L. (1974). Radiological Surveillance Study a t the Haddam Neck PWR Nuckar Power Station, Report No. EPA-520/374-007 ( U S . Environmental Protection Agency, Washington). KANAZAWA, T.. KANAZAWA, K. AND BASSHAM, J. A. (1972). "Tritium incorporation in the metabolism of Chlorella pyrenoidosa," Environ. Sci. Technol. 6,638. KANDEL,R. J. (1964). "Methane-tritium system. 11. Kinetics of the exchange reaction," J. Chem. P h y s 41, No. 8, 2435. Ihm, M. ET AL. (1963). "A study in river engineering based on the results of field measurements of flow velocities with radioisotopes in the Sorachi River, Japan," p g e 89 in Proceedings of the Sympoeium on Radioisotopes in Hydrology, IAEA Report No. STI/PUB/71 (International Atomic Energy Agency, Vienna). U E , C. W. (1975). Personal communication. K m a , P. (1968). "Induction of recessive lethals by 'H-uridine and 'H-thymidine in

98

/

REFERENCES

Dromphilq" page 65 in -8 of a Panel on Biological Effectsof Trammutation and Decay of I n c o r p o d Radioisotopes, IAEA Report No. STI/PUB/183 (International Atomic Energy Agency, Vienna). K~COBRI. K. (1961). Natural Concentration of Krypton-86, Carbon-14,and Tritium in Recent Years,Report No. A/AC.82/G/L.693 (United Nation8 Sewetatiat, New York). K ~ C O B E ~K., AND T O M ~ U RY. A ,(1961). "Tritium and carbon-14 in the tree rhp," Bd. Chem. Soc. Jpn. 34.1738. R, VAN DEN HOCK,J . AND LAPONTAINE. A. (1971). "Transfer et incorpoKIRCHMANN, ration du tritium dans les constituanta de I'herbe et du lait, en conditions m h u e l l q " Health Phys. 21.61. J. J. (1965). "Preliminary studies of the persistence of tritium and "C in the KORANDA. Pacific proving ground." Health Phys. 11,1445. KORANDA, J. J. AND b n ~J. R , (1969). 'The persistence of radionuclides a t s i t e of nuclear detonations," page 159 in Biological Implications of the Nuclear Age, AEC Symposium Series No. 16, CONF 690303 (U.S. Atomic Energy Commission, Washington). J. J. AND M m m , J. R., (1973). "The movement of tritium in ecological KORANDA. syaterns," page 430 in Tritium, Moghii, A. A. and Carter, M. W., Eds. (Messenger Graphics, Phoenix, Arizona). KOUTS,H. AND LONG,J. (1971). "Tritium production in nuclear reactors," page 38 in Tritium, Moghissi, A. A. and Carter, M. W., Eds. (Messenger Graphics, Phoenix, Arizona). J., DMOWSRI,M.. PIABECKI, E., SOWINSKI,M. AND KROGULSKI, T., CHWA~ZCZEWSKA, RE, J. (1469). " E h k i o n of tight nuclei in thermal neutron fission of %,"Nucl. Phys. A 128,219. KRYMM,R. (1973). 'The world energy context," IAEA Bull. 16, No. 6. KULLEN,B. J., TREVORROW, L E. AND STEINDLER,M. J. (1976). Tritium and NobleGas Fission Products in the Nuclear Fuel Cycle. IZ. Fuel Repmessing Plants, Report No. ANL-8136 (Argome National Laboratory, Lemont, ULinois). KUMAR,R. (1974). Tritium Tramport in wz LMFBR, Report No. ANL-8089 (Argotme National Laboratory, Lemont, Illinois). L N G ,A. R. G. AND MASON,S. G. (1960). 'Tritium exchange between cellulose and water: Accessibility measurements and effects of cyclic drying," Can. J. Chem 38, 373.

LANCE,N. A. AND FORKER,G. M., EDS. (1961). Handbook of Ckmiaby, page 169 (McGraw-HiU Book Company, New York). P. H. (1962). "Tritium-hydrogen exchange in studies of LEACH,S. J. AND SPRINGELL, protein structure," Auat. J. Chem. 16. No. 2,350. LEE, E. K. C., TANG, Y. N. AND ROWLAND, F. S. (1964). 'The mechanism of recoil tritium reactions: Formations of labeled nlkenea from saturated hydrocarbons and halocarbone," J. Am. Chem. Soc. 86. No. 22.5038. L ~ E E. . K. C.. MILLER. G. AND ROWLAND, F. S. (1965). "Moderator effecta on recoil tritium reactions with methyl and methyl-d3 fluorides," J. Am. Chem. Soc. 8, No. 1, 190. LEGER,D., DIRIAN.G. AND ROTH,E. (1970). "Tritium extraction from heavy water in nuclear reactors," Energ. Nucl. Paris 12, 136. 0.I. (1957). "Harmful effects of the radioactivity from explosion8 of pure LEIPUNSKXI, hydrogen b o m b and ordinary atomic bombs," At. Energ. 8,530. LEONARD, J. H. AND KUECK,J. J. (1972). "Cost potential for reducing tritium activity in aqueous efluente," Trans. Am. Nucl. Soc. 16,653. L E m W. B. AND FOBTER, J. S. (1970). Canadian Operating Experience with Heavy

REFERENCES

/

99

Water Power Reactors, Report No. AECL-3669 (Atomic Energy of Canada Limited, Chalk River, Ontario). LIBBY,W. F. (1943). "Vibrational frequencies of the isotopic water molecules; Equilibria with the isotopic hydrogem," J. Chem. Phys. 11, No. 3,101. LIBBY,W. F. (1946). "Atmospheric helium-3 and radiocarbon from cosmic radiation," Phys. Rev. 69,671. LIBBY,W. F. (1947). "Errata: Vibrational frequencies of the isotopic water molecules; Equilibria with the isotopic hydrogens," J. Chem. Phys. 15, No. 5, 339. LIBBY,W. F. (1953). "Tritium in nature," Phys. Rev. 91, No. 2,442. LIBBY,W. F. (1958). "Radioactive fallout," Proc. N a t Acad. Sci. USA 44,800. -BY, W. F. (1963). "Moratorium tritium geophysics," J. Geophys. Res. 68.4485. LIN, K. H. (1972). Tnhiun Enrichment by Isotope Separation Techniques, Report No. ORNLTM-3976 (Oak Ridge National Laboratory. Oak Ridge, Tennessee). LMFBR (1974). LMFBR Program Environmental Statement, Report No. WASH-1535, pages 4.2-49 ( U S . Atomic Energy Commission, Washington). D. D. (1971). ''Tritium in pressurized water reactors," LOCANTE, J. AND MALINOWSKI, page 45 in Tritiwn, Moghissi, A. A. and Carter, M. W., Eds. (Messenger Graphics, Phoenix, Arizona). LOMENICE,T. F., JACOBS,D. G. AND STRUXNESB, E. G. (1967). "The behavior of strontium-90 and cesium-137 in seepage pits a t ORNL," Health Phys. 13, No. 8,897. LONGSWORTH, L. G. (1960). "The mutual diffusion of light and heavy water," J. Phys. Chem. 64,1914. MACETA,L., FERBER, G. J. AND HEFFTER,J. L. (1973). Local and World- Wide Pollutant Concentrations a d Population Exposures from a Continuous Point Source (Air Resources Laboratory, National Oceanic and Atmospheric Administration, Silver Spring, Maryland). MALONEY, J. O., QUINN,G. F., RAY, H. S., EIDINOPF,M. L., JORIS, G. G., TAYLOR,E., TAYU)R, H. S. AND UREY,H. C. (1955). Production of H e a y Water (McGraw Hill Book Company, New York). MARSHALL,M. AND SCOBIE,J. (1966). "The emission of alpha particles and tritons in the thermal neutron fission of =U," Phys. Lett. 23, No. 10, 583. ~ R T E RW. , C. (1974). Environmental Effects of a Tritiwn Gas R e l e u from the Savannah River Plant on May 2, 1974, Report No. DP-1369 ( S a v a ~ a hRiver Operations. Aiken, South Carolina). MARTIN,J. Ft. AND KORANDA, J. J. (1971). "Distribution, residence time, and inventory of tritium in Sadan Center eje-cta," Nucl. Technol. 11,459. MARTIN,J. R AND KORANDA, J. J. (1972). "Biological half-life studies of tritium m chronically exposed kangaroo rats," Radiat. Fks.50,426. C. F., KORANDA, J. J. AND KLINE,J. R. (1970). "Radioecological MARTIN,J. Ft., JORDAN, studies of tritium movement in a tropical rain forest," page 422 in Proceedings of the American Nuclear Society Symposium on Engineering with Nuclear Explosives, January, 1970, &port No. CONF-700101 (National Technical Information Service, Springfield, Virginia). M c C a u , D. W., D O U G L D. ~ , C. AND ANDERSON, E. W. (1959). "Diffusion in liquids." J. Chem. Phys. 31, No. 6, 1656. MCLAREN,J . A. (1962). Electrochemistry, Chemical Technology Division Quarterly Progress Report for Period Ending November 29, 1952, Report No. ORNL-1448 (Oak Ridge National Laboratory, Oak Ridge, Tennessee). MELEHAN, J . B. (1970). Tritium Content of a Yankee Core V. Zircaloy-Clad UOz Fuel Rod. Report No. EIT-70-208 (Westinghouse Electric Corporation, Pittsburgh, Pennsylvania).

