ENVIRONMENTAL RADIATION DOSE
COMMITMENT: AN APPLICATION To
THE NUCLEAR POWER INDUSTRY
ENVIRONMENTAL PROTECTION AGENCY
Office of Radiation Programs
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ENVIRONMENTAL RADIATION DOSE
COMMITMENT: AN APPLICATION TO
THE NUCLEAR POWER INDUSTRY
February 1974
Revised June 1974
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Radiation Programs
Criteria and Standards Division
Washington, D.C. 20460
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FOREWORD
All levels of government and industry are faced with the challenge
of responding affirmatively and fairly to the reality of public demands
for action to improve the quality of the environment and the quality of
life. These demands come from a new general awareness of the
degradation we have inflicted on our surroundings and from a fear we may
destroy ourselves if degrading trends are not reversed.. Concern for
quality of life also stems from an increasing emphasis on human and
social values, and it is clear that a quality of life ethic has become
deeply ingrained in our society and that a growing demand for
maintaining and improving the quality of the environment is a principal
component of that ethic.
The Of fide of Radiation Programs presents this report in the hope
that the concept of "environmental dose commitment" will serve as a
useful tool to assist evaluation of the potential environmental impact
of alternative energy sources. It should be noted, however, that such
discussion is beyond the scope of the present report. A comprehensive
analyses of alternative energy sources will require, in addition to
assessments of the impacts of the variety of environmental releases
associated with normal operations (such as the long-lived radionuclides
addressed here); assessments of the impacts due to mining and waste
disposal, and of safety - both public and occupational. Comments on
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this report are welcomed. These should be sent to the Director,
Criteria and Standards Division of the Office of Radiation Programs (HM-
560).
W.D. Rowe, Ph.D.
Deputy Assistant Administrator
for Radiation Programs
IV
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PREFACE
An analysis of the consequences of the discharge and dispersal of
long-lived radionuclides into the general environment is one of a
variety of considerations required in the setting of standards for
radiation protection. By virtue of the long persistence of these
materials these consequences may extend over many generations and, in
this respect, these discharges can represent irreversible public health
commitments.
We have developed the concept of "environmental dose commitment" to
encompass the radiation doses to populations implied by this
irreversibility, extended it to include the calculation of resultant
potential adverse health effects, and applied it to the specific case of
the potential consequences of the next 50 years of normal operations of
the United States nuclear power industry. Only the potential impact of
the release of four types of long-lived radionuclides, namely tritium,
krypton-85, iodine-129, and the actinides has been considered, and
therefore the report does not purport to provide an evaluation of the
overall impact of the industry- In addition, although these
radionuclides have half-lives ranging from a decade to millions of years
and can be projected to migrate over large areas, on the basis of
present knowledge we cannot meaningfully project their persistence in
the biosphere for periods much longer than a number of decades.
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Therefore the potential consequences on health have been calculated only
for the first 100-year period following release.
Two different viewpoints for preparing estimates of these potential
future consequences have been utilized in the analysis. The first
attempts to make an assessment of potential consequences giving due
allowance for expected performance of current emission controls. The
second attempts to establish estimates of upper limits of potential
adverse consequences that are useful for public health and safety
planning purposes, such as in assessing the adequacy of the margin of
safety provided by the controls assumed in the first viewpoint.
Cfoviously, these numerical estimates of projected impact are subject to
considerable uncertainty; this is due both to the variability associated
with all projections and the currently indeterminate character of some
of the important parameters in the analysis. Expanded research efforts
to better define the possible environmental pathways and health impact
of these radionuclides are needed.
The report projects, by the end of the 50-year period considered,
upper estimates for some of the radionuclides considered of as many as
5,000 to 25,000 committed potential health effects over the succeeding
100 years. To provide a perspective any such potential health impact
can be viewed in the light of the many-fold greater number of health
effects attributable to natural background radiation. The National
Academy of Sciences, in its report entitled "The Effects on Populations
of Exposure to Low Levels of Ionizing Radiation," has given a most
likely estimate of approximately 3,000 to 4,000 cancer deaths annually
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as attributable to levels of natural background radiation in the U.S.
This is equivalent to roughly one percent of the spontaneous cancer
deaths per year. Effects attributable to natural background radiation
exposures are estimated on an annual basis and therefore for any
comparison to the projections made in the report the time period covered
would have to be taken into account.
Unlike the situation with respect to natural background radiation
exposures, however, most of the projected potential impact of long-lived
radionuclides from the nuclear power industry can be avoided. The
timely imposition of controls, which considers the environmental dose
conmitment concept, can minimize the potential effects attributable to
release of these materials. It is concluded, therefore, that the
overall environmental dose commitment resulting from the release of
these long-lived radionuclides by normal operations of the United States
nuclear power industry for the next 50 years can be relatively small. A
summary of the major findings of the report will be found in section IV.
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CONTENTS
Page
FOREWDRD iii
PREFACE V
ABSTRACT xii
I. INTRODLICTION 1
H. ENVIRONMEtTTAL DOSE COMMITMENT - GENERAL CONSIDERATIONS 4
III. APPLICATION TO SELECTED LONG-LIVED RADIONUCLIDES FROM THE
NUCLEAR PO^ER INDUSTRY 10
A. General Considerations * 10
B. Numerical Values of Key Parameters for Specific Radio-
nuclides 15
1. Actinides 15
2. Iodine 18
3. Krypton and Tritium 19
C. Expected Minimum Performance by Industry - A First View-
point 20
D. Public Health Planning Projections - A Second Viewpoint.. 22
IV. SUMMARY AND CONCLUSIONS 27
BIBLIOGRAPHY 30
A. GENERAL EQUATIONS FOR ENVIRONMENTAL DOSE COMMITMENT
I. INTRODUCTiaj A- 1
II. GENERAL EQUATIONS A- 2
B. ANNUAL RADIONUa.TDE INVENTORIES AND POPULATION PROJECTIONS
I. INTRODUCTiaj B- 1
II. ANNUAL RADIONUCLIDE INVENTORIES B- 1
III. POPULATION PROJECTIONS B- 8
A. Regional B- 8
B. United States B- 8
C. World B- 8
B-10
IX
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Page
C. ENVIRONMENTAL TRANSPORT
I. INTRODUCTION ............................................. C- 1
H. TRANSPORT TO LOCAL POPULATIONS ........................... C- 1
III. TRANSPORT TO REGIONAL POPULATIONS ........................ C- 3
A. Tritium .............................................. C- 4
B. Krypton-85 ...................... ..................... C- 4
C. Iodine-129 ........................... . ............... C- 5
D. Actinides ............................................ C- 6
3V. TRANSPORT TO WORLD POPULATIONS ........................... C- 7
A, Krypton-85 ........................................... C- 7
B. Tritium .............................................. C- 7
D. CONVERSION FACTORS FOR RADIOLOGICAL DOSE AND HEALTH
I. INTRODUCTION ............................................. D- 1
II. MEDIA CXMEbJTRATICN-TO-DOSE CONVERSION FACTORS ........... D- 1
A. Krypton-85 ........................................... D- 3
B. Tritium .............................................. D- 4
C. Iodine-129 ........................................... D- 6
D. Plutonium-239 and Other Actinides .................... D- 8
HI. DOSE-TO-RISK CONVERSION FACTORS .......................... D-10
A. Krypton-85 ........................................... D-ll
1. Total Body Dose-to-Somtic Risk .................. D-ll
2. Gonadal Dose-to-Genetic Risk ..................... D-12
3. Lung Dose-to-Cancer Risk ......................... D-13
4. Skin Dose-to-Cahcer Risk ......................... D-14
B. Tritium .............................................. D-15
1. Total Body Dose-to-Somtic Risk .................. D-15
2. Gonadal Dose-to-Genetic Risk ..................... D-15
C. Iodine-129 ........................................... D-15
D. Plutonium and Other Actinides ........................ D-17
[[[ D-18
FIGURES
Figure 1 Model for estimating health effects from the nuclear
power industry 12
Figure 2 Estimated cumulative potential health effects com-
mitted by projected releases from the United States
nuclear power industry 25
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TABLES
Page
Table 1 Numerical values for sane significant parameters used
in the analysis 14
Table 2 Projected numbers of health effects attributable to
release of certain long-lived radionuclides by normal
operation of the nuclear power industry (estimated for
anticipated minimum performance by industry assuming
current release practices) 21
Table 3 Projected numbers of health effects attributable to
release of certain long-lived radionuclides by normal
operation of the nuclear power ijidustry (estimated as
maximum plausible projections for purpose of planning
for adequate public health and safety considerations).. 24
Table B.I Estimated U.S. nuclear power production and fuel re-
processing requirements B- 2
Table B.2 Representative quantities of potentially significant
fission products in spent reactor fuels B- 4
Table B.3 Representative quantities of potentially significant
activation products in spent reactor fuels B- 5
Table B.4 Representative quantities of actinides present in
spent reactor fuels B- 6
Table B.5 Estimated annual inventories of selected nuclides in
reprocessed fuels B- 7
Table D.I Summary of air concentration-to-dose conversion factors D- 3
Table D.2 Air concentration-to-lung dose conversion factors for
actinide radionuclides relative to that for plutonium-
239 D- 9
XI
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ABSTRACT
The concept of environmental dose cotmitment is developed and
illustrated by application to projected releases of selected radio-
nuclides from the nuclear power industry over the next fifty years. The
concept encompasses the total projected radiation dose to populations
committed by the irreversible release of long-lived radionuclides to the
environment, and forms a basis for estimating the total potential con-
sequences on public health of such environmental releases. Because of
the difficulty of making projections of radionuclide transport on the
basis of present knowledge, these potential consequences have been cal-
culated only for the first one hundred-Year period following release.
The particular radionuclides considered are tritium, krypton-85, iodine-
129, and the actinides.
xii
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ENVIRONMENTAL RADIATION DOSE COMMITMENT:
AN APPLICATION TO THE NUCLEAR POWER INDUSTRY
I. INTRODUCTION
In recent years mankind has beccne aware that decisions made to
achieve short-term gains must take into account their impact on future
generations. Contamination of the environment due to the use of such
materials as pesticides, mercury/ lead, and a variety of other toxic
substances which persist for long periods of time is well known. These
substances, even though discharged at low rates, can over a period of
years gradually build up to undesirable levels. Since there are usually
no practical methods to remove these materials from the environment,
their introduction represents, in fact, an irreversible cormitment
ameliorated only by natural decomposition or occlusion.
Current and projected technologies for the utilization of nuclear
energy introduce a variety of radioactive materials to the environment.
Most of these materials are short-lived, due to radioactive decay, and
have their primary impact near the sources of their discharge. A
number, however, are long-lived and represent a long-term potential
source of exposure of a large number of people. In general, no methods
are available to effectively remove such materials from the environment
once they have been released, and such releases thus imply irreversible
commitments for exposure of future generations, except for natural
occlusion in environmental sinks. In cases where these materials have
physical or chemical properties which allow their widespread dispersal
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through one or more environmental media, the impact of these commitments
may be significantly enhanced..
The current contamination of the general environment by nuclear
weapons fallout from tests conducted in the 1950's and early 1960's is a
prime example of general environmental contamination by radioactive
materials that is now irreversible. This source of radiation is
worldwide and, next to natural background and medical exposure, it is
the largest component of man's current radiation exposure. The
recognition that fallout represents a general population risk (not
primarily an individual one) and the associated public reaction which
occurred were strong factors in the movement leading to cessation of
atmospheric nuclear weapons tests by the major world powers in 1962.
