Krypton - 85 in the Atmosphere: Accumulation, Biological Significance, and Control Technology (Ncrp Reports Ser. : 44)

85 Pages·1975·3.13 MB·English

by  National Council on Radiation Protection

NCRP REPORT No. 44
KRYPTON-85 IN THE
ATMOSPHERE-AccumuIation,
Biological Significance, and
Control Technology
Recommendations of the
NATIONAL COUNCIL ON RADIATION PROTECTION
AND MEASUREMENTS
Issued July 1,, 1076
National Council on Radiation Protection and Measurements
7910 WOODMONT AVENUE/WASHINGTON, D.C. 20014
Copyright @ National Council on Radiation
Protection and Measurements 1975
All rights resewed. This publication is protected by copyright. No part of this
publication may be reproduced in any lform or by any means, including photo-
copying, or utilized by any informat~ons torage and retrieval system without
wntten permission from the copyright owner, except for brief quotation in
critical articles or reviews.
Library of Congress Catalog Card Number 76-11458
International Standard Book Number 0-913392-26-x
Preface
This report of the National Council on Radiation Protection and Meas-
urements (NCRP), successor to the National Committee on Radiation
Protection and Measurements, is concerned with the accumulation and
biological significance of 86Kri n the atmosphere, and the possible tech-
niques available for its control. 8%r is relesased to the atmosphere through
nuclear weapons tests and the generation of nuclear power. With the
cessation, for the most part, of atmospheric testing of nuclear weapons,
86Kri n the atmosphere results primarily from the reprocessing of nuclear
fuel, very little s6Kr being released from the actual operation of the
nuclear power plants themselves. This report estimates the future global
concentrations of 85Krin the atmosphere resulting from projected future
levels of nuclear power use, the absorbed doses to man resulting from
these concentrations, and possible techniques which may prove pract,ica-
ble for the future control of E6Kr atmospheric levels.
The present report was prepared by the Task Group on sSKr of the
Council's Scientific Committee 38 on Waste Disposal. Serving on the
Task Group during the preparation of this report were:
MERRILE ISENBUDC, hairman
Members
ROYE . ALBERT
KENNETHC OWSER
EDWARDD . GOWBERQ
JOSEPHA . LIEBERMAN
LESTERM ACHTA
ARTHURC . UPTON
The Council wishes to express its appreciation to the members and
consultants for the time and effort devoted to the preparation of this
report.
LAURISTONS . TAYLOR
President, NCRP
Washington, D.C.
March 6, 1976
contents
...
Preface . . . . . . . . . . . . . . . . . . . . . . . . . . 111
List of Tables . . . . . . . . . . . . . . . . . . . . . . vii
...
L.is t of Figures . . . . . . . . . . . . . . . . . . . . . . Vlll
1 Introduction . . . . . . . . . . . . . . . . . . . . 1
1.1 General Remarks . . . . . . . . . . . . . . . . . . . .
1.2 Properties of Krypton and 86Kr . . . . . . . . . . . .
1.3 Sources of 86Kr . . . . . . . . . . . . . . . . . . . .
.
2 Estimates of Future Power Requirements. 86KrR eleases
and e6Kr Inventory . . . . . . . . . . . . . . . . . .
2.1 Future Power Requirements . . . . . . . . .
2.2 86Kr Generation and Inventory to the Year 2000
.
3 The Fate of Discharged to the Atmosphere . . .
3.1 The Oceans ns a Sink for 86Kr . . . . . . . . . . . .
3.2 Washout and Deposition of 86Kr . . . . . . . . . . . .
3.3 Atmospheric Dispersion of 86Kr . . . . . . . . . . . .
.
4 Dosimetry . . . . . . . . . . . . . . . . . . . . .
4.1 Dose from Photons Produced in a Semi-Infinite Cloud . .
4.2 Dose from Bremsstrahlung Produced in Air or Skin . . . .
4.3 Dose from 8bKri n the Body . . . . . . . . . . . . . .
4.4 Dose from Beta Rays in an Infinite Cloud . . . . . . . .
4.5 Dose from 8%r in the Airways of the Lungs . . . . . .
4.6 Summary of Doses . . . . . . . . . . . . . . . . . .
.
5 Projected 86KrC oncentrations . . . . . . . . . . . .
5.1 esKr Concentrations . . . . . . . . . . . . . . . . . .
5.2 Projected Population Dose Commitments . . . . . . . .
.
6 The Biological Significance of the Absorbed Dose . . . .
6.1 Genetic Effects . . . . . . . . . . . . . . . . . . . .
6.2 Overall Carcinogenic Effects . . . . . . . . . . . . . .
6.3 Carcinogenic Effects on Skin . . . . . . . . . . . . . .
6.4 Possible Interaction of Ionizing and Ultraviolet Radiation .
~i / CONTENTS
.