100

/

REFERENCES

M E R R ~W. , F. (1962). "Routine measurements of groundwater velocity wing %S," Health Phys. 8. 185. MERBHM, E. A. (1975). "Monaanto/Mound Laboratory tritium effluent control systems,"page 825 in Proceedings of the Third Environmental Protection Conference, Chicago, September 23-26, 1975, Report No. ERDA-92 (U.S. Energy Research and Development Adminiitration, Washington). MEWISSEN,D. J. AND RUST.J. H.(1973). "Tumor incidence in C57 black/6 mice treated with tritiated thymidine," page 252 in Tritium, Moghissi, A. A. and Carter, M. W., Eds. (Messenger Graphics, Phoenix, Arizona). MEWISSEN,D. J. AND RUST,J. H. (1975). Personal communication. MEWISSEN,D. J., FUREDI,M. A N D RUST, J. H. (1972). "Activite m i d d l e du tritium apres administration de thymidine tritiee chez la sowis," C. R. Seances SOC.Biol. Paris 166.465. , UGARTE,A. A N D RUST,J. H.(1975). I l l ~ ~ r p ~ l ' aof ti~n MEWISSEN,D. J., ~ R E D IM., Tritium from Tritiated Water: Comparison with Tritiated Thymidine, Uridine, o r Leucine, December 12-16, 1975 (Presented a t Second World Congress on Water Resources,New Delhi, India). MEWISSEN,D. J., FUREDI,M. AND RUST,J. H. (1977). "Comparative incorporation of tritium from tritiated water versus tritiated thymidine, uridine, or leucine," Curr. Top. Radiat. Res. 12.225. MICHEL,R. L. (1976). "Tritium inventories of the world oceans and their implications." Nature 283,103. MILES, C. C., WEXLER,S. AND EBERSOLE,E. R. (1974). Tritium Retention in EBR-I1 Irradiated Boron Carbide, Report No. ANL-8107 (Argonne National Laboratory, Lemont, Illinois). J. MILLS, R. G. (1973). "Self-diffusion in normal and heavy water in the range 1-45',' Phys. Chem. 77. No. 5,685. MrNDEq W. (1969). "Internal contamination with tritium ( t m d a t e d title)," Strahlentherapie 137,600. MIBKEL,J. A. (1964). "Characteristics of radioactivity produced by nuclear explosives," page 153 in Proceedings of the Third Plowshare Symposium, Engineering with Nuclear Explosives, April 21-23, 1964 (University of California, Lawrence Radiation Laboratory and Sen Francisco Operations Office, Livermore, California). MISKEL,J. A. (1971). "Production of tritium by nuclear weapons," page 79 in Tritium, Moghissi. A. A. and Carter, M. W., Eds. (Messenger Graphics, Phoenix, Arizona). Mocnrssl, A. A. AND CARTER, M. W., E m . (1973). Tritium (Messenger Graphics, Phoenix,Arizona). R (1971). "Long-term evaluation of MOGHISSI,A. A., CARTER,M. W. AND LIEBERMAN, the biological half-life of tritium," Health Phys. 21, 57. (An error in this paper was corrected by a subsequent publication: Moghiasi, A. A., Carter, M. W. and Bretthauer, E. W. (1972). "Further studies on the long-term evaluation of the biological half-life of tritium," Health Phys. 23, 805.) MORTON,R. J., ED. (1961). Status Report No. I o n Clinch River Study, Report No. ORNL3119 (OakRidge National Laboratory, Oak Ridge, Tennessee). MORTON,R. J., ED. (1962). Status Report No. 2 on Clinch Riwr Study, Report No. ORNL3M2 (OakRidge National Laboratory, Oak Ridge, Tennessee). MORTON,R. J., ED. (1963). Status Report No. 4 o n Clinch Rioer Study, Report No. ORNL3409 (OakRidge National Laboratory, Oak Ridge, Tennessee). E. W., CARR,W. H. AND GRAY,J. H., I11 (1974). Fission Product Gas MURBACH, Retention Process and Equipmed Design Study, Report No. ORNL-TM-4560 (Oak Ridge National Laboratory, Oak Ridge, Tennessee).

REFERENCES

/

101

MUSCRAVE, B. C. (1974). Tritium Distribution in the Nuclear Industry. The Requirements for Control Strategies, Report No. ICP-1041 (Allied Chemical Corporation, National Reactor Testing Station, Idaho Falls, Idaho). R. D. (1963a). "Diffusion of tritiated water in agar gel NAXAYAMA, F. S. AND JACKSON, and water," J. Phys. Chem. 67, No. 4,932. R. D. (1963b). "Diffusion of tritiated water in soh," NAKAYAMA, F. S. AND JACKSON, Soil Sci. Soc. Am., b. 27, No. 3, 255. NMH, J. B. (1965). The Production of Tritium-Labeled Methane and Ethane in the CH4-Tz System, Report No. UCRL-16009 (University of California at Berkeley, Berkeley. California). NCRP (1954). National Committee on Radiation Protection and Measurements, Permissible Dose from External Sources of Ionizing Radiation, NCRP Report No. 17. published as National Bureau of Standards Handbook No. 59 (National Council on Radiation Protection and Measurements, Washington). NCRP (1959). National Committee on Radiation Protection and Measurements, M w imwn Permissible Body Burdens and Maximum Permissible Concentrations of Radionuclides in Air and in Water for Occupational Exposwe. NCRP Report No. 22, published as National Bureau of Standards Handbook 69 (National Council on Radiation Protection and Measurements, Washington). NCRP (1971). National Council on Radiation Protection and Measurements, Basic Radiation Protection Criteria, NCRP Report No. 39 (National Council on Radiation Protection and Measurements, Washington). NCRP (1975). National Council on Radiation Protection and Measurements, Kmton85 in the Atmosphere-Accumulation, Biological Significance, and Control Technology, NCRP Report No. 44 (National Council on Radiation Protection and Measurements, Washington). NCRP (1979). National Council on Radiation Protection and Meawuements, Tritium and Other Radionuclide Labeled Organic Compounds I n c o p r a t e d in Genetic Material, NCRP Report No. 63 (National Couneil on Radiation Pmtection and Measurementrt, Washington). NIR, A. (1964). "On the interpretation of tritium 'age' measurements of groundwater," J. Geophys. Res. 69,2589. R E. AND FLAMM, E. J. (1966). "Natural NIR, A., KRUGER,S. T.. LINGENFELTER, tritium," Rev. Geophys. 4, No. 4, 441. NOAA (1976). National Oceanic and Atmospheric Administration. U.S. Standard Atmosphere, 1976, Report No. NOAA-S/T76-1562 (National Oceanic and Atmospheric Administration, Boulder, Colorado). NOBLES,R A. (1962). "Long-range particles Gom nuclear fission," Phys. Rev. B 126, No. 4, 1508. NORTH,E. D. AND BOOTH,R. L. (1973). Fission Product Gas Retention Study, Final Report, Report No. ORNL-TM-4409(Nuclear Fuel Services,West Valley, New Yo*). (1962). Nuclear Fwl Services Safety Analysis Report, Report NUCLEAR FUELSERVICES No. Docket-50-201 (National Technical Information Service, Springfield, Virginia). OLIVIER,J. P. (1976)."Sea-disposal practices for packaged radioactive waste," page 667 in h c e e d i n g s of the International Symposium on the Management of Wastes from the L WR Fuel Cycle (National Technical Information Service, Springfield, Virginia). ORM, (1970). Oak Ridge National Laboratory, Siting of Fuel Reprocessing Plants and Waste Management Facilities, Oak Ridge National Laboratory Staff Report No. ORNL-4451 (Oak Ridge National Laboratory, Oak Ridge, T e ~ e s s e e ) . ORNL (1973). Oak Ridge National Laboratory, Monitoring Control and Disposal of Tritium, A Selected Bibliography, Report No. TID-3337 (Oak Ridge National Lab-