It is generally accepted that no threshold can be assumed for health
effects due to radiation exposure; therefore, the perspective that must
govern discharges of these materials to the environment is that all
doses which accrue to exposed populations result in some increment of
risk to these populations. The perspective that all radiation dose
results in some risk to the 'individuals exposed, or to their progeny,
plus the fact that projected large-scale use of nuclear energy will
produce large quantities of long-lived radionuclides, some of which may
be discharged to the environment, make it especially important to
consider the consequences of irreversible commitment of these discharges
to the environment before they have occurred.
This paper develops general concepts for calculating the cumulative
consequences of release to the environment of such long-lived
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radionuclides and illustrates these with an analysis of the potential
environmental consequences of projected releases of certain of these
long-lived radionuclides associated with operations of the nuclear power
industry for the next 50 years. These consequences are developed
through calculation of the entire cotinitment of doses (i.e., dose
equivalent) to populations implied by an environmental release/ a
quantity defined here as the "environmental dose connitment."
Projections of this type are particularly important because the impact
of these releases on populations continues over a long period of time.
Since control must be instituted long before the impacts associated with
these releases occur, projection of anticipated potential health effects
which could result from the release of these radionuclides constitutes a
necessary basis for decisions concerning the need for institution of
control over their release.
Future decisions ought to consider these dose conrnitments with
respect to both the types of development that should occur and the
choice of controls that should be imposed. This analysis attempts to
develop some of the factors associated with the perspective provided by
environmental dose commitment and to illustrate how it may provide
results which apply to the nuclear power industry as it embarks upon an
anticipated period of accelerated growth over the next several decades.
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II. ENVIRONMENTAL DOSE Q3MMTEMENT - GENERAL CONSIDERATIONS
The impact of radioactive effluents on man can be considered from
three different perspectives. The first of these is in terms of the
maximum dose to individuals. This measure has been the one
traditionally used for radiation impact analyses, and existing radiation
protection guidelines are usually expressed as limits on annual doses to
individuals. Although this approach may be adequate when the primary
objective is to limit risk to specific individuals, as in the case of
occupational limits for radiation workers, it is not adequate for use in
limiting the impact of long-lived radioactive effluents on large
populations. These materials typically deliver exposures over many
generations and the exposure of specific individuals is usually very
small. Doses received by members of the public due to the radionuclides
considered later in this report are in general several orders of
magnitude below existing Federal Guides limiting annual individual
doses. The impact of such materials can be large, not because there are
substantial risks to specific individuals, but because there are
substantial numbers of people at low levels of risk, and because the
potential for exposure may persist for a substantial period of time.
A second perspective is provided by summing the individual doses to
each of the members of a population to obtain an index of the total
population impact. This sum is generally expressed in person-reins, and
is conmonly estimated by forming the product of the total number of
persons exposed and their average dose. This population dose is usually
expressed on an annual basis.
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A third perspective of the environmental impact of radioactive
effluents includes the additional impact in subsequent years due to the
buildup and persistence of long-lived radionuclides. This perspective
is termed the "environmental dose coninitment" and, simply defined, is
the sum of all doses to individuals over the entire time period the
material persists in the environment in a state available for
interaction with humans. The unit of measure for this total population
dose is person-reins of environmental dose commitmsnt. It is calculated
for a specific release at a specific time and is obtained by summing the
person-rems delivered in each of the years following release to the
environment until dose increments are inconsequential as the result of
either radioactive decay or removal from the biosphere by other means.
The impact of this dose ccmnitment can be expressed in terms of
cumulative potential health effects. The terminology "cumulative
potential health effects" is used here to describe the sum of projected
deaths and diseases, including birth defects, that may be attributable
to environmental releases from a given radiation source over a specified
time period. The qualifying adjective "potential" is added to emphasize
that the incidence of specific effects is based on extrapolations from
information derived at higher levels of dose than those actually
expected, using a linear, non-threshold dose-effect assumption. In
addition, these effects will not be demonstrable since they are
distributed on a statistical basis throughout the entire exposed
population and are not different in kind from health effects occurring
from other causes. Health effects are here defined as radiation-induced
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somatic effects such as lung, thyroid, or skin cancers, plus certain
serious genetic effects in future generations. Relevant aspects of
health effect considerations are discussed in appendix D.
The idea of dose ccranitment is inherent in the internal dose models
of the International Commission of Radiological Protection used to
compute the maximum dose an individual can receive from internally
deposited radioactive materials which have long physical and biological
ha If-lives. Doses arising from radium and strontium deposition in bone
are examples of this application of the concept of dose commitment. In
addition, the United Nation's Scientific Committee on the Effects of
Atonic Radiation (UNSCEAR) has discussed basic concepts which pertain to
calculating the dose committed by long-term exposures due to
environmental contamination by radionuclides, but these calculations
focus on the maximum potential individual dose rather than on the total
impact of a given release on populations over extended periods of time.
The concept of environmental dose commitment developed here extends
these concepts to incorporate the total population dose implied by the
environmental release of a radionuclide. Even though many of the
principles involved have been previously enunciated, no significant
application of the concept of dose catmitment to evaluations of the
total impact on populations of environmental releases of radionuclides
appears to have been previously reported.
The determination of doses committed by the release of a radioactive
material to the environment involves a multiplicity of factors.
Environmental dose commitment, however, is particularly dependent upon
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the radioactive half-life of the nuclide under consideration, as it will
determine the availability for widespread dispersion in the environment
and hence the total number of persons potentially exposed over both
space and time. For the short-lived radionuclides, the environmental
dose commitment will usually consist only of the short-term exposure of
a limited population group. There is effectively no environmental
buildup of these radionuclides because the actual amount available at
any time represents a balance between incremental additions and
incremental removals by radioactive decay (i.e., equilibrium) that is
achieved in a short span of time. For long-lived radionuclides such an
equilibrium condition will not be reached for many generations. These
radionuclides continue to accumulate in the environment and, even if all
further additions are stopped at some point in time, will persist for
extended time spans as a potential source of cumulative exposures to
successive generations. For some radionuclides this time period may be
of the order of tens of thousands or even millions of years. In theory,
their total impact should be evaluated over this entire time period. In
practice, it is difficult, if not impossible, to make predictions over
such extremely long time periods and seme reasonable cutoff must be
used. For this analysis this cutoff has been arbitrarily chosen as 100
years. This time span includes very nearly the entire potential impact
of radionuclides with half-lives of the order of 10 years (such as
tritium and krypton-85) and it provides at least an evaluation of the
impact over a defined time period for the much longer-lived
radionuclides such as plutonium-239 and iodine-129.
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A schematic mathematical representation of the cumulative population
dose resulting from a given environmental release, i.e., the
"environmental dose commitment," is given by:
00 -X.n
D±(t) = I Qi(t)e 1 Ti(n) P± P(t+n) ,
n=o
vThere D. (t) = cumulative population dose resulting from the release
of radionuclide i in calendar year t.
Q. (t) = quantity of radionuclide i released in the year t.
X. = radioactive decay factor for radionuclide i.
T. (n) = pathway model conversion factor relating quantity
of radionuclide i released to its concentration in
the medium at the location of interest n years
following release.
F. = dosimetry conversion factor relating concentration
of radionuclide in the medium to resultant dose to
individuals exposed.
P (t4n) = number of persons exposed in calendar year (t + n).
t = calendar year of release.
n = number of years from year t.
This illustrative expression is necessarily simplified. In real
applications, the complications introduced by the multiplicity of
environmental pathways, differences in doses to various organs and the
spatial dependence of both the pathway model and population must be
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considered explicitly. This expression applies specifically to the
situation in which exposure of all individuals is uniform and the dose
of interest is to the whole body, or to one organ, and from one medium
only. Appendix A contains more detailed general equations which
consider the complications introduced by the above and other factors.
In converting from environmental dose commitments to health effects
it is necessary to define the particular types of health effects to be
considered and the probabilities that they will be incurred as a
function of the dose delivered. The analyses in this report are
limited, as described earlier, to estimates of cancers and certain
serious genetic effects, and the risk coefficients used have, in
general, been derived from the recent (November, 1972) report of the
Advisory Committee on the Biological Effects of Ionizing Radiations of
the National Academy of Sciences - National Research Council, entitled
"The Effects on Populations of Exposure to Low Levels of Ionizing
Radiation." Although in the future it may become possible to quantify
some of the less serious effects of radiation exposure, it is not
believed that this will substantially modify the inferences for health
impacts derived on the bases used here.
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III. APPLICATION TO S^ECTED IONG-LIVED RADIONUCLIDES FROM THE
NUCLEAR POWER INDUSTRY
The concept of environmental dose connitment is applied to releases
of long-lived radionuclides from the nuclear power industry in order to
illustrate the use of the concept for some specific cases of
environmental releases. The nuclear power industry is only one of
several possible sources of long-lived radionuclides. Others include
testing and other applications of nuclear devices, space power supplies,
and some medical and industrial applications. Because of the projected
rapid growth of the nuclear power industry, releases resulting from the
normal operations of the industry have been selected as the source for
this calculation. Releases associated with normal operations are
defined here to include all routine releases plus those unplanned
releases resulting from minor accidents, such as equipment malfunction
and human error, which can be expected on a recurring basis.
A. General Considerations
Two different viewpoints for preparing estimates of future
consequences have been utilized in this analysis. The first of these
attempts to make an assessment of potential consequences with due
allowance for expected performance of current emission controls, with
the objective of placing the impact of projected releases of a specific
radionuclide in a realistic perspective. The second viewpoint attempts
to establish plausible estimates of maximum potential consequences under
conditions of less effective control and more adverse environmental
behavior. Such a viewpoint is most useful for public health and safety
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planning purposes. These projected maximum potential consequences are
not actually expected to occur. Indeed, it is the purpose of such
projections to develop a rational basis for the control measures that
would prevent their occurrence.
To assess the magnitude of the potential environmental impact of the
release of long-lived radionuclides, four different isotopes (or groups
of related isotopes) have been chosen for this study. This selection
was based primarily on estimated total public health impact. The
radionuclides considered are tritium, krypton-85, iodine-129, and the
actinides including plutonium-238, 239, 240, and 241, americium-241, and
curium-242 and 244. A number of other long-lived radionuclides, such as
strontium-90 and cesium-137, are also produced in substantial quantities
by the nuclear power industry and their total impact could conceivably
be significant compared to that of the illustrative radionuclides
discussed here.
The general considerations included in making these assessments are
outlined in figure 1. Quantities of the various radionuclides produced
were derived from projections of United States nuclear power production
through the year 2020 beginning with the year 1970 and are discussed in
appendix B. Obviously, growth estimates of nuclear power are subject to
differences of opinion and the results of these assessments will be
proportional to the projections used. This appendix also describes
projections used in this report for United States and world populations.
Assumptions concerning control technology and environmental pathways are
described in appendix C. Release of all of the radionuclides considered
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NUCLIDE SOURCE TERM
ENVIRONMENTAL PATHWAYS
AND
MEDIA CONCENTRATIONS
POPULATION DOSE
HEALTH EFFECTS
Half-lives
Chemical and
physical forms
Production rate
Release rate
Dispersion
Dilution
Reconcentratlon
Direct radiation
Inhalation
Ingestion
Population statistics
Cancers
Leukemia
Genetic effects
Meteorology
Hydrology
Soil properties
Media concentration-
to-dose conversion
factors
Dose equivalent to
health effect
conversion factors
1
Radionuclide
sources
Air
Water
Food chains
Whole body
and
Organ doses
(person-rems)
Morbidity
Mortality
Figure 1 Model for estimating health effects from the nuclear power industry
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is assumed to lead to initial short-term exposures of individuals within
an 80 km (50 miles) radius. Iodine-129 and the actinides are then
assumed to be ultimately uniformly distributed over, and confined to,
large portions of the continental United States. Krypton-85 and tritium
are assumed to be ultimately dispersed over the entire world. The
concentration of radioactivity in food, water, air and other materials
was converted to population dose and then to health effects. The
conversion factors used are described in appendix D.
