EPA-520/4-73-002
ASSESSMENT OF THE POSSIBLE ENVIRONMENTAL
DOSE COMMITMENT RESULTING FROM RELEASE
OF LONG-LIVED RADIONUCLIDES PRODUCED BY
OPERATION OF THE NUCLEAR POWER
INDUSTRY FOR THE NEXT FIFTY YEARS
1
U.S.ENVIRONMENTAL PROTECTION AGENCY
Office of Radiation Programs
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ASSESSMENT OF
THE POSSIBLE ENVIRONMENTAL DOSE COMMITMENT
RESULTING FROM
RELEASE OF LONG-LIVED RADIONUCLIDES
PRODUCED BY
OPERATION OF THE NUCLEAR POWER INDUSTRY
FOR
THE NEXT FIFTY YEARS
U. S. ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF RADIATION PROGRAMS
CRITERIA AND STANDARDS DIVISION
WASHINGTON, D. C. 20460
SEPTEMBER 1973
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FOREWORD
This report was prepared by the Office of Radiation Programs of the
U.S. Environmental Protection Agency as part of a continuing program to
assess the population impact from all radiation sources.
The purpose, general methodology, results, and estimates of uncer-
tainties for this study are discussed in the main body of the report. Deri-
vation of numerical data and more detailed descriptive material are given
in the appendices.
The results, projected into the future, are necessarily subject to
considerable uncertainty and are intended primarily to be the basis of dis-
cussions leading ultimately to the establishment of appropriate standards
for environmental quality.
For purposes of this study, health effects are defined as the total
number of incidences of cancer (both fatal and non-fatal) and of extreme
genetic damage estimated as a statistical consequence of a total popu-
lation exposure. The extrapolations to low dose levels are predicated on
the assumption of a linear, non-threshold hypothesis. All health effects
estimates are based on an analysis of the recommendations made by the
National Academy of Sciences Advisory Committee on the Biological Effects
of Ionizing Radiations (BEIR Report - November 1972).
iii
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PREFACE
The following analysis of the potential long-term health effects
impact of long-lived radionuclides is designed to introduce the concept of
considering not only the present effects but also all cumulative future
effects resulting from a given release into the technical considerations
governing radiation protection standard setting. As such, it is designed
to evaluate the total population impact of the release of long-lived radio-
nuclides to the environment, rather than restrict consideration to the
generally used concept of annual dose increments. However, because the
total period of persistence in the environment of some of the nuclides of
interest ranges up to thousands of years, and reasonable predictions over
such lengths of time are simply impossible to make, the document refers
only to the impact over the first one hundred years after release. Such
estimates are essentially accurate only for isotopes such as k.rypton-85
(half-life = 10.7 yrs) and tritium (half-life =12.3 yrs), but obviously
do not include all cumulative effects for iodine-129 (half-life = 1.7 x
107 yrs) and plutonium-239 (half- life = 24,000 yrs).
The projected effects described are based on estimates of total normal
releases anticipated and on the effective cleanup capabilities of current
and near-term future technology. As such, these projections should be
considered as the probable consequence of maintaining the status quo, i.e.,
present technological practices applied in the future, and of not imposing
additional restrictions on releases. Unplanned major accidental releases
are not included because estimates of their magnitude would be purely
speculative. Release estimates have been made in terms of fractions of
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total accumulated inventory. The uncertainties associated with such esti-
mates are discussed in considerable detail.
It can be concluded from the results obtained that releases of the
long-lived radionuclides by the nuclear power industry to date do not
constitute a significant public health problem, and that present accumu-
lations in the environment do not constitute cause for alarm. Therefore
the paper's focus is .to identify a potential problem, estimate its magni-
tude, and begin the dialogue on what preventive actions are indicated and
on what time scale they should be implemented. Obviously standards for
control will require much additional information, and are expected to pro-
pose firm numerical values for releases and/or environmental buildups.
The perspectives derived from the conclusions presented are that
1. short-term risk estimates do not necessarily tell the full story
2. limits may need to be imposed on the release of certain long-lived
toxic materials to the environment even though the risk to popu-
lations over the short-term is relatively slight
3. preventive action is the only option available for control of the
public health impact of long-lived toxic materials
This paper, like any initial technology assessment, is an extrapo-
lation from admittedly inadequate data. As such it is subject to major
revisions as additional and better data and estimates of future develop-
ments become available. For this reason it must not be considered an
official prediction, or basis for policy by the Environmental Protection
Agency. Rather, it is offered as an initial assessment to stimulate thought,
vi
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discussion, and further research in the hope that succeeding assessments
may result in a sound basis for preventive action.
vii
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CONTENTS
Page
FOREWORD iii
PREFACE v
ABSTRACT .' xi
I. INTRODUCTION 1
II. GENERAL METHODOLOGY b
III. RESULTS AND ESTIMATES OF UNCERTAINTIES 9
REFERENCES 21
APPENDIXES
Appendix A. ELECTRIC POWER AND POPULATION PROJECTIONS
I. INTRODUCTION A-l
II. ELECTRIC POWER USE PROJECTION A-l
III. RADIONUCLIDES PRODUCED AND RELEASED BY NUCLEAR POWER INDUSTRY A-A
IV. POPULATION GROWTH PROJECTIONS A-10
REFERENCES A-12
Appendix B. DOSE CALCULATION TECHNIQUES
I. INTRODUCTION B-l
II. REGIONAL POPULATION EFFECTS B-2
III. DOSES TO THE UNITED STATES POPULATION B-5
IV. DOSES TO THE WORLD POPULATION OUTSIDE THE UNITED STATES . . B-10
V. HEALTH EFFECTS B-12
REFERENCES B-14
Appendix C. RADIOLOGICAL DOSE AND HEALTH IMPACT CONVERSION FACTORS
I. INTRODUCTION C-l
II. PATHWAYS C-l
ix
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Page
III. MEDIA CONCENTRATION TO DOSE CONVERSION FACTORS C-3
IV. DOSE-RISK CONVERSION FACTORS C-12
REFERENCES C-24
FIGURES
Figure 1. Model for estimating health effects from nuclear
power industry 7
Figure 2. Estimated numbers of cumulative potential health
effects committed by operation of the United States
nuclear power industry through the given year ... 11
Figure 3. Range of estimates for potential health effects
from the actinides 13
Figure A.I. Projected United States electrical power demand . . A-3
Figure A.2. United States population projection A-ll
TABLES
Table 1. Estimated cumulative numbers of potential health
effects committed by operation of the nuclear power
industry 10
Table A.I. Estimated fuel reprocessing requirements A-2
Table A.2. Representative quantities of potentially significant
fission products in spent reactor fuel A-b
Table A.3. Representative quantities of potentially significant
activation projects in spent reactor fuel A-7
Table A.4. Representative quantities of actinides present in
spent fuels A-8
Table A.5. Estimated annual inventories of selected nuclides in
reprocessed fuel A-9
Table B.I. Conversion factors for dose and health risk
estimates B-13
Table C.I. Milk concentrations of iodine-131 and iodine-129
from given concentration and corresponding doses . . C-9
Table C.2. Actinide air-dose conversion factors relative to
plutonium-239 C-ll
Table C.3. Summary of media-dose conversion factors C-12
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ABSTRACT
The cumulative potential health effects consequences for the release
of tritium, krypton-85, iodine-129, and the actinides have been estimated
for the projected releases of these nuclides by the nuclear power industry
for the next fifty years. These projections are based on models developed
by the staff of the Office of Radiation Programs for release, transport,
and biological effects. Such models are subject to considerable uncer-
tainties, especially for the very long-lived radionuclides. Therefore, the
results are not to be interpreted as definitive, but rather as an order of
magnitude comparison for planning of future radiation protection guidelines.
Results of these numerical estimates indicate that, for the assumed
environmental models, releases of plutonium-239 and other actinides over
the next fifty years could result in an incremental 23,800 additional
potential health effects over the succeeding 100 year period, followed by
krypton-85 with 6,900, tritium with 2,800 and iodine-129 with about 250
additional potential health effects. These projections apply to only the
releases from the U.S. power industry and would be larger if the entire
world production were included.
The conclusions presented are highly tentative because of the uncer-
tainties involved, but do establish a scale of magnitudes and convey the
concept that the release of long-lived radionuclides to the general environ-
ment must be calculated by techniques which include the cumulative conse-
quences instead of only the annual exposure rates.
xi
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ASSESSMEJT OF THE POSSIBLE ENVIRONMENTAL DOGE vJOMl-ilTi^i
RESULTING FROM RELEASE OF LONG-LIVED RADIONUCLIDES
PRODUCED BY OPERATION OF THE NUCLEAR POWER INDUSTRY
FOR THE NEXT FIFTY YEARS
I. INTRODUCTION
The release of radioactive material to the environment results
in radiation doses to human populations which may produce adverse health
effects. Most radioactive material production today occurs as the
result of the fissioning process in nuclear electric power reactors.
The majority of radionuclides produced have short half-lives (the time
required for one-half of a mass of radioactive material to disintegrate
or decay away). However, some radionuclides are long-lived (arbitrarily
defined in this paper as having a half-life longer than 10 years) and
present a long-term potential for exposure of humans. This paper is
concerned solely with a discussion of the environmental consequences
associated with the release of these long-lived radionuclides.
This report uses the terminology "cumulative potential health
effects" to describe the summation over a specified time period of
deaths and diseases, including birth defects, that may be attributable
to radiation exposure. The qualifying adjective "potential" is added
to emphasize that the effects are not demonstrable but are based on
extrapolations from information derived at higher levels of exposure
than to be experiences, using a linear, non-threshold assumption. Ho
attempt is made to qualitatively relate these projected estimates to
health effects that may be attributable to other radiation sources,
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such as natural background or medical exposures but it is recognized
that present releases from the nuclear power industry are small in
comparison. It must also be kept in mind that the primary concern
here is with sources that are controllable, man-made, and primarily
result in involuntary exposures.
Unlike most chemical pollutants (except perhaps for the heavy
metals and certain non-degradable toxic compounds), long-lived radio-
nuclides by virtue of their persistence tend to build up in the environ-
ment and represent a potential hazard for a very long time. As the
nuclear electric power production process (nuclear reactors plus all
the fuel cycle facilities necessary to support the reactor operations)
grows, the amounts of the long-lived radionuclides released to the
environment and the accumulated quantities will also grow. This study
is intended to assess the potential radiological health impact of the
release to the environment of certain long-lived radionuclides which
have been produced by nuclear generation of electricity.
The first widespread recognition that these long-lived nuclides
present a potential hazard to the general population followed revelation
of evidence of strontium-90 (28 year half-life) in the fallout from
nuclear weapons testing during the 1950*s and 19bO's. Other artificial
radionuclides, such as tritium (12.3 year half-life), krypton-85 (10.7
year half-life), cesium-137 (30 year half-life), and plutonium-239
4
(2.4 x 10 year half-life), have since been produced in relatively
large quantities and have also become of concern. In addition, iodine-129
(1.7 x 10 year half-life), although not produced in large quantities,
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3
is of concern primarily because of its high potential for release to
the environment. Releases of the very long-lived radionuclides, such
as plutonium-239 and iodine-129, represent essentially an infinite
commitment to the environment and the consequences of their unrestricted
release must be evaluated in terms of potential health effects to count-
less generations.
Most previous assessments of population radiation doses have
been concerned primarily with the concepts of maximum individual doses
and average total annual doses. This paper is intended to carry these
concepts further by relating total population doses to anticipated
numbers of health effects and by integrating the total effects over
both the entire exposed populations and the total time of persistence
in the environment of any specific radionuclide. In this way, total
cumulative numbers of potential health effects for all releases up to
a specified year can then be evaluated and give a comprehensive picture
of overall consequences. Health effects, for purposes of this study,
are defined as radiation induced somatic effects such as lung, thyroid,
or skin cancers, plus lethal genetic effects in future generations.
