EPA 660/2-74 038
JUNE 1974
Environmental Protection Technology Series
State-of-the-Art. Uranium Mining,
Milling, and Refining Industry
National Environmentat Research Center
Office of Research and Development
U.S. Environmental Protection Agency
Corvallis, Oregon 97330
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and
Monitoring, Environmental Protection Agency, have
been grouped into five series. These five broad
categories were established to facilitate further
development and application of environmental
technology. Elimination of traditional grouping
was consciously planned to foster technology
transfer and a maximum interface in related
fields. The five series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
1. Environmental Monitoring
5. Socioeconomic Environmental Studies
This report has been assigned to the ENVIRONMENTAL
PROTECTION TECHNOLOGY series. This series
describes research performed to develop and
demonstrate instrumentation, equipment and
methodology to repair or prevent environmental
degradation from point and -non-point sources of
pollution. This work provides the new or improved
technology required for the control and treatment
of pollution sources to meet environniental quality
standards.
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EPA-660/2-74-038
June 1974
STATE-OF-THE-ART: URANIUM
MINING, MILLING, AND REFINING INDUSTRY
by
Don A. Clark
Robert S. Kerr Environmental Research Laboratory
Post Office Box 1198
Ada, Oklahoma 74820
Project No. 21 AGF-02
Program Element IBB 040
NATIONAL ENVIRONMENTAL RESEARCH CENTER
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CORVALLIS, OREGON 97330
For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402 - Price $1.66
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ABSTRACT
The report presents an overview of the uranium mining, milling, and
refining industry of the United States. Topics discussed include ore
reserves, geographical locations, production statistics, future require-
ments , processes for extraction and beneficiating, waste characteristics,
including radioactive and other potential pollutants, current treatment
and disposal methods, effects of wastes on the environment, standards
for radiological protection, testing and monitoring programs, techno-
logical advances within the uranium industry, anticipated future
problems and recommended areas for further study.
11
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CONTENTS
Page
Abstract ii
List of Figures v
List of Tables vi
Sections
I Conclusions •*•
II Recommendations ^
III Introduction
•7
IV Uranium Ore Supply
Detection of Uranium Ore Deposits
Ore Reserves "
18
20
Effect of the Nuclear Power Industry on Uranium
Requirements
Mining and Milling Operations
V Mining Processes ^
Open Pit Mining ^
Underground Mining ^6
Solution Mining
VI Milling Processes ^~
Ore Handling
Crushing and Grinding of Ore *;•
Acid Leach ^
Carbonate Leach J"
Liquid-Solid Separation *~
Ion Exchange JT
Solvent Extraction *•?
Eluex Process *:*
Precipitation
Drying and Packaging ^
Secondary Metal Recovery 4°
VII Refining Processes
iii
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CONTENTS (continued)
Sections Page
VIII Waste Characteristics 5°
Mill Process Effluents 51
Sands and Slimes ci
Suspended Solids in Mill Effluents 51
Mine Water Drainage 51
Airborne Radioactivity
53
IX Chemical Classification of Wastes co
Inorganic Pollutants 53
Organic Pollutants 53
Radioactive Pollutants
X Waste Treatment and Disposal °jf
Containment of Wastes ^
Chemical Treatment and Dilution ^i
Underground Disposal
Recycling of Discharges „_
Off Site Disposal
XI Effects of Wastes on the Environment ^
Ground Water
Surface Water jj;:
River Sediment j:'
Reservoir Sediment
Aquatic Biota ^
Crops VU
XII Standards for Radiological Protection 92
International Commission on Radiological
Protection Report 93
National Bureau of Standards Handbook 69 93
Federal Radiation Council Standards 93
USPHS Drinking Water Standards—-1962 94
Water Quality Criteria—FWPCA 96
XIII Testing and Monitoring Programs 98
XIV Technological Advances in the Uranium Industry 102
Physical Upgrading of Low Grade Ores 102
Improved Uranium Extraction Processes 103
Extraction of Uranium from Seawater 104
Underground Uranium Extraction Using Nuclear
Explosives 1°4
Radium Removal from Uranium Mill Effluents and
Tailings Solids 105
106
XV References
iv
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FIGURES
No. Page
1 Resource Regions in the United States *•"
2 Geographical Locations of Major Uranium Mining Districts
3 Process Flow Diagram A •"
34
4 Process Flow Diagram B
5 Process Flow Diagram C "
6 Process Flow Diagram D 3°
7 Process Flow Diagram E 37
8 Process Flow Diagram F 38
on
9 Process Flow Diagram G °7
10 Uranium-Radium Family (minor branches not shown) ^°
QC
11 Colorado River Basin Radium Monitoring Network
v
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TABLES
No.
1 Distribution of Ore Reserves by Resource Region
2 Distribution of Ore Reserves by State ^
3 Uranium Ore Production in Four Leading States *•*
4 Surface Drilling 14
5 Drilling Activity 14
6 Distribution of the 1971 Surface Drilling by State 14
7 Drilling Statistics for Western United States 1^
8 Distribution of 1970 Uranium Oxide Production in Ore
by Depth of Ore 16
9 Distribution of Ore Reserves by Mining Method *'
10 Uranium Ore Reserves and Production—1955 through
1970 17
11 Uranium Requirements 21
12 Uranium Mines and Ore-Processing Plants 22
13 Uranium Ore-Processing Plants 23
14 Colorado River Basin Uranium Mills 24
15 Uranium Milling Plants and Processing Operations 32
16 Chemicals Used in Milling Operations 54
17 Metals Leached from Ore by Milling Process 55
18 Mill Effluent No. 1 6o
19 Mill Effluent No. 2 6o
20 Mill Effluent No. 3 61
21 Mill Effluent No. 4 6l
vi
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TABLES (continued)
No. Page
22 Mill Effluent No. 5 62
23 Mill Effluent Suspended Solids
24 Uranium-Radium Family, MFC Values
73
25 Waste Disposal by Deep Well Injection
83
26 Repetitive Leaching of Mill Tailings
27 Mean Annual Concentrations of Radium-226 in Water g£
at Monitoring Network Stations, 1961-1970
95
28 Graded Scale of Action
29 Ranges of Transient Rates of Intake for Use in 05
Graded Scale of Action
96
30 Surface Water Criteria for Public Water Supplies
31 Direct Operating Costs of Uranium Extraction in
the U.S.A.
vii
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SECTION I
CONCLUSIONS
1. Approximately 95 percent of the known uranium deposits are
located within the Western United States; however, the eastern two-
thirds has many sedimentary deposits similar to those in the west and
exploration activities may uncover new bodies of ore. At present, 40
percent of the United States has potential for uranium ore production.
2. Essentially all of the anticipated uranium requirements in the
future will be for a rapidly expanding nuclear power industry utilizing
uranium as a fuel source. Uranium requirements are expected to double
by 1977, triple by 1981, and continue upward through the year 2000.
3. Exploratory drilling activities have been directed toward finding
ore at greater depths with the average depth of drilling increasing from
148 feet in 1958 to 409 feet in 1970. At present, the average grade of
uranium ore is 0.22 percent; however, as the richer deposits are
depleted in the early 1980's, it will become necessary to mine lower
grade ores. Mining and milling of lower grade ores will involve the
handling and disposal of significantly larger quantities of waste
tailings.
4. Solid waste tailings are accumulating at a rate of approximately
1,960 pounds per ton of ore processed or nine million tons per year from
the uranium mills at full operating capacity. By 1972, the total accumu-
lation of tailings in the United States was estimated at 110 million tons
containing 60,000 grams of radium-226. Studies have been conducted
on various methods of tailings pile stabilization measures against wind
and water erosion, but no definitive remedial measures have been set
forth as a requirement. Laboratory studies have found that radium-226
may be leached from waste solids up to maximum amounts of 50 percent
by contact with water only.
-------
5. Yearly wastes from active uranium mining, milling, and refining
plants contain a total of 41,000 curies of radioactivity (6,822 microcuries/
ton ore) . Radioisotopes with established maximum permissible concen-
trations contribute 20,500 curies of radioactivity to the waste. The most
hazardous of the radioisotopes is radium-226, with a half-life of 1,620
years . Radium is not recovered for commercial uses, as the present
world supply is considered adequate. Current production of uranium
contributes 3,400 grams of radium yearly to the environment (568
micrograms/ton ore)—more than the estimated total world supply of
3,000 grams. More than 98 percent of the radium is discharged with
the solid waste. Other possible contaminants include uranium and
other radioisotopes, vanadium, selenium, molybdenum, arsenic,
nitrates, sulfates, chlorides, organic extractants, and suspended fines.
6. The few uranium mills currently releasing process waste effluents
to rivers and streams treat the waste prior to discharge; however, mine
water containing pollutants is being discharged in several mining loca-
tions with no chemical treatment. Standard treatment procedure for the
removal of radium-226 entails the addition of barium chloride to precipi-
tate radium as a barium-radium sulfate complex. Removal efficiencies
of 99 percent may be obtained by the method; however, the process must
be carefully monitored or treatment efficiencies decline.
;
7. For the mills not discharging liquid wastes to the environment,
chemical treatment is not practiced; hence, the inorganic and radioactive
wastes remain in the dissolved state and are subject to seepage from the
tailings ponds. The extent of ground water contamination from this source
or the ultimate fate of these pollutants is not known.
8. Comprehensive monitoring programs and background surveys have
not been conducted to adequately assess the degree of environmental
pollution resulting from uranium mining, milling, and refining operations .
With the exception of the Colorado River Basin, data collected from other
uranium-producing areas have been insufficient, sporadic, and, in
some instances, unreliable.
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SECTION II
RECOMMENDATIONS
1. Initiate a comprehensive research program to ascertain the
pollutional effects on the environment from all aspects of the uranium
mining, milling, and refining industry and to develop adequate waste
treatment and control technology for the expanding uranium industry.
2. Research should be conducted to develop new or improved
methods to remove radionuclides, vanadium, selenium, molybdenum,
arsenic, nitrates, sulfates, chlorides, organic extractants, suspended
fines, and other inorganic contaminants from uranium mill process
wastes and mine waters regardless of disposal method. Flocculant
aids or mechanical means should be employed for better suspended
solids removal followed by maximum reuse of the treated waters.
3. A treatment process to remove leachable radium-226 from uranium
waste solids prior to disposal should be developed. Countercurrent
washing of the tailings solids followed by precipitation or ion exchange
concentration might prove feasible. The leaching characteristics of sands
and slimes from different types of milling circuits should be studied.
4. Since radium-226 concentrations in uranium concentrates vary
according to the milling process utilized, surveys should be conducted
to determine the amount of radium-226 passing through the refineries. If
levels of the radionuclide are found to be high, treatment of the wastes
for removal would be indicated.
5. Physical upgrading processes for uranium ores should be developed
and employed to reduce the bulk of solid waste tailings that must be con-
tained and stabilized in restricted areas.
6. The most effective method(s) for the location and stabilization of
tailings piles should be determined and uniformly required for all milling
-------
operations. The piles should receive perpetual care with follow-up
studies over a period of years to determine efficiency and longevity of
the stabilization procedures.
7. Studies should be conducted to ascertain the degree and extent of
radioactive and inorganic pollution of surrounding soils and ground waters
caused by seepage from uranium tailings ponds and piles. Potential long-
range environmental effects could be predicted from this information.
Development and utilization of impermeable sealants for tailings ponds
would greatly reduce pollution from seepage.
8. A continuous monitoring program should be established for all
uranium mining, milling, and refining areas to assure that maximum
permissible concentrations of radionuclides and other inorganic constit-
uents are not exceeded. Background surveys to obtain baseline data
should be conducted in new areas prior to the initiation of operations.
9. Standards should be established regulating concentrations of
pollutants in mine water discharges. A study should be made to deter-
mine whether allowable uranium concentrations in water and radium-226
in suspended solids are excessive, and to establish a maximum permis-
sible concentration for molybdenum.
10. Every effort should be made to reduce the concentrations of pollut-
ants released to the environment to the lowest possible level, regardless
of the preselected maximum permissible concentrations allowable.
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SECTION III
INTRODUCTION
The production of uranium has become a major industry in the United
States since the end of World War II. Fission of the atom was successfully
demonstrated in 1942, and led the way to the tremendous potential of
nuclear power. With the advent of the atomic age, the demand for uranium
to be used in the production of nuclear weapons caused extensive explora-
tion for uranium-bearing ore deposits. Major ore deposits are located in
the Colorado Plateau encompassing parts of western Colorado, eastern
Utah, northeastern Arizona, and northwestern New Mexico. Other exten-
sive deposits are located in Wyoming and the Grants-Ambrosia Lake area
of New Mexico. Smaller deposits are located in Texas, North Dakota,
South Dakota, and Washington.
By the late 1950's, uranium mills constructed in these areas were proc-
essing in excess of 20,000 tons per day of ore with an average uranium
oxide (U-O8) content of 0.28 percent. The extraction of uranium from
the ores leaves large amounts of solid and liquid waste for disposal.