The calculated consequences of the release of the long-lived
radionuclides are critically dependent on the assumptions made. A wide
range of possible values for input parameters exists in addition to the
normal uncertainties inherent in making any future projections. The
estimated range of possible values for certain parameters and the actual
values used in this report are shown in table 1. The rationale for the
selection of these values is discussed below in section B. This table
lists only the parameters for which different values were assumed in
computing the dose commitments for each of the two viewpoints considered
in this report. Using these parameters, the series of environmental
dose cotmitments resulting from each of the annual releases attributable
to operations of the nuclear power industry over the period 1970-2020
was calculated. Using these results, the cumulative numbers of health
effects attributable to releases of each radionuclide through any given
year were estimated. These effects represent the potential irreversible
commitment due to releases through any given year, even if all future
releases should cease at that point. The calculated environmental dose
13
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Table 1
Numerical values for some significant parameters used in the analysis
Parameter
Actinide resuspension (m )
Iodine-129 release fraction
Krypton- 8 5 release fraction
Tritium release fraction
Range
of
possible
values
in~^ - in"~^
J.U J.U
ID"5 - 1
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cotmitments take into account all of the exposures occurring during the
period of persistence of krypton-85 (half-life 10.7 years) and of
tritium (half-life 12.3 years), but include only that fraction of the
total environmental dose commitment occuring during the initial 100
years after release for iodine-129 (half-life 1.7 x 10 years) and the
4
actinides (half-lives ranging up to 2.4 x 10 years).
B. Numerical Values of Key Parameters for Specific Radionuclides
Calculations of environmental dose commitments attributed to
releases from operations incorporating emission controls are highly
dependent upon the parameters chosen to characterize the effectiveness
of these controls. In addition, certain of the radionuclides considered
here undergo environmental transport processes which are not yet
quantitatively well-defined. The existence of large uncertainties in
these release and transport properties led to the choice of two
viewpoints to estimate the potential impact of these radionuclides. The
factors involved in the choice of numerical values for these key
parameters for the two viewpoints are discussed below for each
radionuclide considered.
1. Actinides;
Relatively small quantities of plutonium and the actinides have been
produced by the nuclear power industry to date, and projections of
future releases are subject to considerable uncertainties. Thus, it
should be recognized initially that these estimates should be reviewed
and revised as additional information is developed.
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Current control practices for actinide releases at a single
operation, such as nuclear fuel chemical reprocessing, are expected to
8 9
restrict releases to the order of 10 to 10 of the total amount
processed, and future experience may justify the assumption of even
smaller release fractions. However, when allowance is made for
inclusion of cumulative releases from the variety of fuel processing
operations as well as transportation and handling throughout the entire
fuel cycle, the fractional loss of plutonium and the actinides to the
environment for the entire fuel cycle must be assumed to be greater than
that from a single operation. In this context the fractional release of
the actinides is not realistically expected to exceed 10 of the total
amount handled in any given year. This value was used for projecting
expected minimum performance of the industry. For public health
planning purposes a more conservative viewpoint was adopted; a release
fraction ten times greater was used.
Transport pathways for the actinides through the environment to man
are not well defined. In this analysis the only pathway to man has been
assumed to be inhalation of aerosol particles initially suspended in air
and subsequently resuspended in the atmosphere after initial deposition.
Additionally, the simplifying assumption was made that the fraction
released was uniformly distributed over the continental United States.
In view of the large uncertainties associated with the estimation of
other factors in the analysis, these assumptions are not considered to
represent a serious deficiency.
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Resuspension - the ratio of material per unit volume of air to that
per unit surface area of soil - is critically dependent upon a variety
of parameters, including the depth profile of the deposited material,
the size distribution of aerosol particulates, and especially upon local
variations of topography, surface vegetation, and wind velocities.
_o
Resuspension factors ranging from a low of 10 per meter to a high of
about 10 per meter have been reported for newly deposited plutonium,
with most values clustered in the 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
-9
deposition. A value of about 10 appears to be a reasonable estimate
of the average availability of plutonium deposited on soil for
relatively long periods of time at the Nevada Test Site.
The difference between newly deposited sites and undisturbed areas
is probably due to downward migration of these compounds through the
soil, which depletes the quantity near the surface, rather than to a
fundamental change in the physical characteristics of resuspension. It
is expected that actual resuspension at specific locations decreases
with time, and that migration through most soils represents a pseudo-
sink for the actinides. Thus, the long-term impact of inhaled actinides
may be overestimated by assuming a constant value for resuspension.
However, adequate data are presently lacking, and a time-averaged
resuspension factor appears appropriate for use at the present state of
knowledge. Because of the availability of data for only a few isolated
sites and the known somewhat greater tendency for larger resuspension of
17
-------
-8
particulates in populated urban areas, a numerical value of 10 was
chosen as an appropriate numerical national average for the resuspension
factor for purposes of estimating the anticipated impact of the
industry. For public health planning purposes a more conservative
(pessimistic) value of 10 was selected.
It must also be recognized that the uncertainties associated with
human uptake pathways for the actinides give only limited validity to
the applicability of the single pathway model assumed for these
estimates and that this model must be updated as more information
becomes available.
2. Iodine:
Releases of iodine-129 by the nuclear power industry can be expected
to be almost exclusively restricted to fuel reprocessing facilities.
Nearly all of ^ie iodine produced by fission in the reactor is released
when the fuel cladding barrier is destroyed and the spent fuel is
dissolved for fuel reprocessing. Iodine control technology is becoming
available which appears to be capable of restricting releases to the
-3 -4
environment to the order of 10 to 10 of the total amount present in
the fuel. If this degree of control is achieved a release fraction of
10~~ will be an achievable objective for the industry, even if allowance
is made for possible additional losses in waste handling programs for
this material. However this control equipment is designed primarily to
control iodine-131, which has a much shorter half-life than iodine-129.
For public health planning purposes a more pessimistic view of the
18
-------
performance of this technology for iodine-129 was assumed; a release
factor of 10 was used.
The pathway model for iodine-129 in the environment used in this
analysis is subject to considerable uncertainty. Uniform distribution
of iodine-129 over the entire eastern land area of the United States is
an idealized concept, but this probably does not introduce significant
error when used in the evaluation of health effects in national
populations. However, the migration of iodine-129 in the environment,
its pathways to man, and its ultimate disposition are not yet well
established.
3. Krypton and Tritium;
Assumptions relative to the quantities of krypton-85 and tritium
released and of possible environmental pathways are subject to
considerably less uncertainty than those for plutonium and iodine-129.
Krypton is an inert gas and tritium is found in the environment
principally in the form of tritiated water (i.e., HTO). Control methods
3 2
which have decontamination factors of 10 and 10 for krypton and
tritium, respectively, have been proposed, but none is currently in use
in the nuclear power industry. Therefore, release of all krypton-85 and
tritium produced has been assumed.
Environmental pathway models for tritium are subject to somewhat
larger uncertainties than those for krypton. Krypton-85 is assumed to
expose local and regional populations via a finite cloud model and then
to mix uniformly in the world's atmosphere. Pathway assumptions for
tritium are somewhat less well established, and assumptions concerning
19
-------
the initial regional dispersion of tritium prior to its entering the
hydrological cycle are not well documented. The model chosen assumes
rainout over the eastern United States of half of the tritium released
followed by dilution and recirculation in the world's hydrological cycle
of the entire amount released.
C. Expected Minimum Performance By IndustryA First Viewpoint
Table 2 lists the projected numbers of health effects resulting from
projected releases from the United States nuclear power industry over
the next 50 years; these are based on the parameters shown in table 1
for this viewpoint. These projections assume that presently anticipated
performance of controls currently in use will obtain in the future.
Releases of krypton-85 and tritium are currently not controlled. The
imposition of controls which would reduce the fraction of radionuclides
released to the environment would decrease the environmental dose
cormitment proportionately. However, this decrease would affect only
the additional number of health effects attributable to the releases
prevented.
The following is an example of how to use the data contained in
table 2. If the present absence of control is assumed to continue and
all krypton-85 produced through the year 2000 is released to the
environment, the calculations indicate that an estimated 230 health
effects (on a worldwide basis) will be committed by krypton-85 doses
received prior to the end of the year 2000, and that an estimated
additional 760 health effects will be caused by doses delivered after
the year 2000 by krypton-85 remaining in the environment from all
20
-------
Table 2
Projected numbers of health effects attributable to release
of certain long-lived radionuclides by normal operation of the nuclear power industry
Cestimated for anticipated minimum performance by industry assuming current release practices)
Year(t)
i Q7n__
1 QftO__
1 QQ £____
i oon___
1 QQ (\____________
2000
2005
9m o__
on-i c_
orjon
Cumulative number of health effects
Iodine-129
Past-
present
0
0
0
0
0
0
0.1
0.2
0.3
0.5
0.8
Future
0
0
0
0
0.1
0.2
0.3
0.5
0.8
1.2
1.7
one- fourth fatal
Tritium
Past-
a
present
0
2
11
35
88
190
360
630
1,000
1,600
2,300
Future
0
0.5
3
8
21
A3
81
140
230
340
500
two-thirds fatal
Krypton-85
Past-
a
present
0
0.3
3
14
42
110
230
460
830
1,400
2,300
Future
0
5
26
79
190
410
760
1,300
2,100
3,200
4,600
two-thirds fatal
Actinides
Past-
present
0
0
0
0
0.1
0.2
0.4
0.7
1.2
2
3
Future
0
0
0.1
0.4
1
2
4
7
10
15
21
all fatal
The number of health effects committed from doses received through year(t).
The number of health effects committed from doses delivered after year(t) by radionuclide
releases up through year(t) only.
-------
releases prior to the end of the year 2000. Operations of the U.S.
nuclear power industry through the year 2020 could result in a total
worldwide population impact (i.e., cumulative potential health effects)
of about 7,000 health effects attributable to the release of krypton-85
and as many as 10,000 health effects due to all the radionuclides
considered here. This number is derived by summing all entries for the
year 2020. An obvious conclusion from the results is that, under the
conditions assumed for this part of the analysis, krypton and tritium
are the radionuclides of major concern for the 100-year period
considered.
D. Public Health Planning Projections A Second Viewpoint
The importance of developing projections for public health planning
purposes is to gain a perspective of the maximum plausible impact man's
activities may have on the total quality of life. Predictions made for
this purpose must necessarily adopt a more conservative (i.e.,
pessimistic) perspective, especially for activities which may result in
an irreversible deterioration of the environment and on which controls
must be imposed long before an unacceptable level of impact is reached.
The expectation is not that these conservative estimates will cone to
v>
fruition, but rather that constant vigilance and effective application
of technology can and must be utilized to prevent these estimates from
being realized.
The values of input parameters which were used for these planning
projections are shown in table 1. The choice of this set of numerical
values resulted from a series of judgments at least as difficult to make
22
-------
as those for the previous projections for expected minimum industry
performance. The general approach taken in choosing the values of
parameters for these second viewpoint projections was to attempt to
avoid the use of worst case assumptions simultaneously for all of the
variables. Calculated impacts resulting from the parameters used for
this second viewpoint are listed in table 3 and displayed in figure 2.