A detailed description of numerical values used is given in appendix C.
We have attempted to develop projections of the total release
of several long-lived radionuclides to the environment through the
year 2020, and from this have derived the estimated number of resultant
cumulative potential health effects. This report is intended only to
present upper bound estimates of the potential long-term impact of
the release of long-lived radionuclides to the general environment.
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4
As such, it emphasizes the magnitude of the potential problem which
could result, rather than attempting to give the most probable impact
of such releases based on the limited information currently available.
Estimates of uncertainties are also given.
Projections of potential public health impact made here are primarily
for the purpose of developing a data base for standard setting. As
stated above, most environmental contaminants are relatively short-lived
and standards are based on current ambient levels of contamination
only. When the source term for such contamination is removed, the
problem ceases to exist a short time thereafter. However, the long-lived
contaminants continue to present a public health hazard long after
their release to the environment. Their public health impact is neces-
sarily cumulative and build-up in the environment is irreversible
(except by radioactive decay). Therefore, control measures must be
instituted at a time sufficiently far in advance of when the cumulative
effects of these long-lived contaminants becomes a significant long-term
health problem. This paper has only attempted to survey the potential
magnitudes of releases of long-lived radionuclides from the nuclear
power industry over the next fifty years. Even in this respect, we
have not attempted to include all possible radionuclides but have chosen
to highlight only a few which, because of the release quantities or
the biological risk potential, were considered to probably be the most
significant from this viewpoint. A number of other long-lived radio-
nuclides, such as strontium-90 and cesium-137, are produced in substantial
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5
quantities but are generally considered to be reasonably well contained
and therefore present a waste disposal rather than environmental exposure
problem.
For a comprehensive analysis of the role of all long-lived radio-
nuclides, other sources must be considered. The wide distribution of
strontium-90 and of plutonium-239 from nuclear bomb test fallout is
well documented. Future use of nuclear weapons could substantially
increase the environmental burden. Applications of nuclear isotopes
in industry and medicine utilize a wide range of radionuclides. Neither
the discharge rates to the environment nor the pathway models for most
of these are well documented yet. However, the analysis of the conse-
quences of their release follows the techniques outlined here. Nuclear
devices, such as those employed in Project Plowshare, are generally
designed to be relatively "clean", but nonetheless may release substantial
amounts of long-lived radionuclides such as krypton-85 and tritium to
the environment. Because the future of this program is in doubt, no
realistic projections can be made. Utilization of long-lived radio-
isotopes in power sources, especially for space vehicles, presents
another potential source of unknown dimension. Such units are well
contained and designed to withstand reentry, but absolute predicitons
are not possible.
'the above examples are not intended to be all-inclusive but merely
indicate the magnitude of the potential problem for an expanding inuustry.
The primary consideration is that, for all the long-lived radionuclides,
control is possible only by restricting releases, and the consequences of
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fo
their distribution in the general environment must be considered essen-
tially irreversible. Projections of anticipated potential health effects
which could result from the release of these radionuclides constitute
a useful technique for decision-making in the time frame in which controls
should be instituted for specific radionuclides.
II. GENERAL METHODOLOGY
In order to assess the magnitude of the potential environmental impact
of the release of the long-lived radionuclides from the nuclear power
industry, four different isotopes (or groups of related isotopes) have
been chosen for this study. Selection was based primarily on estimated
order of total public health impact. The radionuclides considered in this
analysis are tritium, krypton-85, iodine-129, and the actinides including
plutonium-238, 239, 240, 241, americium-241, and curium-242, 244. Esti-
mates have been made of release quantities, dispersion through environ-
mental pathways, and of the resultant population exposures. Results are
given in terms of radiation doses and potential health effects to the ex-
posed populations. The general method is outlined in figure 1. In prin-
ciple, the total environmental dose and health commitments resulting from
all of the releases of a specific radionuclide during a specified time
period are obtained by integrating over all time and space.
Details concerning source terms are given in appendix A. Projections
of nuclear power production have been made to the year 2020. Quantities of
the various radionuclides produced have been derived from these projections.
Assumptions have been made with respect to release fractions and control
technology. Various pathways in the environment from the points of re-
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FIGURE 1 .
Model for estimating health effects
from nuclear power industry
Nuclides
Half-lives
Forms
Production
Radionuclide
Sources
R
Ri
ates of
e lease
1
Media Concentrati
Dispersion
Dilution
Reconcentrati
Air
Water
Food Chp-ins
Pathways
ons
on
Modes of Exposure
Direct Radiation
Inhalation
Ingestion
Population Statistics
; Dose
1 Equivalent
1
1
Morbidity
Mortality
Health
[_ ^ i
Risk
i
Hydrology
Soil Properties
Media concentration
To Dose Conversion
Factors
Source
Tertr.
Environmental
Transport
Population
Exposure
Dose Equivalent To
Health Effect
Conversion Factors
Health
Effects
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8
lease to the exposure of people have been postulated. These are detailed
in appendix B. All of the included radionuclides are assumed to lead to
initial short-term exposures of individuals within an 80-km radius.
Iodine-129 and the actinides are then assumed to ultimately be uniformly
distributed over, and confined to large portions of the total U. S.
land area. Krypton-85 and tritium are assumed to be ultimately dispersed
over the entire world, with some additonal effect on the total U. S.
prior to complete distribution.
The concentration of radioactivity in food, water, air and other
materials has been converted to population dose and then to health effects.
Conversion factors used are described in appendix C. The growth of the
U. S. and world populations is taken into account (see appendix A for
population projections), and the buildup in the environment due to the
release of these radionuclides over a long period of time is also considered.
For the estimation of health effects a linear non-threshold dose-effect
relationship has been used. Effects noted at high doses have been extra-
polated linearly to zero effects at zero dose. Thus, all doses, no matter
how small, have been postulated to present some health risk. For purposes
of this study, health effects are defined as radiation-induced somatic
effects such as lung, thyroid or skin cancers, plus lethal genetic effects
in future generations. A detailed discussion of the numerical values
used is given in appendix C.
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III. RESULTS AND ESTIMATES OF UNCERTAINTIES
Estimated maximum numbers of potential cumulative health effects
attributable to tritium krypton-85, iodine-129 and the actinides dispersed
in the environment are shown in table 1 and figure 2. The numerical
values represent the total estimated numbers of current and future poten-
tial health effects, based on conservative assumptions, which may be
attributed to these nuclides from all pathways of exposure by contami-
nation already committed to the environment through any given year.
Therefore, these health effects represent an irreversible commitment
through any given year, even if future contamination should cease at
that point. Future commitments have been estimated for the complete
decay of krypton-85 (half-life 10.7 years) and of tritium (half-life
12.3 years), but are estimated only for the initial 100 years after
release for iodine-129 (half-life 1.7 x 10 years) and for plutonium-239
(half-life 24,000 years). For example, if release of all krypton-85
through the year 2000 is assumed, then (from table 1) the calculations
indicate that an estimated 230 health effects will have been committed
by radiation doses from this source received prior to and during the
year 2000 and an estimated additional 7bO health effects will be caused
by doses to be received by the exposed populations after the year 2000
due to krypton-85 already in the environment from the releases through
that year.
The largest range of uncertainties is probably associated with the
number of potential health effects which can be related to the release and
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TABLE 1
Estimated cumulative numbers of potential health effects
committed by operation of the nuclear power industry
Year
1970
Cumulative potential health effects
lodine-129
Past-
Present
0
1975 0
1980 i 0
1985 i 1
1990 : 3
1995
2000
2005
2010
2015
2020
6
Future
0
0
1
4
9
17
11 32
Tritium
Past-
Present
0
2
11
35
88
190
360
21 53 630
Future
0
0.5
3
8
21
43
Krypton-85 i Actinides
Past-
Present
„ _ Past-
Future Present
0
0.3
3
14
42
110
81 230
140 1 460
34 i 82 1,000 230 830
53 120 1,600 i 340 1,400
78 170 2,300 ] 500 i 2,300
,
0 0
5 2
26 12
79 38
190 96
Future
0
26
140
440
1,100
410 210 ; 2,200
760 400 ! 3,900
1,300 720 6,500
2,100 1,200 ; 10,000
3,200 1,900 15,000
4,600 2,800 21,000
about 25% fatal about 64% fatal about 61% fatal about 100% fatal
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35,000
Figure 2. Estimated numbers of cumulative potential health effects
committed by operation of the United States" nuclear power
industry through the given year
30,000
25,000
ACTINIDES.
a
UJ
20,000
U
UJ
LL.
Ll_
UJ
I
15,000
10,000
5,000
1970 1980 1990 2000
Year
2010
2020
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12
dispersion of the actinides in the environment. The values shown in
table 1 and figure 2 give only projected conservative estimates of num-
bers of potential health effects associated with releases resulting from
normal operation of the U.S. nuclear power industry. The range of vari-
abilities involved in the assumptions used here indicates that the poten-
tial consequences for the actinides are uncertain over a wide range and
may be overestimated by at least two orders of magnitude and possibly by
considerably more. This range is indicated in figure 3. However, even
the curves designated "most probable estimate" and "optimistic estimate"
shown here should only be considered as indicative of this wide range of
uncertainties and not as definitive numerical values. As indicated below,
the range of uncertainties associated with the other radionuclides dis-
cussed in this paper is considerably smaller. Neither accidental releases
nor other potential sources have been included in this analysis.
It should be noted that the curves differ from each other by only a
constant numerical ratio, and that the number of estimated cumulative
potential health effect calculated for releases through a given year differs
by this same factor. The slopes of the curves are identical and the time
required to reach a certain number of health effects for different assump-
tions can be derived from any curve. Thus, for example, the "Conservative
Estimate" curve reaches 1,200 in 1990 and 24,000 in 2020, or a difference
of 30 years. The "Most Probable Estimate" curve reaches 1,200 in 2020 and
"Conservative estimate" refers to results of calculations incorporating
the maximum factors of conservatism thought appropriate and leads to the
highest anticipated number of health effects. "Optimistic estimate" refers
to the assessment with minimum conservatism and leads to the lowest antic-
ipated number of health effects.
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30,000
Figure 3. Range of estimates for potential health effects from the actinides
25,000
^ 20,000
z
ILJ
6
CL
15,000
LLJ
CO
10.000
5.000
CONSERVATIVE ESTIMATE
MOST PROBABLE
ESTIMATE
OPTIMISTIC
ESTIMATE
1970
1980
1990 2000
Year
2010
2020
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14
would reach 24,000 in 2050.
It should be recognized that considerable uncertainty is associated
with all the numerical values given because of variabilities in the many
factors involved in their derivation. However, release fractions and
environmental pathways are more easily established for certain radio-
nuclides, such as the inert gases, leading to more realistic estimates for
these Isotopes. In general, a realistically conservative viewpoint was
used in the development of the models used in these calculations. There-
fore, the more uncertainty involved in a given calculation, the n.ore
conservatism is built into the result. Thus, the krypton-85 results are
considered the most realistic (and least conservative), followed by those
for tritium, iodine-129 and the actinides in increasing order of conser-
vatism, i
For the assumptions used here, the projected numbers of health effects
would be greatest for the actinides and range through krypton-85, tritium,
and iodine-129 in decreasing order. However, the associated uncertainties
may change this order (especially in the case of the actinides) and neither
the actual numbers nor the given order of ranking should be considered as
more than grossly indicative of the magnitude of the potential problem
associated with the release of that specific radionuclide.
The principal uncertainties in the analysis include, not necessarily
in the order of importance, the following:
1. quantity of radionuclides which will actually be released to the
environment,
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15
2. The pathway through the environment, including distribution path-
ways, kinetics of dispersal, and existence of ultimate sinks,
3. the specific conversion factors used to convert population exposures
to estimated numbers of health risks, and
4. statistics used to estimate growth of populations and of energy
demand.