Initially, little attention was given to the possibility of significant envir-
onmental contamination by the uranium mill wastes. As a result, large
quantities of both solid and liquid waste were discarded into streams
causing widespread contamination of the affected areas. During the
1950's extensive studies were conducted to determine the fate of radio-
active waste materials in the environment and their effects on human
health.
Standards for maximum permissible concentrations of radioisotopes in
water for human consumption were established; as more was learned
about the hazards of radiation, the standards were revised to lower levels.
Methods of waste handling and control were developed in an attempt to
lower the pollution to a level that would meet the established standards.
The uranium milling industry has implemented pollutional abatement
-------
procedures in the plant process to solve some of the problems. With
adequate surveillance of the environment, problems can be recognized
quickly as they occur, and abatement procedures established to prevent
pollution.
A downward trend in uranium production occurred in the early and
mid-1960's, as the demand for uranium changed from a military to a
smaller commercial market. While nuclear power was feasible, it was
not yet economically competitive with other types of fuel. As a result,
many mills closed and others reduced their production rate. Exploration
activities were curtailed to a greater extent than the milling operations.
Nuclear energy was used solely for military purposes until 1954 when
President Eisenhower initiated the "Atoms for Peace" program. Since
that time a tremendous amount of effort and money has been spent to
utilize nuclear energy for peaceful uses, including electrical power
generation, medical diagnosis and therapy, food and materials irradia-
tion, and nonmilitary nuclear explosives.
By 1966 uranium-fueled reactors for production of electric power were
developed to the extent that they were economically competitive with
other sources of power, thus creating a new market for uranium. Nuclear
power generation represented less than one percent of the total electricity
generated in 1968, but is expected to provide 40 to 60 percent of the
Nation's electricity by the year 2000. In anticipation, a marked increase
in exploration for uranium ore deposits to supply future needs has been
undertaken.
Advances in technology can be expected in exploration, mining, and
processing that will reduce the cost and increase the supply of
uranium. Newer methods may pose problems requiring advanced
technology in pollution abatement.
-------
SECTION IV
URANIUM ORE SUPPLY
DETECTION OF URANIUM ORE DEPOSITS
In the early days of prospecting for uranium ore, Geiger counters were
2
used to detect deposits within 18 inches of the surface. At the present
time, test holes for deeper deposits are drilled and the core measured
for radioactivity by means of a scintillation counter or analyzed specifi-
cally for uranium by fluorometric or colorimetric methods.
Drilling is the most economical and widely used method of exploration.
Most exploratory drilling has been done in districts known to contain
uranium deposits. Many new discoveries in these areas are at much
greater depths and contain lower grade ore than that previously mined.
Exploratory drilling is usually performed using 200 foot centers followed
by developmental drilling on 50 foot centers. Small ore bodies have been
missed completely when using 100 foot centers . Developmental drilling
provides the information needed for mine layout and cost estimates.
Another method of detecting uranium reserves is aerial reconnaissance.
The method gives a quick scan of .unexplored areas for high radiation
zones. The aircraft fly a grid pattern approximately 500 feet above
the ground with the grid spacing the same distance apart as the height.
Sensitivity is gained by flying closer to the ground, but smaller grid
patterns must be made which increase the cost of exploration. Radiation
levels obtained may be plotted on a map and the information used for
ground instrument surveys or drilling operations to indicate the exten-
siveness of the deposit.
Monitoring of the ground air for the presence of radon gas is another
2
method that has shown some promise in ore detection. A measurement
of the alpha activity is made in auger holes 1.5 to 3 feet deep. This
method has been shown to detect radon over uranium-bearing ore
covered by considerable thickness of overburden.
-------
ORE RESERVES
The chief sources of ore in the United States are found in sedimentary
strata consisting of sandstone, mudstone, and limestone. The uranium
minerals occur as pore fillings, replacements of woody tissue or other
carbonaceous matter, and as a cement between quartz grains or along
fractures.
Uranium deposits occur in either of two modes, stratiform or vein type.
Approximately 95 percent of the Nation's reserves is found in the strati-
form type consisting of sandstone and conglomerate, limestone, and
lignite formations. The deposits lie parallel to the bedding plane and
have large lengths and widths as compared to their thickness. Vein-4
type deposits occurring at steep angles along fractures and structural
faults account for the other reserves.
The principal known deposits of uranium ores in the United States are
4
located in three major districts:
1. Wyoming Basins—Shirley Basin, Powder River,
and Gas Hills;
2. Colorado Plateau—Uravan Belt, Big Indian, Laguna,
and Ambrosia Lake; and
3. Texas Gulf Coast.
Table 1 shows the percentage distribution of ore reserves by resource
region as of January 1971. The reserves are restricted to ore that may
be economically produced for $8/lb of U^Og. The distribution of ore
reserves by State is shown in Table 2, while uranium ore production in
the four leading States from 1960 through 1970 is shown in Table 3. Ore
reserves now known lie in over a thousand individual deposits in the
Western States; however, half of the reserves are in fifteen deposits
containing over a million tons of ore. The ore grade ranges from less
than 0.1 percent to well over 0.5 percent uranium oxide. Figure 1 shows
the geographical location of the ore reserves by resource region. Geo-
graphical locations of the major uranium mining districts in the Western
States are shown in Figure 2.
8
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Table 1. DISTRIBUTION OF ORE RESERVES BY RESOURCE REGION7
(recoverable at $8/lb U0O0)
J O
Resource region
Colorado Plateau
Wyoming Basins
Northern Rockies
Gulf Coastal Plains
Northern Plains
Others
Grade (%)
U3°8
.24
.19
.13
.16
.24
.35
% Total tons
U3°8
51.08
38.63
4.26
4.22
0.63
1.18
Table 2. DISTRIBUTION OF ORE RESERVES BY STATE7
(recoverable at $8/lb U-Ofi)
State
Grade (%)
U3°8
% Total tons
U3°8
New Mexico .24 44.04
Wyoming .19 38.71
Utah .31 3.68
Colorado .27 4.14
Texas .16 4.22
Others .14 5.21
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COLUMBIA
Ifn
11
c^
% BASIN
rAND
COLORS
^
(A
SOUTHERN
PLAINS
"^
GULF
COASJAL
PLAINS
Figure 1. RESOURCE REGIONS IN THE UNITED STATES
10
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Figure 2. GEOGRAPHICAL LOCATION OF MAJOR
URANIUM MINING DISTRICTS
11
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7 8
Table 3. URANIUM ORE PRODUCTION IN FOUR LEADING STATES '
Year
1960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
Percent of total production
New Mexico
48
_
50
-
37
46
48
-
51
50
46
Wyoming
17
-
18
-
26
24
25
-
25
28
26
Colorado
14
-
16
-
15
13
15
-
11
12
12
Utah
13
—
11
—
13
9
5
-
7
-
7
The ore deposits in the Texas Coastal Plain were discovered in 1954,
when a plane carrying scintillation detection equipment recorded strong
anomalies in Karnes County. Probably less than five percent of the
total prospectable acreage in the area had been explored as of January
1967. Some deposits of ore are expected to occur in the High Plains
area of Texas, but will likely be less productive than the Coastal Plains.
Lignite ores are located in North Dakota, South Dakota, and Texas. The
Uravan mineral belt in the Colorado Plateau contains vanadium-bearing
minerals, making it profitable to recover both uranium and vanadium
from the ore. Much of the uranium ore contains molybdenum in quantities
sufficient for economic recovery.
Canadian companies are conducting exploration activities in the United
9
States. Rio Algom Mines Limited is developing a mine in the Lisbon
Valley district, about 30 miles southeast of Moab, Utah, and is partici-
pating in an extensive exploration program in Wyoming with Mitshubishl
Metal Mining Company. Several major uranium-producing companies
12
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from the United States are becoming involved in Canadian uranium
exploration activities in anticipation of future uranium requirements.
Many new companies are entering the field of uranium exploration; the
number of companies exploring for uranium more than doubled from
1965 through 1967. The discovery rate from exploratory drilling in the
previous uranium-producing areas has been about six pounds of uranium
oxide per foot drilled. Recently, exploration has spread into previously
unexplored areas and, combined with the search for deeper deposits,
has resulted in a reduction in the discovery rate to about three pounds
of uranium oxide per foot drilled.
Uranium has been found and produced in 17 States, but 95 percent has
been from Arizona, Utah, New Mexico, and Wyoming. The eastern
two-thirds of the United States has many sedimentary deposits similar
to those in the uranium-producing areas. As exploration activities
spread into the newer areas, new bodies of ore may be discovered to
greatly expand reserves. About 40 percent of the United States has
potential for producing uranium ore.
Drilling activities have increased rapidly since 1967. Table 4 shows
the surface drilling from 1967 through 1970 with the projected drilling
plans for 1971 through 1973. The previous peak in drilling was in 1957
when 9.2 million feet were drilled. In comparison, drilling from 1951
through I960 was only 52 million feet.
Table 5 shows both exploratory and surface drilling for the period 1966
through 1970. The exploratory drilling has increased at a much faster
rate than developmental drilling, indicating a rush to find new reserves
for future demands. The previous high in exploratory drilling was in
1957 when 7.3 million feet were drilled.
Table 6 shows the distribution of the 1970 surface drilling by States. Of
interest is the high drilling activity in Texas for new reserves. While
producing only five percent of the uranium, it ranks second in drilling
activity. This may be an indication of a forthcoming rise in production
rate.
13
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Table 4. SURFACE DRILLING7
Year
1967
1968
1969
1970
1971-1973
Million feet
10.7
23.8
29.9
24.0
54.2 (projected drilling plans)
TableB. DRILLING ACTIVITY7
Year
1966
1967
1968
1969
1970
1971
1972
1973
Exploratory
1
5
16
20
17
12
11
9
,800
,435
,227
,470
,981
,200
,600
,900
,000
,000
,000
,000
,000
,000
,000
,000
ft.
ft.
ft.
ft.
ft.
ft.
ft.
ft.
(estimate)
(estimate)
(estimate)
2
5
7
9
5
7
6
6
Developmental
,400
,329
,527
,385
,547
,000
,700
,800
,000
,000
,000
,000
,000
,000
,000
,000
ft.
ft.
ft.
ft.
ft.
ft.
ft.
ft.
(estimate)
(estimate)
(estimate)
Table 6. DISTRIBUTION OF THE 1970 SURFACE DRILLING BY STATES7
State
Wyoming
Texas
New Mexico
Colorado
Utah
South Dakota
Others
Drilling
9,812,000
6,075,000
5,180,000
1,007,800
641,300
436,900
374,900
% of Total
41.7
25.8
22.0
4.3
2.7
1.9
! 1.6
Total 23,528,000 100.0
14
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A trend toward deeper drilling has taken place since 1965. Shallow
deposits were more readily located by airborne or ground surveys and
more economical to mine. As these deposits become depleted, exploration
at deeper depths will be required. Table 7 shows the drilling statistics
for the Western United States. From I960 through 1965 the average depth
per hole drilled was 160 feet. The average depth of drilling has steadily
increased through the years from 148 feet in 1958 to 409 feet in 1970.
From 1965 to 1970 the average depth more than doubled. Table 8 shows
the distribution of ore by depth for the year 1970. Approximately 65
percent of the ore reserves lie at depths of less than 500 feet allowing
recovery by open pit mining. The ore is more concentrated at two zones:
150 to 200 feet and 350 to 400 feet where 14.3 and 16.2 percent of the ore
is found.
Table 9 shows the distribution and grade of ore reserves by mining
method as of January 19.71, Open pit mines are located in Wyoming,
New Mexico, and Texas. Underground mines are located in all the
uranium-producing States except Texas .
As early as 1957, large ore reserves had been developed, but as the
requirements for uranium decreased, production experienced a down-
ward trend from 1960 through 1966. Exploration activities were halted
and many mills were closed. As the nuclear power industry began to
grow, increased exploration activity in 1967 resulted in more new
reserves discovered than those mined in that year. The reserve estima-
tion from 1955 through 1970 is shown in Table 10.
Should the market price rise substantially, reserves can be increased
by mining lower grade ore containing as little as 0.03 percent uranium
oxide. Phosphates in Florida have a uranium content of 0.005 to 0.03
percent uranium oxide. Marine shales range from 0.001 to 0.02 percent
uranium oxide and are found in Kentucky, Tennessee, and Alabama. New
technology in mining and milling processes may make mining of low grade
15
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7
Table 7. DRILLING STATISTICS FOR WESTERN UNITED STATES
Year Average depth (ft.)
