United States
Environmental Protection
Agency
Office of
Radiation Programs
Washington, DC 20460
EPA 520/3-80-009
October 1980
Radiation
&EPA
Population Risks
From
Uranium Ore Bodies
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EPA REVIEW NOTICE
The Office of Radiation Programs, U.S. Environmental
Protection Agency, has reviewed this report and approved
it for publication. Mention of trade names or commercial
products does not constitute an endorsement.
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High-level Waste Environmental EPA 520/3-80-009
Standards Program
Technical Support Document
Population Risks from Uranium Ore Bodies
W. Alexander Williams
October 1980
Office of Radiation Programs
U.S. Environmental Protection Agency
Washington, D.C. 20460
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PREFACE
The Office of Radiation Programs, U.S. Environmental Protection
Agency, carries out a national program to evaluate individual and
population exposure to ionizing and nonionizing radiation and to
promote development of controls for the protection of public health
and the environment.
This report is technical support for EPA's high-level
radioactive waste standards program; it estimates the radiological
releases and impact of unmined uranium ore.
The Office of Radiation Programs invites readers to report
omissions or errors, submit comments, or request further information.
OFFICE OF RADIATION PROGRAMS
U.S. ENVIRONMENTAL PROTECTION AGENCY
m
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ACKNOWLEDGMENTS
I am Indebted to Dr. Cheng-Yeng Hung who programmed the solution
to the diffusion equation and provided the enrichment factors used
in this work. I thank the distinguished scientists outside EPA who
kindly reviewed this report prior to publication. Within EPA
Dr. Abraham Goldin, Dr. James Neiheisel, Mr. Nels Nelson,
Mr. Dan Hendricks, Dr. Tin Mo, and Mr. Jay Sikhanek made many
helpful suggestions, which I gratefully acknowledge. Mrs. Linda
Martin, Mr. Tom Kelly, and Miss Bertha Clow provided editorial and
organization assistance, for which I thank them.
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ABSTRACT
This report estimates the minimum radiological releases and
potential impact of deep-lying uranium ore, so that they may be
compared with projected releases and impacts from radioactive
waste. Uranium concentrations and groundwater flow rates are used
as input data for three models developed by EPA for analyzing the
impact of high-level radioactive waste. One set of data is obtained
from some ore bodies which are being mined by the in situ solution
process. Another, the minimum impact case, is obtained by using
conservative data on uranium concentrations in uraniferous
groundwaters in conjunction with a model aquifer developed by EPA.
The estimated releases from actual ore bodies prior to mining
range from .19 to 1.1 curies per year for 226Ra< por a generic
model ore body with parameters chosen to minimize the impact, a
release of 1.2xlO~4 curies 226Ra per year is estimated. To take
into account the different size of these ore deposits, the impacts
can be adjusted or normalized to the amount of ore from which a
100,000-metric-ton heavy metal nuclear waste repository would be
derived. After normalization, the estimated yearly releases range
from 7.4 millicuries for the minimum case to 30 or 300 curies for
the actual ore bodies. This corresponds to .023 fatal cancers per
year for the minimum case and 100 to 1000 fatal cancers per year for
the actual ore bodies using EPA environmental pathway and dosimetry
models.
The approach used in this work can serve as a starting point for
making more detailed assessments using other assumptions.
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CONTENTS
Page
Preface iii
Abstract v
Introduction 1
Method 3
Environmental Impact Analysis—Basic Assumptions 8
Generic Model of Natural Ore Body 10
Site-Specific Case Studies 14
Discussion 19
Conclusion 22
References 24
Tables
I. Uranium, Daughters, and their Retardation and Dose
Conversion Factors 5
II. Data Used for Individual Case Studies 12
III. Estimated and Normalized Health Effects for Site
1 Specific and Generic Uranium Ore Bodies 15
vii
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Introduction
Many authors have compared the health hazard from unmined
uranium ore with that from nuclear waste. Several (Cohen, 1977;
Hamstra, 1975; and the review by Voss, 1979) believe that the hazard
of high-level radioactive waste after decay of several hundred years
is less than that of unmined uranium ore. Their comparisons used
hazard indices which do not indicate how these materials behave in
the natural environment.
This assessment estimates the releases and impact of actual,
natural uranium ore bodies, rather than just a measurement of
potential impact. For this purpose, I have used an assessment
methodology incorporating models that EPA is using to assess the
impacts of high-level waste repositories. In addition to examining
a few actual ore bodies, this report presents an approach for
estimating the minimum radiological impact from unmined uranium
ore. The report deals only with the population risk from unmined
ore bodies and not with the risks and benefits from the nuclear
generation of electricity or from other uses of nuclear energy.