102

/

REFERENCES

oratory, Technical Information Center, Oak Ridge, Tennessee). OSBORNE, R. V. (1966). "Absorption of tritiated water vapour by people," Health Phys. 12, 1527. OSBORNE, R. V. (1972). "Permissible levels of tritium in man and the environment." Radiat. Res. 60, 197. PAUXER.F. L. (1964). "Movement of radionuclides in the Clinch River." page 78 in Proceedings of the Third Sanitary Engineering Conference, Nasiwille, Tennessee, May 25, 1964, Report No. CONF-772 (National Technical Information Service, Springfield, Virginia). PARKER,F. L. ET AL. (1966). "Dilution, diepemion and mass transport of radionuclides in the Clinch and Tenneesee Rivew" page 33 in Proceedings of the Symposium on Disposal of Radioactiw Wastes into Seas, Oceans, and Surfaee Waters, IAEA Report No. STI/PUB/126 (International Atomic Energy Agency, Vienna). PARSONS, P. J. (1963). TheMouemenl of Trih'um from Ihe Chalk Riwr Liquid Disposal Area, Report No. CRER-1146 (Atomic Energy of Canada Limited. Chalk River, Ontario). R. G. (1968). Radiation Dose From Non-Exchangeable 'Ritium in Rats After PATZER, Tritium Oxide Ingestion, Doctoral Thesis (University of Michigan, Ann Arbor. Michigan). PATZER,R. G., MOCHISBI,A. A. AND MCNELIS.D. N. (1974). Accumulation of llZitiwn in Various Species of Fish Reared in ZYitiated Water, Report No. EPA 680/4-74001 (National Environmental Research Center, Las Vegas, Nevada). PAUTROT, P. AND ARNAULD, J. P. (1975). "The tritium extraction plant of the Laue Langevin Institute," First European Nuclear Conference, Paris, April 21-25, 1975, Trans.Am. Nucl. Soc. 20,202. PELTO,R. H., WIERDAK, C. J. AND MARONI, V. A. (1975). "Tritium trapping kinetics in inert gas streams," page 35 in Liquid Metals Chemisby and Tritium Control Technology Annual Report, Report No. ANL-75-50 (Argonne National Laboratory, Lemont, Illinois). PINSON, E. A. (1951). The Body Absorption, Distribution, and Excretion of Tritium in Man and Animals, USAEC Report No. LA-1218 (Los Alamos Scientific Laboratory, Los Alamas, New Mexico). W.H.(1957). "Physiology and toxicology of tritium in PINSON,E. A. AND LANDHAM, man," J. AppL Physiol. 10, 108. PRICE,A. H. (1958). "Vapour presure of tritiated water," Nature 181, No. 4604,262. P u e ~ r cSERVICE COMPANY OP COLORADO (1964). Fort St. Vrain Final Safety Analysis Report, Public Service Company of Colorado, Report No. Docket-50-267 (National Technical Information Service, Springfield, Virginia). RANCHO SECOPSAR (1971).Rancho Sen, PWR Preliminary Safety Analysis, Appendix 11B, Report No. Docket 50312.24 (National Technical Information Service, Springfield, Virginia). RANKAMA, K. A N D SAHAMA, T. G.(1949).Geochemistry, page 316 (Universityof Chicago Preas, Chicago). RAY,J. W. (1968). "Tritium in power reactors," React. Fuel-Process. Technol. 12, No. 1, 19. REICHERT, S. 0. (1962). "Radionuclides in groundwater at the Savannah River Plant Waste Disposal Facilities," J. Geophys. Res. 67,4363. REINIG,W. C. AND SANDERS, S. M. (1967). Assessment of Tritium in Man, Report No. CONF-670521-12 (National Technical Information Service, Springfield, Virginia). RENNE,D. S., SANDUSKY, W. F. A N D DANA,M. T. (1975). An Analysis of Tritium Releases to the Atmosphere by a CTR, Report No. BNWL-SA-5481 (Presented a t the 3rd ERDA Environmental Protection Conference in Chicago, Illinois-September

REFERENCES

/

103

23-26,1975, Battelle Pacific Northwest Laboratories, Richland, Washington). UINEHAMMER, T. B. AND LAMBERCER, P. H. (1973). Tritiwn Control Technology, Report No. WASH-1269 (Mound Laboratory, U.S. Atomic Energy Commission, Washington). ~ I N E H A M M E R , T. B. AND MERSHAD, E. A. (1974). "Techniques and facilities for handling and packaging tritiated liquid wastes for burial," page 1067 in Proceedings of the 2nd AEC Environmental Protection Conference, Albuguerque, New Mexico, April 1619, 1974, Report No. WASH-1332(74), CONF-740405 (National Technical Information Service, Springfield, Virginia). ~~INEHAMM T.E B. R , ET AL. (1973). Fusion Power: An Assessment of Ultimate Potential, Report No. WASH-1239 (Division of Controlled Thermonuclear Research, U.S. Atomic Energy Commission, Washington). ~ B N I K AS.RA. , AND PUPEZIN, J. D. (1974). "Poesibilities of tritium removal from waste waters of pressurized water reactors and fuel reproceasing plants," page 926 in Proceedings of the Thirteenth Air Cleaning Conference, Sun Francisco, August 12-15, 1974, Report No. CONF-740807 (National Technical Information Service, Springfield, Virginia). J. B. (1974). N i t 0 1 Modeling of Radioactive and Chemical Waste ROBERTSON, Transport in the Snake River Plain Aquifer a t the National Reactor Testing Station, Idaho, USGS Open-File Report No. IDO-22054 (Idaho Operations Office, Idaho Falls, Idaho). ROESCH,W. C. (1950). P-10 Chemical Equilibriu, USAEC Report No. HW-17318 (Hanford Atomic Products Operation, Richland, Washington). ROULIN, J. (1964). "Contamination par le tritium a parter d l'atrnosphere," Seminair sur la Protection Contre les Dangers du Tritiwn; le Vesinet, April 1618, 1964 (Cited by Grathwohl, 1972). RUBXNI, J. R., CRONKITE, E. P. AND REIDNER, T. M. (1960). "The metabolism and fate of tritiated thymidine in man," J. Clin. Invest. 39,909. RUBINI,J . R., KELLER,S., WOOD,L. AND CRONKITE, E. P. (1961). "Incorporation of tritiated thymidine into DNA after oral administration," Proc. Soc. Exp. Biol. Med. 106, 49. RUNION, T. C. (1970). Testimony Before Joint Committee on Atomic Energy, Ninety First ConSecond Sesaion, Hearings on Environmental Effcta of Producing Electric Pocuer, page 1704, Vol. 1, Part 2 (U.S. Congress, Washington). SANDERS, S. M. AND REINIC,W. C. (1967)."Assessment of tritium in man," page 534 in Proceedings of the Symposium on Diagnosis and Treatment of Deposited Radionuclides, Report No. CONF-670521 (National Technical Information Service, Springfield, Virginia). G. (1973). World Distribution of Environmental Tritium, ~CHELL, W. R. A N D SAUWY, Report Nos. IAEA-SM-181/34, CONF-731110-3, RLO-2225-T18-6 (International Atomic Energy Agency, Vienna). ~ H N E Z H., , ~ E RM., AND MERZ,E. (1974). Tritium in Reprocessing Plunta. A Study of the Inventory, Behavior, and the Possibilities of Sepamtion of the Tritium Isotope, Report No. GERHTR-139 (originally JUL-1099-CT) (National Technical Information Service, Springfield, Virginia). ~ C H W I B AJ.C(1969). H, "The question of defining the highest permissible values for the release of tritium-containing waste water," page 43 in Radiation Protection Problems in the Rekcure and Incorporation of Radioactive Materials, Report No. CONF690510, Hacke, J. and Jacobi, W., Eds. (Hahn-Meitner-Institut fuer Kernforschung, Berlin, West Germany). ~EELENTAC, W. (1971). '"ho cases of tritium fatality," page 267 in Tritium, Moghissi, A. A. and Carter, M. W., Eds. (Messenger Graphics, Phoenix, Arizona).

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/

REFERENCES

SECHAL. B. R. AND REMPERT,R. H. (1971). "Tritium production in fast reactors containing B4C," Trans Am. Nucl. Soc. 14.779. SEPAU. 0.AND MASON.S. G. (1960). "Vaporfiquid partition of tritium in tritiated water," C a n J. Chem. 23.2024. SHORES, R. D. AND MOBER.H. C. (1961). "Reactions of tritium atoms with frozen hydrocarbons," J. Phys. Chem. 66,570. SILINI, G., MBTAUI,P. AND VULPIB,G. (1973). Rodioaetivi~of Trdiwn in Manun&, Report NO. EUR-M)33e (Commissionof the European Communities, Brussels). SIRl. W. AND EVERS. J. (1962). "Tritium exchange in biological systems," page 71 in Ditium in the Physical and Bwlogical Sciences, IAEA Report No. STI/PUB/39 (International Atomic Energy Agency. Vienna). SKAGIT NUCLEAR POWERPROJECT (1975). Environmental Report, SKAGIT (Washington) Nuclear Power Pro~ect,Report No. DOCKET STN-50522 (National Technical Information S e ~ c eSpringfield, , V i a ) . SLADE, D. H., ED. (1968).Meteorology and Atomic Energy-1968, USAEC Report No. TID-24190 (National Technical Information Service, Springfield. Virginia). SLOTH,E. N., HORROCKB, D. L., BOYCE,E. J. AND STUDIER,M. H. (1962). "Tritium in the thennal neutron-fmion of uranium-235," J. Inorg. Nucl. Chem. 24,337. SMITH,H.A. AND M H , K. R. (1965). "Determination of the separation factor for the vaporization of mixtures of protium and tritium oxides," J. Phys. Chem. 67, No. 4, 920. SMITH,J. M. A N D GILBERT, R. S. (1971). "Tritium experience in boiling water reactors," Trans. Am. Nucl. Soc. 14, No. 1,160. SMIT~I, T. E. A N D TAYLOR,R. T. (1969).Incorporation of Tritium from Triliuted Water into Carbohydrate, Lipida, and Nucleic Acids, Report No. UCRL-60781 (Lawrence Radiation Laboratory, Livermore, California). SNYDER, W. S., FIBH, B. R., BERNARD, S. R., FORD,M. R AND MUIR,J. R. (1968). "Urinary excretion of tritium following exposure of man to HTO-A two exponential model," Phya. Med. Biol. 13,547. A. (1965). "Reactions of tritium recoil atoms in liquid organic mixtures," Souowspage 255 in Proceedings of a Symposium on Chemical Effecta of Nuclear Transformations, IAEA Report No. STI/PUB/91 (International Atomic Energy Agency, Vienna). STEAD,F. W. (1963). "Tritium distribution in groundwater around large underground fusion explosions," Science 142, No. 3596,1163. STEINDLER, M. AND KULLEN,B. (1976). "heparation of caiketed radionuclide wastes for storage," page 6.1 in In Contmlling Airborne EfIZuents from Fuel Cycle Plants (American Nuclear Society, Hinsdale, Illinois). Sum, H. E. (1969). 'Tn'tium geophysics as an international research project," Science 168,1405. SVERDRUP, H. U., JOHNSON,M. W. AND PLEMING,Ft. H. (1942). The Oceans, Their Physics, Chemiaby, and General Biology (Prentice-Hall, Inc., New York). SWAIN,C. G. AND KRESCE,A. J. (1958). "Exchange reactiom between hydrogen gas and h y b x y l g r o u p A convenient preparation of tritium-labeled water," J. Am. Chem Soc. 80, No. 19,5281. SWAIN. C. G. AND SCHMD,. L J. (1958).A RelaCion Between Prolh-fidium and ProtiwE-Deuterium Isotope Effects, USAEC Report No. AECU-3698 (Massachusetts Institute of Technology, Cambridge, Massachusetts). SYXES,G.H., B ~ M A N H. N K., , KICER,E. O., JACOB=,W. J. (1973). "Tritium in fuel recovery planta (chemicalplants)," page 424 in Tritium Control Techlogy, USAEC Report No. WASH-1269, Rhinehammer, T. B. and Lamberger, P. B., Eds. (U.S. Atomic Energy Commission, Washington). TAYLOR, G. R AND PETERS,F. E. (1972). "Tritium transport in LMFBR's," 'Prans. Am.