Exploratory Developmental
1958 148 152
1959 146 168
1960 191 173
1961 160 165
1962 230 189
1963 104 146
1964 162 126
1965 187 129
1966 313 182
1967 425 314
1968 422 385
1969 428 335
1970 409 373
Table 8. DISTRIBUTION OF 1970 URANIUM OXIDE PRODUCTION IN ORE
BY DEPTH OF ORE7
Feet Percent
0-
50-
100-
150-
200-
250-
300-
350-
400-
450-
500-
550-
600-
650-
700-
750-
800-1
50
100
150
200
250
300
350
400
450
500
550
600
650
700
750
800
,500
2.47
4.90
8.13
14.30
4.10
'3.65
0.51
16.18
2.57
1.46
8.22
0.90
6.94
6.90
6.15
5.62
4.67
16
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Table 9, DISTRIBUTION OF ORE RESERVES BY MINING METHOD7
Mining method Grade (%) % Total tons
U3°8 U3°8
Open Pit .19 53,72
Underground Mines ,24 46,23
Others* .13 0.05
Heap and in situ leaching, extraction from mine water.
Table 10. URANIUM ORE RESERVES AND PRODUCTION
1955 THROUGH 19707
Year
end
1955
1956
1957
1958
1959
1960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
Shipment
to millsa
tons of U,Og
4,425
8,434
9,837
14,003
17,377
18,842
18,513
17,085
14,721
13,888
10,578
10,051
10,866
12,850
12,595
13,073
Reserve
estimation
tons of U,Og
67,595
164,055
210,109
225,644
240,996
231,785
178,885
167,738
160,231
150,927
144,702
140,835
147,741
160,819
204,080
246,100
Includes miscellaneous U^Og receipts from mine waters, heap leach,
in situ, and refining residues.
17
-------
minerals economical without greatly raising the market price. The leach-
ing of uranium from low grade copper dumps and recovery from phosphate
fertilizer is projected to supply 100,000 tons of uranium oxide through
the year 2000.
Another source of uranium may be the surplus stockpiled uranium con-
centrate held by the Atomic Energy Commission. The AEC stopped
procurement at the end of 1970 with 40,000 to 50,000 tons of stockpiled
uranium oxide. Release of the surplus for commercial use may begin in
1975, but be controlled so as to protect uranium producers. Should a
shortage develop due to nuclear power demands, the surplus could serve
to alleviate the situation.
EFFECT OF THE NUCLEAR POWER INDUSTRY ON URANIUM REQUIREMENTS
The introduction of uranium-fueled nuclear power generators has created
a new market for uranium . Nuclear energy for the production of electricity
has become economically competitive with other types of energy.
It is believed that practically all of the demand for uranium for non-
military purposes to the end of the century will be to fuel nuclear power
reactors. Uranium's greatest advantage as a fuel for the production of
t
electricity is that an enormous amount of energy is stored in a compara-
tively small space. One pound of uranium has the same energy potential
as three million pounds of coal. After years of development by govern-
ment and industry, the manufacturing facilities in the United States are
capable of producing an estimated 20 large nuclear power reactors each
15
year.
During 1970, five new nuclear power reactors began operations with 14
more under contract, making a year-end total of 108 central station
nuclear power reactors under contract, under construction, or operable
in the United States. It is predicted that penetration of the electric
18
-------
utility market by nuclear power plants will increase from less than one
percent of the total generation in 1968, to 25 to 30 percent in 1980, and
1 12
range from 40 to 60 percent in the year 2000. '
It is expected that breeder reactors will be developed by the mid-1980's.
Only one percent of the uranium-235 portion of the uranium oxide con-
centrate is consumed in the nuclear reactors presently in use. In
contrast, the breeder reactor will actually produce more fuel than it
13
consumes. The breeder reactor will produce fissionable plutonium-
239 and uranium-233 from uranium-238 and thorium-232, respectively.
The ultimate effect of utilizing the breeder reactor will be to reduce the
amount of uranium required, thereby increasing the currently predicted
uranium depletion times from decades to centuries. Another advantage
is that the breeder reaction is relatively insensitive to cost of uranium
oxide, thus allowing mining and milling lower grade ores at a higher
market price to provide additional ore reserves.
The Liquid Metal Fast Breeder Reactor has been chosen by the Atomic
Energy Commission as the prime contender for reactors of the future
14
and a development program is under way to perfect its design. This
type of reactor should compare economically with reactors now in opera-
tion, and use the nuclear resources more efficiently than present reactors,
Additionally, it will be able to operate on reprocessed spent fuel from
present reactors, thus eliminating uranium isotopes and plutonium-239
from the current and perplexing waste disposal problem.
Should breeder reactors be introduced in the early 1980's, the effect on
the uranium requirements will probably not be evident until the end of
the century. Should plutonium-239 be reserved for breeder fuels, the
demand for uranium to fuel light water reactors would increase. Also
a large amount of uranium will be required for the initial fueling of these
new reactors.
Plutonium recycle in thermal reactors is planned to start in 1974, thus
reducing annual requirements. Many uncertainties in requirements for
19
-------
the late 1980's and the 1990's exist, such as the timing of commercial
fast breeder reactors. A substantially greater amount of uranium will
be required, but a close estimate is difficult at this time. Table 11 shows
the projected domestic uranium requirements through the year 2000. The
requirements include the initial fuel for reactors under construction and
makeup fuel for operating reactors. Requirements for operating reactors
ranged from 15 percent of the total annual requirements in 1966, to 60
percent in 1980.
Current figures for the number of nuclear power plants to the end of the
century indicate a steeply rising annual demand for uranium far beyond
the capacity of existing mills. Existing mills produced 13,073 tons of
uranium oxide in 1970, as seen from Table 10. The projected annual
requirements will reach this level in 1973, as seen in Table 11, will
double by 1977, and triple by 1981. New mines and processing mills
will have to be placed in operation if the projected requirements are to
be met. An eight-year forward reserve is needed to assure an adequate
supply of ore for the requirements; hence, each year the addition to the
reserves must equal the annual requirements eight years later.
MINING AND MILLING OPERATIONS
The number of operating mines has steadily decreased from 1,000 in 1960
to 310 in 1969, as shown in Table 12. Many of the earlier mines were
one-man operations producing small quantities of ore. The ore was
hauled from the many locations to a processing mill some distance away.
The ore production rate in 1969 was 75 percent of that in I960, despite
the fact that the operating mines had decreased to 30 percent of the 1960
figure. This was due to the larger companies taking over the majority
of the smaller mining operations .
There were 25 mills in operation in 1960 that produced 17,646 tons of
uranium concentrate. The number of mills decreased to 15 in 1969, due
to the lowered demand. In anticipation of the increased demand for
uranium as a fuel for nuclear power, two new mills were placed in
20
-------
Table 11. URANIUM REQUIREMENTS1' 4» 5» 7» 9, 11, 16
Year
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
Annual
tons of U,Oo
4,000
5,000
7,000
8,700
10,500
13,000
16,000
18,500
21,500
25,000
28,000
32,000
36,000
41,000
46,000
51,000
56,000
60,000
62,500
65,000
67,000
68,500
69,500
70,500
71,000
72,000
72,500
73,200
74,000
75,000
75,500
76,500
77,000
Cumulative
tons of U,Og
4,000
9,000
16,000
24,700
35,200
48,200
64,200
82,700
104,200
129,200
157,200
189,200
225,200
266,200
312,200
363,200
419,200
479,200
541,700
606,700
673,700
742,200
811,700
882,200
953,200
1,025,200
1,097,700
1,170,900
1,244,900
1,319,900
1,395,400
1,471,900
1,548,900
21
-------
Table 12 . URANIUM MINES AND ORE-PROCESSING PLANTS
8
Year
1960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
Operating
mines
over 1,000
over 1,000
over 1,000
730
600
650
-
500
320
310
-
"
Tons of
ore
produced
8,000,000
8,000,000
7,000,000
5,900,000
5,700,000
4,400,000
4,352,651
5,300,000
6,500,000
5,900,000
_
"
Operating
mills
25
26
24
24
21
19
17
16
16
15
17
17
Tons of U-Og
concentrate
to AEG
17,646
17,348
17,010
14,218
11,847
10,442
9,487
8,425
7,338
6,184
2,500
""*
Tons of UjOg
concentrate to
private industry
' " •!?•
-
-
..-
-
-
-
700
5,000
6,400
11,200
«
operation in 1970. One of these was Susquehanna-Western, Incorporated,
located near Three Rivers, Texas; the other was Utah Construction and
Mining Company at Shirley Basin, Wyoming. Two more acid leach-solvent
extraction plants were placed in operation in 1972. Continental Oil Company
opened a mill near Falls City, Texas, with a capacity of 1,750 tons of ore
per day, and Humble Oil and Refining Company began operations at a mill
near Douglas, Wyoming, with a capacity of 2,000 tons of ore per day. An
alkaline leach plant with a 500 tons of ore per day capacity was also placed
into operation in 1972 by Rio Algom Corporation near La Sal, Utah. Table
13 lists operating mills, location, and capacity at the end of 1972.
At one time 34 mills were located in the Western United States with 17
located within the Colorado River Basin. The locations of the Colorado
River Basin mills are shown in Table 14. Only three of the mills are
still in operation. Although operations have ceased at 14 of the mills,
waste tailings piles containing potential radioactive pollutants remain
at the sites.
22
-------
Table 13. URANIUM ORE-PROCESSING PLANTS
1972
State and company
Colorado:
Si
Cotter Corp .
Union Carbide Corp .
Union Carbide Corp .
New Mexico:
The Anaconda Co.
Kerr-McGee Corp.
United Nuclear-Homestake Partners
South Dakota:
Mines Development, Inc.
Texas:
Susquehanna-Western , Inc .
Susquehanna-Western , Inc .
Continental Oil Company
Utah:
Atlas Corp .
Rio Algbm Corporation
Washington: ,
Dawn Mining Co. '
Wyoming:
Federal American Partners
Petrotomics Co.
Union Carbide Corp.
Utah Construction & Mining Co.
Utah Construction & Mining Co.
Western Nuclear, Inc.
Humble Oil and Refining Co.
Plant location
Canon City
Rifle
Uravan
Blue water
Grants
Grants
Edgemont
Falls City
Three Rivers
Falls City
Moab
La Sal
Ford
Gas Hills
Shirley Basin
Gas Hills
Gas Hills
Shirley Basin
Jeffrey City
Douglas
TOTAL
Nominal
capacity
(tons ore
per day)
450
2,000
3,000
7,000
3,500
650
1,000
1,000
1,750
1,500
500
500
950
1,500
1,000
1,200
1,200
1,200
2,000
31,900
Private sales only. Mines Development, Inc. shipped a small quantity
,to AEC.
Reactivated early in 1970.
23
-------
Table 14. COLORADO RIVER BASIN URANIUM MILLS
Mill location Began operation
Rifle, Colorado (old mill) 1947
Rifle, Colorado (new mill) 1958
Uravan, Colorado 1949
Naturita, Colorado 1947
Slick Rock, Colorado 1958
Maybell, Colorado 1957
Gunnison, Colorado 1958
Durango, Colorado 1949
Grand Junction, Colorado 1951
Moab, Utah 1956
Mexican Hat, Utah 1957
Monticello, Utah 1949
Kite, Utah 1949
Green River, Utah 1958
Monument Valley, Arizona 1955
Shiprock, New Mexico 1954
Tuba City, Arizona 1956
24
-------
SECTION V
MINING PROCESSES
OPEN PIT MINING
Open pit mining accounts for slightly more than half of the reserves mined,
and uncovers more ore per mine than does underground mining. In
1969 there were 25 open pit mines and 214 underground mines being
worked.
Open pit mining is used where the ore deposits are near the surface and
covered with loose, easily removable soil. Some open pit mining may be
done at depths of more than 500 feet; but usually, below 300 feet, under-
ground methods are preferred. The ratio of overburden to ore removed
in uranium mines is unusually large as compared to other types of mining
with ranges from 8:1 to 35:1. The expense of removing the larger amounts
of overburden is justified by the greater value of the product being
recovered.
Conventional earth-moving equipment is used for mining: scraper-
loaders , bulldozers, gas and diesel shovels, and rippers. The size of
the mining operation determines to some extent the equipment employed.
In some small ore bodies backhoes are the most economical means of
digging and loading ore.
Ground water intrusion has been a problem in many of the open pit mines.
The water is pumped from the mine to keep the floor surface workable.
A trench several feet deep may be dug around the periphery of the pit
floor and as the ground water drains from the pit floor into the ditch, it
is pumped front,the mine. As the ore is removed to the level of the ditch
depth, the process is repeated. The water is discharged to the surface
to seep into the ground or drain into nearby creeks or rivers.
25
-------
UNDERGROUND MINING
Underground mining is carried out in Utah, Colorado, Wyoming, and
New Mexico with Utah and Colorado supporting three-fourths of the
producing mines, many of which are small. About 70 percent of the New
Mexico production is underground. Underground mining is done on a
small scale in the Gas Hills and Crooks Gap District of Wyoming.
The largest ore bodies mined by underground methods measure as much
as half a mile in length, several hundred feet in width, from 5 to 100 feet
thick, and are located several hundred feet below ground. Many of the
smaller deposits are mined using simple adits in canyon walls with
removal of ore by wheelbarrows. Most mines require shaft entry, but
some ore is mined using inclines and adits. Shafts, located at depths of
800 feet, are generally concrete-lined for lowered maintenance. Stoping
methods are generally used with various forms of room and pillar methods.