Most of the uranium ore bodies in the contiguous portion of the
United States are secondary deposits of waterborne uranium in
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permeable geologic formations. The source of the uranium was
igneous, uranium-bearing rocks, which were oxidized or weathered and
later leached by water. The dissolved uranium moved with the
water. In some cases the waterborne uranium reached the ocean; in
others the solution infiltrated the ground and either the uranium
was deposited in permeable rock that was strongly reducing or the
solution was mixed with agents (such as phosphates or vanadates)
forming insoluble uranium salts. The factors that control the
deposition of uranium are diverse but interrelated: the
oxidation-reduction potential (Eh), acidity (pH), presence of
complexing and/or precipitation agents, and the presence of
adsorbing solids, such as marine muds, iron oxyhydroxides, clays,
and organics. Despite this diversity of mechanisms of uranium
deposition, almost all U.S. uranium reserves currently commercial at
production costs not exceeding $50 per pound are found in coarse
clastic rocks (DOE, 1979), where uranium was deposited from ground
water. Qidwai and Jensen (1979) and Deffeyes and MacGregor (1980)
discuss the formation of these "roll front" sandstone deposits in
further detail.
After deposition of uranium, the daughter products will
accumulate according to the laws of radioactive decay. If the ore
deposit is in a permeable geological medium, it is possible for both
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the uranium and its daughters to dissolve into water moving through
the deposit (See, for example, Fix, 1955; Phoenix, 1959; Germanov
and Panteleyev, 1968; Kaufmann et al., 1975; Langmuir, 1978;
Capuano, 1978; Lueck, 1978; or Runnel Is et al., 1980). This
dissolution can also be selective; activity ratios of 234u/238u
in groundwater as high as 12 have been reported (Fleisher and Raabe,
1978).
The remainder of this report presents a methodology for
estimating the radionuclide releases from an ore body, the transport
of the radionuclides, and the resulting effect on people. The
methodology is applied to a model ore body designed to estimate a
lower bound of its effects and also to actual ore bodies to get a
more realistic, but probably high, effect estimate.
Method
The method used in this paper consists of applying three
models. One considers the transport of radionuclides from an ore
body to a stream via groundwater. Another considers the movement of
radionuclides in the biosphere once released to a stream. The third
estimates the effect of released radionuclides on people. Uranium
concentrations and groundwater flow rates can be used as input data
to these three models.
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The geosphere transport, biosphere transport, and dosimetric models
(Smith et al., 1980a and Smith et al., 1980b) were developed
initally to analyze the consequences of high-level nuclear waste
burial. The biosphere transport and dosimetric models consider
various means of contamination reaching people. These include
direct exposure, drinking water, eating fish, eating irrigated food
(crops, beef, milk), and breathing air. Table I summarizes the
results of Smith et al. (.1980b), who estimated the number of fatal
cancers that would result in their model population for each curie
of various radionuclides entering a stream. They gave 3.1
cancers/curie of 226Ra and 1.3 cancers/curie of 234U. in this
analysis I consider only the impact of 226Ra. Since 226Ra is
reconcentrated in groundwater (as discussed later) its effect will
be larger than that of any other daughter of 238U. This simpli-
fication will not affect a minimum impact estimate, since the
contribution of other uranium daughters can only increase the
radiological impact. Radon-222 (the most significant air pollutant
in uranium ore) has a half-life of 3.8 days. Radon in groundwater
would probably decay before reaching the surface. Since all
nuclides except 226Ra are ignored, my estimate of health effect
will be low.
One set of data used in this modeling is taken from several ore
bodies being exploited by the in situ (solution mining) process.
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Table I
Uranium, Daughters, and their Retardation
and Dose Conversion Factors
Fatal Cancers/Ci
Isotope
238U
234U
?3f>
"uTh
226Ra
222Rn
Half-life
4.5 x 109y
2.5 x 105y
7.8 x 104y
1.6 x 103y
3.8 days
Retardation
Factor'c
14,300
14,300
50,000
500
1
Releasebto
Stream
.
1.3
-
3.1
-
aSource: Arthur D. Little (1979); originally from Denham et al.
(1973).
bSource: Smith et aU (1980a, 1980b).
cRetardation factor:
Time in years a given radionuclide takes to travel 10 feet
Time in years groundwater takes to travel 10 feet
The amount of uranium leached from an ore body per year before mining
began is the product of the annual volume of water moving through it
-times the measured premining concentration of uranium in the
groundwater. Another set of inputs is obtained by using lower bound
data for uranium concentrations in uraniferous groundwaters (Fix,
1955; Germanov and Panteleyev, 1968; Langmuir, 1978; Capuano, 1978)
in conjunction with EPA's model aquifer, which is one mile long
(Smith et al., 1980a).
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The total annual amount of water moving through an ore body is
given by the velocity of the water times the porosity of the ore body
times the cross-sectional area. The quantity of uranium leached by
the groundwater will be the product of the amount of water and the
concentration of uranium in the water. All of this data is routinely
measured for economic deposits.