7 Status of 86KrR emoval from Waste Gases . . . . . . 40
7.1 Adsorption at Ambient Temperature . . . . . . . . . .
7.2 Cryogenic Adsorption . . . . . . . . . . . . . . . .
7.3 Cryogenic Distillation . . . . . . . . . . . . . . . .
7.4 Selective Absorption . . . . . . . . . . . . . . . . . .
7.5 Permelective Membranes . . . . . . . . . . . . . .
7.6 Clathrate Precipitation . . . . . . . . . . . . . . . .
.
8 Discussion . . . . . . . . . . . . . . . . . . . . . .
.
9 Summary . . . . . . . . . . . . . . . . . . . . . .
APPENDIX A . Calculation of Long-Term Air Concentra-
tions . . . . . . . . . . . . . . . . . . . . . . . . . .
APPENDIX B . Phantom Description . . . . . . . . . .
References . . . . . . . . . . . . . . . . . . . . . . . .
The NCRP . . . . . . . . . . . . . . . . . . . . . . . .
NCRP Reports . . . . . . . . . . . . . . . . . . . . . . .
Index . . . . . . . . . . . . . . . . . . . . . . . . . .
List of Tables
1. Primary radiations from 8bKrd eca,y . . . . . . . . . . . .
2. Secondary radiations from s6Kr decay . . . . . . . . . .
3. Projections of annual electric energy generation in the United
States . . . . . . . . . . . . . . . . . . . . . . . .
4. Cumulative installed nuclear electric power capacity in the
United States . . . . . . . . . . . . . . . . . . . .
5. Projection of electric power generating capacity in the world. .
6. Cumulative installed nuclear electric power capacity in the
world . . . . . . . . . . . . . . . . . . . . . . . .
7. Assumed nuclear reactor mix and world accumulation of s6Kr
in year 2000 . . . . . . . . . . . . . . . . . . . .
8. Estimated production and accumulation of 86Kri n world nu-
clear power economy . . . . . . . . . . . . . . . .
9. The oceans as a sink for S6Kr . , , . , . . . . . . . . .
10. World population weighted concentration from uniform release
rate of 1 curie of 85Kri n 1 year . . . . . . . . . . . .
11. Percentage of separable adipose tissue and nonfat tissues and
the Ostwald coefficient for subdivisions of the human body. .
12. Equilibrium absorbed dose rate to body organs per unit air
concentration from immersion in a semi-infinite cloud of
86Kr . . . . . . . . . . . . . . . . . . . . . . . .
13. Comparison of equilibrium absorbed dose rates to body organs
per unit air concentra.tion from immersion in a semi-infinite
cloud of 8bKr . . . . . . . . . . . . . . . . . . . .
14. Estimated world population dose commitments from annual
worldwide reIeases . . . . . . . . . . . . . . . .
15. Several processes available for 85Kr off-gas treatment . . . .
A-1. Phase 4 average surface air concentration of 86Kr . . . .
vii
List of Figures
1. Decay scheme of 86Kr . . . . . . . . . . . . . . . . . .
2. Atmospheric 86Kr concentratio~lsf rom weapons testing and
plutonium production . . . . . . . . . . . . . . . .
3. Energy spectrum for scattered photons . . . . . . . . . .
4. Depth dose in tissue from beta radiation . . . . . . . . . .
5. Concentration of 86Kr measured in northern hemisphere air
samples . . . . . . . . . . . . . . . . . . . . . .
6. Predicted average concentrations and annual skin dose equiva-
lent rates due to 86Kri n the atmosphere . . . . . . . .
A-1. Mean annual surface air concentration contours (10-20
Ci/ma) for the release of 1 Ci/y of 86Kra t Morris, Illinois
(Phase 1) . . . . . . . . . . . . . . . . . . . .
A-2. Mean annual surface air concentration contours
Ci/m3) from Phase 2 . . . . . . . . . . . . . . . .
A-3. Mean annual surface air concentration contours
Ci/m3) from Phase 3 . . . . . . . . . . . . . . . .
B-1. Legs and male genitalia of phantom . . . . . . . . . .
viii
1. Introduction
1.1 General Remarks
The projected rapid growth of the nuclear power industry necessitates
a careful assessment of any related potential for environmental pollution.
86Krr eleases deserve special attention because of the inherent difficulty
in their control and their essentially nonreactive and mobile nature in
the atmosphere. The purpose of the present report is to estimate the fu-
ture global concentrations of 86Kr, their potential significance, and possi-
ble techniques for their control. Projections of SGKra ccumulations will be
made to the year 2000, as this is now sufficiently close to permit reason-
able approximations to be made of the world's energy requirements and
the extent tro which they will then be fulfilled by nuclear power reactors.