For the actinides, the release fraction was taken as 10~° of the
plutonium processed during the appropriate time interval. Anticipated
control for nuclear fuel reprocessing facilities is expected to be of the
—fi
order of 10 or better, but allowance must be made for transport and
handling losses throughout the entire fuel cycle. Overall control of the
actinides may be expected to improve with time and may eventually equal
that estimated for the fuel reprocessing facilities alone. Therefore, the
value of the release fraction used may be larger than will actually be
realized, and may introduce a factor of conservatism of the order of 100 or
more.
The primary pathway of the actinides to man has been assumed to be by
inhalation of aerosol particles resuspended in the atmosphere after depo-
sition. A uniform surface distribution, a soil retention factor of 0.5,
and a resuspension factor of 10 (in terms of activity per m^ of air com-
pared to m2 of surface) have been assumed. Therefore, the effective value
for the resuspension factor used in this analysis is 5 x 10" . Resus-
—8 — "\
pension factors ranging from a low of 10 to a high of about 10 have
been reported for newly deposited plutonium, with most clustered in the
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region of 10 . For undisturbed areas, considerably lower values, ranging
from 10 to 10 generally seem to apply for time periods ranging from a
few months to several years after deposition. The change is probably due
to migration of these compounds through the soil, thereby depleting the
quantity near the surface, rather than to a fundamental change of physical
characteristics. Long-term values for the resuspension factor for specific
geographical areas are presently indeterminate, and could quite possibly
lead to higher average values because of soil disturbances on a periodic
basis. It may ultimately prove that a resuspension factor decreasing with
—7 —8
time, with an averaged value of 10 to 10 , would probably represent the
situation more realistically, that this migration through most soils
represents a pseudo-sink for the actinides, and that their long-term signif-
icance has been overestimated. Use of the resuspension factor chosen here
may introduce a factor of conservatism of the order of 10 - 100 and perhaps
considerably more. However, the wide range of possible values for the
time averaged resuspension factor, and the uncertainties associated with
human uptake pathways, do introduce a finite probability that both the
quantity of actinides available and the resultant doses to populations
could be higher than calculated and that the numbers of potential health
effects could have been underestimated.
The foregoing has only considered the dispersion of the actinides
from normal releases by the nuclear power industry. As opposed to some of
the other radionuclides considered here, the magnitude of the source term
-4
has been taken as only 10 of the total quantity available, further
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17
_2
modified by a reduction factor of 10 expected to be provided by available
air cleaning technology. Therefore, the possibility of significant acci-
dental releases must also be considered as potentially increasing this
source term and consequently increasing the potential numbers of estimated
health effects. In addition, weapons uses, possible peaceful applications
of nuclear materials, and other potential sources have already contributed
some environmental contamination and may add substantially more in the
future. Thus the evaluation of the consequences only from anticipated
releases by the nuclear power industry may not indicate the full dimension
of the potential problem resulting from release of the actinides to the
general environment.
For iodine-129 a fractional release of 1/10 of the amount available
has been used. This estimate is consistent with current U.S. regulatory
practice and may introduce a factor of conservatism of the order of 10 or
greater. However, long-term retention of iodine on adsorbers had not yet
been demonstrated conclusively. Uniform distribution of iodine-129 over
the entire eastern land area of the U.S. is an idealized concept but, as
noted below, this probably does not introduce significant error when used
in the evaluation of health effects. The migration of iodine-129 in the
environment, pathways to man, and ultimate disposition are not yet well
established and the pathway model used in this analysis is largely specu-
lative.
In accord with current practice, all of the krypton-85 and tritium
produced are assumed to be released to the environment. Krypton-85, as an
-------
18
inert gas, is assumed to mix in the world atmosphere. Little uncertainty
is associated with such an assumption over the time span of interest.
Similarly, the distribution of tritium over most of the water of the world
is realistic over a long time period. However, the assumptions concerning
the regional dispersion of tritium in the hydrological cycle, especially
the rainout over a restricted area, are subject to considerable uncer-
tainty.
The question of uncertainties introduced by assumptions related to
both the extent of geographical dispersion of radionuclides and population
densities is relatively complex. Doses to individuals are strongly de-
pendent on the concentrations of radionuclides. However, doses averaged
over an entire population are nearly independent of actual distribution
provided approximately uniform distributions of either radioactivity con-
centrations or population density can be assumed. For example, if a cer-
tain amount of radioactivity were uniformly deposited in a 20,000 square
kilometer area (circle of radius 80 km) containing the Eastern U.S. average
of about 42 people/km2 (840,000 people) and if each person received a dose
of one rem, then the total exposure would be 840,000 man-rem. However,
since the remainder of the population (assumed as 2 x 10s persons) is
assumed to receive no exposure, the total exposure to the entire country
would be equal to the regional value. If the same amount of radioactivity
were uniformly distributed over the entire Eastern U.S. land area of 3.75
x 106 km, the average dose per individual would be 20,000/3.75 x 106, or
5.3 x 10~3 rem. Multiplied by 80% of the total U.S. population (the
-------
19
Eastern half portion), this yields 850,000 man-rem. For calculations
involving statistical averages, such as calculation of potential numbers
of health effects at low dose levels, the results are therefore identical,
and essentially independent of the area considered for dispersion.
The hypothesis used in the derivation of the dose to potential health-
risk conversion may also be considered to contribute to an overall indeter-
minate variability in these estimates. The linear non-threshold approach
of extrapolating from observed effects at high doses to give estimated
effects at low doses may result in conservative estimates (greater than
expected numbers of potential health effects).
Finally, population and power demand projections are subject to only
limited uncertainties for the next decade but this uncertainty increases
with time into the future. Recent information indicates that power demand
projection may have to be revised, but the values chosen are considered
the best currently available.
It must be recognized that any conclusions resulting from an analysis
of this type are highly tentative. While it may be possible to indicate
uncertainties in the light of current experience, any projections such as
those presented here are indicative only of possible consequences and are
not intended to present more than general future trends. In order to be
most useful for policy decision, such an analysis must be updated at
frequent intervals and as new information is developed.
The purpose of this study has been to attempt to delineate the scope
of the potential problem associated with the unrestricted release of
-------
20
several of the long-lived radionuclides to the general environment. There-
fore, it is important that the most conservative case be determined to
demonstrate what possibly could occur if prudent concern and constant con-
trol are not exercised to minimize releases and prevent buildup in the
environment. In this context, we have attempted to assess the magnitude
of this worst expected case as well as give a best estimate of the actual
expected situation. It should be recognized that the conservative pro-
jections given are not necessarily expected to occur, that lower levels
(even down to zero release) are obtainable, and that this paper only
attempts to point out what could occur if proper concern and controls are
not exercised on an appropriate time scale. As such, the paper is intended
to provide a guideline for positive intervention by the Federal government.
-------
21
SELECTED REFERENCES
Allied Gulf Nuclear Services, Barnwell Nuclear Fuel Plant Safety
Analysis Report, AEC Docket No. 50-332, (1969).
Bryant, P. M., "Derivation of Working Limits for Continuous Release
Rates of 129l to Atmosphere," Health Physics, Vol.19, pp. 611-616,
(1970).
Burch, et al, Transuranium Processing Plant Semiannual Report of
Production, Status and Plans for Period Ending June 30, 1971, Oak
Ridge National Laboratory, ORNL-4718, (1971).
Crandall, J. L., Tons of Curium and Pounds of Californium, Presented
at the American Nuclear Society International Meeting, Washington, D. C,
November 10-15, 1968.
Deonigi, D. E., Formulation of Transuranium Isotopes in Power Reactors,
Battelle Northwest Laboratory, BNWL-140 Rev 1, (1966).
Deonigi, D. E., et al, Isotope Production and Availability from Power
Reactors, Battelle Northwest Laboratory, BNWL-716, (1968).
Drumheller, K., Pacific Northwest Laboratory Division of Isotope
Development Programs Quarterly Report, Battelle Northwest Laboratory,
BNWL-1010, (1969).
Gamertsfelder, C. C., Statement on the Selection of as Low as Practi-
cable Design Objectives and Technical Specifications for the Operation
of Light Water Cooled Nuclear Power Reactors, Presented at AEC Hearings
on Revision of Appendix I, 10 CFR 50 (1972).
General Electric Company, Midwest Fuel Recovery Plant Safety Analysis
Report, AEC Docket No. 50-268, (1969).
Hofman, P. L., "U. S. Civilian Nuclear Power Cost-Benefit Analysis,"
Fourth United Nations Conference on the Peaceful Uses of Atomic
Energy, Geneva, Switzerland, 6-16 September 1971, A/CONF. 49/P/072.
Klement, A. W., et al, Estimates of Ionizing Radiation Doses in the
United States - 1960-2000, U. S. Environmental Protection Agency,
EPA/CSD/ORP 72-1, (1972).
Knox, J. B., "Airborne Radiation from the Nuclear Power Industry,"
Nuclear News, Vol. 14, pp. 27-32, (February 1971).
-------
22
Lindell, B., "Assessment of Population Exposures," Symposium on
Environmental Behaviour of Radionuclides Released in the Nuclear
Industry, Alx-en-Provence, France, (May 1973).
Hachta, L., National Oceanic and Atmospheric Administration, Un-
published Data.
National Academy of Sciences, National Research Council, "The Effects
on Populations of Exposure to Low Levels of Ionizing Radiation,"
Report of the Advisory Committee on the Biological Effects of Ionizing
Radiation. (1972).
Nodvik, R. J., Supplementary Report on Evaluation of Mass Spectro-
metric and Radiochemical Analyses of Yankee Core I Fuel, Including
Isotopes of Elements Thorium Through Curium, Westinghouse Atomic
Power Division, WCAP-6086.
Nuclear Fuel Services, Inc., Environmental Report No. 11, (1971).
Oak Ridge National Laboratory, Siting of Fuel Reprocessing Plants
and Waste Management Facilities. ORNL-4451, (1970).
United Nations Statistical Office Report, (1966).
U. S. Bureau of the Census, 1970 U. S. Census of Populations;
Preliminary Report.
U. S. Department of Commerce, Statistical Abstract of the United
States, 1969.
U. S. Environmental Protection Agency, Compendium of Environmental
Surveillance Around the Rocky Flats Plutonium Plant. FOD/ORP/EPA, (1972).
University of California, Los Alamos Laboratory, Proceedings of the
Environmental Plutonium Symposium, LA-4756, (1971).
Wayne, S. J., et al, Clinical Aspects of Iodine Metabolism, F. A.
Davis Co., Philadelphia, (1964).
-------
APPENDIX A
ELECTRIC POWER and POPULATION
PROJECTIONS
-------
A-l
I. INTRODUCTION
This appendix contains the electric power demand, radionuclide production
and population projections utilized in the calculations presented in this
paper. These projections are based on information in the literature and
were not developed independently by the staff.
II. ELECTRIC POWER USE PROJECTION
As a starting point in the assessment of the radiological impact of the
nuclear power industry on the general population, an estimate of the total
quantity of radioactive materials present in spent fuels produced by nuclear
electric power generation must be obtained.
These estimates are based primarily on the projected electric power
demand, and on the fraction of that demand expected to be satisfied by nuclear
plants. To some extent, they are also contingent on the projected number
of various reactor types resulting in differing amounts of the various
radionuclides produced.
Electrical power demand forecasts, and the fractional amount expected
to be produced by the nuclear industry through the year 2020 are summarized
in table A.I and figure A.I.