The dissolved uranium and daughters will move down the hydrologic
gradient slower than the groundwater because they react chemically
and physically with the rock. Retardation factors in a desert soil
are given in Table I for 238u and some of its daughters. If one
assumes a groundwater velocity of 10 meters per year, 230jh win
travel 10 meters in 50,000 years; 22*>Ra win move IQ meters in 500
years; and 222Rn, because of its short half-life, will decay before
it moves 10 meters. Since it takes a significant fraction of their
half-lives for the 230Th and the 226Ra to move this short dis-
tance, they will decay before they are transmitted long distances in
the groundwater.
Uranium-238 and its daughters are present in all the aquifer
since uranium's long half-life permits it to move long distances from
the source ore body. Radium-226 is found at higher activity concen-
trations in the groundwater than 238u because of differential
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adsorptions of elements by the rocks (Burkholder and Cloninger, 1977,
1978; Lester et al., 1975). Approximating the decay chain by
238y + 234y + 230jh -»• 226Ra, and using the approximation
method outlined by Rogers (1978), the ratio between the 22*>Ra
activity and the initial 238U activity released will be less than
or equal to 39 when the retardation factors are those in Table I, the
travel time of the groundwater is 290 years (the shortest time to
travel one mile of any reported for the specific cases later
examined), and the preferential enrichment ratio of 234u to 238y
is 12 (the largest reported by Fleisher and Raabe (1978)). The exact
solution for the four-member decay chain shown above is very
difficult. However, the solution of a three-member chain has been
solved by Lester et al. (1975) and has been applied to this system:
Uranium-238->- Thorium-230'•*• Radium-226
The enrichment factor of 226Ra relative to 238U is highly
dependent on the retardation factors, aquifer velocity, and travel
distance. The solution of Lester et al. (ignoring dispersion) shows
an activity for 226Ra that is 33 times higher than the initially
released 238U activity using the data shown above. The activity
enrichment factor will be used for some cases but may overestimate
the enrichment. Since this enrichment factor changes when the
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8
retardation factors, distance, or travel time change, an enrichment
factor of 10 will be used for the minimum case, to make certain this
case is conservatively low.
Environmental Impact Analysis—Basic Assumptions
To analyze the impact, one must know the boundary conditions at
the ore body and the geochemical characteristics of the aquifer. It
is difficult to determine these characteristics precisely. I assume
that (1) solubility considerations limit the uranium concentration in
groundwater at one part per billion, (2) uranium leaves the ore body
at a rate of solubility times water flow, (3) all of the uranium
released from the ore body reaches the stream at the same rate it
enters groundwater, (4) 226Ra reaches the stream at activity levels
either 10 or 33 times higher than the 238|j activity, and (5) one
curie of 226Ra released to the stream causes a commitment of 3.1
fatal cancers.
This model assumes that solubility controls the concentration of
aqueous uranium in the ore at one part per billion. The concen-
tration of uranium in the groundwater of ore bodies has been shown to
decrease down dip, after water has moved through the ore body
(Germanov and Panteleyev, 1968 and Phoenix, 1959). This argues
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strongly that thermodynamics are more important in limiting the
uranium concentration rather than the kinetics discussed by
Grandstaff (1976) at higher concentrations. For any given daughter
of 238u it is reasonable to assume that after several million
years, the daughter will be in equilibrium with the parent as they
both migrate in an aquifer, except that the daughter might migrate
•
faster or slower as discussed above. Groundwater chemistry can
change radically along an aquifer and this can change the amount of
dissolved uranium. For example, a rise in the solution CO^
pressure from 3x10-4 atmospheres to 10-2 atmospheres increases
the solubility of uraninite (for Eh values above -.05 Volts) by over
1000 times (Langmuir, 1978). Despite the uncertainty of the data,
there is evidence that the groundwater in some ore bodies is
saturated or even supersaturated with some uranium mineral species
(Boberg and Runnells, 1971; Lueck, 1978; Runnel Is et al., 1980).
If one assumes that uranium is dissolved by groundwater at a
known rate per year and travels 1 mile to a surface stream, the
annual release rate to the stream will eventually be the same as the
release rate from the ore body. The release rate of 238y win
control the release rate of the daughters to the stream, because the
daughters dissolved directly from the ore body do not migrate fast
enough to reach the stream prior to decay. Although a travel
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10
distance of 1 mile has been used throughout this work, the long
half-life of 238u obviously permits it to be transmitted for much
longer distances in groundwater.