On the other hand, the year 2000 is sufficiently far off to allow for periodic
reappraisal of the projections of 86Kr accumulation in relation to de-
veloping information about the biological effects of this nuclide and the
technology for control of 86Krr eleases. In addition to the global projec-
tions, the present report also includes estimates of S6Kr concentrations
near nuclear fuel chemical reprocessing plants.
Problems associated with S6Kr disposal have been previously reviewed
by Kirk (1972), Dunster and Warner (1970), Coleman and Liberace
(1966), Diethorn and Stockho (1972), Karol et al. (1971), and Bryant
and Jones (1973).
1.2 Properties of Krypton and 86Kr
1.2.1 Chemical Properties.
Krypton is one of the class of noble gases which includeshelium, neon,
argon, krypton, xenon, and radon. These are colorless, tasteless, and in
general, chemically inert. In recent years, however, they have been shown
to be capable of entering into ionic or covalent bonding with highly re-
active elements such as fluorine or oxygen. Bartlett (1962) reported a
chemical reaction between xenon and HE' yielding XeF4.T he first report
1
2 / INTRODUCTION
of a chemical rewtion involving krypton came from Grome et al. (1963),
who reported the production of KrF, from a mixture of krypton and
fluorine through which an electric discharge had been passed at 86OK.
Later work, however, indicated that the resultant compound was
KrFz (Schreiner et al., 1965), a white crystalline solid which sublimes at
temperatures well below 273"K, but which can be stored for several
weeks at dry ice temperature (195'K) without appreciable loss. Re-
cently, the crystal structure of KrFa has been investigated by low
temperature x-ray diffraction techniques (Burbank et ad., 1972).
Noble gases, including krypton, have been shown to enter into com-
pounds called clathrates (Lindquist and Diethorn, 1968; McClai and
Diethorn, 1964; Balek, 1970; Chernick, 1967) in which the noble gas
atoms are physically entrapped in molecular cages of hydroquinone, or
other organic compounds. In addition, the noble gases have been shown
to be highly soluble in nonpolar solvents (Steinberg and Manowitz,
1958) with this solubility increasing with decreasing temperature
(Nichols and Binford, 1971). The solubilities of the various noble gases
are related as Rn > Xe > Kr > Ar > Ne > He.
1.2.2 Physical Data.
The Handbook of Chemistry and Physics (Wesst and Selby, 1971) and
C~:ryogeniRc eference Dda (Union Carbide Corp., 1967) give the following
values for physical constants of krypton:
Atomic number = 36
Atomic weight (naturally occurring) = 83.80
Melting point = - 156.6'C (116.6"K)
Boiling point = - 152.30 & 0.1O0C (120.85 f 0. 10°K)
Triple point = - 157.Z°C, 548.2 mm Hg (116.0°K, 73.09 kPa)
Critical point = - 63.8OC, 4.12 X lo4m m Hg (209.4'K, 5.49 MPa)
Density = 3.733 g/l <O0C, 760 mm Hg) (273OK, 101.3 kPa)
Atomic radius = 4.0 A (0.4 pm)
The naturally occurring stable krypton isotopes and their atom per-
centages of natural abundance are: 78Kr (0.35 percent), (2.27 per-
cent), 82Kr (11.56 percent), MKr (11.55 percent), MKr (56.9 percent),
86Kr (17.37 percent). The radioactive isotopes of krypton include mass
numbers of 74-77, 79, 79m, 81, 81m, 85, 85m, 87-95, and 97. Some of
these occur naturally in insignificant traces due to cosmic ray induced
reactions of stable krypton isotopes and spontaneous fission of natural
uranium.
1.2 PROPERTIES OF KRYPTON AND 8bKr / 3
1.2.3 Racliologieal Properties.
has a half-life of 10.7 years; its decay scheme is rather simple, in
that only two beta rays and a single gamma photon are emitted. The
decay scheme, as given in Martin (1973), is shown in Fig. 1. Table I
gives information on the primary decay products, while Table 2 gives
Fig. 1. Decay scheme of 86Kr (Martin, 1973).
TABLE1- Prima~y radiations from 'KT decayh,b
~ ~ d i . ~ Mi e~an~ N* Endpoint Energy0
Pm Decay (MeV)
Martin (1973).
These values are slightly higher than earlier reported
values (Lederer et al., 1968) for the endpoint energies of
81- and BI- of 0.16 and 0.672, respectively (mean energies
of 0.0437 and 0.251 MeV, respectively). These earlier
values are the one8 used in Chapter 4.
Mean energies of 81-a nd 0%-a re 0.0475 + 00.0006 and
0.251 1 0.008, respectively.
TABLE2- Secodary radiations from &KTd ecay
Radiation Mean Number Per Decay Energy (MeV)
--
Shell converaion electron 0.00003 0.49880
&, x ray O.OOOO1 0.01340
L,, Auger electron 0.00004 0.00139
Mxy Auger electron 0.00008 0.00024