-------
Year
Nuclear electric
generation, GW(e)
Table A.I
Estimated fuel reprocesisng requirements
Metric tons of fuel discharged annually8
Number of 5 MT/day
1970
1975
1980
1985
1990
1995
2000
2005
2010
2015
2020
2.6
40
110
220
420
650
1000
1360
1780
2220
2700
LWR-U
25
700
1900
2700
3700
4100
3700
3700
4300
5300
6100
LWR-PU
0
90
500
2600
3800
4100
3800
3700
4400
5400
6100
LMFBR
0
0
0
0
480
2,600
11,500
20,600
32,800
43,800
58,000
HTGR
0
0
0
100
2,420
6,600
7,800
10,000
10,000
10,000
8,000
Total
25
790
2,400
5,400
10,400
17,400
26,800
38,000
51,500
64,500
79,000
reprocessing piancs
required
1
1
2
4
7
12
18
26
35
43
53
3Burnup: 33 GWd(t)/MT and 0.35 thermal efficiency.
-------
10.000
5.000
A-3
Figure A. 1 Projected United States electrical power demand
2,000
1,000
500
U.S. ELECTRIC POWER DEMAND
ju
O.
a
z
y
ae.
i—
U
Q
LLJ
U
Ul
3
Sf
200
100
50
20
10
PORTION OF DEMAND
SUPPLIED BY NUCLEAR POWER
I
1970 1980 1990 2000
Year.
2010
2020
-------
A-4
III. RADIONUCLIDES PRODUCED AND RELEASED BY NUCLEAR POWER INDUSTRY
The quantity of radionuclides to be produced can be determined from
the projected nuclear electric power demand of the previous section. A
conversion to metric tons of fuel discharged in any given year is made by
using data on power generated two years earlier, a thermal efficiency of
0.35, and a burnup of 33 GWd(t) per metric ton of fuel:
metric tons of fuel discharged per year = (gigawatt [GW] power capacity)
x (0 64 power generated . x . 365 days . ' 1 thermal power .
power capacity year 0.35 electrical power
. 1 metric ton fuel .
x l 33 GW days ' '
For purposes of this study, it has been assumed that tritium, the
noble gases and the halogens are released only during the fuel reprocessing
stage. Actinides are assumed to be available for release at each stage of
the nuclear fuel cycle.
There are three sources for radioactive material present in spent
reactor fuel: fission products, activation products, and actinide isotopes.
The quantities of specific radionuclides present are determined primarily
by fuel type, amount of burnup, and time of cooling (time between removal
from the reactor and time of reprocessing).
i
Tables A.2 and A.3 show quantities of the potentially significant
fission product and activation radionuclides present in one metric ton of
spent fuel with 33 GW(t) days burnup and 150 days cooling time. These
values are considered reasonably representative of all nuclear fuel types.
-------
A-5
There is indication that cooling times shorter than 150 days may be used
in the future, since faster recycling of the recovered fuel produces an
economic benefit. This would significantly increase the amounts of shorter-
lived radionuclides in the fuel and available for release, but not signifi-
cantly affect the long-lived fission product inventories.
The amounts of actinides estimated to be present in uranium fuels
and in plutonium-recycle fuels are given in table A.A. It is assumed
that all fuels (including those used in HTGR's) other than uranium-235
fuels can be considered equivalent to plutonium-recycle fuels.
Based on the amounts of spent fuel to be processed, and on the estimated
quantities of radionuclides per metric ton of spent fuel, the projected
annual quantities of several of the most significant radionuclides in pro-
cessed fuel were calculated and are presented in table A. 5.
The fractions of the radionuclides which may be released to the environment
have been chosen on the basis of the most conservative current estimates.
Therefore, all of the tritium and krypton-85 are assumed to be released,
10% of the xodine-129, and 10 of the total actinide inventory. These
values represent the product of the maximum amount assumed available for
release and the least effective decontamination factor achievable with current
industrial technology.
-------
TABLE A.2
Representative Quantities of Potentially Significant Fission Products In Spent Reactor Fuels
Isotope
H -3
Kr -85
Tc -99
Ru -103
106
Te -125m
127m
129m
I -129
131
Cs -134
135
137
Sr -89
90
Y -91
Zr -93
-95
Mb -95
Sb -125
Ce -141
144
Pm -147
Eu -155
Half-life
(Years)
12.3
10.7
2. 13x10 5
0.11
1.01
0.16
0.30
0.09
17xl06
0.02
2.05
3x10 6
30.2
0.14
28.9
0.16
0. 95x10 6
0.18
0.10
2.73
0.09
0.78
2.62
5.0
Curies per
tonne
800
10,500
15
180,000
820,000
6,500
25,000
13,000
0.04
2.0
100,000
1.2
106,000
100,000
60,000
190,000
2
400,000
800,000
13,000
80,000
800,000
200,000
40,000
Grams per
tonne
0.083
27
880
5.7
240
0.36
2.7
0.42 •
250
0.01
77
1400
1200
3.5
430
7.8
490
19
21
12
2.8
250
220
87
Release
state
Gas
Gas
seni volatile
Semi volatile
Seni volatile
Semi volatile
Semi volatile
Seni volatile
Volatile
Volatile
Seni volatile
Semi volatile
Scmivolatile
Solid
Solid
Solid
Solid
Solid
Solid
Solid
Solid
Solid
Solid
Solid
Notes
95% released as HTO
Oxide b.p. 200 °C
Tetroxide b.p. .80°C
169Rh + lcsRh daughters
Oxide b.p. 750 °C
Oxide b.p.12-7 Tc daughter
Oxide b.p.129 Te daughter
b.p. 184°C
b.n. 184°C
Oxide b.p. 750°C
Oxide b.p.
Cxide b.p. 750°C137^3a daughter
9°Y daughter
35tnNb + 95Nb daughters
l^Pr 4- l^Hd daughters
Burnup = 33 GWd(t)/tonne
C'jolinp, Time =» 1.50 d^ys
-------
A-7
Table A.3
Representative quantities of potentially
significant activation products in spent reactor fuel
Isotope
54Mn
55Fe
59Fe
58CO
6°Co
Half-life
(years)
0.86
2.7
0.12
0.20
5.26
Curies per
metric ton
30,000
20,000
500
30,000
2,000
Grams per
metric ton
3.9
8.3
<.01
1.0
1.8
Release
state
Solid
Solid
Solid
Solid
Solid
Based on 33 GWd(t) burnup/MT
150 days cooling time
-------
A-8
TABLE A. 4
Representative Quantities of Actinides Present in Spent Reactor Fuels
Isotope
U-235
236
238
Np-237
Pu-238
239
240
241
242
Am-241
243
Cm-242
244
TOTAL
(excluding
Half-life
(years)
710xl06
24xl06
4510xl08
2x10 6
86
24,400
6,580
13
379,000
458
7,800
0.45
17.6
uranium)
Urnniura
Ci/tonnc
. <1
<1
<1
<1
4,000
500
650
150,000
2
750
20
35,000
2,000
193,000 -
fuels
g/ tonne
8,000
4,000
950,000
600
230
8,100
2,900
1,300
510
230
100
10
25
14,000
Pu-rpcvc]e
Ci/ tonne
<1
<1
<1
<1
6,000
750
1,000
300,000
5
2,000
200
250,000
25,000
585,000
fuel
g/ tonne
3,000
1,500
950,000
200
340
12,000
4,400
2,600
1,300
620
1,000
75
300
23,000
Cooling time = 150 days
Burnup = 33 GWd(t)/tonne
-------
TASLE A. 5
Estimated Annual Inventories of Selected Nuclides in Reprocessed Fuel
(Curies)
Year
1970
1975
19SO
1985
1990
1995
2000
2005
2010
2015
2020
Fuel Discharge
25
790
2,400
5,400
10,400
17,400
26,800
38,000
51,500
64,500
79,000
Tritium
2 . OxlO1*
6.3xl05
l.SxlO6
4.3xl06
S.3xl06
l.AxlO7
2.1xl07 •
3. OxlO7
4.1::107
5.2>:107
6.3xl07
Krypton- 8 5
2. 6x10 5
I
8.3xl05
'2.5xl07
5.7xl07
l.lxlO8
l.SxlO3
2.8xl08
4.0xlOe
5.4xl08
G.SxlO8
'8.3xl08
Iodine-129
1.0
3.2X101
9.6X101
2.2xl02
4.2xl02
7.Cxl02
l.lxlO3
l.SxlO3
2.1xl03
2.6xl03
3.2xl03
Plutonium-239
1.9X101*
5. 9x10 5
l.SxlO6
4 . IxlO6
7.8xlOs
l.SxlO7
2. OxlO7
2.9xl07
3.9xl07
4.8xl07
5.9xl07
Plutoniura-241
7.5xl06
2.4xl08
7.2x10°
1.6xl09
3.1xl09
5.2xl09
8. OxlO9
l.lxlO10
l.SxlO10
1.9xl010
2.3xl010
Baicd on Pu-rccycle fuel p.r.d reactor type distribution in Table A.I
(33 GWd/MT burnup and 130 I'.iys cuo'. isifj period.)
-------
A-10
IV. POPULATION PROJECTIONS
A. Regional
The regional population growth within 80 km of a plant was estimated
from population growth projections for reactor sites given in environmental
reports submitted to the AEC by electric power companies. These indicated
a regional population doubling time of approximately 40 years. This value
was considered to be representative of fuel reprocessing plants and other
nuclear facilities also.
B. United States
The population projection for the United States is shown in figure
A.2. This growth curve approximates the 1970 Series C projections of the
Bureau of the Census with the added variation that the population will level
off at 400 million. A straight line approximation to the curve was used to
simplify calculations.
C. World
The world population growth was estimated from median values from a
United Nations projection. The 1970 world population was estimated at
9
3.56 x 10 with an annual growth rate of 1.9%.
-------
5.0
Figure A. 2 United States population projection
4.0
O
a.
O
a.
3.0
2.0
U.S. POPULATION PROJECTION
1970
1980
1990
2000
2010
2020
2030
2040
2050
2060
Year
-------
A-12
REFERENCES
Burch, W. D., Bigelow, J. E., and King, L. J., Transuranium Processing
Plant Semiannual Report of Production, Status and Plans for Period
Ending June 30, 1971, Oak Ridge National Laboratory, ORNL-4718, pp. 29-30,
(December 1971).
Crandall, J. L., Tons of Curium and Pounds of Californium, Presented
at American Nuclear Society International Meeting, Washington, D. C.,
November 10-15, 1968.
Deonigi, D. E., Formation of Transuranium Isotopes in Power Reactors,
Battelle Northwest Laboratory, BNWL-140 Rev. 1, (January 1966).
Deonigi, D. E., McKee, R. W., and Haffner, Isotope Production and
Availability from Power Reactors, Battelle Northwest Laboratory,
BNWL-716, (July 1968).
Drumheller, L., Pacific Northwest Laboratory Division of Isotope
Development Programs Quarterly Report November 1968 to January 1969,
Battelle Northwest Laboratory, BNWL-1010, (February 1969).
Hofmann, P. L., "U. S. Civilian Nuclear Power Cost-Benefit Analysis,"
Fourth United National International Conference on the Peaceful Uses
of Atomic Energy, Geneva, Switzerland, 6-16 September 1971, A/CONF.
49/P/072.
Nodvil, R. J., Supplementary Report on Evaluation of Mass Spectrometric
and Radiochemical Analyses of Yankee Core I Fuel, Including Isotopes
of Elements Thorium Through Curium, WCAP-6086, (August 1969).
Oak Ridge National Laboratory, Siting of Fuel Reprocessing Plants
and Waste Management Facilities, ORNL-4451, (July 1970).
U. S. Atomic Energy Commission, Nuclear Power 1973-2000, WASH-1139,
(December 1972).
U. S. Department of Commerce, Statistical Abstract of the United
States, 1969.
U. S. Department of Commerce, Bureau of Census, Population Estimates
and Projections, Series P-25, No. 493, (December 1972).
U. S. Federal Power Commission, The 1970 National Power Survey, (1971).
United Nations Statistical Office, Demographic Yearbook, Publishing
Service, United Nations, New York, (1971).