In order to compare the impact of ore bodies with that of a
high-level waste repository, the two must be put on a comparable
•
basis. The amount of fuel used by a 1000 MWe reactor in 1 year is
about 35 metric tons enriched uranium; therefore, a 100,000-metric-
ton heavy metal repository will contain waste equivalent to 2900
reactor years of operation. Because 1140 metric tons unenriched
U30g are the annual requirements for 5.3 1000 MWe reactors (EPA,
1973), the annual requirement per reactor is 215 MT unenriched
ILO . Therefore, a 100,000-metric-ton heavy metal repository
inventory was derived from 620,000 metric tons U30g (equal to 215
metric tons per reactor year times 2900 reactor years).
Generic Model of Natural Ore Body
I propose a generic model to estimate the minimum impact of an
unmined uranium ore body. The data used for this case is summarized
in Table II.
The model ore body is located in an aquifer that has a slower
velocity than those of the actual ore bodies considered later. The
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11
model aquifer is the upper, or overlying, aquifer in the model
high-level waste repository developed by EPA (Smith et al., 1980a and
Arthur D. Little, Inc., 1979). The aquifer has the following
characteristics:
horizontal permeability = 10~4 cm/sec,
gradient = .01,
porosity = 15%, and
thickness of strata = 30 meters
The cross-sectional width of the model ore body is 3.7
kilometers, perpendicular to the groundwater flow. This width has
been selected because 1) it falls within the range of actual ore
bodies listed in Table II, and 2) it is the approximate width of a
high-level waste repository (as described by Smith et al., 1980a and
Egan, 1978). One would expect a roll front deposit to form perpen-
dicular to the flow of groundwater. The interstitial velocity in
this generic ore body will approximate 2.1 meters/year. Since the
width of the ore body is 3.7 kilometers, the annual flow of water
through the hypothetical ore body will be 35,000 cubic meters. If
this entire volume of water leaves the ore body with a concentration
of one part per billion of uranium, the amount of uranium leached per
year will be 35 grams/year (12 microcuries/year of 238y). A
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Table II
Data Used for Individual Case Studies
Site
Model Case
Nine Mile Lake
Natrona Co., Wyo.
Irigaray
Johnson Co., Wyo.
Highland (Case 1)
Converse Co., Wyo.
Highland (Case 2)
Converse Co., Wyo.
Interstitial
Groundwater
Velocity
(meters/year)
2.1
5.3
4.3
5.5
5.5
Thickness
of Ore Strata
(meters)
30
20
37
40
40
Cross Sectional
Width of Ore Body
(meters)
3,700
5,600
11,000
bl,500
C7.600
Poro-
sity
.15
.28
.23
.30
.30
Uranium
Concen-
tration
(ppm)
.001
a.l
.1
.2
.2
Uranium
Released
(mCi/y)
.012
5.7
13
6.7
33
Estimated
Uranium Reserves
(metric tons U30g)
10,000
2,000
5,900 - 6,800
450 - 1,400
25,000
^Measured values range from .640 to levels not detectable.
bAssumes all groundwater flow is to the southeast and ignores the effects from dewatering for mining operations in
the area. This includes ore reserves only from the solution mining operations.
cThis includes ore and reserves from the entire Exxon Highland operation and ore and reserves from the adjacent
Morton Ranch project and assumes that all water flow is to the southeast. This may not be true because mine dewatering
has changed the site hydrology. Reserves are as reported in the environmental reports of the projects.
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uranium concentration of 1 part per billion is lower than that
measured in uranium mines and in uraniferous aquifers (Phoenix, 1959;
Langmuir, 1978; Germanov and Panteleyev 1968; Kaufmann et al., 1975;
Runnel Is et al., 1980) and is the lowest value reported for
uraniferous aquifers by Fix (1955). It compares favorably with the
thermodynamic values of Capuano (1978), and Langmuir (1978).
It might be argued that the location of the model ore body in an
aquifer is inappropriate since the presence of the aquifer would tend
to maximize the impact by providing a ready source of geological
transport. However, over 9(Tpercent of known U.S. uranium reserves
(at production costs not exceeding $50 per pound) are found in coarse
clastic sediments (DOE, 1979), terrains in which aquifers would be
expected.
Additionally, it is possible that 226Ra can be reconcentrated
into aquifers while it and its parents migrate, as discussed
previously. To make certain that the model produces a lower bound,
an activity enrichment factor of 10 will be used for this case,
rather than the 33 obtained from the decay and diffusion equations
discussed earlier. Using this factor, the projected yearly release
of 226Ra to the stream is 120 microcuries, which produces a
commitment of 3.7xlQ-4 fatal cancers per year (1.2xlO-4Ci x 3.1
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14
cancers/Ci) (Smith et al., 1980a and Smith et al., 1980b). If other
radionuclides in the decay chain were considered, the impact would be
larger, but this fact does not affect this minimum estimate. The
release and impact of the model ore body are summarized in Table III.