When possible, waste or low grade ore is left as pillars. Tunnels extending
from the shaft are supported by steel plate, timber, or concrete, depending
on ground conditions and permanency of the tunnel.
The ore bodies are outlined by underground long-hole drilling of 100 to
300 feet from the underground shaft and tunnels. New tunnels are
placed from the long-hole drilling data. The mine is continually
developed in this manner until the vein is depleted. Ground water from
the ore bodies is pumped to the surface for discharge or used as process-
ing water in the mill. The volume of water pumped from mines may range
from 200 to 3.000 gallons per minute.
Lack of proper ventilation in uranium mines constitutes a hazard since
radon-222, a radioactive gas, is produced as one of the daughter products
of uranium. Without adequate ventilation the gas will concentrate in
i7 18
levels considered hazardous to the miners' health. ' Daughter
products of radon-222 are solids that may deposit on the lung surfaces
until decay. Concern has been expressed that uranium miners may be
26
-------
subject to an increased risk of lung cancer due to radon-222 and its
daughters. Epidemiological studies of lung cancer among miners have
been under way by the U.S. Public Health Service for some years.19
Fans are installed to circulate the air and large-diameter vent holes are
drilled to get sufficient fresh air into the mine.
SOLUTION MINING
Solution mining or in-place leaching is a process by which an acid solu-
tion is pumped into the underground ore body, allowed to solubilize the
desired element, and the pregnant solution recovered by pumping to the
surface. Uranium is extracted from the solution by chemical means.
Since 1963 the Utah Construction and Mining Company has been using a
solution mining process routinely to extract uranium from an under-
20
ground ore body in Shirley Basin, Wyoming. Certain conditions must
exist for solution mining of uranium:
1. Uranium ore must lie in a generally horizontal bed
underlain by a relatively impermeable stratum.
2. The ore must occur below the static water table.
3. The direction and velocity of regional waterflow
must be known.
4. Mineralogy of the ore must be determined to
choose the proper leaching and extracting process.
The well locations and the inflow-effluent rates must be carefully
planned using regional water flow data and experimental drilling. The
Shirley Basin mining operation is composed of three inflow wells up-
gradient from a production well with the center inflow well directly up-
gradient on the regional ground water flow direction. The remaining
two inflow wells are located on radii diverging at an angle of 75 degrees
from one another, equally spaced from the center inflow well. The
distance from the inflow wells to the production well is approximately
25 feet.
27
-------
A five percent sulfuric acid solution is pumped into the inflow wells at
a slightly slower rate than is being withdrawn from the production well.
Sodium chlorate may be added as an oxidant to increase the leaching
efficiency. The flow of solution is continued until the concentration of
uranium in the leach solution decreases, indicating the leach zone is
depleted. Approximately one month is required for depletion of a zone
with three to five well patterns in operation simultaneously. Uranium
recovery approaches 100 percent except when multiple-horizon areas
occur, and upper horizons are not underlain by impervious layers.
The uranium-bearing liquor, containing between 0.10 and 0.30 grams
uranium oxide per liter, is passed through an ion exchange column
for adsorption on a resin. The loaded column is stripped with a mixture
of nitric acid, sodium nitrate, and sulfuric acid. The barren leach solu-
tion is discharged as waste to a tailings pond with no outflow. The strip
solution is then precipitated with a lime or magnesium slurry at pH 7.5;
the precipitate allowed to settle, and separated by decanting. The slurry
is shipped to the mill for further purification. The decant, containing
neutral nitrate salt, is recirculated to eluate makeup with nitric acid.
Solution mining costs approach or exceed those of open pit mining but
are lower than those of underground mining. The operation is much
safer for mining personnel, however. Disadvantages are that the proper
ground conditions for recovery must be present for utilization of the
process. Also, in poor recovery zones, injected solution may be lost
in multiple ore horizons and underground fractures, thus becoming a
contaminant to ground waters. Solution mining can be used on mined-out
stopes and tunnels of underground mines by flooding with leach solution
and then pumping the loaded solution out of the mine for extraction of
the uranium. Natural leaching of uranium ore by the ground water
results in uranium concentrations containing up to ten parts per million
that may be extracted by ion exchange processes.
28
-------
Bacterial leaching, a solution mining technique, involves the oxidation
of pyrite (FeS2> in the presence of water to form ferrous sulfate and
sulfuric acid. Certain acid tolerant bacterial species are capable of
further oxidizing ferrous sulfate to ferric sulfate, which in turn oxidizes
the insoluble tetravalent uranium to the acid soluble hexavalent state.
In practice, mines are flooded with water which gradually decreases in
pH to between 1.8 and 3.5 as sulfuric acid is formed. The pregnant
mine water is pumped to an ion exchange extraction circuit for uranium
separation.
Studies in Canada have been conducted to determine whether the bacterial
? "1
leaching process could be used in the mill with run-of-mine ore. Sul-
furic acid requirements for leaching were reduced from 80 pounds per
ton to 25 pounds per ton. Underground bacterial leaching has been
used in Canada with success, but is unlikely to supersede conventional
mining and milling methods due to the long period of time required for
22
efficient leaching. The chief uses have been to scavenge worked-out
mines, caved areas, or low grade materials above or below ground that
are uneconomical to treat by conventional methods. The process also
holds promise for the recovery of uranium from material rejected by
flotation, heavy media, electronic sorting, or other upgrading processes.
The bacterial leaching of United States ores may never be effective
because most presently known reserves contain insufficient pyrite and
an abundance of neutralizing calcium carbonate.
Stockpiles of low grade ore removed from mines may be profitably proc-
essed by heap leaching . ' Heap leaching does not require a large
capital expenditure for equipment and manpower requirements are
minimal. Heap leaching has been practiced by the Utah Construction
and Mining Company and Western Nuclear, Incorporated in Wyoming.
A typical heap leaching pile is constructed by grading the ground at
the site area to a smooth sloping surface. The area, approximately 300
feet wide by 700 feet long, is covered by a polyethylene sheet of six mil
29
-------
thickness, Four-inch perforated plastic pipe is placed parallel to the
width at 18 foot centers. The pipe is covered with one foot of gravel
followed by emplacement of low grade ore to a depth of approximately
25 feet. The top of the pile is graded and divided into sections of 300
feet by 60 feet with dikes made from the ore. A sulfuric acid solution is
placed in the diked sections of the pile, allowed to percolate through the
ore, collected by drainage from the pipes, and removed to storage tanks.
The uranium is extracted from the leach solution by conventional solvent
extraction or ion exchange methods. Waste acidic solutions are recycled
through the pile for maximum leaching efficiency. The final strip solu-
tion contains approximately 25 grams of uranium per liter that may be
further processed by a mill. Airborne radiation surveys are made
during the operation of the system to check for radon-222 in the air.
The pile, containing approximately 250,000 tons of ore, is abandoned as
leaching operations are completed. The residual material contains less
than 0.05 percent uranium. Western Nuclear's facility produces approxi-
mately 12,000 pounds of uranium per month at the Day Loma heap leach
site.
30
-------
SECTION VI
MILLING PROCESSES
The uranium recovery process varies from mill to mill depending upon
the presence of undesirable constituents in the gangue of the ore or other
valuable constituents to be recovered. The milling process may be
broken down into separate circuits; each of the operating mills is
composed of various combinations of circuits as shown in Table 15. The
organic extractants and precipitating agents utilized are listed in the
respective columns. Uranium precipitates containing sodium impurities
are further purified by acid dissolution followed by reprecipitation with
ammonia. As far as possible, the process solutions are recovered and
recycled in the milling processes. The remainder is discharged as
waste to the disposal area along with leached sands and slimes and
dissolved constituents from the ore.
Flow diagrams of various milling processes are shown in Figures 3
through 9. The flowsheets reflect only the sand-slime discharges to the
tailings pond. Recycling of process solutions within the plant is not
shown because of mill variations in volume, chemical content, and
point of discharge to tailings pond. Unrecycled process solutions are
used to carry sand and slimes to the tailings area. Additional water is
added as necessary to supplement process solutions in slurrying the
solids for transport to the tailings pond. Excessive chemical buildup
in the recycled mill solutions from the dissolution of minerals in the
ore is prevented by discharging a portion of the solution to the tailings
pond and replenishing that volume with additional water and chemicals.
A number of mills reuse tailings pond water following removal of the
suspended solids.
31
-------
Table 15. URANIUM MILLING PLANTS AND PROCESSING OPERATIONS
Mill and location
Processes used
Leaching Liquid-solid Ion
process separation exchange
Colorado:
Cotter Corp . (dual process)
Union Carbide Corp. , Rifle
Union Carbide Corp . , Uravan
New Mexico:
The Anaconda Co .
Kerr-McGee Corp.
United Nuclear-Homestake Partners
South Dakota:
Mines Development, Inc.
Texas:
Susquehanna-Western, Inc. , Falls City
Susquehanna-Westem, Inc . , Three Rivers
Utah:
Atlas Corp. (dual process)
Washington:
Dawn Mining Co.
Wyoming:
Federal American Partners
Petrotomics
Union Carbide Corp .
Utah Construction and Mining Co. , Gas Hills
Utah Construction and Mining Co. , Shirley Basin
Western Nuclear, Inc.
AL Drum filters
ALKL Drum filters
AL CCD
AL CCD DC
AL CCD RIP
AL CCD
ALKL Drum filters
AL CCD RIP
AL CCD
ALKL Drum filters —
AL CCD
ALKL RIP
AL CCD RIP
AL CCD RIP
AL CCD
AL CCD RIP
AL CCD DC
AL CCD DC
AL CCD RIP
Solvent
extraction
EHPAb
EHPA
AMINE
___
EHPA
AMINE
—
AMINEC
___
—
AMINE
AMINE
SX
AMINE
AMINE
Eluex
process Precipitation
NaOH, H-SO., NH-
NaOH * J
NH3
MgO
NH,
NaOH, H2SO4, NH,
Yes H202
NH3
NH3
NH3
NH3
Yes NH,
NH,
Yes NH?
Yes NHf
NH, or MgO
Yes 3 NH3
a AL - Acid Leach NaOH - sodium hydroxide
ALKL - Alkaline Leach H2SO4 ~
CCD - Countercurrent Decantation NH-
RIP - Resin in Pulp MgO
DC - Column Ion Exchange H2°2
SX - Solvent Extraction
sulfuric acid
ammonia gas
magnesium oxide
hydrogen peroxide
The loaded strip solution is combined with the filtered alkaline leach solution from the alkaline mill process for precipitation.
C The loaded strip solution is combined with the loaded strip solution from the alkaline-RIP circuit for precipitation.
-------
CRUSHING AND GRINDING
ACID LEACH
LI QUID-SOLID SEPARATION
SOLVENT EXTRACTION
PRECIPITATION
DRYING AND PACKAGING
Sands
Slimes
TAILINGS
POND
Figures. PROCESS FLOW DIAGRAM A
33
-------
CRUSHING AND GRINDING
SAND-SLIME SEPARATION
Slimes
t
RESIN-IN-PULP
ION EXCHANGE
PRECIPITATION
DRYING AND PACKAGING
— Sands
TAILINGS
POND
Slimes
Figure 4. PROCESS FLOW DIAGRAM B
34
-------
CRUSHING AND GRINDING
ACID LEACH
SAND-SLIME SEPARATION
— Sands
Slimes
t
RESIN-IN- PULP
ION EXCHANGE
— Slimes
CLARIFICATION
Fine
Solids
SOLVENT EXTRACTION
PRECIPITATION
DRYING AND PACKAGING
Figure 5. PROCESS FLOW DIAGRAM C
TAILINGS
POND
35
-------
CRUSHING AND GRINDING
ACID LEACH
LIQUID-SOLID SEPARATION
Sands 8
Slimes
TAILINGS
COLUMN
ION EXCHANGE
PRECIPITATION
DRYING AND PACKAGING
Figure 6. PROCESS FLOW DIAGRAM D
36
-------
CRUSHING AND GRINDING
I
ACID LEACH
i
LIQUID-SOLID SEPARATION
COLUMN ION EXCHANGE
SOLVENT EXTRACTION
PRECIPITATION
DRYING AND PACKAGING
H_ Sands
Slimes
Figure 7. PROCESS FLOW DIAGRAM E
37
-------
CRUSHING AND GRINDING
ALKALINE LEACH
LIQUID-SOLID SEPARATION
FIRST PRECIPITATION
SECOND PRECIPITATION
DRYING AND PACKAGING
L SondsB
Slimes
TAILINGS
POND
Figure 8. PROCESS FLOW DIAGRAM F
38
-------
CRUSHING AND GRINDING
ALKALINE LEACH
SAND-SLIME SEPARATION
Slimes
t
RESIN-IN- PULP
ION EXCHANGE
PRECIPITATION
DRYING AND PACKAGING
Sands
TAILINGS
POND
Slimes
Figure 9. PROCESS FLOW DIAGRAM G
39
-------
ORE HANDLING
The majority of operating mills in the United States blend the ore to some
degree before delivery to the mill for crushing and processing. Blend-
ing is performed to provide a grade of ore with more uniform physical
characteristics and uranium content. Radiometric analysis of the ore
as loaded onto the trucks establishes the grade which varies from less
than 0.10 percent uranium oxide to greater than 1.0 percent. The ore
may be stockpiled in a manner to provide a uniform grade of approximately
0.25 percent to the crusher. Ores can be hard, slimy, or sandy, which
may cause difficulty in the milling circuits. Hard ores limit the capacity
of the grinding circuits, slimes interfere in ion exchange circuits, and
sandy ores settle too rapidly in pipelines causing plugging. Blending
eliminates extremes and allows a smoothly flowing process to be main-
tained .