Results from the first viewpoint are also displayed in figure 2, for
comparative purposes.
The most significant result of the public health planning viewpoint
is the relatively large number of health effects attributable to
releases of the actinides. Under these assumptions, by the year 2020 an
additional commitment of 24,000 health effects is projected for normal
operations of the United States nuclear power industry. The bulk of
these effects are evenly distributed over the 100-year period following
release for which the environmental dose commitment was calculated. Two
points should be emphasized. First, the number of effects calculated is
based on a highly conservative (pessimistic) set of assumptions and is
expected to overestimate the actual impact of such releases over the
100-year period chosen for this analysis. Second, the actinides are, in
general, very long-lived materials and their eventual total impact over
many centuries may be many times that experienced during the first 100
years following release. Current knowledge does not permit estimation
over such long time periods.
Until existing uncertainties in these projections are resolved,
concern for protection of public health dictates that such estimates as
23
-------
to
Table 3
Projected numbers of health effects attributable to release
of certain long-lived radionuclides by normal operation of the nuclear power industry
(estimated as maximum plausible projections for purposes of planning
for adequate public health and safety considerations)
Year(t)
1970
1975
i QRn__ _____
1985
1990
1 QQ «;_____ _____
2000
2005
2010
2015
9O9n__ ______
f.\j DJ*-^*- ________ _
Cumulative number of health effects
Iodine-129
Past-
present
0
0
0
1
3
6
11
21
34
53
78
Future
0
0
1
A
9
17
32
53
82
120
170
one-fourth fatal
Tritium
Past-
present
0
2
11
35
88
190
360
630
1,000
1,600
2,300
Future
0
0.5
3
8
21
A3
81
1AO
230
3AO
500
two-thirds fatal
Krypton-85
Past-
present
0
0.3
3
1A,
A2
110
230
A60
830
1,AOO
2,300
Future
0
5
26
79
190
A 10
760
1,300
2,100
3,200
A, 600
two-thirds fatal
Actinides
Past-
present
0
2
12
38
96
210
AGO
720
1,200
1,900
2,800
Future
0
26
1AO
AAO
1,100
2,200
3,900
6,500
10,000
15,000
21,000
all fatal
number of health effects committed from doses received through year(t).
The number of health effects committed from doses delivered after year(t) by radionuclide
releases up through year(t) only.
-------
20,000
o
LLJ
o
15,000
X
u.
O
Z 10,000
LLJ
>
I
5
u
5,000
Expected Minimum Performance of Industry
Public Health Planning Projection
ACT IN IDES
85
Kr,
1970
2000
2010
ACTINIDES
129
^*>
^m
2020
YEAR
Figure 2. Estimated cunulative potential health effects
conmitted by projected releases from the
United States nuclear power industry
25
-------
these of potential consequences be made in order to assure the public
that uncertainties have been considered and that reasonable margins of
protection will be provided. This approach is especially important in
cases where current releases may be small but the cumulative potential
impact of a rapidly expanding industry is significant. It is important
to recognize that these large uncertainties exist because adequate data
are not available, a condition that can be remedied only through
additional research and monitoring efforts.
26
-------
IV. SUMMARY AND CONCLUSIONS
This report has developed the concept of environmental dose
commitment to examine the implications of the irreversible commitment of
releases of long-lived radionuclides to the environment. It is found
that a comprehensive assessment of the iinpact of such releases can be
conducted within the analytical framework provided by this concept. An
assessment of the iinpact of such materials on individuals or on local
populations on the basis of annual exposure alone does not provide an
adequate measure of the total impact of their release. The scope of
analysis must include not only all members of the population initially
exposed, but also all exposures during the entire time frame during
which these radionuclides remain in the biosphere. Although not all of
the projections for the radionuclides considered here satisfy both of
these criteria completely, the perspective provided by even a partial
calculation of environmental dose commitment is considerably more
meaningful than such a traditional measure as annual individual dose.
The concept of environmental dose commitment was applied to the
projected normal releases of several long-lived radionuclides over the
next 50 years due to operations of the nuclear power industry in the
United States. The results of the analysis are expressed in terms of
numbers of potential health effects. Although the impact was evaluated
on a worldwide basis, only the contribution of releases from the United
States nuclear power program was considered. In view of uncertainties
involved in projecting the impact of these releases, the results are
presented both in terms of minimum expected industry performance as well
27
-------
as in terms of estimates useful primarily for public health and safety
planning purposes.
Application of the concept of environmental dose commitment leads to
the conclusion that, in general, the impacts of projected future
releases of the long-lived radionuclides considered here can be
relatively small if appropriate and timely attention is given to their
minimization. . Although these impact are particularly small for current
levels of environmental releases, it is clear that future radiation
guidance, standards, and regulations must address the implications of
environmental dose commitments due to these materials. The perspective
provided by this concept is essential in order to insure that proper
attention is focused on minimizing the impact of man's rapidly expanding
uses of these radioactive materials on future generations.
Numerical results of this study indicate two potential trends of
significance. First, the potential future impact of the release of
krypton-85, especially if other releases around the world are added to
these estimates, is sufficiently large that active consideration should
be given to controls to limit releases of this radionuclide. Second,
the potential implications of release of the actinides are large.
Additionally, the carrying out of this study made it clearly evident
that there is a need for comprehensive research efforts to delineate
release terms, environmental pathways, and biological effects of the
radionuclides considered, and in particular for the actinides.
It should be recognized that any calculation of environmental dose
commitment is subject to uncertainty. The projections presented here
28
-------
are indicative only of current best estimates of possible consequences
and cannot indicate more than potential future general trends. In order
to reduce uncertainties and thereby be more useful for policy decisions,
such analyses must be updated at frequent intervals as new information
is developed. Fortunately, the vast majority of the adverse health
effects estimated by application of the concept of environmental dose
commitment are not yet committed. Because of this, and in spite of the
inherent uncertainty of any projection, the concept of environmental
dose commitment can provide a useful basis for dealing with the
challenge of protecting the environment from avoidable and irreversible
detriment.
29
-------
BIBLIOGRAPHY
Allied Gulf Nuclear Services, Barnwell Nuclear Fuel Plant Safely
Analysis Report, ABC Docket No. 50-332, (1969).
Bryant, P.M., "Derivation of Working Limits for Continuous Release Rates
of I to Atmosphere/1 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 LaboratoryT
BNWL-1010, (1969).
Gamertsfelder, C.C., Statement on the Selection of as Low as Practicable
Design Objectives and Technical Specifications for the Operation of
Light Water Cooled Nuclear Power Reactors, Presented at ABC 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).
Healy, J.W., Surface Contamination; Decision Levels. IA-4558-MS
(1971).
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 - 1960-20*007 U^SlEnvironmental Protection Agency,
EPA/CSD/ORP 72-1, (1972).
Khox, J.B., "Airborne Radiation from the Nuclear Power Industry" Nuclear
News, Vol. 14, pp. 27-32, (February 1971).
30
-------
Langham, W.H., Plutonium Distribution as a Problem in Environmental
Science. Proceedings of Environmental Plutonium Symposium held at Los
Alamos Scientific Laboratory, IA-4756 (August 4-5, 1971).
Lindell, B., "Assessment of Population Exposures," Symposium on
Environmental Behavior of Radionuclides Released in the Nuclear
Industry, Aix-en-Provence, France, (May 1973).
Machta, L., National Oceanic and Atmospheric Administration, Unpublished
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 Spectroinetric
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 Scientific Committee on the Effects of Atomic Radiations,
Ionizing Radiation; Levels and Effects, United Nations, New York,
(1972).
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);
31
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APPENDIX A
EQUATIONS
FOR
ENVIRONMENTAL DOSE OOMMTIMENT
-------
I. INTRODUCTION
The "environmental dose commitment" attributable to a release of
radioactive material is defined as the sum of all doses to individuals
over the entire time period the material persists in the environment in
a state available for interaction with humans. It is calculated for a
specific release occurring at a specific time. Environmental dose
commitments are expressed in terms of the number of person-rems to the
whole body or to specific body organs. The health impact of these
commitments can be expressed in terms of the numbers of different kinds
of health effects attributable to these doses by using a linear non-
threshold dose-effect model. Finally, the total health impact of a
release may be characterized by a single value derived by applying
weighting factors to different categories of health effects and summing.
In general, however, health impacts are most usefully expressed as
separate categories of effect without such weighting.
In order to develop mathematical expressions for environmental dose
ccmmitment and their associated health impacts, a variety of terms must
be coupled to the quantity (Q) of the radionuclide released to the
environment. These are the pathway transfer function (T), dose
conversion factor (F), population density (P), health effects conversion
factor (R), and a weighting factor (W) that expresses the seriousness of
a health effect. These terms may differ depending upon the radionuclide
(i), pathway (j), body organ (k), type of health effect (1), and
transfer medium (m) under consideration. In addition, the pathway
A-l
-------
transfer function and population density will, in general, be functions of
geographical location and time.
II. CittNimAL EQUATIONS
To develop a general expression for environmental dose cotmitment we
first consider an individual at seme location, 4, away from the source of
the release of a quantity/ Q / of a radionuclide, (tQ ) at calendar time t$ , and the term
'V-
-»
T- m(X-r£) converts the quantity released to the concentration after a time
-x.j In
t at the location t in medium m from the j pathway, and carries the units
curies per unit volume per curie released. The pathway .model, T- (1,-t) ,
^*J M I
must be considered a function of time as well as of location for two
reasons: environmental sinks may have a time dependence quite apart from
normal radioactive decay, and the model, if expressed as a function of
A-2
-------
function of £ only, can be multivalued due to recirculation in such
environmental transport systems as the hydrological cycle or general
atmospheric circulation. The exponential is the radioactive decay
factor, where X. is the decay constant for radionuclide t . The
**O
concentration to which an individual is exposed through a particular
medium is converted to dose rate to the whole body or to any organ or
tissue of interest by the factor F^. ^fe will use a generalized
definition of organ that includes the whole body and skin as well as
internal organs and tissues. For each specific nuclide it is, of
course, necessary to determine which of these "organs" are of
significance. This factor generally has no time or location dependence,
although it is possible that individual uptake from some media could
vary throughout the year, or from one location to another. In those
situations where buildup of body burdens of internal emitters can occur,
it will also be necessary to reflect the sum of all future doses to the
individual committed by each incremental body burden in calculating the
factor F. . .
4JT?fe
Equation (1) expresses the basis required for the calculation of
individual exposures. In order to extend the calculation to populations
an additional factor, P(£,.£0+£), the population density as a function of
location and calendar time must be introduced. In general, a number of
different characteristics of population subgroups must be considered in
order to properly calculate the effects of radiation exposure. These
may include age-specific variation in uptake and organ size as well as
additional variations in radiosensitivity due to age or sex. In cases
A-3
-------
involving long-term (greater than a few years) cormitments for exposure,
however, it will usually be possible to avoid separate calculation for
each population subgroup by using a suitably weighted average of the
dose conversion factors appropriate to each population subgroup for the
factor F:~k *° represent the average for the entire population exposed.
Similarly, in converting from dose to health effects in equation (3)
below, an analogously constructed conversion factor can easily
acconnodate variations in sensitivity due to age or sex. For
simplicity, therefore, we have not specified subgroups of the exposed
population, although the extension for special situations requiring it
is straightforward.