For the sake of comparison with the actual ore bodies discussed
subsequently, the model ore body is assumed to have reserves of
10,000 metric tons U308. This corresponds to an ore body 50 meters
thick, 30 meters high, and 3.7 kilometers wide, with an ore grade of
.09% (assuming the density of the host is 2g/cc). This ore grade
compares favorably to the average of .07% for ore reserves (at costs
not exceeding $50 per pound) reported by DOE (1979). If the ore
reserves were smaller, the impact per ton of U^Og would be larger
after normalization. This normalization process puts the effects of
different size ore bodies on a comparable basis. This adjustment is
done by dividing the effects of an ore body by its reserves and
multiplying the quotient by 620,000 metric tons, the amount of
uranium from which a 100,000-metric-ton heavy metal repository was
derived.
Site+Specific Case Studies
The Nine Mile Lake, Irigary, and Highland sites have been
selected for site-specific analysis, since field data are available
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Table III
Estimated and Normalized Health Effects for Site Specific
and Generic Uranium Ore Bodies
Site
Generic Model
Ore Body
(Minimum case)
Nine Mile Lake
Natrona Co., Wyo.
Irigaray
Johnson Co., Wyo.
Highland (Case 1)
Converse Co., Wyo.
Highland (Case 2)
Converse Co., Wyo.
Uranium
Released
(mCi/y)
.012
5.7
13
6.7
33
Radium
Released
(mCi/y)
.12
190
430
220
1100
Estimated Fatal
Cancers from
Radium Released
(per year)
3.7x10-4
.59
1.3
.68
3.4
Normalized
Effectsa
2.3xlO-2
180
120-140
300-940
84
aEstimated yearly fatal health effects for ore from which a 100,000 MTHM
radioactive waste repository was derived.
from them. The adsorption of the radionuclide by the geological
medium plays an important role in retarding the migration of
radionuclides. The results of laboratory tests on the retardation
factors indicate that this parameter may vary greatly because of the
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16
chemical characteristics of the solution and the geological and
geochemical characteristics of the geological medium. The
retardation factors used are shown in Table I. These are for a
typical western desert soil with low-to-moderate cation exchange
capacity. This sandy-to-sandy-loam soil contained about one
milligram of free CaC03 per gram (Oenham et al., 1973).
The site characteristics for the specific cases studied are
summarized in Table II. I used premining hydrologic and chemical
data obtained from some ore bodies now being mined by the in situ
solution method. These data are probably superior to that from
other kinds of uranium mines. In Table III the cancer commitment is
summarized in terms of the ores from which a 100,000 metric-ton-
heavy metal repository was derived. The cancers were obtained by
multiplying the 226Ra releases in curies/year by 3.1 cancers/curie
(Smith et al., 1980a, and Smith et al., 1980b). The contribution
from all other isotopes is relatively insignificant because of the
large enrichment of 226Ra relative to 238y in the groundwater.
Since only premining data has been used in this work, it does not
assess the environmental impact of current mining operations. These
actual ore bodies are in arid regions where the population density
is lower than the population density in the EPA model.
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Nine Mile Lake:
Using premining data from the Rocky Mountain Energy Company's
Nine Mile Lake in situ solution-mining operation, the ore body
released about 190 millicuries of 226Ra per year before mining
began. This release causes .59 fatal cancers per year using EPA's
model pathways and populations. The reserves shown in Table II will
permit operation of the proposed 227 metric tons per year plant for
9 years (Rocky Mountain Energy Co., 1979).
Irigaray Project:
Using data from Wyoming Mineral Company's Irigaray in situ
solution-mining project, an annual release of 430 millicuries of
226Ra per year occurred in the ore body prior to mining. An
average of 1.3 fatal cancers per year might be expected from this
release using EPA's model pathways and populations (Wyoming Minerals
Corp., 1978).
Highland Project:
The Highland Project of Exxon Minerals is divided into two
cases. In one of these only the release from the ore bodies
currently being mined by the in situ method is considered (220
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18
millicuries of 226Ra per year); in the other the release of all
the ore bodies in both the Highland and adjacent Morton Ranch
projects are assessed (1100 millicuries of 226Ra per year). These
releases would cause a yearly commitment of .68 and 3.4 fatal
cancers. The site specific chemical and hydrologic data developed
for the original Highland Mill have been supplemented with more
recent data from the solution-mining proposal. Mine dewatering
operations have changed the local hydrology of the area. Because of
this uncertainty, the first available report on hydrology has been
used, although later references show very different measurements
(see, for example, Final Environmental Statement for Highlands
Uranium Solution Mining Project, pages 2-14 and 2-16, Exxon Minerals
Co., 1978).
The stated uranium reserves for the second case are probably too
low because the price of uranium has increased substantially since
the Highland mill was licensed. Of the ore bodies at the Highland
area, 1 to 3 million pounds U^Og are reported as the Highland
solution-mining reserves, 32 million pounds U30g are from the
Highland surface operations, and 21 million pounds are attributed to
the adjacent Morton Ranch mines. These reserves total about 55
million pounds or 25 thousand metric tons.