United Nations Statistical Office, World Population Prospects as
Assessed in 1963. Population Studies No. 41, United Nations, New
York, (1966).
-------
APPENDIX B
DOSE CALCULATION TECHNIQUES
-------
B-l
I. INTRODUCTION
This appendix presents the general dosimetry equations developed for
this document.
Models for the environmental transport of the radionuclides con-
sidered in this document have been developed, subject to the uncertainity
of assumptions which must be utilized in a situation where only short-
term data are yet available. Assumptions used are based on anticipated
rather than known behavior, but are expected to conservatively model
the environmental dispersion over the time span under consideration.
Only the environmental pathways of principal importance from the view-
point of human uptake and potential health impact have been considered.
Population doses have been derived in terms of man-rem/year for
the populations involved. These calculated population doses are then
used as one of the input parameters in the derivation of numbers of
potential resultant health effects. The calculation of doses involves
two time parameters: t, the time at which the total integrated dose
is desired,and t*, the time of release of a given quantity of radio-
nuclide. For purposes of these calculations, both of the time parameters
are taken as zero in 1970 and t _<_ t*. To obtain the dose in year t,
the contributions from all prior releases corrected for radioactive
decay must be summed. For calculations of genetically significant
organ doses, one half of the appropriate populations numbers have been
used.
-------
B-2
II. REGIONAL POPULATION EFFECTS
The regional population around a nuclear facility is exposed to higher
radioactive material concentrations due to releases from the plant than
an average individual in the U.S. The greatest fraction of these releases
occurs at fuel reprocessing plants. Therefore, this regional population
group is considered as a special case. The total regional population dose
to a specific human body organ i caused by a specific radionuclide j is
estimated by using the following equation:
D (t) - Q, (!)/„, x F.. C Pn(t) man-rem in
ij J Q ( 3 km ) ij R
where:
Q. = Release rate of radionuclide j from the nuclear facility in
curies released per second (Ci/s)
<*>
0 (3 km) = Tne meteorol°9ical dispersion factor (3 km from the plant),
i.e., the radionuclide concentration in air X, compared to the
effluent radioactivity release rate. A distance of 3 km was
chosen as a reference point since the air concentration at this
point is generally not significantly affected by the stack
height of the plant. Annual average meteorological conditions
were assumed, resulting in a value of (X/Q)... . of
i j Km)
_Q O
5 x 10 yCi/cm per yCi/s released for the sector
averaged value for a typical plant. Actual values may vary
from this by an order of magnitude or more.
-------
B-3
F.. = The pathway dependent dose conversion factor, in terms of
(rem/year) / (viCi/cm ), which gives the dose to organ i due
to a media (air, water, or food) concentration of radionuclide j.
For example, iodine exposure of the thyroid gland by inhalation
and milk ingestion would have two separate dose conversion
factors. For radionuclides with long retention times in the
body, e.g., the actinides, the conversion factor represents
the equilibrium dose rate resulting from a continuous constant
intake for several years.
C = The regional dilution and population distribution correction
factor. It is a ratio of the average dose to an individual
within 80 km of the plant to the average individual dose at
3 km, and takes into account both the increased dilution as
the radionuclides are transported further from the plant and
an uneven distribution of population around the plant. It can
be calculated theoretically by assuming a population distri-
bution, or it can be determined from population dose calcula-
tions around real plant sites. For this study the results of
dose calculations for about 50 reactor sites were analyzed
and a value of 0.028 rem/person within 80 km per rein/person
at 3 km was obtained which was assumed constant for all nuclides.
Individual plant correction factors may vary by as much as a
factor of five from the average value given above. The distance
of 80 km (50 miles) was chosen as a cutoff on regional calcu-
-------
B-4
lations since the distance is large enough to include any
nearby large population center yet small enough so that it can
be considered a local area.
P (t) = The population within 80 km of the nuclear facility site.
R
The population values of the above mentioned 50 reactor sites,
taken primarily from environmental reports, lead to an average
population around a site of 1.5 x 10 people in 1980. Popu-
lation density around individual plants can vary from this
by a factor of three. The doubling time of this population is
about 40 years. • For purposes of age specific factors, 2.5%
of the population is considered to be under 1 year old, 45%
between 1 and 20 years old, and the remainder over 20.
Using the above factors, the average annual peculation dose for a
40-year period of constant emissions during constant plant operation can be
calculated from the following equation:
D. . = (Q. Ci/s) x (5 x 10'8 !£i£SL ) x (F £SS&£ , x o.028
13 D C1/S XD
x 1.5 x 10 persons x 1.5 (to account for population growth)
3.2 x 10 Q. P. . man-rem/year .
-------
B-5
III. DOSES TO THE UNITED STATES POPULATION
The transport of radionuclides in the environment is a function of both
their physical and chemical states. Some radionuclides released in the
gaseous effluents from a nuclear facility may spread from the local region
to all or part of the total United States land area or even be diluted over
the entire globe. The method of estimating effects to the U.S. population
depends on the radionuclide being considered. Iodine-129 and the actinides
are assumed to build up only on U.S. soil. Tritium and krypton-85 are assumed
to expose both the eastern U.S. population and ultimately the northern hemi-
sphere or world populations, respectively.
A. Tritium
It is assumed that the tritium released as a gaseous effluent from a
nuclear facility enters into the hydrologic cycle, it deposits over the
6 2
Eastern United States (1.5 x 10 mi ), and it is diluted by the annual rainfall
(40 inches) over this area. With some further dilution by uncontaminated
water this then becomes the water concentration to which the population
of the Eastern United States (80% of the total U.S. population) is exposed.
The total population dose is given by:
X °'80 Pus(t)
where :
C = The water concentration of tritium determined by diluting the yearly
input, Q. (Ci/s) x 3.15 x 10 s/yr, of tritium to the environment
-------
B-6
by the average annual rainfall over one-half of the U.S.
f = A factor to take into account dilution of tritium by uncontaminated
water from deep artesian wells and the fact that not all tritium will
fall out over the Eastern U.S. An indeterminate fraction will pass
over the Atlantic Ocean and be diluted in a larger volume. For this
evaluation a value of f = 0.5 has been used.
Ftj = Dose conversion factor [100 (rem/yr)/(yd/ml) for this case]
Pus = p°Pulation of tne U. S., adjusted for population growth.
Tritium concentration, Cj is related to the environmental input by:
c, -«; r-' «>61 *
3.15 x 107 s/vr
(1.5 x 106 mi2) x (1.61 x 105 cm/mi)2 x (40 in)x(2.54 cm/in)
• 8.0 x 10~6 Q yCi/ml
Therefore:
-6
D.. = 8.Ox 10 xO.SOxfxQ. xF..xP
i] *3 13 us
D..(t) = 3.2 x 10 Q. F.. P (t) man-rem during time t to U.S. population
1D 3 1D us from tritium.
B. Krypton-85
Part of the population of the Eastern United States is exposed to air
concentrations of krypton-85 as it passes from the nuclear facility to the
Atlantic Ocean on its first pass around the world. The dose from this ex-
posure pathway is taken from a study recently performed at the National
Oceanic and Atmospheric Administration. For a plant in Morris, Illinois,
-------
B-7
releasing one curie of krypton-85 per year the population-weighted concen-
tration on its first pass over the Eastern United States to the Atlantic
Ocean is 2.5 x 10 man-Ci/cm . For purposes of this evaluation, this
value is considered adequate to use for all plants. This value is then
multiplied by total annual releases and dose conversion factors to obtain
dose values. The average annual dose is given by:
D±. = [2.5 x 10~16 man"^1] x io6 -^ x Q x F^ x 1.5
cm
where Q. = total annual release in curies for this case. (The 1.5 factor
is to account for population growth with a doubling time of 40 years.)
Therefore:
-10 man-rem/yr to U.S. population
ij " j ij from krypton-85
C. Iodine-129
As a first approximation, all of the iodine-129 release is assumed
to deposit over the Eastern United States (1.5 x 10 mi )and uniformly mix
with the stable iodine in the soil to a depth of 20 cm. This then becomes
the specific activity of iodine in the diet to which all persons in this
part of the country are exposed. Because of its long half-life (1.6 x
10 years), iodine-129 will build up in the soil and expose the population
long after it has been released to the environment. The movement of iodine-129
in the biosphere is not well documented at the present time. Therefore,
the estimates of population exposure are subject to considerable uncertainty.
The specific activity of iodine-129 in the soil at time t, curies
129T. 127T .
I/gram I is:
-------
B-8
t
f Z Q (t*)
t*=0 D
Specific (1.5 x 106 mi2)(1.6 x 1Q5 cm/mi)2
Activity -
cm
t _. 129
= 2.2 x 10"13 f E GJt*) Cl 127
t*=0 -1 g I
where f is the fraction of iodine-129 released that remains in the soil and
it also Includes dilution by iodine taken in from other sources. For purposes
—6 127
of this evaluation f is taken as 0.5. The value of A x 10 I/g soil is
taken from a single reference and may not be representative of the Eastern
United States.
The annual thyroid population dose rate is determined from:
Ci129 127 1Q d±e
D. . (t) = (specific activity *" ) (C I ^ id ) (3.7) (10 ^5- )
13 g I
x (3.15 x 107 —^ ) (0.07 x 1.6 x lo"6 g^S. ) ( I
x(
~6 127
Using an adult value for C (3.50 x 10 g I/g thyroid), the population
thyroid dose rate is given by:
R t
D (t) = 4.0 x 10 P (t) I Q.(t*) man-rem in year t.
ij us t*=0 3
-------
B-9
The dose rate is similar for infants. Therefore, the above dose rate is
used for all ages.
D. Actinides
The actinides are assumed to build up in the Eastern United States
similar to iodine-129, with the principal exposure pathway believed to be
resuspension of the material and inhalation. The annual population dose to
the lungs is:
Z Q.(t*)x f x R x F. . x 0.80 P (t)
62 "^ 9
(1.5 x 10 mi ) (1.6 x 10 m/mi)
where R is the resuspension factor in terms of Ci/m air per Ci/m on the
s
ground. Based on calculations using fallout data and data from around
—6
Rocky Flats a value of R =10 /m is used in this study. The uncertainty
of this value may be several orders of magnitude. The fraction of actinides
released that remains on the soil, f, is taken as 0.5 for this study.
Therefore:
D..(t) = 2.1 x 10~19P (t)f F.. I Q.(t*) man-rem in year t.
1] US 1] . . - X;j '
J t*=0 J
The dose calculation is performed for plutonium-239 and the total for
all the actinides is about 10 times the plutonium-239 dose for long-term
exposure.
-------
B-10
IV. DOSES TO THE WORLD POPULATION OUTSIDE THE UNITED STATES
The releases of krypton-85 and tritium by the nuclear power industry
are expected to be dispersed on a global scale and result in doses to the
world population.
A. Krypton-85
The worldwide dose due to krypton-85 exposure can be estimated by
diluting the output from one year of fuel reprocessing into the world's
21 3
atmosphere (5.4 x 10 g; sea level air density = 0.00129 g/cm ) and then
determining population dose while it decays away. The annual dose rate
from the build-up in the atmosphere of krypton-85 released at all previous
times, corrected for radioactive decay, is given by:
= E [Q.(t*) . x 3.15 x 107 i- x t~"*~»> x 106
t*=0 •* y
. . 0.00129 g/cm3 . _ -,«.,,
x [ ( - a^= - ) x F. . x P (t) ]
_ , . i«Zl Li W
5.14 x 10 g
where :
Q.(t*) = annual average release rate (curies/sec)
A - decay constant for krypton-85 (0.0645/yr)
P (t ) = world population at time t , where t=0 in 1970. Five percent of
the world effect is subtracted to account for the U.S. contribution
to the world population dose.