REFERENCES

/

105

NucL Soc. 15, No. 1,431. M. S., WEAVER, C. L. AND WIEDER.S. (1971)."Dose assessment of ionizing TERPILAK, radiation exposure to the population," Radiol. Health Data Rep. U,No. 4, 171. THEIS, C. V. (1961). "Notes on dispersion in fluid flow by geologic features," page 166 in Second Ground Disposal of Radioactive Wastes Conference. Held a t Atomic Energy of Canada Limited, Chalk Riuer, Canada, September 26-29, 1961, USAEC Report No. TID-7628 (National Technical Information Service, Springfield, Virginia). THEIS, C. V. (1963). "Hydrologic phenomena affecting the use of tracers in timing groundwater flow," page 193 in Proceedings of a Symposium on Radioisotopes in Hydrology, IAEA Report No. STI/PUB/71 (International Atomic Energy Agency, Vienna). THCMPSON, R. C. (1952). "Studies of metabolic turnover with tritium as a tracer: I. Gross studieson the mouse," J. Biol. Chem. 197.81. R. C. (1953). "Studies of metabolic turnover with tritium ae a tracer: 11. THOMPSON, Gross studies on the mouse," J. BioL Chem. 200,731. THOMPSON,R. C. (1971). Review of Laboratory Animal Experiments Related to the Radiobiology of Tritium, USAEC Report No. BNWLSA-3739 (Battelle Pacific Northwest Laboratory, Richland, Washington). THOMPSON, R. C. AND BALLOW.J. E. (1954). "Studies of metabolic turnover with tritium as a tracer:IV. Metabolically inert lipid and protein hctione from the rat," J. Biol. Chem. 208,883. THOMP~ON, S. 0. AND SCHAEPFER, 0. A. (1955). "Radiation induced equilibrium of hydrogendeuterium mixturee," J. Chem. Phys. 23, No. 4,759. TREYORROW, L. E. AND WARNER,D. L. (1975). "Storage and dispoeal of tritium," page 21 in Chemical and Engineering Division Wuste Management Program Quarterly Report J ~ u a r y - M a r c h1975. , Report No. ANG75-13 ( A r g m e National Laboratory, Lemont, Illinois). L. E., KULLEN,B. J., JARRY,R. L. AND STEMDLER, M. J. (1974). Tritium TREVORROW, and Noble-Gas h i o n M u d s in the Nuclear Fuel Cycle. I. Reactors, Report NO. ANL-8102 ( A r g o ~ National e Laboratory, Lemont, Ulinoia). TREVORROW, L. E., WARNER. D. L AND STEINDLER, M. (1977). Co~iderations Affecting Deep-Well Disposal of Tritiwn-Bearing Low-LevelAqueous Waste frwn Nuclear Fuel Reprocessing Plants, Report No. ANL-76-76 (Argonne National Laboratory, Argonne, Illinois). UNITEDSTATESGEOLOGICAL SURVEY (1970). "Estimeted world water supply and budget," Table 2-3 in The Water Encyclopediq Todd, D. K.. Ed. (Water M o m t i o n Center Inc., Port Washington. New York). UNSCEAR (1977). United Nations Scientific Committee on the EEects of Atomic Radiation, 1977 Report to the General Assembly, Sources and Effects of Ionizing Radirrlion, U.N.E.77.IXl (United Nations, New York). USAEC (1972a). U.S. Atomic Energy Commission, Environmental Swvey of the NUclear Fuel Cyck, Chapter F, Irradiated Fuel Reprocessing, Report No. WASH-1337 (USAEC Diredorate of Licensing, U.S. Atomic Energy Commission, Washington). USAEC (1972b). US. Atomic Energy Commission, An Evaluation of the M o k n Salt Breeder Reactor, Report No. WASH-1222 (U.S. Atomic Energy Commission, Washington). USAEC (19731). U.S. Atomic Energy Commission, The Sofety of Nuckar Power Reactors (Light-Water-Cooled) and Relaled Facilities, Report No. WASH-1250 (US. Atomic Energy Commission, Washington). USAEC (1973b). U.S. Atomic Energy Cornmiesion, Final Enuironmental Statement Concerning Proposed Rule Making Action: Numerical Guides for Design Objectives and Limiting Conditions for Operation to Meet the Criterion "As Low as Practicabk" for Radioactive Materiul in Light-Water-Cooled Nuckar Power Reactor Ef-

106

/

REFERENCES

fluents, Report No. WASH-12% (Directorate of Regulatory Standards, U.S. Atomic Energy Commission, Washington). USAEC (19733. U.S. Atomic Energy Commission, Tritium Control Technology, Report No. WASH-1269, Rhinehammer, T . B. and Lamberger, P. H., Eds. (U.S. Atomic Energy Commission, Washington). USAEC (1973d). U.S. Atomic Energy Commission, Fusion Powec An Assessment of Ultimate Potential, Report No. WASH-1239 (U.S. Atomic Energy Commission, Washington). USAEC (1974a). U.S. Atomic Energy Commission, N u c k a r Power Growth 1974-2000, Report No. WASH-1139 (Office of Planning and Analysis, U.S. Atomic Energy Conunission, Washington). USAEC (1974b). U.S. Atomic Energy Commission, Proposed Final Environmental Statement Liquid Metal Fast Breeder Reactor Program, Vol. 2, page 4.2-36, Report No. WASH-1535 (US. Atomic Energy Commission, Washington). USERDA (1975). U.S. Energy Research and Development Administration, Final Environmental Statement, Waste Management Operations, Hanford Reservation, Richland, Washington, Vols. 1and 2, Report No. ERDA-1538 (U.S. Energy Research and Development Administration, Washington). USERDA (1976). U.S. Energy Research and Development Administration, Alternatwes for Managing Wastes from Reactors a n d Post-Fission Operations in the L WR Fuel Cycle, Vols. 1 and 2, Report No. ERDA-76-43 (U.S. Energy Research and Development Administration, Washington and Battelle Pacific Northwest Laboratories, Richland, Washington). VARSHAVSKII, Y. M. (1962). "General rules governing thermodynamic isotope effects in tritium-protium exchange," page 170 in Proceedings of a Symposium on Tritium in the Physical a n d Biological Sciences, Vol. I, IAEA Report No. STI/PUB/39 (International Atomic Energy Agency, Vienna). VENNART,J. (1968). "The quality factor for low-energy p-emitters," Health Phys. 14. 541. VENNART,J. (1969). "Radiotoxicity of tritium and "C compounds," Health Phys. 16. 429. VERNIANI,F. (1966). "The total mass of the earth's atmosphere," J. Geophys. Res. 71, 385.