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Discussion
Measured concentrations in uraniferous areas are generally
higher than the assumed concentration (one part per billion) of
uranium in the model. This is the same concentration used in some
risk analysis cases for a model high-level radioactive waste
repository (Smith et al., 1980a); increases or decreases in this
solubility-limited concentration would affect uranium in both models
in a parallel manner. Although the concentration of uranium in a
saturated solution can be lower under some conditions (Langmuir,
1978), field measurements and some thermodynamic studies show this
one-part-per-billion limit to be a reasonable uranium concentration
in the reducing down-dip groundwater (Kaufmann et al., 1975; Fix,
1955; Phoenix, 1959; Germanov and Panteleyev, 1968; Capuano, 1978).
Additionally, factors which might vary, such as changes in cancers
per rem, retardation factors, or target populations, would affect
both the repository and ore body impacts in a parallel, although not
necessarily identical, manner.
The estimated effects from the actual ore bodies considered have
great uncertainty. This is because (1) trace concentrations of
uranium are difficult to measure and vary within the ore, (2) small
changes in Eh can produce large changes in dissolved uranium
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20
concentrations, (3) the groundwater transport and dosimetric models
are, in part, hypothetical (Smith et al., 1980a) and (4) the
retardation factors used are from one medium and might not reflect
the range of values that exist in nature. The area of largest
potential uncertainty is in interpreting the available data for
uranium solubility, which can vary by several orders of magnitude.
The release and impact assessments for the actual ore bodies
should be looked upon as high estimates for the groundwater pathway
because the uranium concentrations used are higher than one might
expect down dip. Although the actual impact of these ore bodies
could be higher, due to limitations of the transport and dosimetric
models, it is more likely that the impact would be lower, because
uranium solubility decreases as the groundwater migrates down dip
into a more reducing geological environment (Phoenix, 1959 and
Germanov and Panteleyev, 1968). Since the reported uranium
concentrations are averages, they may include samples taken from
both the oxidizing and reducing side of the ore body. It is my
judgment that the averages reported for the actual ore bodies are
overestimates for this reason. Additionally, it is possible that
drilling in the ore body, to obtain samples, introduced oxygen,
causing an increase in the uranium concentration. Therefore, these
estimates can be looked upon only as a high impact estimate, since
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21
the high uranium concentration tends to maximize the estimated
releases and impacts.
The releases from unmined uranium ore bodies to groundwater are
"chronic" or continuous. If one postulated or assumed various
accidents (such as drilling into the ore), the impact might be much
larger, if no environmental or institutional controls are assumed.
The impact estimate for the actual ore bodies is over a thousand
times higher than that from the model ore body. The actual effects
from deep ore bodies would probably fall between these estimates
because the uranium concentrations reported from the actual ore
bodies are not typical of the down-dip concentrations. If the
uranium concentration is raised by a factor of 120 (the highest
reported by Fix (1955)) and the reconcentration factor is raised by
a factor of 3.3, the estimated effects from the model ore body fall
near the range found for the actual ore bodies.
The differences in the impacts can be explained: a) there are
factors which make the effects from the model ore body smaller:
solubility of uraninite (2 orders of magnitude), interstitial
aquifer velocity (factor of 2 more), enrichment of radium-226 in
aquifer relative to parents (factor of 3), and cross-sectional width
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22
of the ore body (factor of 2); b) there are factors which tend to
make the effects from the model ore body larger than that of the
actual ore bodies examined: estimated uranium reserves (factor of
3, but possibly more or less); and c) there are factors which do not
affect the actual and model ore body estimates significantly:
thickness and porosity of ore strata (each less than a factor of 2).
One obvious source of bias is the fact that the actual ore
bodies discussed are of the relatively large size that make uranium
milling economically feasible. A recent study by the Department of
Energy (1979) indicates that small ore bodies are far more numerous
than larger ones. Because information concerning the reserves,
mineralization, location, etc., of ore bodies is generally
considered proprietary, it is possible that consideration of only
large ore bodies for this analysis has introducted other, unknown
biases. Despite this, it is likely that the groundwater impact of
the uranium ores, from which a 100,000-metric-ton heavy metal waste
repository was derived, lies somewhere between the two estimates.
Conclusion
A simplified hydrologic model along with environmental transport
and dosimetric models has been used to assess the environmental
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23
impact of several actual uranium ore bodies. Although the impacts
are only approximate, it is likely they represent the upper impact
of ore bodies through groundwater pathways. The relatively large
impact can be explained by the existence of ore bodies in aquifers.