The population dose cormitted by a release at time t§ is now
computed by integrating equation (1) times the population density
function over space and time:
(2)
where 3L and t. are the limits of geographical area and of time for
which the population dose is being calculated. Ideally, the calculation
of dose committed by a release should consider all locations at which
individuals may receive exposures, and all time until the exponential
decay factor in equation (1) reduces the integrand to insignificant
values. In practice this is often either not possible or not practical.
The detailed examples elsewhere in the report examine the question of
appropriate choices of these limits for some specific radionuclides.
A-4
-------
The quantity D., given by equation (2) is the required environmental
dose commitment and is specified in person-rems of population dose to the
whole body or to any organ, k, attributable to release of a quantity,
Q.(£g)* of a particular radionuclide -c to the environment. It provides in
A*
a single value, or index, the means for comparative assessments of the
impact of such environmental releases. However, two additional operations
are required to transform D -^ into a more useful measure of the
consequences of an environmental release. The first is to estimate the
various health consequences or the total impact of such a dose due to a
single release, and the second is to project the cumulative consequences of
all of the projected releases over some future time period from the
particular activity under examination.
The health consequences of a radiation dose may range all the way from
inconsequential to lethal. We will assume that it is possible to
categorize health effects into groups having similar importance and
probability of occurrence in the exposed population. If this can be done,
then the number of such health effects, H;», of a particular category, t,
due to an exposure from the release Q- can be expressed as:
where &» is the probability of incurring an effect of category t in the
population due to an exposure of organ fe. If the desired endpoint of the
analysis is the number of a particular category of effects that may be
induced, such as the number of lethal effects, the sum over those
A-5
-------
quantities, H££, which are lethal expresses this endpoint. If, however,
it is desired to express the total impact of the release by a single
result, then it is necessary to pursue the calculation one step further
by introducing a weighting factor which expresses the relative severity
of the various categories of health effects, as follows:
t4)
where I. is a single index representing the total iitpact of the release,
*C-
Q., expressed in some convenient unit, such as dollars or days or life
^f
shortening or disccmforture, and W. is an appropriately constructed
^.
weighting factor for the t category of health effects.
Environmental dose cotitdtments are calculated in order to make
assessments of operations to be conducted, usually, over an extended
period of time. To calculate the total projected consequences of
conducting such an operation it is necessary to determine the iitpact of
cumulative releases from the operation over a specified period of
interest. Since the population exposed will, in general, vary with
calendar time, the calculation must be performed by considering Q. in
4~
equation (1) as a variable which expresses the rate of release as a
function of time. The calculation of the cumulative dose commitment is
then easily accomplished by performing an additional integration over
time in equation (2) as follows:
= f
2
A-6
-------
where the integrand is given by the right-hand side of equation (2), but
the time dependence of the release rate, Q-, is shown explicitly and t2 i-s
^
the end of the period over which releases due to the operation under
investigation are included. The quantity 3D., is defined as the cumulative
environmental dose commitment and is specified in person-rems of population
dose, to the organ of interest, attributable to environmental releases from
a particular operation over a specified period of time. The examples
derived below and discussed elsewhere in this report estimate health
effects as a function of t2 (the year to which the activity continues)
resulting from such cumulative environmental dose commitments. These
health effects and their related impacts can be calculated from
IVL (i-i ,£Q tt\ ,t2) in a manner analogous to that shown in equations (3) and
(4) for D.(£lr£o»*l)
A*
The above dose equations involve three time perameters: t0, the year
of initial release of a given radionuclide; t^, the period over which the
dose commitment of each release is accumulated; and t2 > t^6 final year for
which releases contributing to cumulative environmental dose commitment are
included. For purposes of the calculations in this report, the parameter
tQ is 1970, ^j equals 100 years, and t2 varies from the year 1970 to 2020.
A-7
-------
APPENDIX B
ANNUAL RADIONUCLIDE
AND
POPULATION PROJECTIONS
-------
I. INTRODUCTION
This appendix is concerned with two important factors utilized in
the calculations presented in this report: (a) projected annual
inventories of radionuclides of interest, and (b) population
projections. These projections are based on information in the
literature (see attached bibliography).
II. ANNUAL RADICMUCUDE INVENTORIES
For purposes of this study the annual quantities of the
radionuclides of interest potentially available for release to the
environment are assumed to be those quantities present in spent reactor
fuel reprocessed each year. Only the U.S. nuclear power industry was
considered. The number of metric tons of fuel to be reprocessed in any
given year was estimated by using data on power generated 2 years
earlier and assuming a thermal efficiency of 0.35 and a burnup of 33
gigawatt-days (thermal) per metric ton of fuel:
metric tons _ GW(e) 1 GW(th) 1 metric ton 365 days
year(t) year(t-2) 0.35 GW(e) 33 GW(th) days year
The estimated nuclear power generation and the metric tons of fuel
to be reprocessed per year are given in table B.I for the expected mix
of reactor types.
There are two types of radioactive material present in spent reactor
fuel: fission products and activation products including actinide
isotopes. The quantities of specific radionuclides present are
B-l
-------
Table B.I
Estimated U.S. nuclear power production
and fuel reprocessing requirements
Year
1970
1975
1980
1985
1990
1995
2000
2005
2010
2015
2020
Nuclear
electric
generation ,
GW(e)
2.6
40
110
220
420
650
1000
1360
1780
2220
2700
a
Metric tons of fuel to be reprocessed annually
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
8,800
TOTAL
25
790
2,400
5,400
10,400
17,400
26,800
38,000
51,500
64,500
79,000
aA burnup of 33 GW-day/MT to discharge was assumed for all fuel.
Fuel burnup is a highly variable parameter and the value chosen repre-
sents an estimated design average for normal operation of current light
water reactors. Fast breeder reactors are expected to have a design
average fuel burnup up to 100 GW-days/MT. The value chosen may thus
greatly overestimate the fuel discharges in later years, and the num-
bers shown here should not be considered the actual expected numbers.
The resultant radionuclide inventories derived from these calcula-
tions, as used in this report, however, are largely independent of the
burnup assumed and the results derived in this analysis are only
slightly affected by this assumption.
B-2
-------
determined primarily by fuel type, amount of burnup, and time of cooling
(time between removal from the reactor and time of reprocessing).
Tables B.2 and B.3 shew 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
types. There is some possibility that cooling times shorter than 150
days may be used in the future, since faster recycling of the recovered
fuel may result in a significant economic benefit. This would greatly
increase the amounts of shorter-lived radionuclides in the fuel and
available for release, but would not significantly 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 B.4. 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 processed fuel were calculated and are presented in
table B.5.
The release fractions applied to these annual inventories to
determine the estimated amounts released to the environment are
discussed in detail in the text of this report. In the computations
carried out in this study, it was assumed that environmental releases of
B-3
-------
Table B.2
Representative quantities of potentially significant fission products in spent reactor fuels
Isotope
3H
85Kr
99Tc
103Ru
106Ru
X fc O IWpo^»»»«»
1 £. 1 Wpo^^^
129imje
129X
131j
1 3**Cs -
135Cs
137Cs
89Sr
90Sr
91y
93Zr
95Zr
95Nb
125Sb
141Ce
14'tCe
lt*7pm____
155Eu
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
3xl06
30.2
0.14
28.9
0.16
0.95xl06
0.18
0.10
2.73
0.09
0.78
2.62
5.0
Curies per
metric ton
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
metric ton
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
Semivolatile
Semivolatile
Semivolatile
Semivolatile
Semivolatile
Semivolatile
Volatile
Volatile
Semivolatile
Semivolatile
Semivolatile
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
103mRh +106^ daughters
Oxide b.p. 750° C
127Te daughter
129Te daughter
b.p. 184° C
b.p. 184° C
Oxide b.p. 750° C
137mBa daughter
90Y daughter
95mNb + 95Nb daughters
14Upr + 14lfNd daughters
Burnup = 33 GWd(t)/MT
Cooling time = 150 days
-------
Table B.3
Representative quantities of potentially
significant activation products in spent reactor fuels
Isotope
5^
55Fe
59Fe
58Co
60Co
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
Burnup = 33 GWd(t)/MT
Cooling time = 150 days
B-5
-------
Table B.4
Representative quantities of actlnides present in spent reactor fuels
Isotope
235u
236u
238n
237Np
238pu
239pu
2fOpu
241pu
2U2pu
24iAm
243^
242^
21*0,
Half-life
(years)
710xl06
24xl06
4510xl08
2xl06
86
24,400
6,580
13
379,000
458
7,800
0.45
17.6
Total (excluding uranium)
Uranium fuels
Ci/MT
< 1
< 1
< 1
< 1
4,000
500
650
150,000
2
750
20
35,000
2,000
193,000
g/MT
8,000
4,000
950,000
600
230
8,100
2,900
1,300
510
230
100
10
' 25
14,000
Pu-recycle fuels
Ci/MT
< 1
< 1
< 1
< 1
6,000
750
1,000
300,000
5
2,000
200
250,000
25,000
585,000
g/MT
3,000
1,500
950,000
200
340
12,000
4,400
2,600
1,300
620
1,000
75
300
23,000
Burnup = 33 GWd(t)/MT
Cooling time - 150 days
B-6
-------
Table B.5
Estimated annual inventories of selected nuclides in reprocessed fuels'
(curies)
Year
1 Q7n_ _____
1Q7C ____ __ __
1980
1 QRS_ _______
i Qon_ _
i QQt; ___
onnn
onf»«;_
oft-i n _
ofti c
2020
Fuel
reprocessed
(MT)
oi
t.j
7Qn
/y\J
2,400
5 Ann
jtUU
i n Ann
J.U jHUU
i 7 Ann
J./ , HUU
of> snn
zo , ouu
oo ft,ftft
jo , UUU
ci cnn
Jj. , JUU
fiA ^nn
O4* ) JUU
79,000
Tritium
o rjvi n1*
Z UXJ.U
6o_i rt5
JXJ.U
1.9xl06
A ^-vinS
*r JX-LU
8O-.-1 r»6
JXJ.U
i Avi n7
J-« tX-LU
21 -wi n"7
J.XXU
3n-wi n7
UXJ.U
41 -.1 (\7
* J.X1U
c o_i r»7
3 ZXJLU
6.3xl07
Krypton-85
2f.,.i (\5
oxxu
8q~i r\6
-JXJ-U
2.5xl07
c 7-».in7
J / XJ.U
i i-vin8
J. . J.X1U
i Rvin8
X* oXJLU
2ftvi n8
OXJ.U
4n-iri n8
uxxu
c A..1 n8
J HXXU
6Rvi n8
OX-LU
8. 3x10 8
Iodine-129
i n
j. \>
q o v-i ft I
J ^AJ-U
9.6X101
o ?v1 0^
A 9-vl n2
f &X.LU
7 n-wi n2
/ UXJ.U
IT vi r« 3
J.X-LU
1c_.i r\3
DXJ.U
21 ..1 ft 3
J.X.LU
o A-win3
Z. OXJ-U
3. 2x10 3
Plutonium-239
i Qvi n1*
JL -7XJ.U
R QvinS
J 7XJLVJ
l.SxlO6
A iv-in^
H XXJ.U
7 R-vl n6
/ OXJ-VJ
10-..1 ft?