CRUSHING AND GRINDING OF ORE
The ore is moved from the stockpiles to the crusher feed by means of
front-end loaders or bulldozers or by trucks to receiving bins. Jaw
crushers ranging from 15 to 40 inch size are used as primary units but
may be bypassed for fine ore. Grizzly circuits are employed to screen
and remove undersize material from the crushing circuit, bypassing the
fine ore to storage bins. Both impact-type and cone or gyratory crushers
are also used as required by ore type.
Moisture content is important in the crushing operation and should be in
the range of five to ten percent. Some ore must be dried before crushing
by either kiln drying or natural drying. After crushing to sizes of
approximately 1/4 to 1 inch, the ore is carried by a conveyer belt to the
fine ore bins where it is held until needed for processing.
Some mills employ a roasting circuit for use with special types of ore.
Pretreatment of lignite ores by roasting improves the leaching character-
istics . Improved settling and filtration characteristics of clay minerals
40
-------
are obtained by roasting. Vanadium-bearing ores require a salt-roasting
process to improve the solubility of vanadium. Carbonaceous ores are
roasted to remove organic carbon and prevent contamination of leach
solutions.
The roasting circuit consists of feeding the ore from the crushing circuit
through a rotary kiln at a temperature of 600° F and returning the ore to
the grinding circuit. The roasting circuit is bypassed when not needed
with the ore going directly from the crushing to the grinding circuit.
The ore is carried by belt-type feeders at the desired feed rate to the
grinding circuit and sampled at some point between the crushing and
grinding circuit for laboratory analysis. Rod mills and ball mills are
used almost exclusively for grinding the ore to approximately 28 mesh
for an acid leach process and 200 mesh for an alkaline leach process.
Water is added to obtain a slurry of approximately 65 percent solids for
grinding. Recycled acidic wash solutions from other plant circuits are
sometimes added to reduce the water requirements. Classifiers are some-
times placed in a closed circuit with the grinding equipment to size the
ore and return coarser particles for further grinding. In some instances,
the pulp density in the grinding circuit is different from that required
for the leaching circuit and must be adjusted by means of cyclones and
thickeners.
ACID LEACH
The leaching process selected for removal of uranium from the ore is
dependent on the physical and chemical characteristics of the ore. Among
these are the type of uranium mineralization, ease of liberation, and the
nature of other constituent minerals present. The most important factor
in choosing the leaching process, however, is based on the lime content
of the ore. Ores with low lime content (12% or less) are leached with
acid, while those with a high lime content require large quantities of
41
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acid for neutralization purposes; hence, employ the alkaline leach proc-
ess for economic considerations. Sulfuric acid, rather than hydrochloric
or nitric, is commonly utilized for leaching purposes due to its less
corrosive nature and lower cost.
Uranium in the ore in the tetravalent form must be oxidized to the hexa-
valent state before dissolution occurs. Iron present in the ore or intro-
duced from wear of the metal in the grinding circuit serves as the
principle oxidant. to be effective, however, the iron must be present
in the oxidized or ferric state. Sodium chlorate or manganese dioxide
is employed for this purpose. The oxidation-reduction potential (emf)
of the ore slurry is important and should lie within the range of -400 to
-500 millivolts. Failure to maintain uranium in the hexavalent state
throughout the leaching process will result in premature precipitation.
The ore slurry is pumped into the leach circuit maintaining a pulp
density of 50 percent solids ground less than 28 mesh. Leaching is
performed in a series of wooden tanks equipped with agitators. Sulfuric
acid is added in an amount to maintain a free acid concentration ranging
from 1 to 90 grams acid per liter (40 to 120 pounds per ton) . Higher
acid concentrations are used for vanadium extraction due to its greater
insolubility.
CARBONATE LEACH
As mentioned previously, the alkaline sodium carbonate leaching process
is utilized for ores containing excessive amounts of lime. Since many of
the minerals in the ore do not react with the carbonate^solution, the ore
•I.
must be ground much finer so as to expose more uranium mineral surface
area for efficient leaching. The ore is normally ground to 70 to 80 percent
less than 200 mesh size. Factors that affect the leaching rate of uranium
are temperature, pressure, contact time, oxidation, reagent concentra-
tion, degree of agitation, fineness of grind, and pulp density. Due to
the selectivity of the carbonate leach solution, uranium may be precipi-
tated without further treatment following liquid-solid separation.
42
-------
The carbonate leaching process consists of the transfer of a 65 percent
slurry from the grinding circuit to a thickener circuit that adjusts the
slurry to about 55 percent solids. Carbonate solution from the precipi-
tation circuit is adjusted for chemical content and recycled to the grind-
ing circuit to make the slurry.
The adjusted slurry is pumped to a series of Pachuca leach tanks and
heated to 180° F with steam. The leach solution contains 40 to 50 grams
of sodium carbonate per liter and 10 to 20 grams of sodium bicarbonate
per liter. Bicarbonate is added to prevent reprecipitation of the dissolved
uranium through reaction with the hydroxyl ion. Air is bubbled through
the solution to oxidize uranium from the tetravalent to the hexavalent
state. The circular tanks are 20 feet in diameter and 40 to 60 feet deep;
pressure from the solution depth increases the leaching rate. Leaching
time varies from 24 to 72 hours depending on the ore characteristics and
plant operating conditions. Pressure leaching prior to or following the
atmospheric leaching process is used to increase the rate of leaching in
some milling circuits.
LIQUID-SOLID SEPARATION
After the ore has been processed through the acid leach or carbonate
leach circuit, the loaded leach liquid must be separated from the sands
and slimes prior to entering ion exchange or solvent extraction circuits.
The resin-in-pulp ion exchange process represents an exception to the
separation procedure in that the slimes do not have to be removed from
the leach slurry.
Separations are accomplished by countercurrent decantation washing
in cyclones, classifiers, and thickeners, or by filtration. Counter-
current decantation washing procedures are the most efficient and current
means of separating solids from acid leach liquid. The method is used in.
all but one of the,acid leach process mills with washing efficiencies
better than 99 percent. The circuit usually has five or more stages of
43
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countercurrent washing in which the wash solution and solids flow in
opposite directions . Flocculants are added to increase separation rates.
Pressure precoat filters or activated carbon are used to further clarify
the feed solution for the Amex solvent extraction process.
Complete separation of liquid and solids is unnecessary for resin-in-pulp
ion exchange processes. Cyclones and classifiers are used to separate
sands from slimes of less than 325 mesh size. Sands are wasted to the
tailings pond.
Alkaline leach liquids and solids are separated by vacuum drum filtration
to minimize the volume of wash water required. The solids are repulped
and wasted to the tailings pond.
ION EXCHANGE
Ion exchange circuits are employed to concentrate and purify the leached
uranium. Strong and intermediate base anionic type resins are loaded
from either a sulfuric acid or a carbonate leach feed solution. The loaded
resin is stripped with a chloride, nitrate, bicarbonate, or an ammonium
sulfate-sulfuric acid solution.
Four types of ion exchange circuits are utilized by the processing mills.
The fixed-bed type consists of stationary columns packed with resin. As
the feed solution passes through, uranium is sorbed on the resin. The
resin is washed and the uranium desorbed. The extraction columns are
sensitive to plugging by solids in the feed solution. The moving-bed
column circuit has stationary columns, but resin is transferred to differ-
ent columns to perform loading, washing, and eluting operations. In
the continuous resin-in-pulp process, sorption, washing, and desorption
are performed by contacting the resin and process solutions in a series
of tanks. The resin and solution flow countercurrently in the tanks and
are separated by screens . Forced air is employed for agitation. The
basket resin-in-pulp process utilizes a series of resin-filled cubical
baskets that are jigged up and down in the process solution contained
44
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in tanks. Feed slurry, eluant, and wash solution are circulated through
the tanks to extract the uranium. Both of the latter processes will toler-
ate high solids content in the feed solution.
SOLVENT EXTRACTION
Two solvent extraction processes, the Dapex and the Amex, are currently
used in about one-half of the mills to concentrate and purify uranium. The
processes are efficient, economical, and readily adaptable to automatic
control; however, the feed solution must be essentially free of solids.
The uranium is extracted from the clarified feed solution into the organic
phase followed by stripping operations into an aqueous phase. The cir-
cuit consists of a series of extraction tanks in which the feed solution
flows continuously countercurrent to the organic solvent for maximum
extraction efficiency. Phase separation is improved by optimizing
mixing rates of solutions and by installing settlers in the circuit.
The Dapex extraction process employs the alkyl phosphoric acid
extractant, di(2-ethylhexyl) phosphoric acid (EHPA) at a four percent
concentration in kerosene with tributyl phosphate (TBP) added as a
modifier. The modifier improves the phase separation and increases
the efficiency of the uranium extraction. Long chain alcohols such as
isodecanol are also used as modifiers. The extraction circuit will toler-
ate suspended solid concentrations in the feed solutions of 300 ppm
without interference. The loaded organic is stripped of uranium with
a sodium carbonate solution and recycled to the extraction stage of the
circuit for reuse.
The Amex process consists of an amine extraction followed by stripping
with ammonium sulfate, chloride, or sodium carbonate solutions . A six
percent concentration of a tertiary amine such as almine-336 in a kerosene
diluent is used as the organic extractant. Isodecanol is added as a
modifier. Stripping with ammonium sulfate at a controlled pH of 4.0 to
4.3 eliminates sodium impurities .
45
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ELUEX PROCESS
The Eluex process is a combination ion exchange-solvent extraction
process. The eluate produced by sulfuric acid elution of the ion exchange
resin is fed to either the Dapex or Amex solvent extraction process. The
Eluex process eliminates the requirement for nitrate and chloride reagents,
thus preventing potential pollution by these elements. Additionally, a
purer end product is obtained.
PRECIPITATION
Uranium is precipitated from solution by addition of sodium hydroxide,
gaseous ammonia, hydrogen peroxide, or magnesia. Several stages of
precipitation at controlled pH are often used with the pH being readjusted
in a precipitation tank near the end of the circuit. Gaseous ammonia is
used as the precipitating agent in most mills. When sodium hydroxide
is used to precipitate uranium, resolution with sulfuric acid followed by
reprecipitation with gaseous ammonia produces a purer product with
little sodium remaining.
DRYING AND PACKAGING
The slurry from the precipitation circuit is dewatered in thickeners
followed by drum, plate, or frame filters. The filtercake is repulped
and transferred to a multiple hearth dryer operating at 700° to 800° F.
The dried product containing approximately 96 percent uranium oxide
is crushed and sealed in shipping drums.
SECONDARY METAL RECOVERY
In several instances, other metals are present in uranium ores in
sufficiently high concentrations to warrant economic extraction. The
Atlas Corporation mill at Moab, Utah, extracts copper as a by-product
by means of a flotation circuit. Copper, cobalt, and nickel are recovered
from the acid leach process solutions by the Cotter Corporation at Canon
City, Colorado. Vanadium is extracted at two Union Carbide mills at
46
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Uravan and Rifle, Colorado, and also by the Mines Development Corpora-
tion mill in South Dakota. Molybdenum is present in some ores in con-
centrations sufficient to cause fouling of the extraction circuits in the
mills and must be stripped. Concentrations of molybdenum in ores
mined in Texas are sufficient to justify by-product recovery.
47
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SECTION VII
REFINING PROCESSES
Uranium concentrate must be further purified and converted to uranium
hexafluoride before utilization as a feed for gaseous diffusion plants.
The process is performed in government-owned operations and two
commercially-owned refineries, the Allied Chemical Corporation plant
on the Ohio River at Metropolis, Illinois, and the Kerr-McGee Corporation
facility on the Illinois River at Gore, Oklahoma. The commercially-
operated plants will be discussed below.
In the Kerr-McGee process the uranium concentrate feed is digested with
hot nitric acid to solubilize uranium and countercurrently extracted with
24
tributyl phosphate in hexane. The loaded organic is then stripped of
uranium with water, concentrated in a two-stage heating process,
dehydrated and denitrated in a stirred reactor to form pure uranium
trioxide. Next, uranium trioxide is fed to a two-stage fluid bed opera-
tion at approximately 1100° F, and reduced to uranium dioxide by counter-
current flow of dissociated ammonia. Conversion to uranium tetrafluoride
is accomplished by countercurrent contact with a stream of anhydrous
hydrogen fluoride gas. Final conversion to uranium hexafluoride is by
contact with fluorine gas in a series of fluorination towers. The gaseous
product is cooled and filtered twice by sintered metal particulate filters,
condensed to a solid at 50° F in a cold trap, and sealed in 10-ton cylinders
for shipping. The Gore, Oklahoma, facility is presently processing
approximately 5,000 tons per year of uranium concentrate, but can be
expanded to 10,000 tons per year.