If ore bodies were not formed in aquifers, the effects of unmined
ore would be both more difficult to assess and much lower. Using
this model the estimated fatal cancers vary for three actual ore
bodies from a low of .59 to 3.4 fatal cancers/year; these fatal
cancers result from estimated releases ranging from 190 millicuries
to 1100 millicuries of 226Ra per year.
A model ore body model would release 120 microcuries of 22f>Ra
per year. This would be the expected minimum impact from an ore
body.
When normalized to the expected health effects of the ores from
which a 100,000 metric-ton-heavy metal repository was derived, the
number of fatal cancers ranges from 2.3x10-2 per year for the
model case to 102 to 103 per year for actual ore bodies. It
appears likely that the actual impact of individual ore bodies lies
within this range, due to the assumptions made in the analysis.
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24
REFERENCES
W. W. Boberg and D. D. Runnel Is (1971) Recconnaissance Study of Uranium
in the South Platte River, Colorado. Economic Geology, 66, 435-450.
Harry C. Burkholder and Michael 0. Cloninger (1977) The Reconcentration
Phenomenon of Radionuclide Chavin Migration. Battelle Pacific Northwest
Laboratories Report BNWL-SA-5786, April 1977, 30pp.
Harry C. Burkholder and Michael 0. Cloninger (1978) The Reconcentration
Phenomenon of Radionuclide Migration. American Institute of Chemical
Engineers Symposium Series, 74, 83-90.
Regine M. Capuano (1978) Preliminary Analysis of the Formation of
Uranium Roll Deposits as a Result of Reactions between Circulating
Fluids and an Arkose. Economic Geology, 73, 308.
Bernard L. Cohen (1977) The Disposal of Radioactive Wastes from Fission
Reactors. Scientific American, 236, 21-32. Also see: High-Level
Radioactive Waste from Light Water Reactors. Rev. Mod. Physics, 49, 1.
Kenneth S. Deffeyes and Ian D. MacGregor (1980) World Uranium
Resources. Scientific American, 242, 66-76.
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25
D. H. Denham, D. A. Baker, J. K. Soldat, and J. P. Conley (1973)
Radiological Evaluations for Advanced Waste Management Studies.
Battelle Pacific Northwest Laboratories Report BNWL-1764, 42pp.
Daniel J. Egan, Or. (1978) Risk Assessment in Support of Environmental
Standards: EPA's High-level Radioactive Waste Standards. Presented at
the 71st Annual Meeting, American Institute of Chemical Engineers,
Miami, Florida, November 16, 1978.
Department of Energy (DOE) (1979) Statistical Data of the Uranium
Industry. Grand Junction Office Report GJO-100 (79), January 1, 1979.
Environmental Protection Agency (EPA) (1973) Environmental Analysis of
the Uranium Fuel Cycle. Part I - Fuel Supply, U.S. Environmental
Protection Agency Report EPA-520/9-73-003-B.
Exxon Minerals Company (1977) Supplemental Environmental Report for
Highland Uranium Solution Mining Project and U.S. Nuclear Regulatory
Commission, 1978, Final Environmental Statement, for Highland Uranium
Solution Mining Project (NUREG-0489), NRC Docket 40-8102. Also see
United Nuclear Corp., Environmental Report - Morton Ranch Mill, 1976.
Philip F. Fix (1955) Hydrogeochemical Exploration for Uranium. U.S.
Geologica^ Survey Professional Paper, 300, 667-671.
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26
Robert L. Fleisher and 0. G. Raabe (1978) Recoiling Alpha-emitting
Nuclei: Mechanisms for Uranium-series Disequilibrium. Geochim.
Cosmochim. Acta, 42_, 973-978.
A. I. Germanov and V. M. Panteleyev (1968) Behavior of Organic Matter in
Groundwater During Infiltrational Epigenesis. Internat. Geology Rev.,
JO, 826-832.
D. E. Grandstaff (1976) A Kinetic Study of the Dissolution of Uraninite.
Economic Geology, 71_, 1493-1506.
J. Hamstra (1975) Radiotoxic Hazard Measure for Buried Solid Radioactive
Waste. Nuclear Safety, 16, 180-189.
Robert F. Kaufmann, Gregory G. Eadie, and Charles R. Russell (1975)
Summary of Groundwater Quality Impacts of Uranium Mining and Milling in
the Grants Mineral Belt, New Mexico. U.S. Environmental Protection
Agency Technical Note ORP-LV-75-4, 70pp.
Donald Langmuir (1978) Uranium Solution-Mineral Equilibria at Low
Temperatures with Applications to Sedimentary Ore Deposits. Geochim.
Cosmochim. Acta, 42, 547-569.
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27
D. H. Lester, G. Jansen, and H. C. Burkholder (1975) Migration of
Radionuclide Chains through an Absorbing Medium. American Institute of
Chemical Engineeering Symposium Series No. 152, Absorption and Ion
Exchange, 7J[, 202.