JXJ.U
2ftv1 ft?
uxxu
2 Qvi n7
. 7XJ.U
3 Qvi n7
7X-LU
Aftvi n7
OXJ-U
5. 9x10 7
Plutonium-241
7 Svl 0^
2 4v1 0^
7.2xl08
1 fivl 0^
q ivin9
J J-XJ-U
59vi n9
ZXJ.U
8nvi n9
UXJ.U
11 vi nl 0
. J.XJ.U
IC-,1 ftl 0
JXJ.U
IQvi nl 0
yxxu
2.3xl010
Tiased on Pu-recycle fuels and reactor type distribution in table A.I. (33 GWd(t)/MT burnup and
150 days cooling period.)
-------
tritium, krypton-85 and iodine-129 occurred only from reprocessing
plants. Releases of the actinides were assumed to occur from other
stages of the fuel cycle as well as from reprocessing plants.
III. POPUIATION PROJECTIONS
A. Regional
The regional population growth within 80 km (50 miles) 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 also considered to be applicable
to fuel reprocessing plants and other nuclear facilities.
B. United States
The population projection used for the United States is shown in
figure B.I. 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 as
3.56 x 10^ with an annual growth rate of 1.9 percent.
B-8
-------
500
T
vo
1980
1990
2000
2010 2020
Year
2030
2040
2050
2060
Figure B.I United States population projection
-------
Burch, W.D., Bigelow, J.E., and King, L. J., Transuranium Processing
Plant Seminannual Report of Production, Status and Plans for Period
Ending June 30, 1971, Oak Ridge National Laboratory, ORNL-4718, pp. 29-
30, (December 1971).
trandall, J.L., Tons of Curium and Pounds of Californium, Presented at
American Nuclear Society International IVfeeting, 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).
Hbfmann, 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.
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, WZAP-6086, (August 1969).
Oak Ridge National Laboratory, Siting of Fuel Reprocessing Plants and
Waste Management Facilities, ORNL-4451, (July 1970).
U. S. Atomic Fjiergy Commission, Nuclear Power 1973-2000, WASH-1139,
(December 1972).
U. S. Department of Conmerce, 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 Ccmmission, The 1970 National Power Survey, (1971).
United Nations Statistical Office, Demographic Yearbook, Publishing
Service, United Nations, New York, (1971).
United Nations Statistical Office, Vforld Population Prosp^j-g **_
Assessed in 1963, Population Studies No. 41, United Nations, New York,
(1966).
B-10
-------
APPENDIX C
ENVIPONMENTAL TRANSPORT
-------
I. INTRODUCTICN
Radioactive materials released to the environment become dispersed
in the surrounding media (air, water, etc.) and ultimately may produce
health effects in man. A factor necessary to assess the impact of a
given radionuclide release on populations is the transport factor which
converts quantity released to concentration of the radionuclide in a
specific medium at a given location and time following its release.
This appendix discusses this factor, as applied in the calculations
carried out in this study.
For reasons discussed below, different environmental transport
models were used for: (a) local populations (defined as those within 80
km, or approximately 50 miles, of the point of release); (b) regional
populations (including portions of the eastern United States and
Canada); and (c) the world population. In developing these models, only
the environmental pathways of principal importance from the viewpoint of
human uptake and potential health impact have been considered.
II. TRANSPORT TO LOCAL POPULATIONS
Members of the local population around a source of radionuclides
discharged to the environment are exposed to higher concentrations of
these radioactive materials than is the average individual in the U.S.
In general, these higher concentrations arise because environmental
transport is at an early stage and ultimate dilution has not yet
occurred. The doses delivered to local populations during this "first
pass" of an effluent will usually constitute a substantial fraction of
the entire environmental dose commitment that accrues to these local
C-l
-------
populations. For this reason, these local populations are considered a
special case for which the initial contribution to environmental dose
commitment is calculated separately.
For the nuclides considered (with the exception of tritium) airborne
releases constitute the most important release mode. For tritium, since
doses resulting from waterborne releases are on the average comparable
to those from airborne releases, all tritium was assumed to be
discharged to the atmosphere. Annual meteorological conditions for a
variety of representative facilities were analyzed. These data
_o
indicated an average value for (x/Q) at a distance of 3 km of 5 x 10
3
uCi/cm per VCi/s for a representative facility. This value was used
for all airborne-release calculations in this study.
The effect of local population distribution on the average dose to
an individual within 80 km of a facility can be calculated theoretically
by assuming a "typical" population distribution, or it can be determined
directly from actual or projected populations around real plant sites.
For this study an analysis of the results of calculations of doses due
to gaseous effluents for real and projected populations at 50 reactor
sites was used. These results yielded an average value of 0.028
rem/person within 80 km per rem/person at 3 km. This ratio is
\
sufficiently insensitive to variations for specific radionuclides to be
representative of all long-lived nuclides in airborne releases that were
addressed by this study. Factors for individual long-lived
radionuclides at specific facilities may vary by as much as a factor of
5 from the average given above.
02
-------
The population within 80 km of a nuclear facility site was taken as
the average of population values for the above-mentioned 50 reactor
sites, obtained primarily from environmental reports. The average
population around a site was found to be 1.5 x 10 people in 1980.
Population density around individual plants can vary from this by a
factor of 3. The average doubling time of these populations is about 40
years. For purposes of calculating age specific factors, 2.5 percent of
the population is taken to be under 1 year of age, 45 percent between 1
and 20 years, and the remainder over 20 years of age.
III. TRANSPORT TO REGIONAL POPUIATTCNS
The transport of radionuclides in the environment is dependent upon
both their physical and chemical states. It is assumed that each of the
radionuclides considered in this report is released as a gaseous
effluent. These effluents spread from the local region to major parts
or all of the eastern United States and Canada and, in some cases, are
then transported over the entire globe. The pathway leading to doses to
these population differs for each radionuclide considered. Iodine-129
and the actinides are assumed to produce population exposures only
through buildup in soils in the United States. Tritium is assumed to
expose only the population in the eastern United States initially, and
ultimately the entire population of the northern hemisphere. Krypton is
assumed to expose populations in the eastern United States and Canada
initially, and ultimately the world population.
C-3
-------
A. Tritium
It is assumed that tritium is released as a gaseous effluent and
that a portion of the amount released enters the hydrological cycle
through deposition by rainout over the eastern United States (1.5 x 10
2
*mi ), where it is diluted by the average annual rainfall (40 inches)
over this area and then works its way through soil into river systems
and finally into the oceans. With sane further dilution by
uncontaminated water this rainout becomes the water concentration to
which the population of the eastern United States (80% of the total U.S.
population) is initially exposed. The balance of the amount released is
assumed to rainout directly into the oceans where it is augmented by
tritium from river outfalls and gives rise to population exposures in
the northern hemisphere via the hydrological cycle.
The annual water concentration of tritium in the eastern United
States is taken to be the yearly input to the environment diluted by the
average annual rainfall over the eastern United States, with an
additional dilution factor of one-half applied to take into account
dilution of tritium by uncontaminated rainfall and water from deep
artesian wells, as well as that portion of tritium effluents that does
not fall out over the eastern United States but passes directly out over
the eastern coast to the Atlantic Ocean.
B. Krypton-85
Part of the population of the eastern United States and Canada is
exposed to air concentrations of krypton-85 as it passes from the points
of release to the Atlantic Ocean on its first pass around the world in
C-4
-------
general meteorological patterns of flow. The dose from this exposure
pathway was derived from the results of a study recently performed at
the National Oceanic and Atmospheric Administration. That study
estimated that for a plant located in Morris, Illinois, releasing one
curie of krypton-85 per year, the population-weighted concentration on
its first pass over the eastern United States and Canada to the Atlantic
Ocean is 2.5 x 10 man-Ci/cm . For purposes of this study, this value
was considered sufficiently representative for all release points.
C. Iodine-129
As a first approximation, all iodine-129 releases are assumed to
deposit uniformly over the eastern United States and to assume a uniform
equilibrium distribution with stable iodine in the soil to a depth of 20
cm. This mixture is assumed to give rise to the specific activity of
iodine-129 in the diet to which all persons in this part of the country
will be exposed. The movement of iodine-129 in the biosphere is not
well documented at the present time. For the purpose of this analysis
no further dilution or reconcentration in the environment was assumed
beyond this equilibrium mixing in the first 20 on of soil. Thus, these
estimates of population exposure to iodine-129 are subject to
considerable uncertainty. However, because of its long half-life (17
million years), even if a substantial fraction of iodine-129 migrates
into environmental sinks, the total impact of environmental iodine-129
may be considerably larger than that calculated here for 100 years only.
05
-------
D. Actinides
The actinides are assumed to build up in the eastern United States
in a manner similar to that postulated for iodine-129, but with the only
exposure pathway taken to be inhalation of resuspended material. The
fraction of actinides released that deposits on the soil was taken to be
0.5 for this study; the balance was assumed to rainout over the oceans,
where it remains unavailable for human uptake. The assumption that the
actinides are uniformly distributed over the eastern United States is
made for simplicity in calculating exposures. It would have been
equally simple to assume a uniform distribution of population and a non-
uniform dispersion of actinides. The essential question for evaluating
the acceptability of either of these assumptions is in what direction
does the actual population density depart from the average value for the
eastern United States at locations where the actinides are most likely
to be initially deposited. A review of population densities in the
vicinities of three existing fuel reprocessing plants indicates that
average population densities are generally higher, by up to an order of
magnitude, in the vicinities of such plants. However, in view of the
possibility of releases from a wide variety of facilities, and
operations such as transportation and waste disposal which may occur in
sparsely populated regions, as well as of migration of the actinides to
yield a more uniform dispersal, it was judged acceptable to make the
less conservative assumption of uniform deposition for this analysis.
06
-------
IV. TRANSPORT TO WORLD POPMATIONS
Releases of krypton-85 and tritium are dispersed on a global scale
and result in exposures of the entire world's population. Doses from
releases of iodine-129 and the actinides were assumed to be restricted
to the United States population.
A. Krypton-85
This effluent attains close to a uniform distribution in the world's
atmosphere in less than a year following its release. The worldwide
f
concentration of krypton-85 can be estimated by diluting a release into
21
the world's atmosphere (5.14 x 10 g; sea level air density =
0.00129 g/cm ). For the purposes of this study, the small correction
required for non-uniform distribution during the first year following
release has been ignored, except for the previously calculated first
pass doses delivered to local and regional populations.
B. Tritium
The worldwide dose due to tritium releases is estimated by diluting
the amount released into the circulating waters of the northern
18
hemisphere (7 x 10 liters) and assuming that the northern hemisphere's
population (80 percent of the world's population) is exposed to the
resulting concentration.
0-7
-------
APPENDIX D
CONVERSION FACTORS
FOR
RADIOLOGICAL DOSE AND HEALTH EFFECTS
-------
I. INTRODUCTION
Two factors required to assess the impact of radionuclide releases
to the environment on pqpulation-s are: (1) a medium concentration-to-
dose conversion factor, and (2) a factor for converting population dose
to an expected number of a specific adverse health effect. These
factors are discussed below for tritium, krypton-85, iodine-129, and
selected actinides.
II. MEDIA COKmm&TION-TO-DOSE CONVERSION FACTORS
Dose estimates are sensitive to assumptions made concerning the
mode of exposure, 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. Other
necessary elements entering into dose computations are the physicial
considerations of organ mass and radionuclide distribution within the
organ. In the present state of the art, the complexities of the
radionuclide distribution within organs are nearly always circumvented
by assuming a uniform distribution. Information concerning other inputs
is based mainly on empirical evidence, gathered largely 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 postulated 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
D-l
-------
industrial worker and it is not clear to what extent parameters so
defined are applicable to an environmentally exposed population.