VOGEL,J. C. AND EHHALT,D. (1963). "The use of carbon isotopes in groundwater studies," page 383 in Proceedings of a Symposium on Radioisotopes in Hydrology, IAEA Report No. STI/PUB/71 (International Atomic Energy Agency, Vienna). VON BUTTLAR,H. (1958). "Investigating groundwater by analysis of atmospheric tritium," J. Am. Water Works Assoc. 50, 1533. I. A., NI~ITIN,A. M. VOROBIEV,A. A., GRATCHEV, V. T., KOMAR,A. P., KONDUROV, AND S E L I V E R ~ D. V , M. (1969a). "Yield of light nuclei formed in the fission of by thermal neutrons," Sov. At. Energy 1969,713 (translated h m At. Energ. 27, No. 1, 31). D. M., GRATCHEV, V. T., KONDUROV, I. A., NIKITIN, VOROBIEV,A. A, SELIVERSTOV, A. M., YEGOROV, A. I. AND ZALITE,Yu. K. (1969b). "Light nuclei from Z53Uneutron h i o n , " Phys. Lett. B 30, No. 5, 332. VOROBIEV, A. A.. S E L N E ~ VD., M., GRATCHEV, V. T., KONDUROV, I. A,, NIKITIN. A. M., SMIRNOV, N. N. A N D ZALITE,Yu. K. (1972). "Light nuclei from %U neutron h i o n , " Phys. Lett. B 40, No 1, 102. I. A., MIROSCHNICHENKO, Yu. A., VOROBIEV,A. A., GRATCHEV, V. T., KONDUROV, NIKITIN,A. M., SELIVERSTOV, D. M. AND SMLRNOV, N. N. (1974). 'Ternary fission of "VUand ""Am by neutrons," Yad. Fiz. 20, 461 (translated in Sov. J. Nucl. Phys. 20, No. 3, 248). WALTON,A., FISHER, E. L. AND KREY,P. W. (1962). Studies of Nuckar Debris in

REFERENCES

/

107

Precipitation, USAEC Report No. NYO-9532 (US. Atomic Energy Commission, New York Operationa Office. New York). C. V. AND EDELMAN, I. S. (1953). "Self-diffusion and structure WANG,J . H..ROBINSON, of liquid water, 111. Measurement of the self-diffusionof liquid water with Hz, H3, and 0'" tracem," J . Am. Chem. Soc. 75, No. 2,466. WESTINGHOUSE ELECTRICCOMPANY (1974a). Westinghouse Nuclear Energy System, Reference Safety Analysis Report, Report No. RESAR-41. Docket-STN-50480-1 (National Technical Information Service, Springfield, Virginia). WESTINGHOUSE ELECTRICCOMPANY (1974b). Sowce Term Data for Westinghouse Pressurized Water Reactors, Report No. WCAP-8253 (Westinghouse Electric Company, Pittsburgh, Pennsylvania). WEXLER, S. (1963). "On the mechanism of the isotopic exchange of tritium with methane," J. Am. Chem. Soc. 85, No. 3,272. R. D. (1975). Deuterium WAITAEER,T. J., MORREY, J. R., BURGER,L. L. AND SCHEELE, and Tritium Sepamtion in Water by Selective Moleculw Excitation, Report No. BNWGB-432 (Battelle Pacific Northwest Laboratories, Richland, Washington). WULIAM~ON, H. E.AND DITMORE,D. C. (1970). Current State of Knowledge of High Perfonncurce BWR Zircaloy Clad U02Fuel, Report No. NEDO-10173 (General Electric Corp., Atomic Power Equipment Department, San Jose, California). WILSON, R. L., LEE, J. Y. AND STXENS, R (1970). "Radwaste design for no plantoriginated radioactive-liquid discharge," Trans. Am. NucL Soc. 13,405. K. E. (1957). 'Tritium labeling by exposure of organic compounds to tritium WILZBACH, gas," J. Am. Chem. Soc. 79, No. 4, 1013. WOLMANG, R ETAL. (1955). "Production of radioactive compounds with recoil tritons," Science 121, 715. H. Q. (1970). The Biological Effects of Tritium,Report No. HASG229 WOODARD, (Health and Safety Laboratory, U.S. Atomic Energy Commission, New York). WOODS, F. W. AND (YNEAL,D. (1966). 'l"ritiated water as a tool for ecological field studies," Science 147, 148. WOOLP,L. A. (1976). "Tracer diffusion of tritiated water (THO) in ordinary water ( H a ) under preawre," J. Chern. Soc. London 71, No. 4,784. WUST,G. (1954). " k t z m a s s i g e wechsalbeziehungen zwischen ozean und atmosphare in den zonalen verteilunger von oberflachensalzgehalt, verdunstung und niederschlag," Arch. Meteor01 Geophys. Bioklimatol. Ser. A 7,305. YANG,J. Y. AND GEVANTMAN, L. H. (1960). Tritium-fl-Radiafion-Induced-IsoLopk Exchange in the T r H B System, Report No. USNRDLTR-471 (Naval Radiological Defense Laboratory. San h c i e c o , California). L. H. (1964). "Tritium beta-radiation-induced isotopic YANG,J. Y. AND GEVANTMAN, exchange with water vapor," J. Phys. Chem. 68, No. 11,3115. YANG,K. AND GANT,P. L. (1962). "Reactions initiated by beta decay of tritium. IV. Decay and beta labeling," J. Phys. Chem. 66, No. 9, 1619. YARBRO,0. O., JR. (1974). Supplementary Testimony Related to Fission Product Source Tenns and Ef/lwnts from the Barnwell Nuclear Fuel Reprocessing Plant, Report No. Docket 50-332 (Director of Regulation, U.S. Atomic Energy Commission, Washington). YARBRO, 0 . O., JR., HARRINGTON, F. E. AND JOY,D. S. (1974). Efluent Control in Fuel Reprocessing Plants, Report No. ORNL-TM-3899 (Oak Ridge National Laboratory, Oak Ridge, Tennessee). ZIMMERMAN, U., MUNNICH, K. 0. AND ROETHER.W. (1967). "Downward movement of soil moisture traced by means of hydrogen isotopes," page 28 in Isotope Techniques in the Hyahlogical Cycle, Geophysical Monograph Series No. 11, Stout, G. E., Ed. (American Geophysical Union, Washington).

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LAUR~STON S. TAYLQR, Honorary President EDGARC. BARNPAULC. HOWEB ED^ H. QUXMBY JOHNH. RUST CARLB. BRAE~TRUP GEORGE V. LaRoy AUSTIN M.BRUES ?haZ. MORGAN SHIELDSWARREN FREDERICK P. COWAN R u s s ~ H. u MORGAN HAROLD0.WYCXOPP ROBLEY D. EVANB M. PARKER HERBERT

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Title Perceptions ofRisk, Proceedings of the Fifteenth Annual Meeting, Held on March 14-15, 1979 (Including Taylor Lecture No. 3) (1980) Quantitative Risk in Standards Setting, Proceedings of the Sixteenth Annual Meeting, Held on April 24,1980 (Including Taylor Lecture No. 4) (1981) Critical Issues in Setting Radiation Dose Limits, Proceedings of the Seventeenth Annual Meeting, Held on April 8-9,1981 (Including Taylor Lecture No. 5) (1982) Radiation Protection and New Medical Diagnostic Procedures, Proceedings of the Eighteenth Annual Meeting, Held on April 6-7, 1982 (Including Taylor Lecture No. 6 ) (1983) Environmental Rcrdhtivity, Proceedings of the Nineteenth Annual Meeting, Held on April 6 7 , 1 9 8 3 (Including Taylor Lecture No. 7)(1984) Some Issues Important in Developing Basic Radiation Protection Recommendations, Proceedings of the Twentieth Annual Meeting, Held on April 4-5, 1984 (Including Taylor Lecture No. 8)(1985) Radioactive Waste, Proceedings of the Twenty-First Annual Meeting, Held on April 3-4, 1985 (Including Taylor Lecture No. 9) (1986)

NCRP PUBLICATIONS

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Nonionizing Electromagnetic Radiations and Ultmsound, Proceedings of the Twenty-second Annual Meeting, Held on April 2-3, 1986 (Including Taylor Lecture No. 10 (1988) New Dosimetry at Hiroshima and Nagasaki and Its Implications for Risk Estimates, Proceedings of the Twenty-third Annual Meeting held on April 6-6, 1987 (Including Taylor Lecture No. 11)(1988). Symposium Proceedings The Control of Exposure of the Public to Ionizing Radiation in the Event of Acciclent or Attack, Proceedings of a Symposium held April 27-29,1981(1982) Lauriston S. Taylor Lectures No. 1

Title and Author The Squares of the Natural Numbers in Radiation Protection by Herbert M . Parker (1977) Why be Quantitative About Radiatwn Risk Estimates? by Sir Edward Pochin (1978) Radiation Prdectior+Concepts and Tmde 0fi by Hymer L. Friedell (1979)[Available also in Perceptions of Risk, see above] From "Quantity of Radiation" and "Dose" to "Exposure" and 'Xbsorbed Dose"-An Historical Review by Harold 0.Wyckoff (1980)[Available also in Qwmtitcrtive Risks i n Standards Setting, see abovel How Well Can We Assess Genetic Risk? Not Very by James F. Crow (1981)[Available also in Critical Zssues in Setting Radiation Dose Limits, see abovel Ethics, Trade-offs and Medical Radiation by Eugene L. Saenger (1982)[Available also in Radiation Protection and New Medical Dmgnostic Approaches, see abovel The Human Environment-Past, Present and Future by Meml Eisenbud (1983)[Availablealso in Environmental Radioactivity, see abovel Limitation and Assessment in Rachtion Protection by Harald H. Rossi (1984)[Available also in Some Issues Importunt i n Developing Basic Radiation Protection Recommendutions, see abovel

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Truth (and Beauty) in Radiation Measurement by John H. Harley (1985) [Available also in Radioactive Waste, see above] Nonionizing Radiation Bbefects: Cell& and Zntemctions by Herman P. Schwan (1987)[Availablealso in Nonionizing ElecLmmugndic Radiations and Ultmsound, see above] How to be Quantitative about Radiation Risk Estimates by Seymour Jablon (1987) [Available also in New Dosimetry at Hiroshima and Nagasaki and Its Implications for Risk Estimates, see above] How Safe is Safe Enough? by Bo Lindell(1988)