Arthur D. Little, Inc. (1979) Technical Support of Standards for
High-Level Radioactive Waste Management. Volume C, Final Report for EPA
Contract No. 68-01-4470, EPA Report EPA 520/4-79-007C.
Steven Lynn Lueck (1978) Computer Modelling of Uranium Species in
Natural Waters. Thesis presented to University of Colorado (abstract).
Also see Lueck, Runnells, and Markis, Computer Modelling of Uranium
Species in Natural Waters: Applications to Explanation. 1978 Joint
Annual Meeting of the Geological Society of America (with 10 other earth
sciences professional groups), October 23-26, 1978, Toronoto, Canada
(Abstract).
D. A. Phoenix (1959) Occurrence and Chemical Character of Ground Water
in the Morrison Formation. U.S. Geological Survey Profesional Paper
320, 55-64.
H. A. Qidwai and M. L. Jensen (1979) Methodology and Exploration for
Sandstone-Type Uranium Deposits. Mineralium Deposita, 14, 137-152.
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28
Rocky Mountain Energy Company (1979) Nine Mile Lake Project Environ-
mental Report, January 1979, U.S. Nuclear Regulatory Commission Docket
40-8721.
V. C. Rogers (1978) Migration of Radionuclide Chains in Groundwater
Nuclear Technology, 40, 315-320.
Donald D. Runnel Is, Ralph Lindberg, Steven L. Lueck, and Gergely Markos
(1980) Applications of Computer Modelling to the Genesis, Exploration,
and In-Situ Mining of Uranium and Vanadium Deposits. New Mexico Bureau
of Mines Memoir or± the Grants Mineral Belt, in press.
C. Bruce Smith, Daniel J. Egan, W. Alexander Williams, James M. Gruhlke,
Cheng-Yeng Hung, and Barry Serini (1980a) Population Risks from Disposal
of High-level Radioactive Wastes in Geologic Repositories. U.S.
Environmental Protection Agency Report 520/3-80-006.
J. Michael Smith, Ted W. Fowler, and Abraham S. Goldin (1980b)
Environmental Pathway Models for Estimating Population Risks from
Disposal of High-level Radioactive Waste in Geologic Repositories. U.S.
Environmental Protection Agency Report EPA 520/5-80-002.
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29
J. W. Voss (1979) Safety Indices and their Application to Nuclear Waste
Management Safety Assessment. Battelle Pacific Northwest Laboratory
Report PNL-2727, prepared for the U.S. Department of Energy under
contract EY-76-C-06-1830, 67pp. and three appendices.
Wyoming Minerals Corporation (1977) Environmental Report for Irigaray
Project and U.S. Nuclear Regulatory Commission, Final Environmental
Statment, for Irigaray Solution Mining Project (NUREG-0481), NRC Docket
40-8502.
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IBLIOGRAPHIC DATA
MEET
1. Report No.
EPA 520/3-80-009
3. Recipient's Accession No.
Title and Subtitle
Population Risks from Uranium Ore Bodies
5. Report Date
October 1980
6.
Author(s)
W. Alexander Williams
8. Performing Organization Rept.
No.
Performing Organization Name and Address
Office of Radiation Programs (ANR-461)
U.S. Environmental Protection Agency
Washington, D.C. 20460
10. Project/Task/Work Unit No.
11. Contract/Grant No.
2. Sponsoring Organization Name and Address
Office of Radiation Programs (ANR-461)
U.S. Environmental Protection Agency
Washington, D.C. 20460
13. Type of Report & Period
Covered
14.
15. Supplementary Notes
16. Abstracts
This report estimates the minimum radiological releases and potential impact of
deep-lying uranium ore, so that they may be compared with projected releases and
impacts from radioactive waste. Uranium concentration and groundwater flow rates
are used as input data for three models developed by EPA for analyzing the impact
°f high-level radioactive waste. One set of data is obtained from some ore bodies
which are being mined by the in situ solution process. Another, the minimum impact
case, is obtained by using conservative data on uranium concentrations in uranifer-
ous groundwaters in conjunction with a model aquifer developed by EPA.
17. Key Words and Document Analysis. 17a. Descriptors
unmined uranium ore
radiological releases
Radium-226
uranium in groundwater
population effects
17b. Identifiers/Open-Ended Terms
17c. COSATI Field/Group
18. Availability Statement
Release unlimited
19.. Security Class (This
Report)
UNCLASSIFIED
20. Security Class (This
UNCLASSIFIED
21. No. of Pages
38
22. Price
FORM NTis-38 (REV. 1O-73) ENDORSED BY ANSI AND UNESCO.
» V.S. GOVERNMENT miNTDJO OFFICE : 1980- W1-08Z/M'
THIS FORM MAY BE REPRODUCED
USCOMM-DC B26S-P74
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