The primary waste from the refining process is the raffinate from the
solvent extraction circuit. The solution contains approximately one
molar concentration of nitric acid, nitrates, radium-226, and other
radioactive impurities. The waste is permanently retained in an evap-
oration pond after neutralization with lime. Injection well waste disposal
is planned to replace evaporation ponds, if approval can be obtained.
48
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The waste solution from the fluorination process, containing 0.3 percent
hydrofluoric acid, is treated with calcium fluoride. Sulfuric acid is
then added to precipitate excess calcium and to neutralize the effluent
before discharge.
Large quantities of cooling water are used in the plant and returned to
the river with little change in temperature. Contaminated air is passed
through vacuum transfer and cleaning systems prior to atmospheric
discharge.
The Allied Chemical process eliminates the acid dissolution and solvent
extraction purification steps. The uranium concentrate is reacted in
a series of fluid beds, reduced to uranium dioxide, and converted to
crude uranium hexafluoride. The crude product is purified by frac-
tional distillation. Raffinate wastes are eliminated in the process since
a solvent extraction circuit is not used. Uranium concentrate impurities
are present in purification circuit wastes.
A refinery produces liquid wastes containing 5.2 grams radium-226 per
kiloton of processed alkaline leach concentrate and 0.26 grams per kilo-
ton of processed acid leach concentrate. In comparison, a mill produces
liquid waste containing 0.1 grams of radium-226 per kiloton of alkaline
leach concentrate and 0.77 grams per kiloton of acid leach concentrate.
This estimate demonstrates that dissolved radium-226 in refinery wastes
can be greater than in uranium mill wastes.
Small losses of uranium in liquid wastes and air may occur but should
be far below the allowable maximum permissible concentration. Although
the concentration is low, uranium will be the chief contributor to the
gross alpha activity of the waste and will mask alpha activity of radium-
226.
49
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SECTION VIII
WASTE CHARACTERISTICS
In-plant surveys were conducted in uranium mills representing all of the
typical processing methods in 1962. Findings from the studies, as well
as others, were used in the assembly of a waste guide manual for the
26
uranium industry. While milling processes have changed to some
extent through the development of new technology, the processes used
today are basically similar to those in use at the time of the 1962 surveys.
The waste characteristics will be discussed below according to types of
waste products.
MILL PROCESS EFFLUENTS
During processing, one to three percent of the ore is dissolved in the
mill process water. Other chemicals used in the milling process con-
tribute to the dissolved solids content of the effluent. Concentrations
vary according to the leaching process utilized. During leaching of the
ore with sulfuric acid solutions, a large portion of the acid is consumed
in chemical reactions and cannot be reused for extraction purposes.
Additionally, large volumes of water are utilized in countercurrent
decantation washing of the leached ore solids. The spent acid and wash
waters are discharged to tailings ponds in volumes of approximately
1,000 gallons per ton of ore processed.
The alkaline leach process utilizes a sodium carbonate-sodium bicarbonate
leaching solution to extract uranium from the ore solids. The solution is
not consumed in the process and is reusable following separation of the
uranium and recarbonation. Ore solids are separated from the leach
liquor by a filtration process rather than washing, thus reducing water
requirements to 250 gallons per ton of ore processed. To prevent a
buildup of dissolved solids, a portion of the alkaline leach process
water is discharged to the tailings pond and fresh water added to
replenish the volume. Tailings pond water is returned to the mill to
reslurry sands and slimes for disposal.
50
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Other milling process solutions from the precipitation, solvent exchange,
and ion exchange circuits are partially recovered and recycled
SANDS AND SLIMES
The spent ore solids are discharged to the tailings pond as a slurry by
mixing with water or mill process effluents. Approximately 97 percent of
the ore processed through the mill leaching circuit remains in a solid
form and is discharged from the mill to the tailings pond as spent ore
solids—80 percent sands and 20 percent slimes.
SUSPENDED SOLIDS IN MILL EFFLUENTS
The greater majority of solid particles settle to the bottom of the pond
leaving an apparently clear liquid. However, a small amount of fine ore
particles are held suspended in the mill effluent or are resuspended from
settled solids through agitation of the liquid. The weight of these solids
varies from 10 to 500 milligrams per liter.
MINE WATER DRAINAGE
Mining operations for uranium are being performed at greater depths as
ore near the surface is being depleted. At the deeper depths, ground
water often flows through the ore bodies and dissolves chemical constit-
uents from the ore. 'The water must be pumped from the mining area to
permit removal of the ore. Mine water is discharged from mines in the
Ambrosia Lake area of New Mexico at a rate of five million gallons per
day.27 Open pit mines in the Gulf Coast Area of Texas release 840,000
gallons per day. The mine water is usually discharged to the surface to
flow into a nearby waterway or seep into the ground. Mine water from an
operating mine is pumped into a nearby abandoned mine by a company
in the Texas Gulf Coast Area. Uranium is recovered from mine water by
ion exchange methods at several locations prior to discharge.
AIRBORNE RADIOACTIVITY
Airborne radioactivity in the form of a gas or fine solid particles is found
in uranium mines, in areas of stockpiled ore awaiting processing, and in
51
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waste disposal areas. Radioactive dust is found in mill areas concerned
with crushing and grinding, precipitation, and packaging. In the
surrounding vicinity of the mill, airborne radioactivity may be created
by mining operations, or by wind erosion of the stockpiled ore or the
dry tailings solids.
The radioactive gas emitted from the ore is found in the greatest concen-
trations in restricted areas of poor ventilation, such as underground
mines. The gas will also accumulate around stockpiled ore and tailings
areas under conditions of limited air movement.
52
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CHEMICAL CLASSIFICATION OF WASTES
INORGANIC POLLUTANTS
The sources of inorganic pollutants in mill discharges are chemicals
utilized in the milling process and solubilized materials from the ore.
Inorganic chemicals employed in both the acid and alkaline leach proc-
esses are listed in Table 16. Metallic elements that may be solubilized
during the milling process are enumerated in Table 17. Some mills
economically recover a number of these elements, thus reducing a
potential source of pollution. Chlorides, nitrates, and sulfates are also
solubilized during the milling process.
The milling process chemicals are somewhat different from those used
several years ago. Ammonium sulfate has replaced ammonium nitrate
in most current milling processes. Air is used as the oxidizing agent in
the alkaline leach process rather than chemicals. The majority of the
mills employ ammonia for precipitation of the uranium.
ORGANIC POLLUTANTS
Organic chemicals are introduced into the processing circuit during
liquid-solid separation and solvent extraction. The chemicals used are
listed in Table 16. Organic extractants are recycled in the milling
process. Due to incomplete phase separation, however, the organic
loss is approximately one-half gallon per 1,000 gallons of solution pass-
ing through the solvent extraction circuit.
RADIOACTIVE POLLUTANTS
The average grade of uranium-bearing ore is 0.22 percent uranium
oxide.28 The uranium is present as uranium-238 and uranium-234 from
the uranium-radium family and uranium-235 from the uranium-actinium
family. Natural uranium contains 99.28 percent uranium-238, 0.0057
53
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Table 16. CHEMICALS USED IN MILLING OPERATIONS
Acid leach process
Alkaline leach process
Acid Leach Circuit:
sulfuric acid
sodium chlorate
Liquid-Solid Separation Circuit:
polyacrylamides
guar gums
animal glues
Ion-Exchange Circuit:
strong base anionic resins
sodium chloride
sulfuric acid
sodium bicarbonate
ammonium nitrate
Solvent Extraction Circuit:
tertiary amines
(usually alamine-336)
alkyl phosphoric acid
(usually EHPA)
isodecanol
tributyl phosphate
kerosene
sodium carbonate
ammonium sulfate
sodium chloride
ammonia gas
hydrochloric acid
Precipitation Circuit:
ammonia gas
magnesium oxide
hydrogen peroxide
Alkaline Leach Circuit:
sodium carbonate
sodium bicarbonate
Ion-Exchange Circuit:
strong base anionic resins
sodium chloride
sulfuric acid
sodium bicarbonate
ammonium nitrate
Precipitation Circuit:
ammonia gas
magnesium oxide
hydrogen peroxide
54
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Table 17. METALS LEACHED FROM ORE BY MILLING PROCESS4' 26
Magnesium
Copper
Manganese
Barium
Chromium
Molybdenum
Selenium
Lead
Arsenic
Vanadium
Iron
Cobalt
Nickel
percent uranium-234, and 0.71 percent uranium-235. The uranium-
radium family is of primary concern as a radioactive waste since it is
the major constituent of natural uranium in the ore.
Uranium-238 is the first member of a long series of radioactive isotopes
which decay to stable lead-206. The series contain eight alpha emitters
and six beta emitters. The decay chain for the radioactive family is
shown in Figure 10. Two minor branches occur but are not shown
because their effect is negligible. As seen in Figure 10, uranium-238
decays by an alpha emission to thorium-234 with a half-life of 4.5
billion years; the thorium-234 decays by beta emission to protactinium-
234 with a half-life of 24.1 days; the protactinium-234 decays by beta
emission to uranium-234 with a half-life of 1.1 minutes with decay con-
tinuing until stable lead-206 is formed. Most ores occur with the members
of the radioactive family in equilibrium, the state that prevails when the
ratios between the amounts of successive members of family remain
55
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U2?8 Thi51__ Pa2!4. _ U^f _
92 Alpha 90 Beta 9I Beta 92 Alpha
4.5 x I09yr 24.1 day I.I min 2.5 x I05yr
RQ226 Rn222 P02I8 pb2!4
"*~88 *~ 86 *^84 "^82
c
Alpha Alpha Alpha Alpha
8.0 x IQ4 yr 1620 yr 3.8 day 3.05 min
Bi!!! ^ Po?!! _Pb!^ Br2l°
^83 ^84 ^2 ^83
Beta Beta Alpha_^ Beta
26.8 min 19.7 min 1.6 x 10" sec 22 yr
Po2!? Pb206
— 84 ^-82
Beta Alpha STABLE
5.0day 140 days
Figure 10. URANIUM-RADIUM FAMILY (minor branches not shown)
-------
constant. One million years are required to obtain the equilibrium.
Natural leaching by ground water of some members of the family may
disturb the equilibrium and has occurred in some ores.
Uranium-238 has an alpha activity of 152 microcuries per pound. If the
series is in equilibrium, each of the daughters will have the same
activity. The eight alpha emitting daughters will have an activity of
1,216 microcuries per pound of uranium and the six beta emitting
daughters will have an activity of 912 microcuries per pound, resulting
in a total alpha and beta activity of 2,128 microcuries per pound of
uranium: As only uranium is recovered from the ore, the other radio-
active members of the family are discharged as waste. The activity of
the recovered alpha-emitting uranium isotopes is 304 microcuries per
pound, resulting in the discharge as mill waste of the other 12 alpha and
beta-emitting isotopes with an activity of 1,824 microcuries per pound;
hence, 85 percent of the total activity is contained in the mill waste.
Because of the importance of radium-226 as a pollutant, a detailed survey
was made with one of the main objectives to determine the radium distri-
25
button throughout the milling process. A study of an acid leach proc-
ess revealed that 0.2 to 0.4 percent of the radium contained in the ore
was dissolved; 0.05 to 0.10 percent was precipitated along with the
uranium concentrate, and 0.15 to 0.30 percent was discharged to the
tailings pond in the liquid waste from solvent extraction or ion exchange
circuits. The remaining 99.6 to 99.8 percent of the radium was dis-
charged into the tailings pond in sands and slimes. It was also deter-
mined that the radium-226 distribution between the sands and slimes
was 20 and 80 percent, respectively.
A greater amount of radium is dissolved from the ore in an alkaline leach
process. From the study it was found that 1.5 to 2.0 percent of the radium
was dissolved and precipitated with the uranium concentrate. The remain-
ing 98.0 to 98.5 percent was discharged into the tailings pond in the sands
and slimes. Although none of the mill surveys were performed at an alka-
line leach mill using an ion exchange circuit, it is probable that the
57
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majority of the dissolved radium would be separated from the uranium
at this point, thus producing a uranium concentrate with much less
radium present.
Using 0.22 percent as the average grade of uranium oxide in ore, the
radium-226 concentration in the ore is 0.6 milligrams per ton of ore
processed. The uranium ore processing plants operating in 1971, with
a maximum production capacity of 27,650 tons per day, had a discharge
potential of 16.0 grams of radium per day in the mill waste.
Since uranium is the radionuclide being recovered, only small quantities
will be present in the waste material. An extraction circuit is being
installed in one of the Texas mills to recover the small amount of
uranium discharged.