For particular radionuclides, the sensitivity of certain age groups
may be the limiting factor. For example, in the case of iodine-131
exposures, the Federal Radiation Council has defined children as the
most sensitive population group; therefore, the biplogical parameters
used in the media-to-dose conversion factors for this radionuclide 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, little is known concerning differences
between adults and children. Such differences are seldom considered in
the literature. Thus, the conversion factors listed in the subsequent
sections, while adequate, must be considered only as first order
approximations and not as definitive estimates of doses from
environmentally distributed radionuclides.
Media conoentration-to-dose conversion factors used in this report
are listed in Table D.I and discussed below for the radionuclides
considered in this reportkrypton-85, tritium, iodine-129, and certain
of the actinides.
D-2
-------
Table D.I
Summary of air ooncentration-to-dose conversion factors
Radionuclide
SH-
I29j_
239^.
Critical Organ
body
Gonads (female)
Gonads (male)
Lung
Skin
Whole body
Infant thyroid
Adult thyroid
Lung
Conversion Factora
(rem/yr)/(pCi/m3 air)
1.5x10
~
1.5xlO
~8
2.0xlO
~8
3.0xlO
~8
SO.OxlO
"8
~
15
4.6
aThese factors are for continuous exposure to concentrations
expressed in pCi/m3 of air.
A. Krypton-85
About 99 percent of the decay energy of krypton-85, a noble gas, is
dissipated by beta particles which have no potential for deep
penetration in tissue.
Kirk has recently reviewed the literature on krypton-85 dose and
established relationships between the krypton-85 concentration in air
and the resultant doses to various organs. A review of these results
shows which radiations are important. For the whole body, dose and risk
estimates can be based on a consideration of external photon exposures,
i.e., gamma rays and bremsstrahlung. For genetic risk calculations, the
D-3
-------
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 gatrroa-ray dose. Skin dose is based on the dose delivered by
external beta radiation after making an allowance for the shielding
provided by clothing and the nonviable epithelium (a 75 percent
reduction of dose).
B. Tritium
Dose estimates from tritium exposure are usually based on the
assumption that the isotope is contained in body water. Chronic
exposure to environmental tritium, however, has been shown to result in
the incorporation of tritium into organic molecules from which tritium
is lost at a slower rate than from body water. 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/liter body
water would lead to a body burden of 63 pCi, as opposed to 43 pCi if, as
in the ICRP model, distribution in body water alone is considered.
Evans found that tritium was not, in fact, quite uniformly distributed
through deer tissues. Assuming his observed factors to be applicable to
man, he calculated a body burden of 60 pCi for standard man with
sustained concentration of 1 pCi/liter in body water, i.e., a body
burden a factor of 1.4 higher than that based on the ICRP ntodel. A
factor of 1.5 (63/43), although only marginally different from Evans,
was selected as an appropriate value for this analysis.
D-4
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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.
However, from both experimental and theoretical considerations, it has
been concluded that it is the absorbed dose to mammalian cell nuclei
from incorporated internuclear tritium which determines quantitatively
the degree of effect. The assumption made in these calculations is that
the appropriate value for the quality factor for tritium dose equivalent
estimation is 1.0 as recently adopted by both the National Council on
Radiation Protection and Measurements (NCRP) and the ICRP.
A sustained concentration of 1 pCi tritium per liter of body water
would thus be equivalent to a specific activity (assuming uniform
labelling of all body hydrogen) of 9x10"3 pCi tritium/g hydrogen, and
would deliver an annual dose to body tissues of approximately 10"^
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 1.7xlO~3
mrem for an air concentration of 1 pCi tritium/m3.
D-5
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C. Iodine-129
Atmospheric releases of iodine-129 may result in its accumulation
in the thyroid glands of persons living in the area surrounding the
point of release. For radioiodines, the most significant pathway for
exposure of man is generally the grass-cow-milk chain, particularly when
milk is not diluted with uncontaminated supplies. Direct deposition on
foliage is likely to be the most important route of contamination of
edible herbage.
Because of the long half-life of iodine-129, plant uptake of this
radionuclide from the soil should also be considered. In general, it is
assumed that such plant uptake will be proportional to its specific
activity (curies of iodine-129 per gram of stable iodine) in the soil.
The specific activity in the soil at a specific location will be a
function of distance from the point of release and the buildup from
continuing releases. 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.
For a given concentration of iodine-129 in milk, it has been
determined that a 6-month-old child would sustain the highest dose when
considering the exposure of individuals to this radionuclide via the
s
grass-cow-milk chain. According to Durbin, the average daily intake of
whole milk by U.S. children during the first year of life is about 760
ml. Appropriate representative data to define the relationship between
D-6
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the amount of iodine ingested by a 6-month-old child and its resultant
concentration in the thyroid gland are: thyroid weight, 1.8 g; fraction
of ingested iodine in thyroid, 0.35, and biological 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; thyroid weight, 20 g; fraction ingested reaching critical organ,
0.3; and biological half-life in thyroid, 138 d. Use of these values
yields an annual dose to the adult thyroid of 1.9 mrem for an iodine-129
concentration of 1 pCi/liter of milk. The corresponding annual dose to
the thyroid of children whose daily consumption of milk during the first
year of life contains 1 pCi/liter is 6.3 mrem.
To determine milk concentrations from given ground and air
concentrations, use was made of the following factors derived from
references by Bryant (1970) and the Federal Radiation Council Report No.
1:
(a) 2.4x103 pCi/liter of milk per pCi/m3 of air; and
(b) 0.28 pCi/liter of milk per pCi/m2 of ground surface.
For these intermediate conversion factors, it was assumed that the
grazing area for a dairy cow is 80 m2 per day and that airborne
radioiodine has a deposition velocity of 0.5 cm/s.
The annual thyroid *dose rate corresponding to unit specific
activity (1 pCi iodine-129/g total iodine) in the thyroid is 0.44 rem/yr
for an adult and 0.24 rem/yr for a 6-month-old child. Adoption of a
value of 0.44 rem/yr as the dose delivered to a thyroid containing 1 pCi
iodine-129/g total iodine would thus appear to be a conservative
D-7
-------
estimate for all cases. This factor was applied in conversions of
medium concentrations to thyroid dose rate for the long-term assessment
of iodine-129 releases.
D. Plutonium-239 and Other Actinides
The potential health risks from inhalation of a radionuclide depend
on whether it is in a soluble or an insoluble form. In this report, it
was assumed that all actinides were in an insoluble form. Present
experience indicates that this is the case for plutonium effluents to
the atmosphere from fuel reprocessing plants.
In this report, dose estimates from inhaled actinides are based on
the new ICRP lung model. However, the biological half-life of insoluble
actinides in the lung (pulmonary region) was assumed to be 1,000 days.
Using this mode, sustained exposure to an air concentration of 1
pCi/m3 of insoluble plutonium-239 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-conoentxaticto-to-dose conversion factors for other actinide
radionuclides relative to plutonium-239 were computed by taking into
account the effective energy absorbed per disintegration and the
physical half-life of each radionuclide, as given in ICRP Publication
Nbs. 2 and 6. These relative conversion factors are listed in table
D.2
D-8
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Table D.2
Air oanoentration-to-liong dose conversion factors
for actinide radionuclides relative to that for plutonium-239
Radionuclide
238^
239^
Pelative conversion factor
1
0.001
i
0.25
0.17
0.33
Flutonium-239 conversion factor = (12 rem/yr)/(l pCi/m3).
It is realized that there are a number of complexities involved in
the computation of doses resulting from inhalation of radionuclides.
For example, the health risk resulting from a given amount of a
radionuclide in the pulmonary region of the lung is dependent upon its
distribution as well as the total amount present. However, due to
limitations of current models, the amount of radionuclide in the organ
was assumed to be uniformly distributed. In the case of alpha emitters,
such averaging is obviously inappropriate if there are only a few
particles present. ICRP Publication No. 6 recognized 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 "
-------
For the purposes of this report, inhalation was the only route of
intake considered for plutonium-239 and other actinides. Because of the
assumed insoluble form for the actinides, doses resulting from other
pathways were considered to be of relatively minor importance.
III. DQSE-TQ-RISK CONVERSION FACTORS
The numerical values of the dose-to-risk conversion factors used in
this study were derived primarily from the recent (November, 1972)
National Academy of Sciences Carmittee on Biological Effects of Ionizing
Radiation (BEER) report. It is emphasized that although these numbers
may be used as the best available for the purpose of making risk- and
cost-benefit analyses, they cannot be used to accurately predict the
number of casualties. For a given dose equivalent, the BEIR report
estimates a range for the health impact per million exposed persons.
For example, the BEIR results frcm a study of the major sources of
cancer mortality data yield an absolute risk1 estimate of 54-132 deaths
annually per 106 person-rems for a 27-year followup period. Depending
on the details of the risk model used, the BEIR Committee' s relative
risk2 estimate is 160-450 deaths per 106 person-rems. It is seen that
these estimates differ by a factor of 3 to 4, even when applied to
sample populations studied on the basis of the same dose rates.
1Absolute 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.
2Relative risk estimates are based on the percentage increase of the
ambient cancer mortality per rem.
D-10
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The application of the BEIR risk estimates to exposures at lower
dose rates and to population groups more heterogeneous 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
differences in health impacts projected by this analysis rather than on
the absolute numbers. Where the absolute numbers must be used for risk-
cost-benefit balancing, it should be remembered that these health effect
estimates are likely to be revised as new information becomes available.
A basic assumption used in the derivation of the dose-to-risk
conversion factors was the existence of a no-threshold, linear
relationship between absorbed dose and biological effects.
Following are discussions concerning the dose-to-risk conversion
factors for the radionuclides of interest in this report.
A. Krypton-85
1. Total Body Dose-to-Somatic Risk
The BEIR report calculates the cancer (including leukemia)
mortality risk from whole body radiation exposure by two different
models. The absolute risk mode predicts about 100 cancer deaths per 106
person-rems; the relative risk model predicts between 160 and 450, or an
average of about 300 deaths per 106. The average value 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. Since
some types of cancer are not always lethal, cancer mortality is not a
D-ll
-------
measure of the total cancer risk, which the Connittee states as being
about twice that of the cancer mortality risk.
For krypton-85 whole-body doses, the following conversion factors
were used in this report:
a. 200 cancer deaths per population whole body dose of 106
person-rems, and
b. 400 total cancer cases per population whole body dose of 106
per-rems.
2. Gonadal Dose-to-Genetic Risk
The range of the risk estimates for genetic effects set forth in
the BEER 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 background
radiation, and (2) the fraction of deleterious mutations eliminated per
generation, the overall uncertainty is about a factor of 25. In a
population of one million assumed to receive 30 years of exposure prior
to reproduction, the total number of live births showing very serious
genetic effects such as congenital anomalies, constitutional and
degenerative diseases, etc., is estimated at somewhere between 1,800 and
44,000 if the population is exposed continuously at a dose rate of 1 ran
per year. This applies to an equilibrium condition, which occurs after
continuous exposure of 5 or more generations. As such, there are
expected to occur 60 to 1,500 cases per year at a dose rate of one rem
D-12
-------
per year, if a 30-year regeneration period is assumed. The risk to the
first generation following initial exposure is about a factor of 5 less.
For the purposes of this study, the geometric average of this
annual range was used as the value of the dose-to-risk conversion
factor, that is, 300 effects per year for a gonadal dose of 106 person-
rem per year. This conversion factor was considered to be applicable
only for persons up to 30 years of age.