-------
B-ll
Therefore:
D. .(t) = 2.7 x 10~2 F.. e"°'0455t x Z Q.(t*) e°-0645t* man-rem in year t
13 X] t*=0 D
to world's population (less U.S. dose).
To estimate future doses due to the environmental buildup of krypton-85,
-0 0645T 0 019T
the above annual dose is multiplied by e x e and then inte-
grated from T=0 to T=". This accounts for radioactive decay and for population
growth.
B. Tritium
The worldwide dose due to tritium exposure is estimated by diluting
the tritium release into the circulating waters of only the northern hemi-
19
sphere (one-half of 2.7 x 10 1) and assuming that the northern hemisphere's
population (80% of world population) is exposed to the resulting concentration.
The U.S. contribution (about 7%) is subtracted.
The annual dose rate at time t from the buildup of tritium released
to the environment at time t* is given by:
t
D. . - E [Q.(f) x 3<15 x 107 s_ -X(t-t*> 6
ID t«=0 D s yr 1U ci J
x [( 2 ) x F. . x P (t) ]
i]
2.7 x 10 ml
where t = t* = 0 in 1970. This simplifies to:
D.. =6.2 F.. e~0-0372t i Q.(t*) e°-0562t* man-rem in year t to the
13 1] t*=0 D
-------
B-12
world's population from the U.S. nuclear power industry produced tritium
(less U.S. dose). Again, to evaluate future doses due to the environmental
. . . . -0.0562T 0.019T
buildup of tritium, the annual dose is multiplied by e • x e
and integrated from T=0 to T=» to account for radioactive decay and population
growth.
V. HEALTH EFFECTS
The determination of health effects, H, from the doses derived in the
previous sections is obtained from:
H= Z JiDij
where J. = health effects conversion factor for organ i.
and D. . = the dose to organ i from an exposure by radionuclide j .
The projected number of regional, United States, and worldwide health
effects associated with the distribution of specific radionuclides in the
environment is obtained by use of the appropriate combination of calculated
dose and health effect conversion factor. The numerical values used in this
study are summarized in table B.I and derived in detail In appendix C.
-------
TABLE B.I
Conversion Factors for Dose & Health Risk Estimates
Radionuclide
Kr-85
H-3
1-129
Actinides
Pu-238
Pu-239
Pu-240
Pu-241
Am-241
Cm-242
Cni-244
Media-Dose Dose-Health Risk
Activity (A ) Conversion Factor (F^j) Conversion Factor (J^)
(Ci/HT) J (reT'/vr)/(vjCi/cm3) (risk/man-rera)
10,500 < whole body
gonads (female)
gonads (irale)
lung
skin
800 whole body and
gonads
0.04 infant thyroid-4/
adult thyroid —
U-fuel Pu-fuel lung
4x103 6:<10-* _
5:110^ , 7.5x10
6.5x10- 1x10 ;:
1.5x10, 3-xlO;?
7.5x107 2x10
3.5x10 2. 5x10 .
2:<103 2.5x10
/ -6 I/
1.5x10* 400xlO_g ±.
1.5x10* 30QxlO~j! —
2.0x10* 300xlO~, 27
3.0x10* 50xlO~^ 4/
50.0x10* 3x10"° -'
6 -6
1.7x10 (air) 400x10 fi
or 300xlO~
100 (water)
is in12 age risk fi .
/Ainl220 5xlO~
12 -6 2/
12 \ a i r )
12xloJ2
3x10^
2x10"
4x10
NOTE: _!/ 50% mortality
2_l very hi;;h mortality
3/ low or zero mortality
kj probably le.ss than 25% ir-ortality
'Iodine Dose Calculation Factors
Fraction Uptake Infant =0.35 Adult - 0.30
Thyroid Mass (g) 1.8 20
Biological t1/2 2,
to
-------
B-14
REFERENCES
Compendium of Environmental Surveillance Around the Rocky Flats
Plutonium Plant. U. S. Environmental Protection Agency, FOD/ORP/EPA,
(November 1972).
U. S. Department of Commerce, Statistical Abstract of the United
States. 1969.
Gamertsfelder, C. C., Statement of the Selection of as Low as Practi-
cable Design Objectives and Technical Specifications for the Operation
of Light Water Cooled Nuclear Power Reactors. Presented at AEC Hearings
on the "As Low as Practicable Concept," (1972).
Klement, S. W., Jr., Miller, C. R., Minx, R. P., and Shleien, B.,
Estimates of Ionizing Radiation Doses in the United States - 1960-2000.
U. S. Environmental Protection Agency, CSD/ORP 72-1, (1972).
Knox, J. B., "Airborne Radiation from the Nuclear Power Industry,"
Nuclear News. 14: 27-32, (February 1971).
Machta, L., National Oceanic and Atmospheric Administration, Unpublished
data.
Wayne, E. J., Dontros, Demetrios A., and Alexander, W. D., Clinical
Aspects of Iodine Metabolism, F. A. Davis Co., Philadelphia, (1964).
United Nations Statistical Office Report. (1966).
-------
APPENDIX C
RADIOLOGICAL DOSE AND
HEALTH IMPACT CONVERSION FACTORS
-------
C-l
I. INTRODUCTION
Radioactive materials released into the environment from nuclear
fuel reprocessing become dispersed in the surrounding media (air, water,
etc.) and ultimately may produce health effects in man. The inpact
of a given radionuclide release on the population surrounding a source
is assessed here in terms of three factors: (1) a. dilution factor to
calculate the concentration of the released activity in the medium of
interest, (2) a medium concentration to dose conversion factor, and
(3) a risk factor which relates the likelihood of a given biological
effect to an absorbed dose of one rad. J These factors are discussed
below for tritium, krypton-85, the radioiodines, and alpha-emitting
transuranics (such as plutonium).
II. PATHWAYS
Releases of radionuclides from a nuclear fuel reprocessing plant
can occur by venting through an exhaust stack to the atmosphere or
drainage to a nearby waterway. The principal pathway of concern in
assessing the health impact due to nuclear fuel reprocessing plant
operations is the atmospheric pathway because such releases can
become dispersed in any direction and lead directly to radiation
exposure to man. The significance of the water pathway is expected to
be quite small for future reprocessing plants because presently proposed
designs do not plan on any releases to waterways.
Atmospheric dispersion of radioactivity has been discussed by a
number of authors (Ref. C-l, C-2) and for the case of interest here, a
Rad - The unit of energy imparted to matter by ionizing radiation
and equal to .01 J/kg in any medium.
-------
C-2
gaussian plume diffusion model is usually assumed to be the best choice.
At distances relatively close to a source (2-3 km) this model can
predict the air concentration of krypton-85, for example, within a
factor of two or three. Its applicability at longer distances depends
upon the local weather conditions at the time of radioactive release
and the topography. For unstable atmospheric conditions, it may be
reasonably accurate as far as 10 km from a source. Since the average
radionuclide concentrations in air around sites have been calculated
for distances as far as 80 km (50 miles) from the source, it is obvious
that the validity of the atmospheric transport model used is an important
limitation. However, the point here is to examine the general case
and provide an overall index of health risk; the risk from a particular
plant will depend on the details of the local meteorological situation.
For worldwide distribution of gases, uniform dispersion was assumed in
determining air concentrations.
An important radionuclide pathway for man is the direct contam-
ination of foodstuffs - particularly milk. For iodine-131, this
pathway has been studied extensively by several authors including
Garner (Ref. C-3) and Bryant (Ref. C-5, C-5). Long-term buildup of
the isotope iodine-129 may be important due to its half-life of
17xl06 years but appreciable buildup has not been documented
in the literature. The short-term behavior of iodine-129 has been
considered, however (Ref. C-6), and health risk estimates are given
for both iodine-129 and iodine-131.
-------
C-3
III. MEDIA CONCENTRATION TO DOSE CONVERSION FACTORS
Organ or total body dose estimates are critically sensitive to
assumptions concerning the route of uptake, the amount of radioactivity
inhaled or ingested daily, the fraction of activity retained in the organ
of interest, and the residence time of the activity in various parts of
the body. The final necessary elements entering into the dose computations
are the physical considerations of organ mass and radionuclide distri-
bution within the organ. In the present state of the art, the complex-
ities of the radionuclide distribution within organs are nearly always
circumvented by assuming a uniform depositon. Information concerning
the other inputs is based mainly on empirical evidence, largely gathered
from fallout studies and medical investigations. In order to reduce
the number of variables to be considered in dose calculations, the
International Commission on Radiological Protection (ICRP) has postu-
lated a "standard man;" i.e., a model system having standardized biological
parameters based on either average values or best estimates as listed
in the scientific literature. The standard man is a hypothetical adult
industrial worker and it is not clear to what extent parameters so de-
fined are applicable to an environmentally exposed population.
For particular radionuclides, the sensitivity of certain age groups
may be the limiting factor. In the case of iodine-131, the Federal
Radiation Council (Ref. C-7) has defined children as the most sensitive
population group and, therefore, the biological parameters used in
these media to dose conversion factors are not based on standard man.
Rather, models appropriate for children's thyroid glands and thyroid
metabolism have been used. For the other radionuclides considered here,
-------
C-4
little is known concerning differences between adults and children.
Such differences are seldom considered in the literature. This being
the case, the conversion factors listed in the subsequent sections, while
adequate, must be considered only as first order approximations and
not as definitive dose estimates from environmentally distributed
radionuclides.
Media concentration-to-dose conversion factors are defined below
for krypton-85, tritium, iodine 131, iodine-129, and some of the
actinides. Other radionuclides are not considered likely to cause
significant environmental exposures of the population based on the
control technologies discussed in appendix B.
A. Range of Expected Doses from Krypton-85 Exposure
Since krypton-85 is not metabolized, exposure to humans is limited
to external beta and gamma rays and, to a much lesser extent, the dose
due to krypton-85 dissolved in body fluids. The health risk from
krypton-85 is further limited by the fact that 99% of the decay energy
is dissipated by beta rays which have no potential for deep penetration.
Four target organs are considered for these dose and risk estimates:
total body, gonad, lung, and skin. In each case it can be shown that
only one type of exposure need be considered, the other contributing
an insignificant fraction of the dose.
Kirk (Ref. C-8) has recently reviewed the literature on krypton-85
dose and established relationships between the concentration in air of
krypton-85 and various organ doses. A review of these results show
which radiations and source locations are important. For the whole
body, dose and risk estimates can be based on a consideration of
-------
C-5
external photon exposures, i.e., gamma rays and bremsstrahlung. For
genetic risk calculations the gonadal dose, in the case of males, is
from exposure from external photons; while for females, the whole body
dose estimate can be used. Dose estimates for the lung are based on
internal beta dose plus the total body gamma-ray dose. Skin dose and
risk estimates are based on the dose delivered by external beta
radiation after making an appropriate allowance (0.25) for the shielding
provided by clothing and the nonviable epithelium.
B. Ranee of Expected Doses from Tritium Exposure
Dose estimates from tritium exposure have been based on the
assumption that the isotope is contained in body water (Ref. C-9).
However, chronic exposure to environmental tritium has been shown to
lead to incorporation into organic molecules from which tritium is lost
at a slower rate than from body water (Ref. C-10, C-ll). If it is
assumed that, under equilibrium conditions, all body hydrogen (7.0 kg in
standard man) is uniformly labelled, a sustained concentration of 1 pCi/1
body water would lead to a body burden of 63 uCi, as opposed to 43 pCi if,
as in the ICRP model only, distribution in body water alone is considered.
Evans (Ref. C-10) found that tritium was not, in fact, uniformly
distributed through deer tissues and, assuming that his observed factors
are applicable to man, has calculated that the body burden carried by
standard man at a sustained concentration in body water of 1 pCi/1 would
be 60 uCi, i.e., higher by a factor of 1.4 than that based on the ICRP
model. While Evans1 factor has been adopted in some dose calculations,
a factor of 1.5 (63/43), although only marginally different, may be a
more appropriate value to use for calculations in man and, therefore, it
is used here.