The distribution of the other members of the uranium-radium family
in the mill waste streams has not been investigated to the extent of
radium-226. Laboratory analyses were performed on mill effluents
from mills located in the Colorado River basin for several years by the
Colorado River Basin Project Laboratory located in Salt Lake City,
Utah. Results of analyses in Tables 18 through 22 illustrate the levels
of concentrations typical of uranium mill effluents. The effluents were
processed through waste treatment circuits for radium-226 removal prior
to laboratory analysis.
Table 23 shows concentrations of radium-226 in mill effluent suspended
solids. The concentration is also expressed as picocuries of radium in
suspended solids contained in one liter of effluent. The radium content
from suspended material is, in general, significantly greater than the
dissolved radium content after waste treatment.
Radon-222, the daughter of radium-226, is a radioactive gas and may
be found in poorly ventilated areas. The isotope is of greatest concern
in underground mining operations. It may be seen from Figure 10 that
radon-222 has four, short, half-life daughters: polonium-218, lead-214,
58
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bismuth-214, and polonium-214. The daughters of radon-222 are solids,
but when formed in air, attach quickly to any solid surface, such as dust
particles. In this manner the radionuclides may remain suspended for
prolonged periods.
59
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Table 18 . MILL EFFLUENT NO. 1
Sample
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
Ra-226
pc/1
8.8
21.2
13.0
23.2
10.8
7.5
12.0
10.0
13.0
21.0
8.4
13.0
14.0
17.0
14.0
8.5
10.8
18.7
U
Ug/1
830
160
220
500
88
50
400
680
490
1,800
1,400
740
510
410
360
140
32
510
Pb-210
pc/1
1,020
660
396
920
207
120
250
552
790
910
430
500
840
1,250
1,090
460
2
773
Po-210
pc/1
707.0
606.0
232.0
198.0
135.0
19-0
4.4
85.0
99.0
70.0
210.0
336.0
340.0
-
990.0
77.0
2.2
528.0
Th
(alpha)
pc/1
54.0
54.0
90.0
117.0
19.0
16.0
20.0
5.2
9.4
300.0
120.0
21.0
17.0
10.0
24.0
13.0
3.3
21.0
Gross
alpha
pc/1
1,100
700
340
400
230
71
480
860
700
2,000
2,200
760
600
800
940
380
88
1,100
Gross
beta
pc/1
2,100
1,400
1,000
1,700
810
690
1,100
1,400
1,500
2,900
2,000
1,700
2,000
2,700
2,400
1,200
780
2,300
Table 19. MILL EFFLUENT NO. 2
Sample
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
Ra-226
pc/1
29
15
16
11
33
15
65
1
57
21
31
18
46
36
U
yg/i
3,500
3,800
1,500
2,100
26,000
1,400
3,000
950
2,600
1,100
1,200
1,200
850
1,300
Pb-210
pc/1
6.2
5.0
0.0
4.0
14.0
0.0
53.0
0.6
36.0
6.6
7.5
0.5
5.0
2.9
Po-210
pc/1
2.6
4.5
2.7
2.8
2.4
0.2
1.2
0.5
3.6
0.8
4.2
0.1
1.9
—
Th
(alpha)
pc/1
364.0
3,680.0
42.0
32.0
71.0
330.0
280.0
1.4
2,700.0
250.0
390.0
1.2
5.6
17.0
Gross
alpha
pc/1
2,100
5,200
680
830
16,000
810
3,700
1,010
5,300
2,500
2,400
930
850
1,300
Gross
beta
pc/1
4,200
3,400
920
910
16,000
930
1,500
330
2,200
860
1,900
1,100
970
1,100
60
-------
Table 20. MILL EFFLUENT NO. 3
Sample
No.
1
2
3
4
5
6
7
8
9
Ra-226
pc/1
15.0
4.4
7.3
13.0
28.0
26.0
40.0
20.0
25.0
U
yg/i
2,500
1,900
1,900
2,300
2,900
1,400
2,000
2,900
1,600
Pb-210
pc/1
22.0
36.0
6.8
1.5
45.0
62.0
260.0
39.0
120.0
Po-210
pc/1
'21.0
6.1
5.5
6.2
11.0
30.0
170.0
21.0
110.0
Th
(alpha)
pc/1
107,000
111,000
87,000
116,000
83,000
92,000
85,000
135,000
76,000
Gross Gross
alpha beta
pc/1 pc/1
72,000 90,000
100,000 65,000
109,000 37,000
170,000 46,000
95,000 51,000
104,000 36,000
99,000 52,000
130,000 71,000
106,000 33,000
Table 21. MILL EFFLUENT NO. 4
Sample
No.
1
2
3
4
5
6
7
8
9
10
11
12
Ra-226
pc/1
31.0
16.0
0.8
1.5
16.0
2.4
3.2
9.5
22.0
31.0
0.5
0.9
U
yg/i
1,900
1,200
1,100
1,400
1,700
1,000
2,000
1,800
1,100
900
640
1,700
Pb-210
pc/1
9.0
4.0
1.0
0.9
13.0
13.0
140.0
200.0
1.6
63.0
0.7
19.0
Po-210
pc/1
14.0
2.2
0.7
0.7
1.8
18.0
30.0
110.0
1.4
22.0
0.3
56.0
Th
(alpha)
pc/1
29.0
30.0
0.0
0.4
1,500.0
17.000.0
28,000.0
9,700.0
32.0
44.0
1.8
3,800.0
Gross
alpha
pc/1
610
400
370
1,400
3,325
21,000
43,000
13,000
1,100
980
600
6,100
Gross
beta
pc/1
740
470
210
210
1,880
6,900
15,000
4,600
670
610
360
1,600
61
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Table 22. MILL EFFLUENT NO. 5
Sample
No.
1
2
3
4
5
6
Ra-226
pc/1
28
38
65
25
25
28
U
yg/i
7,800
1,800
470
980
980
330
Pb-210
pc/1
4.3
20.0
1.5
1.9
6.8
0.7
Po-210
pc/1
3.4
19.0
2.0
2.0
4.8
1.5
Th
(alpha)
pc/1
69.0
64.0
60.0
8.6
3.0
31.0
Gross
alpha
pc/1
6,800
1,500
710
1,100
1,100
390
Gross
beta
pc/1
3,000
1,300
430
750
1,100
540
Table 23. MILL EFFLUENT SUSPENDED SOLIDS
Sample
No.
1
2
3
4
5
6
7
8
9
10
11
12
Mill
No.
A
A
A
A
B
B
B
B
B
C
C
C
Suspended solids
grams per liter
0.0195
0.1190
0.0120
0.1042
0.0427
0.0318
0.0367
0.0376
0.0240
0.0534
0.5110
0.1688
Ra-226
pc/g
3,500
852
1,809
1,400
25
260
230
2,045
238
800
72
837
Ra-226
pc/1
190.0
101.0
22.0
140.0
1.1
8.4
8.4
77.0
5.7
16.0
37.0
141.0
62
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SECTION X
WASTE TREATMENT AND DISPOSAL
Waste retention and treatment practices for control of pollution have
improved greatly since I960. It was common practice in the 1950's to
release the spent ore solids and liquid waste directly to unrestricted
areas, Most of the mills operating at that time were constructed near
streams and the waste discharged directly into the streams.
As a result of the Animas River survey which provided knowledge of the
fate of radionuclides in the water, remedial measures were established to
29
confine the contaminants. The measures included removal by sedi-
mentation of the greater part of the spent ore solids, removal of at least
70 percent of the dissolved radium from the effluents, and removal of the
toxic chemicals that were destroying the aquatic life for many miles down-
stream . Initiated at the Durango mill on the Animas River, the measures
were in operation by late October, 1959. An evaluation survey, conducted
in November, 1959, verified the immediate benefits of the abatement
procedures.
Radioisotope concentrations in water vary in the degree of hazard and
have been given a maximum permissible concentration in water (MPCw>
by various committees. The standards will be discussed in a later
section of the report. Table 24 lists each of the members of the uranium-
radium family in order of increasing maximum permissible concentration
in water.
Radium-226 has the lowest maximum permissible concentration, 3.3 pico-
curies per liter, indicating that it is considered to be the most hazardous
of all the waste products. Picocuries of radium-226 may be expressed as
picograms by applying a 1.02 multiplication factor. As shown in Table 24,
radium is a bone-seeking alpha emitter with a half-life of 1,620 years.
63
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Table 24. URANIUM-RADIUM FAMILY, MFC VALUES'
Nuclide
Ra226
Pb210
Po210
Th230
Th234
u234
u238
Bi210
Pa234
Po218
Po214
Bi214
Pb214
Rn222
MPC
,,.,w
pc/hter
3.3
33.0
233.0
667.0
6,667.0
10,000.0
13,300.0
13,300.0
b
b
b
b
b
(gas)
Critical
organ
Bone
Kidney
Spleen
Bone
GI tract
GI tract
GI tract
GI tract
—
—
—
—
—
Lung
Half-life
1,620 yr
22 yr
140 days
8 x 104 yr
24.1 days
2.5 x 105 yr
4.5 x 109 yr
5 days
1.1 min
3.05 min
1.6 x 10"4 sec
19.7 min
26.8 min
3.8 min
Emission
Alpha
f
Beta
Alpha
Alpha
Beta
Alpha
Alpha
Beta
Beta
Alpha
Alpha
Beta
Beta
Alpha
aMPC value is the Maximum Permissible Concentration
average member of the general population (l/30th HB69
tinuous occupational exposure).
No value given for these short-lived materials.
in water for an
value for con-
64
-------
The nuclide does not precipitate from solution as readily as the other
isotopes and is rapidly leached from suspended waste material, thereby
contributing to the dissolved activity of water.
The MPCw for uranium of 13,300 picocuries per liter is equivalent to 40
milligrams of uranium per liter. Chemical toxicity of uranium, rather
than radioactive hazard, is the determining factor for the high maximum
permissible concentrations permitted. Concentrations in the mill waste
are routinely less than this value since extractive methods employed in
the milling process are extremely efficient.
Lead-210 and polonium-210 have sufficiently long half-lives and a low
MPCw to warrant consideration as potential pollutants. The isotopes are
related in that polonium-210 concentrations in waste are dependent on the
lead-210 present. The polonium-210 will reach equilibrium again with
the lead-210 in a little over a year even if the two isotopes have been
separated in the process. When lead-210 is absent, polonium-210 present
will decay almost completely in a year. Little is known of the fate of the
two nuclides through the milling process, but Tables 18 through 22
show that concentrations for lead-210 range from less than 1.0 to 1,250
picocuries per liter of effluent. Polonium-210 concentrations have been
found to be somewhat less, possibly due to difference in precipitation
characteristics and lack of equilibrium. Lead-210 is the most hazardous
of the two radionuclides with a MPCw of 33 picocuries per liter.
Of the two thorium isotopes, thorium-230 is of the greatest concern in mill
wastes since it is a bone-seeking alpha emitter with an extremely long
half-life. The MFC for thorium-230 is 667 picocuries per liter. Thorium
w
compounds are insoluble at neutral or higher pH levels and are discharged
primarily in the solid waste material in the alkaline leach milling process.
The acid leach process will dissolve a considerable amount of thorium into
the liquid waste. Tables 18 through 22 indicate a range in the concentra-
tion of alpha-emitting thorium isotopes from less than 1.0 to 135,000 pico-
curies per liter in a variety of mill effluents from acid leach processes.
65
-------
Bismuth-210 has been assigned a MFC of 13,300 picocuries per liter,
but along with other nuclides shown in Table 24, has not been considered
significant as a pollutant due to the short half-life.
Due to variances in waste treatment circuits, the radionuelide content of
the effluent may be highly inconstant as seen in Tables 18 through 22. No
data is available for a continued period of time for an alkaline leach mill
effluent.
Waste treatment systems have been designed with the major objective to
remove extremely hazardous radium-226 from the effluent. Various types
of waste treatment and disposal practices will be discussed.
CONTAINMENT OF WASTES
All solid and liquid waste from the mill is completely contained within a
tailings pond providing sufficient land area is available. The size of the
ponds vary from a few acres to over 100 acres, and number from one to
ten or more at individual mills. The ponds are constructed by building
earthen dikes around the disposal area. Soil of a bentonitic nature is
preferred for a tailings pond area to reduce seepage of waste into the
ground. As construction progresses, the earth is compacted to make the
dikes more impervious to seepage. The dikes are usually ten feet across
the top and ten to twelve feet high. Some mills separate the sands and
the slimes by means of cyclone separators. The coarse sand tailings are
used to increase the height of the dikes as the ponds are filled, while the
slimes are discharged to the inner area of the pond to serve as a sealant
against seepage. With the waste contained in the tailings pond area, all
liquid loss is through evaporation or seepage into the ground. Seepage
loss has been estimated to be no greater than seven percent by one mill
in a pond with a large buildup of slimes on bottom.