In the HEIR report the notion of "genetic death" as a measure of
radiation risk is rejected. Risk analysis was in terms of early and
delayed effects observed postpartum and not in early abortion, still-
births, or reduced fecundity. Many of the postpartum effects, however,
lead directly to infant mortality. 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.
less serious genetic effects have also been considered by the BEIR
Cottmittee. These have been quantified under the category "unspecified
ill health." The Conmittee states that a continuous exposure of one rem
per year would lead to an increase in the number of ill health cases by
3 to 30 percent. These less serious genetic effects were not taken into
consideration in this study.
3. Lung Dose-to-Cancer 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 estimate made below,
it is assumed that the fractional abundance for lung tumors in the
D-13
-------
younger group is the same as that in the older one. Qi an absolute risk
basis lung cancer mortality is about 26 deaths per annum per 10s 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 latent period for lung cancer.
Furthermore, lung cancer risks calculated on the basis of relative risk
would be larger. For the risk estimates made here, it was assumed that
the value of the applicable conversion factor was twice that of the
absolute risk value, as was the case with whole-body exposures. As
such, the lung dose conversion factor was taken to be 50 lung cancer
deaths per population lung dose of 106 person-rems.
4. Skin Dose-to-Cancer Risk
The dose to the skin delivered by krypton-85 is a factor of 30
higher than that to other organs. However, there is currently no
epidemiolcgical evidence of actual risk from the skin dose levels
considered here. This does not rule out the linear dose-effect
assumption for skin cancer; but 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." However, rather than
defining a zero risk per rad for any radiation insult from krypton-85,
an upper limit of risk is proposed.
For the purposes of this analysis the following conversion factor
was considered to be indicative of an upper limit of risk from skin
exposures: 3 skin cancers per year for an annual skin dose of 106
D-14
-------
person-rems. This assumes that an individual will accrue 30 years of
exposure and that the incidence of skin cancer will be 10 percent of all
radiation-produced cancers except leukemia, breast, lung, G.I. tract,
and bone cancers. It should be noted that skin cancers are rarely fatal
and usually not very debilitating.
B. Tritium
1. Total Body Dose-to-Somatic Risk
The somatic effects from tritium doses are not expected to be
unique. They are the same as described above for krypton-85. Hence the
same conversion factors are applicable.
2. Gonadal Dose-to-Genetic Risk
Some experiments with bacteria have shown that the location of a
tritium atom on a particular DNA. base can enhance the mutation rate.
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
gonadal dose-to-genetic risk conversion factor for krypton-85 is assumed
to be also appropriate for estimating the genetic risk from tritium
exposures.
C. Iodine-129
Radioiodine intakes by humans are concentrated primarily in the
thyroid. Because of this and other relevant factors the thyroid is
considered to be the critical organ for doses resulting from such
intakes. Doses to other organs are orders of magnitude less. Two
health effects follow high level exposures of thyroid tissue to ionizing
D-15
-------
radiation: benign neoplasms and thyroid cancer. Though the former are
a more cannon radiation effect, only the more serious risk from cancer
is considered in this study.
Children are more susceptible than adults to thyroid damage from
radiation exposures. Thyroid cancer, however, is not usually a fatal
disease for young persons, but mortality from it approaches 25 percent
for persons well past middle age.
The BEIR report provides risk estimates only for morbidity (not
mortality) and only for persons under 9 years of age. 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.
Conversion factors used in this study are based on risk estimates
described in ICRP Publication No. 8 as well as on the mean values
derived from the BEIR Committee's various estimates of incidence per rem
of dose. Infants and fetuses, comprising approximately 2.5 percent of
the population, are the most sensitive group. For this age group, about
150 thyroid cancers may accrue annually per 106 person-rem annual
exposure to the thyroid. For the approximately 40 percent of the
population 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.
Following are the values used in this report for the factor
converting thyroid dose to number of cases of thyroid cancers
(morbidity/ not mortality):
D-16
-------
a. Less than age 1:
150 cases per population thyroid dose of 106 person-rems.
b. Ages 1-19:
35 cases per population thyroid dose of 106 person-rems.
c. Ages greater than 20:
5 cases per population thyroid dose of 106 person-rems.
It is unlikely that the annual number of cases of mortality from
these cancers would be much larger than 25 percent of the total number
of cases.
D. Plutonium and other Actinides
For the purposes of this study, it was assumed that the conversion
factor for lung dose-to-cancer risk for plutonium and other actinides
has the same numerical value as that for krypton-85; namely, 50 lung
cancer deaths per population lung dose of 106 person-rems. It should be
recognized that the use of doses calculated on the basis of uniform
distribution of actinides in the lung introduces uncertainties in this
dose-to-risk conversion factor, since the risk data is based upon such
doses being delivered to the basal cells of the bronchial epithelium.
Revision of this factor may be necessary when more adequate models
become available for dynamic lung clearance and any differences in
effects due to non-uniform dose distribution.
D-17
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Bair, W. J., Plutonium Inhalation Studies, Battelle Northwest Laboratory,
BNWL 1221, 1970.
Bond, V.P., and Feinendegen, L.E., Intranuclear 3H Thymidine,
Dosimetric, Radiobiological and Radiation Protection Aspects, Health
Physics, Vol. 12 pp. 1007-1020, 1966.
Bryant, P.M., Derivation of Working Limits for Continuous Release Rate
of Iodine-131 to Atmosphere in Milk Producing Area, Health Physics, Vol.
10, pp. 249-257, 1964.
Bryant, P.M., Data for Assessments Concerning Controlled and Accidental
Releases of 131I and 137Cs to Atmosphere, Health Physics, Vol. 17, pp.
51-57, 1969.
Bryant, P.M., Derviation of Working Limits for Continuous Release Rates
of 129I to Atmosphere, Health Physics, Vol. 19, pp. 611-616, 1970.
Dolphin, G.W., The Biological Problems in the Radiological Protection of
Workers Exposed to 239Pu, Health Physics, Vol. 20, pp. 549-557, 1971.
Durbin, P.W., Lynch, J., and Murray S., Average Milk and Mineral Intakes
(Calcium, Phosphates, Sodium and Potassium) of Infants in the United
States from 1954-1968: duplications for Estimating Annual Intake of
Radionuclides, Health Physics, Vol. 19, pp. 187-222, 1970.
Evans, A.G., New Dose Estimates from Chronic Tritium Exposures, Health
Physics, Vol. 16, pp. 57-63, 1969.
Federal Radiation Council, Background Material for the Development of
Radiation Protection Standards, Staff Report No. 1, May 13, 1960.
Federal Radiation Council, Background Material for the Development of
Radiation Protection Standards, Staff Report No. 2, September, 1961.
Federal Radiation Council, Background Material for the Development of
Radiation Protection Standards, Staff Report No. 5, July, 1964.
Funk, F., Cytosine to Thymine Transitions from Decay of Cytosine-5 H in
Bacteripphage S 13, Science, Vol. 166, pp. 1629-1631, 1969.
Garner, R. J., and Russell, R.S., Isotopes of Iodine, Radioactivity and
Human Diet, ed. R.S. Russell, Pergamon Press, 1966.
D-18
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International Connission on Radiological Protection Publication No. 2,
Pergamon Press, 1959.
International Ccrrrnission on Radiological Protection, Publication No. 6
Pergamon Press, 1964.
International Commission on Radiological Protection, Publication No. 8
Pergamon Press, 1966.
Kirk, W.P., Krypton-85 - A Review of the Literature and an Analysis of
Radiation Hazards, Environmental Protection Agency, Office of Research
and Monitoring, Eastern Environmental Radiation Laboratory, January,
1972.
Koranda, J.J., and Martin, R., Persistence of Radionuclides at Sites of
Nuclear Detonations, Biological Implications of the Nuclear Age, U.S.
Atomic Energy Commission Symposium Series No. 5, 1965.
McClendon, J.F., Iodine and the Incidence of Goiter, University of
Minnesota Press, Minneapolis, 1939.
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
(BEIR), U.S. Government Printing Office, 1972.
National Council on Radiation Protection and Measurements, Basic
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D-19
^ J"' ftU.S. GOVERNMENT PRINTING OFFICE: 1974 546-319/403' 1-3
-------
THE ABSTRACT CARDS accompanying this report
are designed to facilitate information retrieval.
They provide suggested key words, bibliographic
information, and an abstract. The key word con-
cept of reference material filing is readily
adaptable to a variety of filing systems ranging
from manual-visual to electronic data processing.
The cards are furnished in triplicate to allow
for flexibility in their use.
-------
ENVIRONMENTAL RADIATION DOSE COMMITMENT: AN APPLICATION
TO THE NUCLEAR POWER INDUSTRY, EPA-520/4-73-002. Cri-
teria and Standards Division, Office of Radiation Pro-
grams, Environmental Protection Agency (February 1974).
ABSTRACT: The concept of environmental dose commitment
is developed and illustrated by application to pro-
jected releases of selected radionuclides from the
nuclear power industry over the next fifty years. The
concept encompasses the total projected radiation dose
to populations committed by the irreversible release
of long-lived radionuclides to the environment, and
forms a basis for estimating the total potential con-
sequences on public health of such environmental re-
leases. Because of the difficulty of making projec-
ENVIRONMENTAL RADIATION DOSE COMMITMENT: AN APPLICATION
TO THE NUCLEAR POWER INDUSTRY, EPA-520/4-73-002. Cri-
teria and Standards Division, Office of Radiation Pro-
grams, Environmental Protection Agency (February 1974).
ABSTRACT: The concept of environmental dose commitment
is developed and illustrated by application to pro-
jected releases of selected radionuclides from the
nuclear power industry over the next fifty years. The
concept encompasses the total projected radiation dose
to populations committed by the irreversible release
of long-lived radionuclides to the environment, and
forms a basis for estimating the total potential con-
sequences on public health of such environmental re-
leases. Because of the difficulty of making projec-
ENVIRONMENTAL RADIATION DOSE COMMITMENT: AN APPLICATION
TO THE NUCLEAR POWER INDUSTRY, EPA-520/4-73-002. Cri-
teria and Standards Division, Office of Radiation Pro-
grams, Environmental Protection Agency (February 1974).
ABSTRACT: The concept of environmental dose commitment
is developed and illustrated by application to pro-
jected releases of selected radionuclides from the
nuclear power industry over the next fifty years. The
concept encompasses the total projected radiation dose
to populations committed by the irreversible release
of long-lived radionuclides to the environment, and
forms a basis for estimating the total potential con-
sequences on public health of such environmental re-
leases. Because of the difficulty of making projec-
-------
tions of radionuclide transport on the basis of pres-
ent knowledge, these potential consequences have been
calculated only for the first one hundred-year period
following release. The particular radionuclides con-
sidered are tritium, krypton-85, iodine-129, and the
actinides.
KEY WORDS: Actinides; environmental radiation; iodine-
129; krypton-85; nuclear power; population dose com-
mitment; tritium.
tions of radionuclide transport on the basis of pres-
ent knowledge, these potential consequences have been
calculated only for the first one hundred-year period
following release. The particular radionuclides con-
sidered are tritium, krypton-85, iodine-129, and the
actinides.
KEY WORDS: Actinides; environmental radiation; iodine-
129; krypton-85; nuclear power; population dose com-
mitment; tritium.
tions of radionuclide transport on the basis of pres-
ent knowledge, these potential consequences have been
calculated only for the first one hundred-year period
following release. The particular radionuclides con-
sidered are tritium, krypton-85, iodine129, and the
actinides.
KEY WORDS: Actinides; environmental radiation; iodine-
129; krypton-85; nuclear power; population dose com-
mitment ; tritium.
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