-------
C-6
Since it is apparent that, under chronic exposure conditions,
tritium may become incorporated into the genetic material (DNA), it has
been suggested that the relative biological effectiveness of tritium
in terms of genetic effects may be greater than unity as a result of DNA
degradation from transmutation and recoil processes in addition to that due
to absorbed energy from ionization processes due to beta emissions. How-
ever, from both experimental (Ref. C-12) and theoretical (Ref. C-13)
considerations, it has been concluded that it is the absorbed dose to
mammalian cell nuclei from incorporated internuclear tritium which deter-
mines quantitatively the degree of effect (Ref. C-24). The assumption
made in these calculations that the appropriate value for quality factor
for tritium dose equivalent estimation is 1.0 as recently adopted by the
National Council on Radiation Protection and Measurements (NCR?) (Ref. C-14)
A susstained concentration of 1 yCi tritium per liter of body water
would thus be equivalent to a specific activity (assuming uniform
labelling of all body hydrogen) of 9x10~3 ]fi± tritium/g hydrogen, and
would deliver an annual dose to body tissues of approximately 100 mrem.
The concentration of tritium in body water resulting from exposure
to tritium in air is obtained by diluting the daily intake of tritium
by inhalation into the 43 liters of body water with a biological half-
life of 12 days. This amount of tritium is doubled to account for
absorption of tritium through the skin. This leads to an annual dose
of 1.7xl06 rem2 for an air concentration of 1 UC1 tritium/cm3.
2In the case of beta and gamma rays emitted by fuel reprocessing plant
effluents, the quality factor is one and the dose equivalent in rems
is identical to the dose in rads. Where the effects of such effluents
are considered in this report, doses are expressed in rem units and
biological effects are presented on a per rem basis.
RHl - The rem represents that quantity of radiation that is equivalent—
in biological damage of a specified sort - to 1 rad of 250 kVp x rays.
-------
C-7
C. Range of Expected Doses from Iodine-129 and Iodine-131 Exposures
Atmospheric releases of iodine from fuel reprocessing may result
in an accumulation of iodine-129 and iodine-131 in the thyroid glands
of persons living in the surrounding area. The pathway potentially most
hazardous to man for isotopes of iodine is the grass-cow-milk chain,
particularly in cases where the milk is not diluted with uncontaminated
supplies. Direct deposition on foliage will be the only significant
route of contamination of edible herbage for iodine-131 and is likely to
be the most important for iodine-129, at least over the duration of
plant operation.
Because of the long half-life of iodine-129, recycling through
the soil should be considered. In organically rich soils, the iodine
will be strongly bounded to the soil, but it will be leached rather rapidly
from other types of soils. In any case, plants will incorporate
iodine-129 in ratio proportional to the amount of natural iodine-127
available. The actual amount of iodine-129 incorporated will depend on
the location of the reprocessing plant, and the specific activity of
the iodine-129 (curies of iodine-129 per gram of iodine) in each component
of the terrestrial pathway will change as a function of time as build-
up in the soil increases. At any given time the specific activity in
the ecological chain will be somewhat less that the specific activity of
the iodine-129 in the air. In many cases the specific activity will be
much less because of the large stable iodine reservoir in soils and other
parts of the terrestrial pathway.
-------
C-8
When considering the exposure of individuals to iodine isotopes via
the grass-cow-milk chain, the population potentially at greatest risk
is young children consuming fresh milk (Ref. C-15, C-16). From the data
of Durbin, et al. (Ref. C-17) the average daily intake of whole cows milk
by U.S. children over the first year of life is about 760 ml. Appropriate
representative data to define the relationship between the amount of
iodine ingested by a 6-month-old child and its concentration in the
critical organ, the thyroid gland, are (Ref. C-6); thyroid weight, 1.8 g;
fraction of ingested iodine reaching critical organ, 0.35; and biolog-
ical half-life of iodine in thyroid, 23 d. Equivalent data for adults,
appropriate to the calculation of average population doses, are: daily
milk consumption, 500 ml (Ref. C-17); thyroid weight, 20 g; fraction
ingested reaching critical organ, 0.3; and biological half-life in
thyroid, 138 d (Ref. C-6). Use of these values yields an annual dose
to the adult thyroid of 0.29 mrem for iodine-131 or 1.9 mrem for iodine-
129 for a concentration of 1 pCi/1 of each isotope. The corresponding
annual doses to the thyroid of children whose daily consumption of milk
during the first year of life contains 1 Ci/1 of the respective
radionuclides are 4.3 mrem for iodine-131 and 6.3 mrem for iodine-129.
The media conversion factors presented in table C.I are also derived
from considerations discussed in references C-6 and C-7, an assumed
grazing area for a dairy cow of 80 m2 per day and an iodine deposition
velocity of 0.5 cm/s (Ref. C-5).
-------
C-9
TABLE C.I
Milk Concentrations of Iodine-131 and Iodine-129 from
Given Input Concentration and Corresponding Doses
Input Concentration
of Respective Nuclide
Milk Concentrations
Iodine-131
Iodine-129
1 pCi/m (ground surface)
1 pCi/m3 (air)
1 pCi/m (air)
1 pCi/m (air)
0.20 pCi/1
6.2xl02 pCi/1
0.28 pCi/1
2.4xl03 pCi/1
Annual Dose to Child Thyroid
Iodine-131 Iodine-129
2.7 rem 15 rem
Annual Dose to Adult Thyroid
Iodine-131
Iodine-129
.18 rem
4.6 rem
Estimates of the specific activity (uCi iodine-129/g total iodine) in
the thyroid gland corresponding to an annual dose of 1 rem are, for an
adult, 2.3, and for a 6-month child, 4.1 (Ref. C-6). Adoption of a
value of 0.44 rem/yr as the dose delivered to a thyroid gland containing
1 yCi iodine-129/m3 total iodine would thus appear to be a reasonable
estimate for all cases. The mean concentration of stable iodine in the
atmosphere is given as 0.2 yg/m3 (Ref. C-18). Using this value, it can
be shown that an air concentration of 1 pCi iodine-129/m would lead to
an annual thyroid dose of 1.8 rem. In areas where the atmospheric
-------
C-10
concentration of stable iodine-127 is low, the dose could be up to
40 times higher; this upper limit on the dose is set by the amount
of stable iodine-127 released in fuel reprocessing. Thus, for
adults the higher value presented in table C.I of 4.6 rem/yr
per pCi/m3 of iodine-129 in air is selected for use in this study.
D. Range of Expected Doses from Plutonium-239 and Other Actinide Exposures
s
The potential risks from inhalation of plutonium-239 depend on whether
the plutonium is in a soluble or an insoluble form. Present experience in-
dicates that, in the case of fuel reprocessing, the plutonium will be pre-
sent in the environment in a relatively insoluble form and the present
dose estimates are based on this assumption. There is also evidence that a
considerable fraction of plutonium-239 inhaled in insoluble form is trans-
located, largely to the bronchial and mediastinal lymph nodes (Ref. C-19).
Since the risk to be pulmonary region depends upon both the amount of
plutonium in the organ and its microdistribution, the region containing
the largest amount of plutonium may not be the region at greatest risk.
Particularly, since the relative sensitivity of the various cell types
encountered has not been established, the dose to the lung from inhaled
particules is calculated on the basis of an average dose to the entire
pulmonary region for this report. In the case of alpha emitters, such
averaging is obviously inappropriate if there are only a few particles
present. ICRP Publication No. 6 (Ref. C-20) recognizes this and states, "in
the case of the lung, an estimate of the dose equivalent to the critical
tissue determined merely by the product of quality factor and mean dose
may be greatly in error, but further experimental evidence is needed before
a better estimate can be made."
-------
C-ll
In this report, dose estimates are based on the new ICRP lung model
(Ref. C-21, C-22). The biological half-life of material in the lung
(pulmonary region) is assumed to be 1,000 days. Using this model,
sustained exposure to an air concentration of 1 pCi/m3 of
plutonium-239 in insoluble form would lead to a dose rate of 12 rem per
year in the pulmonary region. It is assumed that the risk to this
region is representative of the total risk to the lung.
Media-dose conversion factors for other actinide radionuclides
are related to the plutonium-239 conversion factor by taking into
account the effective energy absorbed per disintegration of each
radionuclide and the physical half-life as given in ICRP Publication
Nos. 2 and 6 (Ref C-9, C-20). Table C.2 gives the conversion factors
used in this study for several actinides relative to plutonium-239.
TABLE C.2
Actinide Air-Dose Conversion Factors
Relative to Plutonium-239
Radionuclide
Pu-238
Pu-239
Pu-240
Pu-241
Am-241
Cm-242
Cm-244
Relative Conversion Factor*
1
1
1
0.001
0.25
0.17
' 0.33
*Plutonium-239 Conversion Factor - (12xl06 rem/yr)/(l PCi/m3).
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C-12
E. Summary
Table C.3 summarizes the media-dose conversion factors presented
in this section. Conversion factors are expressed in terms of
rem/yr resulting from continuous exposure to concentrations
expressed in yCi/cm3 of air.
TABLE C.3
Summary of Media-Dose Conversion Factors
Radionuclide Critical Organ
Kr-85 Whole body
Gonads (female)
Gonads (male)
Lung
Skin
H-3 Whole body
1-129 Infant thyroid
Adult thyroid
1-131 Infant thyroid
Adult thyroid
Pu-239 Lung*
*See paragraph IV D regarding
IV. DOSE-RISK CONVERSION FACTORS
Conversion Factor
(rem/yr) /(uCi/cm3 air)
l.SxlO1*
l.SxlO1*
2.0X1011
3.0x10**
50. 0x10 *»
1.7xl06 or
100 ( rem/yr) /(uCi/cm3 water)
15. 0x10 l 2
4.6xl012
2.7xl012
0. 18x10 ! 2
12. 0x10 lz
consequences of soluble form of plut
Assumptions made in predicting radiation-induced health effects
from nuclear fuel reprocessing are given in this section. Consistent
with recommendations made in the recent (November 1972) National
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C-13
Academy of Sciences Committee on Biological Effects of Ionizing
Radiation (BEIR) report (Ref. C-23), the health risks presented in this
report are based on an assumed linear relationship between absorbed
dose and biological effects and that any increased risk is in
addition to that produced by natural radiation; i.e., no threshold
exists. It is further assumed that health effects that have been
observed at dose rates much greater than those likely to be encountered
around fuel reprocessing plants are indicative of radiation effects at
lower dose rates. Only insofar as any biological repair of radiation
damage from low dose rate radiation is neglected do the BEIR
health risk estimates represent upper limits of risk. In most cases
the risk estimates are based on relatively large doses where cell
killing may have influenced the probability of delayed effects being
observed. The BEIR risk estimates used in this report are neither
upper nor lower estimates of risk, but simply the "best available."
As the BEIR report points out, a nonthreshold linear relationship
hypothesis is not in itself sufficient for the prediction of health
risk. It is also necessary to assume that all members of the exposed
population have equal sensitivity to the radiation insult so that the
expression of health risk is independent of how individual exposures
are distributed. This requirement is not wholly satisfied. As
documented in the BEIR report, differences in sensitivity do exist;
for example, children are more radiosensitive than adults. There are
two considerations, however, which help validate the application of
available mortality data to a consideration of health effects from
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C-14
fuel reprocessing. Some of these data (those taken from Hiroshima and
Nagasaki) reflect, to a limited extent, exposure of a relatively
heterogeneous population. More importantly, even though the number of
health effects will be dependendent on the exact makeup of the
populations at risk, the relative order of importance of the various
pathways of exposure will not be very sensitive to the population
characteristics near a given fuel reprocessing plant. Finally, it
should be pointed out that the health risk estimates made here assume
that the expected radiation effects are independent of other environ-
mental stresses, which may be either unique to the population surrounding
fuel reprocessing facilities or unique to the exposed groups considered
in the BEIR report.