~~

NCRP Commentaries Commentary Title No. 1 Krypton-85 in the Atmosphere-With Specific Reference to the Public Health Signifioance of the Proposed Controlled Releaae at Three Mile Island (1980) 2 Prelimimry Evaluation of Criteria for the Disposal of Tmnsumnic Contaminated Waste (1982) 3 Screening Techniques fir Determining Compliance with Environmental Standards (1986) 4 Guidelines for the Release of Waste Water fhom Nuclear Facilities with Speciul Reference to the Public Health Significanceof the Proposed Release of Treated Waste Waters at Three Mile Island (1987)

NCRP Reporta No. 8 16 22

23

Title Control and Removal of Radioactive Contamination in Laboratories (1951) Radioactive WasteDisposal in the Ocean (1954) Maximum Permissible Body Burdens and Maximum Permissible Concentmtions of Radionuclides in Air and in Waterfor OccupationalExposure (1959)[IncludesAddendum 1 iesued in August 19631 Measurement of Neutron Flux and Spectm for Physical and Biological Applications (1960)

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Measurement ofAbsorbed Dose ofNeutrons and Mixtures of Neutrons and Gamma Rays (1961) Stopping Powers for Use with Cwity Chambers (1961) Safe Handling of Radioactive Materials (1964) Radiation Protection in Educational Znatitutions (1966) Medical X-Ray and Gamma-Ray Protection for Energies Up to 10 Me V-Equipment Design and Use (1968) Dental X-Ray Protection (1970) Radiution Protection in Veterinary Medicine (1970) Precautions in the Management of Patients Who Have Received Thempeutic Amounts of Radionuclides (1970) Protection Against Neutron Radiation (1971) Protsction Against Radiation fkom Bmchythempy Sources (1972) Specification of Gamma-RayBmhytSources (1974) Radiological Factors Affecting Decision-Making in a Nuclear Attack (1974) Ktypton-85 in the Atmosphem-Accumulation, Bidogical Significance, and Control Technology (1975) Alpha-Emitting Particles in Lungs (1975) Tritium Measumment Techniques (1976) Radiation Protection for Medical and Allied Health Personel (1976) Structural Shielrling Design and Evaluation for Medical Use of X Rays and Gamma Rays of Energies Up to 10 MeV (1976) Environmental Radiation Measumments (1976) Radiation Protection Design Guidelines for 0.1-100 MeV Particle Accelemtor Facilities (1977) Cesium-137 From the Environment to Man: Metabolism and Dose (1977) Review of NCRP Radiation Dose Limit for Embryo and Fetus in OccupationallyExposed Women (1977) Medical Radiation Exposwz of Pregnant and Potentially Pregnant Women (1977) Protection of the Thyroid Gland in the Event of Releases of Radioiodine (1977) Instrumentation and Monitoring Methods for Radiation Protection (1978) A Handbook of Radioactivity Mecrsurements Procedures, 2nd ed. (1985) Opemtional Radicrtion Safety Progmm (1978) Physioal, Chemical, and Bioi+al Properties of RadidurnReleuant toRadiation Protection Guidelines (1978)

NCRP PUBLICATIONS

Radiation Safety Training Criteria for Industrial Radiography (1978) Tritium in the Environment (1979) Tritium and Other Radionuclide Labeled Organic Compounds Incorporated in Genetic Material (1979) Influence of Dose and Its Distribution in Time on DoseResponse Relationships for Low-LET Radiations (1980) Management of Persons Accidentally Contaminated with Radionuclides (1980) Mammography (1980) Radiofreqency Electromagnetic Fields-Properties, Quuntities and Units, Biophysical Interaction, and Measurements (1981) Radiation Protection in Pediatric Radiology (1981) Dosimetry of X-Ray and Gammu-Ray Beams for Radiation Therapy in the Energy Range 10 keV to 50 MeV (1981)

Nuclear Medicine-Factors Influencing the Choice and Use of Radionuclides in Diagnosis and Therapy (1982) Operational Radiation Safety-Training (1983) Radiation Protection and Measurement for Low Voltage Neutron Generators (1983) Protection i n Nuclear Medicine and Ultrasound Diagnostic Procedures i n Children (1983) Biological Effects of Ultrasound: Mechanisms and Clinical Implications (1983) Iodine-129: Evaluation of Releases f h m Nuclear Power Generation (1983) Radiological Assessment: Predicting the Transport, Bioaccumulation, and Uptake by Man of Radionuclides Released to the Environment (1984) Exposures from the Uranium Series with Emphasis on Radon and its Daughters (1984) Evalwtion of Occupational and Environmental Exposures to Radon and Radon Daughters in the United States (1984)

Neutron Contamination from Medical Electron Accelerators (1984) Induction of Thyroid Cancer by IonizingRadiation (1985) Carbon-14 i n the Environment (1985) SI Units i n Radiation Prdedion and Measurements (1985) The Experimental Basis for Absorbed-Dose Calcdations in Medical Use of Radionuclides (1985) General Concepts for the Dosimetry of Internally Deposited Radionuclides (1985)

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Mammogmphy-A Usefs Guide (1986) Biological Effects and Exposure Criteria for Radwfkquency Electromagnetic Fields (1986) Use of Biwssay Pnxedures for Assessment of Internal Radionuclide Deposition (1986) Radiation Alarms and Access-Control Systems (1987) GeneticEffkcts oflnternally Deposited Radionuclides (1987) Neptunium: Radiation Protection Guidelines Recommendations on Limits for Exposure to Ionizing Radiation (1987) Public Radiation Exposure from Nuclear Power Generation in the United States (1987) Ionizing Radiation Exposure of the Population of the United States (1987) Exposure of the Population in the United States and Can& from Natuml Background Radiation (1987) Radiation Exposure of the U S . Population from Consumer Products and Miscellaneous Sources (1987) Comparative Caminogenesis of Ionizing Radiation and Chemicals (1988) Measw-emznt ofRadonandRadonDaughters in Air (1988) Guidance on Radiation Received in Space Activities (1989) Quality Assumnce For Diagnostic Imaging Equipment (1988)

Binders for NCRP Reports are available. Two sizes make it possible to collect into small binders the "old seriesnof reports (NCRP Reports Nos. 8-30) and into large binders the more recent publications (NCRP Reports Nos. 32-99). Each binder will accommodate from five to seven reports. The binders carry the identification "NCRP Reports" and come with label holders which permit the user to attach labels showing the reports contained in each binder. The following bound sets of NCRP Reports are also available: Volume I. NCRP Reports Nos. 8,16,22 Volume 11. NCRP Reports Nos. 23,25,27,30 Volume III.NCRP Reports Nos. 32,33,35,36,37 Volume IV. NCRP Reports Nos. 38,40,41 Volume V. NCRP Reports Nos. 42,44,46 Volume VI. NCRP Reports Nos. 47,48,49,50,51 Volume VII. NCRP Reports Nos. 52,53,54,55,57 Volume VIII. NCRP Reports No. 58 Volume IX. NCRP Reports Nos. 59,60,61,62,63 Volume X. NCRP Reports Nos. 64,65,66,67

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Volume XI. NCRP Reporta Nos. 68,69,70,71,72 Volume XII. NCRP Reports Nos. 73,74,75,76 Volume Xm. NCRP Reports Noe. 77,78,79,80 Volume XN. NCRP Reports Noe. 81,82,83,84,85 Volume XV. NCRP Reports Nos. 86,87,88,89. Volume XVI. NCRP Reports Nos. 90, 91,92,93. (Titles of the individual reporta contained in each volume are given above). The following NCRP Reports are now m p e d e d andlor out of print: No.

Title X-Ray Protection (1931). [Superseded by NCRP Report No. 31 Radium Protection (1934). [Superseded by NCRP Report No. 41 X-Ray Protection (1936). [Superseded by NCRP Report No. 61 Radium Protection (1938). [Superseded by NCRP Report No. 131 Safe Handling of Radioactive Luminous Compounds (1941). [Outof Print] Medical X-Ray Protection Up to TwoMillion Volts(1949). [Superseded by NCRP Report No. 181 Safe Handling OfRadiuactive Isdopes (1949). [Supended by NCRP Report No. 301 Recommendations for Waste Disposal of Phosphorus32 and Iodine-131 for Medical Users (1951). [Out of Print1 RadioMonitoring Methods and Instrument3 (1952). [Superseded by NCRP Report No. 571 Maximum Permissible Amounts of Radioisotopes in the Human Body and Maximum Permissible Concentrations in Air and Water (1953). [Superseded by NCRP Report No. 221 Recommendutwns for the Disposal of Carbon-14 Wastes (1953). [Superseded by NCRP Report No. 811 Protection Against Radiations from Radium, Cobdt-60 and Cesium-137 (1954). [Superseded by NCRP Report No. 241 Protection Against Betutron-Synchrotmn Radiations UP to 100 Millwn Electron V o h (1954). [Supersededby NCRP Report No. 511

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Safe Handling of Cadavers Containing Radioactive Zsotopes (1953). [Superseded by NCRP Report No. 211 Permissible Dose from External Sources of Ionizing Radiation (1954) including Maximum Permissible Exposure to Man,Addendum to National Bureau of Standards Handbook 59 (1958). [Superseded by NCRP Report No. 391