The numerical risk estimates used in this appendix are primarily
from the BEIR report. What must be emphasized is that though these
numbers may be used as the best available for the purpose of risk-cost
benefit analyses, they cannot be used to accurately predict the number
of casualities. For a given dose equivalent, the BEIR report estimates
a range for the health impact per million exposed persons. For example,
the BEIR results from a study of the major sources of cancer mortality
3 6
data yield an absolute risk estimate of 54-123 deaths annually per 10
persons per rem for a 27-year followup period. Depending on the details
of the risk model used, the BEIR Committee's relative risk estimate is
3Absolute risk estimates are based on the reported number of cancer deaths
per rad that have been observed in exposed population groups, e.g.,
Hiroshima, Nagasaki, etc.
i.
Relative risk estimates are based on the percentage increase of the
ambient cancer mortality per rem.
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C-15
160-450 deaths per 106 persons per rem. It is s»en that the precision
of these estimates is at best about a factor of 3-4, even when applied
to sample populations studied on the basis of the same dose rates. The
application of the BEIR risk estimates to exposures at lower dose rates
and to population groups more heterogenous than those studied increases
the uncertainty in the risk estimates. Considering the limitations
of presently available data and the lack of an accepted theory of
radiocarcinogenesis, emphasis should be placed on the difference in
risk estimates between the various procedures and countenneasures
discussed in this report rather than on the absolute numbers. Where the
absolute numbers must be used for risk cost-benefit balancing, it
should be remembered that these risk estimates are likely to be re-
vised as new information becomes available. Notwithstanding these
disclaimers, it is also pertinent to note that we are in a better
position to evaluate the true risks and the accompanying uncertainties
from low levels of radiation than from low concentrations of other
environmental pollutants which might affect populations in the vicinity
of a fuel reprocessing plant.
A. Dose-Risk Conversion Factors for Krypton-85
1. Total Body Dose-Risk
The BEIR report calculates the cancer mortality risk
(including leukemia mortality) from whole body radiation by two quite
different models. The absolute risk model predicts about 100 cancer
deaths per 10 person-rem while the relative risk model predicts between
160 and 450. An average cancer mortality of 300 annually per 106
person-rem would seem to be an appropriate mean for the relative risk
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C-16
model. The average of the absolute and relative risk models is 200,
which is close to the estimates of cancer mortality risk listed as
"most likely" by the Committee. Cancer mortality is not a measure of
the total cancer risk, which the Committee states is about twice that
of the yearly mortality.
The computation of health risk from continuous krypton-85
total body exposure used in this report is the one appropriate for
total body irradiation.
Estimated Cancer Risk from Total Body Irradiation
Cancer mortality = 200 deaths per year for 106 person-rem
annual exposure. Total cancers = 400 cancers per year for
106 person-rem annual exposure.
2. Gonadal Dose-Risk
The range of the risk estimates for genetic effects set forth
in the BEIR report is so large that such risks are better considered on a
relative basis for different exposure situations than in terms of
absolute numbers. The range of uncertainty for the "doubling dose"
(the dose required to double the natural mutation rate) is 10-fold
(from 20 to 200 rad); and because of the additional uncertainties in
(1) the fraction of presently observed genetic effects due to back-
ground radiation, and (2) the fraction of deleterious mutations
eliminated per generation, the overall uncertainty is about a factor of
25. The total number of individuals showing very serious genetic
effects such as congenital anomalies, constitutional and degenerative
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C-17
diseases, etc., is estimated at somewhere between 1,800 and 45,000 per
generation per rad of continuous exposure; i.e., 60-1,500 per year if
a 30-year generation time is assumed. This level of effect will not be
reached until after several generations of exposure; the risk to the
first generation postexposure is about a factor of 5 less.
The authors of the BEIR report reject the notion of "genetic death"
as a measure of radiation risk. Their risk analysis is in terms of
early and delayed effects observed post partum and not early abortion,
stillbirths or reduced fecundity. Because of the seriousness of the
genetic effects considered here, e.g., mongolism, the emotional and
financial stress would be somewhat similar to death impact. Indeed,
many of the effects described are those which lead directly to infant
mortality (fetal mortality is excluded). For the purposes of this
report this class of genetic effects will be considered on the same
basis as mortality data.
Estimated Serious Genetic Risk
from Continuous Gonadal Irradiation
Total risk = 300 effects per year for 106 person-rem annual
exposure.
Less serious genetic effects have also been considered by the
BEIR Committee. These have been quantified under the categorgy "unspeci-
fied ill health." The Committee states that a continuous exposure of
one rem per year would lead to an increase in ill health of between
3 and 30 percent.
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C-18
3. Lung Dose-Risk
Due to the insufficient data for the younger age groups,
estimates of lung cancer mortality in the BEIR report are only for
that fraction of the population of age 10 or more. For the risk esti-
mate made below, it is assumed that the fractional abundance for lung
tumors is the same for those irradiated at less than 10 years of age
as it is for those over 105. On an absolute risk basis lung cancer mortality
is about 26 deaths per annum per 106 persons irradiated continuously
at a dose rate of 1 rem per year. This is a minimum value. The BEIR
report states that the absolute risk estimates may be too low because
observation times for exposed persons are still relatively short compared
to the long latency period for lung cancer. Furthermore, lung cancer
risks calculated on the basis of relative risk would be larger. For
the risk estimate made here, it is assumed that the ratio of absolute risk
to the average relative risk is at least a factor of 0.5, i.e., the
same ratio as in the case of total body irradiation discussed above.
Estimated Lung Cancer Risk
from Continuous Lung Irradiation
Lung cancer mortality = 50 deaths per year for 106 person-rem
annual exposure.
4. Skin Dose-Risk
There is no doubt that the dose to the skin delivered by
krypton-85 exceeds by about two orders of magnitude the insult to other
organs. However, epidemiological evidence of any real risk from such
5An absolute risk estimate is not very sensitive to the inclusions of this
assumption since lung cancer incidence is very small in the young.
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C-19
insults at the dose levels considered here is nonexistent. This is
not to say that the linear dose-effect assumption does not hold for
skin cancer but rather that the BEIR Committee found that from the
extensive evidence they examined "numerical estimates of risk at low
dose levels would not seem to be warranted." The authors of this report
concurred with the BEIR report. However, rather than defining a
zero risk per rad for any radiation insult from krypton-85, an upper
limit of risk is proposed. It should be noted that skin cancers are
rarely fatal and usually not very debilitating. The estimated
upper risk for continuous exposure is:
Skin cancer - upper limit = 3 skin cancers6 per year for 106 person-
rem annual exposure.
B. Dose-Risk Conversion Factors for Tritium
1. Total Body Dose-Risk
The somatic dose-effects from tritium are not expected to be
unique. Risk estimates for total body irradiation are based on the
same information reviewed in Section A for krypton-85 total body
exposure.
2. Gonadal Dose-Risk
The genetic risk from tritium per unit gonadal dose is expected
to be the same as for the beta and gamma radiation from other isotopes.
Some experiments with bacteria (Ref. C-24) have shown that the location
of a tritium atom on a particular DNA base can enhance the mutation rate.
6Assuming 30 years at risk exposure and that the incidence of skin cancer
will be 10% of all radiation-produced cancers except leukemia, breast,
lung, G.I. tract, and bone cancers.
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C-20
However, if it is assumed that tritium labeling is a random phenomenon,
the percentage for such locations that are specifically labeled will be
extremely small at the exposure levels considered here. Therefore, the
risk estimates for gonadal irradiation from krypton-85 listed in section
A are also appropriate for estimating the genetic risk from tritium
exposures.
C. Dose-Risk Conversion Factors for Iodine-129 and Iodine-131
Iodine is concentrated in the human thyroid. Therefore, the insult
from radioiodines is important only for the thyroid. The dose to other
organs is orders of magnitude less. Two health effects follow high
level exposures of thyroid tissue to ionizing radiation: benign neoplasms
and thyroid cancer. Though the former are a more common radiation
effect, only the risk from cancer is considered here.
While children are particularly sensitive to radiation damage to
their thyroid glands, thyroid cancer is not usually a deadly disease
for persons in younger age groups but mortality approaches 25% in
persons well past middle age. It is not presently known if the radi-
ation-induced cancers which are more frequent for persons irradiated
early in life will follow the same patterns of late mortality.
The BEIR report provides risk estimates only for morbidity (not
mortality) and only for persons under 9 years of age, i.e., 1.6-
9.3 cancers per Id6 person-rem years. From the Hiroshima data and
other studies it would appear that for persons over 20 years old the
radiation-induced thyroid cancer incidence is much lower and may
approach zero.
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C-21
Since information in the BEIR report is not sufficient in itself
to estimate the cancer incidence from continuous exposure, tentative
risk estimates for this study are also based on risk estimates described
in ICRP Publication No. 8 (Ref. C-25) as well as the mean of the BEIR
Committee's various estimates of incidence per rem. Infants and fetuses,
composing approximately 2.5 percent of the population, are, of course, the
most sensitive group. For this group about 150 thyroid cancers may accrue
annually per 10 person-rem annual exposure. For the approximately
40% of the populations that is in the 1-19 year age group it is assumed
that the incidence is a factor of about 4 less, and that for the balance
of the population, it is a factor of 30 less.
Estimated Thyroid Cancer Risk from Radioiodines
Morbidity for less than age 1:
150 cases per year for 10° person-rem annual exposure.
Morbidity for less than age 20:
35 cases per year for 10 person-rem annual exposure.
Morbidity for more than age 20:
5 cases per year for 10 person-rem annual exposure.
It is unlikely that the annual mortality from this cancer would be
much larger than 25% of the rate of incidence. As for other radiation
effects, a true measure of the risk from thyroid cancers would be life
shortening, but insufficient mortality data prevents such an approach.
D. Dose-Risk Conversion Factors for Plutonium and other Actinides
The lung cancer mortality risk discussed in Section A is the best
available information on the consequences of lung exposure. While it
is based on mortality information from miners exposed to alpha emissions
from particulates as well as more conventional dose-risk data, it is
-------
C-22
probably not really adequate for describing the risk from inhaled
plutonium. There is good evidence that a fraction of such particulates
are cleared from the lungs and relocated into the respiratory lymph
nodes. The organ dose received by a lymph node in this case is not
really known, but is probably on the order of 50 times the average
dose to lung tissue. The ICRP does not consider these highly irradiated
nodes to be the organ at maximum risk and preliminary results of animal
experiments would tend to confirm their judgment. However, it is not
a settled question.
Even if the lung is the critical organ for such exposures, there
is little reason to believe that the average lung dose, presently used
in health-risk analyses, is really relevant to estimating the risk from
air-borne particles. Estimates of the actual dose from discrete sources
of alpha radiation are subject to large variability simply because
little is known about the volume over which the energy deposition takes
place. Even though as many as 4x10 particles (0.2 Pm diameter) of
plutonium-239 are required to deliver an average energy deposition of
1 rad to the lung, the dose is not evenly distributed; only about 0.2%
of the lung volume absorbs the emitted energy. Health risk estimates
based on dosimetry are probably unwarranted under these circumstances
and use of a body burden approach to health-risk assessments would
appear to be a more likely route to success. Unfortunately, experiments
allowing this approach are not yet complete. Therefore, the lung
cancer risk estimate for exposure to actinides for purposes of this
study is as given in Section A for uniform lung exposure.
-------
C-23
The dose conversion factor for a soluble form of plutonium will
differ from that presented for insoluble plutonium for a given air
concentration. However, the associated risk (expressed in effects
induced per unit air concentration) resulting from the soluble form
is expected to be the same order as for the insoluble form as
analyzed here.
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C-24
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C-25
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