X-Ray Protection (1955). [Superseded by NCRP Report No. 261 Regulation of Radiation Exposure by Legislative Means (1955). [Out of Print1 Protection Against Neutron Radiation Up to 30 Million Electron Volts (1957:). [Superseded by NCRP Report No. 381

Safe Handling ofBodies Containing RadimctiveZsotopes (1958). [Superseded by NCRP Report No. 371 Protection Against Radiations from Sealed Gamma Sources (1960). [Superseded by NCRP Report Nos. 33, 34, and 401 Medical X-Ray Protection Up to ThreeMiUion Vdts (1961). [Superseded by NCRP Report Nos. 33,34,35, and 361 A Manual of R&tivity Pnxdures (1961). [Supended by NCRP Report No. 581 Exposure to Radiation i n a n Emergency (1962). [Supersededby NCRP Report No. 421 Shielding for High Energy Electron Accelerator Installations (1964). [Superseded by NCRP Report No. 51.1 Medical X-Ray and Gamma-Ray Protection for Energies Up to 10 MeV--Structural Shielding Design and Eualuation (1970). [Superseded by NCRP Report No. 491 Basic Radiation Protection Criteria (1971). [Superseded by NCRP Report No. 911 Review of the Current State of Radiation Protection Philosophy (1975). [Superseded by NCRP Report No. 911 Nafttml Background Radiation in the United States (1975). [Superseded by NCRP Report No. 941 Radiation Exposure from Consumer Products and Miscellaneous Sources (1977). [Supersededby NCRP Report No. 951 A Handbook on Radioactivity Measurement P m d u r e s (1978). [Superseded by NCRP Report No. 58 2nd 4.1

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Other Documents The following documents of the NCRP were published outside of the NCRP Reports and Commentaries series: "Blood Counts, Statement of the National Committee on Radiation Protection," Radiology 63,428 (1954) "Statements on Maximum Permissible Dose from Television Receivers and Maximum Permissible Dose to the Skin of the Whole Body," Am. J. Roentgenol., Radium Ther. and Nucl. Med. 84, 152 (1960) and Radiology 75, 122 (1960) Dose Effect Modifying Factors In Radiation Protection, Report of Subcommittee M-4 (Relative Biological Effectiveness) of the National Council on Radiation Protection and Measurements, Report BNL 50073 (T-471) Brookhaven National Laboratory (1967). Available from National Technical Information Service, Springfield, Virginia. X-Ray Protection Standards for Home Television Receivers, Interim Statement of t h National ~ Council on Radiation Protection and Measurements (National Council on Radiation Protection and Measurements, Washington, 1968) Specification of Units ofNatuml Uranium and Natuml Thorium (National Council on Radiation Protection and Measurements, Washington, 1973) NCPR Statement on Dose Limit for Neutrons (National Council on Radiation Protection and Measurements, Washington, 1980) Control of Air Emissions of Radionuclides (National Council on Radiation Protection and Measurements, Bethesda, Maryland, 1984)

Copies of the statements published in journals may be consulted in libraries. A limited number of copies of the remaining documents listed above are available for distribution by NCRP Publications.

Index Absorbed dose, iii Absorbed dose; deiinition, & Absorbed dose index, iii Absorption of tritium by lower plants, 52-53 hngi, 52

lichens, 62 moeeee. 52 water uptake from eubstmtum, 53 Absorption of tritium by vaecular plant4 53-65

atmoepheric sources. 54 equilibration, 64 exchange and absorption of HTO vapor by plant leaves, 63 half-life, 54 hydration etate, 53 soil-water concentrations, 54 transpirational water, 6354 Acronyms, 88 Annual rainfall-continental United Statee, 27

Annual rainfalt over continental a r e a of the world, 27 Aqueous and non-aqueous tritium ratio, 57 Aqueous tritium; definition, & Atmospheric deposition, 1 Atmospheric disperti~n,23-24 aqueous tritium releases, 23 atmospheric concentrations, 23 dynamic model, 24 fluxes of HTO, 24 box model, 24

HT,23 HTO, 23 Mtiated water vapor, 23 Becquerel iii Behavior of tritium in the hydrosphere, 30 direct release streams, 30 di8pereion characteristics, 30 flow vdoeity, 30 precipitation, 30 rivers, 30

surface water%30 Beta labeling. 6 Beta radiolysis of Tp, 6 Biological half-life. 47 Biological half-life; definition, &4 Biology of tritium exposures, 45 DNA incorporation, 5061 elimination, 47-60 in ecological eysteme, 52-68 Q, 51-52

RBE, 61-62 uptake and retention, 45-47 Boiling water reector (BWR);definition, & Breeder reactor, definition, &4 Burnable poison; definition, & Chop leach protege; definition, & Cladding; definition, & Clinch River watershed, 27 Cold trapping; definition. 84 Committed dose, 69 Concentration factor, 47 Coolant; definition, & Cosmic ray interactions. 1 CIQS~section, nuclear, definition. 85 Critical point; definition,85 Deposition, 24-28 Clinch River watershed, 27 concentration in rainfall, 25 continental deposition, 26 deposition over ocxans. 26 deposition rate of natural tritium. 25 deposition velocity, 26 diffueion, 26 direct evaporation, 26 lateral mixing, 26 light rain, 26 meteorological factors. 26 Misaiasippi River valley, 27 Ottawa River l3aain, 27-28 transfer by d a c e runoff,26 trader from the stratosphere, 26 123

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INDEX

tropospheric mean residence time, 24 uniform concentration in the atmosphere, 25

uniform distribution in the stratmphere. 26

watm-vapor content of the atmosphere, 25 Diapoaal of tritiated water in geological stru37 chimneys of underground nuclear explomoll& 37 dome apace in abandoned oil fields, 37 h y d r o h e , 37 DNA incorporation, -51 biological effect, 50 chromosome anorsdk, 51 DNA precumom, 51 histopathologicchanges in ovaries, 51 radiotoxic effect, 60 thymidine, 50 tritiated thymidine. 54 tritium content of purine bases, 50 tritium content of pyrimidine bases, 50 Dose commitment, 70 Dose commitment for the Northern Hemisphere, 80 Dose equivalent (M;definition, 85 Dosimetry. 67-71 body water compartment, 68 bound compartment, 69 chronic intake, 67 committed dose, 69 equilibrium dose, 69 hydrogen content, 69 loose water, 71 retention half-times, 68,69,70 three compartment model, 68,tiesue doee, 69,70,71 tritium concentration in food, 71 tritium concentration in water, 70.71 uniform distribution, 67 water balance, 68,69 water intake by man, 70 Doses from tritium in the environment, 7% 83 fallout, 78-80 natural, 78 nuclear induntry, 8083 Dosetohumane,2 k y s t e m ~62-58 ,

Effective half-life, 48

Effective half-life; definition, 85 Effective neutron croes sections. 10 Elimination of tritium. 4 7 6 0 acute expoeure, 48 biological half-life, 47 content in urine, 48 discrimination againat incorporation, 4748

effective half-life, 48, 49 free water, 47,48.49 half-time. 47,48.49 incorporated into DNA, 47 incorporated into RNA, 47 non-equilibrium conditions, 50 organically bound pools,47,48,49,50 retention time, 48 route of exposure. 49 specific activity of organ, 49 Enrichment effects in eco~yatema,6 5 4 8 aquatic and t e e food chains,& body water, 56 elimination, 56 enrichment in photo-synthetic pro58 equilibrium,57 in animal and plant tissues, 66 mammals,56 man. 56 organically-bound, 56 tissue-bound,67 Entropy unit, 4 Environmental models, 71-78 one compartment model, 72-73 three compartment model, 73-75 seven compartment model, 76-77 Evaporation h m ponds. 36 wepage, 36 area, 36 location, 36 radiation expomm, 36 Expansion of nuclear power, 60-62 energy consumption, M mix of reactore, 61 projections, 6 1 Exposure-ingestion. 2 Exposure-inhalation, 2 Expomm to populations located close to the sources of r e l m 34 Fast fission of q u , 9 Fast fission of %,9 Fast reactor.definition, 85

Fiseion product, 8 W o n yield; definition, 86 Flux denaity (fluence rate); definition, 86 Fuel reproceasing plants, 17-18,21-22 Commercial plants, 17 AUied-Gulf Nuclear Services, 18 Midwest Fuel Recovery Plant. 18 Nuclear Fuel Services, 17 Government plants, 18 Hanford, 18 Idaho Chemical Pmeessing Plant, 18 Savanaeh River Plant, 18 releasea, 17-18 Gray, iii

Growth in energy demand, 59-60 Arab oil embargo, 59 coneewation meamma, 59 gross national product, 59 projected energy consumption, 59 thermal energy conversion, 60 Heavy water reactor (HWR);definition. 85 High temperature gas cooled reactor (HTGR); definition, 86 Hydrohctwing, 37 Isotope e w definition, 85 Iaotope effecta in tritium reaction, 7 bonding, 7 equilibrium conetante, 7 equilibrium processes, 7 kinetic proceeaea. 7 h t o p i c exchange in organic molecules. 6,6 exchange reaction, 6 recovery of tritiated water, 6 Iaotopic exchange in water, 4.5 equilibrium constante, 4 relative abundance of HT. 6 relative abundance of HTO,6 Kerma, iii Kerma; definition, 86 Kinetica of tritium movement, 2

Light water reactor (LWR), 10,21 BWR, 10,21 PWR. 10.21 Linear EnTransfer, 51,52 Linear energy t r a d e r (LET); definition, 85 Liquid metal fast breeder reactor (LMFBR); definition, 86

Long term doaimetric implications of environmental tritium, 67-83 dosea h m tritium in the environment, 78-83

doeimetry, 67-71 environmental models, 71-78 Lpw level aqueous waste. 36.36 M w effect, 55 Maximum permbible concentration (MPC), 49 Maximum permiseible concenhntion (MPC); delinition, 86 Mean residence W,definition, 86 Megaton (MT); definition, 86 Mississippi River valley, 27 Moderator; definition,86 Movement in groundwater and soil,2830 organic matter, 28 state of soil, 28 t m e of soil, 28 & a h r a t e d soil, 29 water associated with minerah, 28 water content, 28 MTU; definition, 86 MWe; definition, 86 MWt; definition. 86 ~ a t u mtritium, l 8,21 global inventory, 8 solar flare. 8 Neutron activation, 21 Nuclear detomtionq 19-20 Test Ban 'Preaty, 20 tritium yield, 19-20 Nuclear reactor, definition, 86 Nuclear tramformation; definition, 86 One compartment model, 72-73 compartment h,72 equilibrium, 72 volume, 72 Organic tritium; definition, 86 ORIGEN Code, 9,16,86 Ottawa River drainage baain, 27-28 Physical Proflea of Tritium, 3-7 critical point of T2.3 -on coefficient, 4 entropy. 4

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INDEX

gaeeoue T2,3 heat of vaporization, 4 isotope effects in tritium reactions. 7 isotope exchange in organic molecules. 57 isotope exchmge in water. 4-5 prop&iea of Gtiated water, 3-4 eelfd£hdon coefficient, 4 triple point of TI, 3 triple point preeeure, 4 triple point temperature, 4 Phyaical transport of tritium, 2 3 3 3 atmospheric diaperaion, 2S24 behavior of tritium in the hydrosphere, 30 deposition, 24-28 movement in groundwater and soil, 28-30 oceans, 32-33 Plant uptake factols, 53, Ei4 Power, defiaition, 86 Preewuized water reactor (PWR); de6nition, 86 Projected sources of tritium release, 62-66 fuel reprocessing, 64-66 reactors, 62-64 boiling water reactors, 62-63 fast breeder reactors, 63-64 heavy water reactors, 63 p r d water reactors, 63 other reactors, 64 Projected tissue doae rate in man,81, 83 Projected tritium production and releases, 69-66

Quality factor, 51, 52 Quality factor (Q); definition, 87 Rsdioactive half-life; definition, 87 Radionctive recoil; definition. 87 Reactione that omu in the atmosphere, 5 Cosmic radiation, 5 HT,5 HTO, 5 TO2,5 Recoil labeling, 6 B 6 hot atoms, 6 recoil tritium, 6 Relative and derived tritium fiseion yields in thermal reactors, 9 Relative biological effectiveness (RBE); definition, 87

Relative biological effectiveness of tritium (RBE),31 biological end point, 51 high LET radiation, 51 low LET radiation, 52 very low doma, 51,52 very low dose rat-, 51,52 Release to groundwater, 3032 contamination of groundwater, 3 1 deep subsurface etrata, 32 W o n , 32 direct release, 31 flow velocity, 32 Hanford, 31 hydrodynamic dispersion, 32 National Fteactor Testing Station in Idaho, 31 near surface releaee, 32 Oak Ridge National Laboratory, 31 permeable aquifexa, 32 Savannah River, 31 underground detonation of nuclear devices, 31 variation of flow velocities, 32 Release to the oceans, 32-33 concentration profile, 33 mixed layer, 33 thermocline, 33 thin surface layer, distribution in, 32 Rhizoids, 53 Seven compartment model, 75-77,8I changes in concentration, 77-78 compartment volume, 75 concentrations from aingle atmoepheric release, 77 integral concentrations, 77 mean residence times, 76 release modela, 76 tissue dose in man, 76,77 transfer coefficients, 75 Sources of tritium, 8-22 fuel r e p r o c d g , 15-19 natural, 8 nuclear detonations, 19-20 nuclear reactors, 8-14 production plants, 15 thermonuclear reactors, %22 Source strength (Q);definition, 87 Specific activity; definition, 87 Specific energy imparted, iii

INDEX Ternary 6ssjon,1,21 Ternary haion; definition, 87 Three compartment model, 66-70.73-75 d m rate factor, 76 instantaneous mixing. 73 integral concentration, 74 tissue dose, 75 tranefer coefficients, 73 uniform mixing, 74 Total dose rate from all sources, 81 Triple point; definition. 87 Tritiated water expwure to embryo-fetus. 50

radiotoxic effscte, 60 tritiated thymidine, 51 Tritiated water in aquatic ecosystems, 55 equilibrium, 55 fish,55 tiesue-bound tritium, 66 h e - w a t e r , 65 Tritiated water-properties, 3 isotope effects on vapor preeawe, 3 oxides, 3 Tritium content of fuel 16.21 W o n through cladding. 17 PWR, 17

CANDU,17 LMFBR, 17 Tritium disposal into deep ocean, 37-88 Tritium diepoeal onto ice packs, 37-38 Tritium =on yields, 9 Tritium incorporation into organic molecules, 62 Tritium in ecological syahne, 52-68 absorption by plants. 52-66 enrichment effecta in ecosystems. 55-68 Tritium in ground water, 2 Tritium in soil, 2 Tritium production in nuclear reactom, 814, 21 experimental breeder reactor, EBRII, 14 heavy water reactors, HWR, 12 CANDU. 12 S G m 12 natural uranium oxide fuel, 12 high temperature gas-cooled reactor, HIGR, 13 light water reacton, LWR, 10-12 PWR, 10-12 BWR, 10-12 primary coolant, 12

1

127

liquid metal fast breeder reactor, LMFBR, 13 boron and litium impuritiee in fuel and blanket material, 14 molten ealt breeder reactor, MSBR, 13 Tritium production from thermonuclear reactors, 20,22 Tritium release to earth, 36-37 buried dispersal crib, 3 6 4 7 d i s p d wells, 36 hydrology, 37 low level aqueoue waste, 36 seepage plumes, 37 seepage ponds, 37 transverse hydraulic dispersion, 36 Tritium release from fuel reprocessing. 15. 19, 21 Tritium releases from production plants, 16, 21 production at the & v ~ M River ~ IPlant, ~ SRP, 16 discharge of tritiated &O, 16 release of tritiated water vapor from reactor& 15 reproeegsiag, 15 solid waate, 16 lithium-aluminum tritium production targets, 15 Tritium release from thermonuclear reactors, 20,22 Tritium releaee to liquid &reams, 35 average dispersion from stack, 36 ground-level release, 36 low-level aqueous waste. 35 a t e boundaries. 35 volume of release, 35 Tritium release to the atmosphere, 34-36 Tritium retention half-time in man, 69 Tritium retention methods-advanced reactom 36-39 Tritium retention methods-control elements, 39 Tritium retention methods-fuel reproceeeing plants, XHO combined voloxidation and total water containment, 40 immediate dissolution with r e l e e or dispasale 39 immediate dissolution with total water containment, 39 voloxidation procees, 39

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INDEX

Tritium retention methods-isotope B e p a r a tion, 40-41 concentration io aqueous wnete, 40 -te. 40 cryogenic dmtiktions. 41 effectivenena of mparation, 40 efficiency, 40 extractive distillation, 41 fractional distillation, 40 HT-HTO exchange, 40 Ha-Hz0 exchange, 40 revemible electrolyeie, 41 Tritium retention methods-reactom, 38 failed fuel, 38 iixation, 38 ofEaite release, 38 recycle plant water,38 Tritium retention methods-removal h m &a% 40 Tri* unit, 29 Trition; definition, 87 Tropic levels, 54 Tropopauee; definition, 87 Tropopauee gap; defmition, 87

deep ocean dumping in cylindem, 41-42 opean ocean release of tritiated water, 41

storage in tanke,41 packaging, 42 fixation in cement plaeter, 42 polyethylene drum, 42 atainlesa steel drum, 42 solids, 42 absorption, 42 fixation, 42 Uptake and retention of tritium, 45-47 free water, 45,46,47 half-time, 46,47 ingestion, 45 inhalation, 46 organically bound,45,46,47 projected exposure, 46 pulsed exp-, 46 skin, 45

Waste management, 84-44 dosimetric considerations, 34-38 deep wells, 37 release to atmosphere, 34 Ultimate disposal, 41-44 release to earth, 36 fixation, 43 release to liquid streams, 35 asphalt coating polymer impregnation release to ponds, 36 of cement bodies, 43 retention, 38-41 clays, 43 control elements, 39 diffusion maee bansport models. 43 fuel r e p d g plan& 39 direct leaching, 44 isotope separation, 40 incorporation of bitiated water in cereactore, 38 ment, 43 removal trom gas, 40 leach test data, 43 ultimate d i s d 41-44 molecular dews, 43 as liquid, 41 polymer impregnated tritiated eonmete as solid, 42 solids, 44 fixation, 43-44 silica gel, 43 packaging, 42 liquid, 41-42 World waste supply end evaporation-predeep well &pod, 41 cipitation balance, 72