The evaporation-percolation pond has been used for tailings disposal
32
following chemical treatment of the wastes . This type of pond is used
where land area is not available for large ponds and discharge into nearby
streams is not desirable. Seven of these ponds have been built by the
66
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Union Carbide Corporation at Uravan, Colorado. The soil is porous and
estimates have been made that evaporation has accounted for 15 percent
and percolation 85 percent of the losses. A small amount of seepage, less
than 50 gallons per minute, has been observed to reach the river. A
decrease in percolation rate has been noted since construction, indicating
an expected gradual drop in the disposal capacity due to sealing from the
deposition of tailings.
The solid waste accumulates at a rate of approximately 1,960 pounds per
ton of ore processed, and by the close of 1969 the total accumulation of
tailings in the United States amounted to 83 million tons,33 Nine million
tons per year of tailings were being produced by mills in 1971. The
tailings are composed of coarse sands and fine solids or slimes. The fine
solids contain more radium-226 per unit weight and are the most easily
distributed by wind erosion.
The prevention of direct discharge of waste solids to surrounding water-
ways has proved to be the most significant pollution control measure
instituted by the uranium milling industry. The solids previously served
as a long-term source of radium-226 in the stream due to leaching.
The environmental effects of tailings piles have been of concern since
1957. Many studies and meetings have been conducted through the years
to identify the hazards, establish rules for controlling tailings disposition,
33
and determine responsibility for stabilization and control of the tailings.
Problems with respect to the contained tailings both during use and after
abandonment still exist. These include (1) wind erosion of solids to
unrestricted areas, (2) slides into river of piles located near river banks,
(3) rising water level during flood conditions to the base of the pile
causing leaching of radium from the material, and (4) percolation of
water through piles into ground water.
Environmental surveys have been made of several uranium mill tailings
piles to evaluate potential radiation hazards. ' ' Samples of air-
borne particles, air, well water, stream water, and tailings material were
67
-------
analyzed for radionuclide content. Geiger survey meters were used to
measure gamma radiation from the tailings material and the surrounding
area. The conclusions from the studies were that (1) the radiation levels
on the tailings were of such levels as to preclude the release of the tailings
area for public use, (2) wind erosion had spread tailings material to dis-
tances of 1,000 feet from the tailings area to the extent that radiation levels
exceeded recommended standards, (3) radium-226 and thorium-230 con-
centrations in air exceeded recommended concentrations downwind from
the pile if left uncovered and unstabilized, (4) radon-222 gas in the area
was not a hazard unless enclosed structures were to be built on the*
material, and (5) well water and stream samples did not show pollution
from the tailings area. Recommendations were to stabilize the tailings
against wind erosion to eliminate the potential long-term hazard to*
inhabitants of the area. Also the area should not be released for public
use until the tailings were covered with uncontaminated soil to a depth
that would lower radiation levels to acceptable limits.
Remedial measures have been undertaken by members of the industry.
Tailings piles near river banks are being retrieved and rocks placed
along the sides of the pile to prevent water erosion. Other companies
have attempted to establish vegetation directly on the tailings material to
prevent wind erosion. The procedure has not been highly successful
due to the low pH of the material, lack of moisture, and blowing tailings
sand which severs the blades of grass soon after sprouting. Most tailings
piles are located in arid regions and would require watering to sustain
vegetation. A study of plants requiring a minimum of fertilization and
ground preparation and possessing the best growth characteristics for
long-term maintenance of tailings piles, has been conducted at the Colo-
37
rado State University. Results have not been encouraging because of
the long-term maintenance measures necessary to insure vegetation cover.
An attempt to establish vegetation on the dikes to prevent wind erosion is
being made by companies. One company located in a timbered area has
planted trees on top of the dikes to prevent wind erosion of the tailings
68
-------
material. Another company sprays tailings solution over the tailings area
to stabilize the fine material and prevent dusting. This method would be
useful for large tailings ponds with exposed disposal areas not covered
by solution and subject to wind erosion.
*r,
Stabilization of the Monticello, Utah, tailings pile was accomplished by
covering with two feet of soil and planting vegetation at a cost of $5,000
per acre. Another report states that coverage with one foot of soil would
cost $1,100 per acre. The costs vary depending on the location of pile
in relation to soil utilized for covering, and the labor involved in moving
tailings solids for consolidation and contouring. Estimated costs, ranging
from $1,360 to $2,910 per acre, have been calculated for several Colorado
River Basin tailings piles by an earth-covering method and a chemical-
39
covering method. A chemical and vegetative method of application in
38
which the Bureau of Mines was involved cost $135.50 per acre. Several
means for stabilization of relatively fine-sized waste, such as those con-
tained in uranium mill tailings piles, have been investigated by the Bureau
38
of Mines.
The Bureau of Mines assisted the El Paso Natural Gas Company in devising
a satisfactory and reasonable cost method of stabilizing the uranium wastes
at Tuba City, Arizona. Vegetation procedures were not considered since
less than nine inches of precipitation per year is insufficient to maintain
continuous coverage. Due to cost considerations, physical stabilization
using rock and soil coverings was considered impractical. From 20 chemi-
cals tested for stabilization ability, an elastomeric polymer and a ligno-
sulfonate were selected for use on the Tuba City tailings. The polymer,
due to its deeper penetration properties (approximately two inches) , was
applied to the tailings pond dike as this area was subject to the greatest
danger of wind and water erosion. The lignosulfonate, having a penetra-
tion depth of only three-fourths inch but resulting in a surface with a hard
crust, was sprayed on the surface of the tailings material contained within
the dike. Both laboratory and field tests revealed no signs of wind
erosion following application of the chemicals. Estimated costs of the
treatment were $335 per acre.
69
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CHEMICAL TREATMENT AND DILUTION
Waste discharge for acid and alkaline leach processes average 1,000 and
250 gallons per ton of ore respectively. Recycling may reduce the total
volume; however, ultimate disposal of the waste liquor must occur by
evaporation, seepage into the ground, or discharge into rivers or streams.
From 1.3 to 3.9 acres of pond surface are required to evaporate one ton of
water per hour depending on rainfall conditions in the Western United
4
States. Assuming no loss through seepage and a factor of 2.6 acres
per ton of water evaporated, a 1,000 ton per day mill using 500 gallons
of water per ton of ore would require a 220 acre pond. At 1,000 and
250 gallons of water per ton, a 440 and 110 acre pond would be required.
Ponds that allow significant quantities of waste liquor to seep into the
ground require proportionately smaller pond areas.
Mills located in areas where sufficient land is not available to contain the
total effluent treat the effluent to reduce the level of radioactivity, and
release controlled amounts into nearby waterways. Neutralization of the
effluent to a pH of about eight effectively removes 90 percent of the dissolved
radium, essentially all of the thorium, and some inorganic contaminants.
The radium-226 content of untreated effluent is in the range of 500 to
1,000 picocuries per liter; following neutralization, the range is from
50 to 100 picocuries per liter.
Initially, barium sulfate (barite) was used to remove radium-226 from
the effluent, but has been replaced by barium chloride due to its greater
40
efficiency. The radium is co-precipitated with barium sulfate upon
addition of barium chloride at a rate of 0.05 to 0.3 gram per liter to the
effluent. Under optimum conditions, 99 percent of the radium is removed.
The precipitate is allowed to settle before the treated effluent is discharged
to a river or stream. Dilution effects further reduce the concentration of
contaminants.
The Union Carbide mill at Uravan, Colorado, has rearranged the barium
chloride decontamination circuit to combine ditch drainage with the plant
70
-------
effluent and to continuously monitor the pH of the effluent. The circuit
modifications have reduced the radium-226 concentration in the effluent
significantly. One industrial company producing uranium and thorium
employs a sodium hydroxide neutralization process to a pH greater than
eight and two barium sulfate precipitations to reduce the radium concen-
41
trations by 99.9 percent. Other laboratory studies have shown that
radium-226 can be removed efficiently from simulated lime-neutralized
acid waste by adsorption on a number of inorganic ion exchange materials.
Anomalies in the radium concentration present in discharges have been
32
noted. Variations in radium-226 content of effluents may be seen in
Tables 18 through 22 and in the suspended solid content in Table 23.
Apparently, the efficiency of decontamination is dependent upon the
initial effluent concentration, variations in the treatment process, and
retention time in the settling ponds.
Mine waters, containing radium-226 concentrations as high as 192 pico-
curies per liter, are released to unrestricted areas at rates up to 3,000
gallons per minute at some sites; settling ponds are utilized to collect
suspended solids prior to mine water discharge.
UNDERGROUND DISPOSAL
Underground disposal of wastes has been used by the petroleum-producing
industries since 1920 for oil field brine. More industries have begun using
this means of disposal through the years so that by 1962 approximately 30
underground disposal systems were in operation. By 1969 almost 200 wells
were in use.
One currently operating uranium mill, the Anaconda Company, is disposing
of a portion of its effluent by deep well injection. Drilling began in
1959 and required 110 days for completion and testing. Cores were
taken to a depth of 2,511 feet and tested to determine the best disposal
zone. The well is located near Grants, New Mexico, and passes through
the San Andres and Glorieta fresh water aquifer at a depth of about 360 to
500 feet. Impermeable formations lie between the fresh water aquifer and
71
-------
the disposal zone. The well was completed in 563 feet of sandstones
in the lower San Ysidro and Meseta Blanca members of the Yeso forma-
tion. The disposal zone lies in the sandstone at a depth of 940 to 1,420
feet.
The well was cased to seal off all of the fresh-water aquifers and to
support the walls of the hole throughout the disposal zone. Surface
casing was installed to a depth of ten feet below fresh water, and injec-
tion casing to a depth of 1,830 feet in an 11-inch hole. Perforating and
fracturing operations were performed in the disposal zone,
The effluent is pumped from a wooden decanter box in the tailings pond
in order to minimize suspended solids. Diatomaceous earth is added to
the effluent to aid filtration, sodium polyphosphate to retard precipita-
tion of calcium sulfate, and copper sulfate to control the growth of micro-
organisms . The effluent is filtered to remove suspended solids, thus
preventing plugging of the disposal zone. Wastes were injected at an
average rate of 80 gallons per minute but rates as high as 600 gallons
per minute were experienced.
Since laboratory tests proved that the disposal zone material would
neutralize 390 gallons of waste per cubic foot without a loss of perme-
ability, the effluent is not neutralized prior to injection. As the disposal
zone material neutralizes the effluent, all thorium-230 and 90 percent of
the radium is precipitated.
From 1960 through 1968, 600 million gallons of effluent were injected into
the well. Table 25 shows the gallons of effluent, picocuries of radium-226
per liter of effluent, and total curies per year of radium-226 injected from
1964 through 1969.
The capacity of the disposal zone was calculated to be two to four billion
gallons. Should the current injection rate continue, the disposal well has
a calculated life to the year 1997.
72
-------
Table 25. WASTE DISPOSAL BY DEEP WELL INJECTION
Radium-226 Radium-226
Year Gallons of waste pc/l of waste curies per year
1964
1965
1966
1967
1968
1969
Total
57,814,250
24,274,342
29,115,770
24,079,220
50,345,550
63,459,275
249,088,407
181
128
79
109
68
205
.0476
.0141
.0104
.0119
.0156
.0592
.1588
RECYCLING OF DISCHARGES
Recycling of the effluent discharge is practiced to reduce the total volume
of wastes for disposal and to conserve water in areas of low water supply.
Mill solutions are recycled within the plant with only a small portion
transferred to the waste disposal area to prevent buildup of interfering
substances.
In other instances the total waste liquid is pumped to the tailings pond
and allowed to settle. Clear effluent is pumped back to the mills to be
reused in the circuits or to slurry leached tailings solids prior to pump-
ing to the disposal area. One mill discharges waste at a rate of 550
gallons per minute while returning clarified waste to the mill for reuse
at a rate of 300 gallons per minute. The limiting factor on reuse of waste
liquor is the dissolved solid content which may interfere with the milling
process.
OFF SITE DISPOSAL
The uranium milling process discards greater than 97 percent of the ore
processed as waste mill tailings. Due to the great hazard to health posed
73
-------
by radium-226, a careful plan providing for the safe disposal of tailings
is a necessity. Several solutions have been proposed for the disposal
problem. Initially, the wastes were to be used for such purposes as
39 44
land fill and highway subgrade fill material. '
In 1966 radon film badges were placed inside newly completed buildings
in Grand Junction, Colorado, in an area where uranium mill tailings had
been used as fill under and around the building. The badges did not
provide the sensitivity for quantitative results, but did show evidence
of elevated radon gas concentrations in the buildings. The State of Colo-
rado ordered a halt in the use of tailings material for building projects
without prior approval by the Department of Health.
The radon-222 gas being formed from the decay of radium-226 in the
tailings can diffuse through flooring material and concrete, and accumu-
late inside buildings to excessive levels due to inadequate air circulation.
The short-lived daughters of radon-222 (polonium-218, lead-214, bismuth-
214, and polonium-214) are deposited as solids.
An intensive survey of all buildings built on tailings pile material was
33
begun to determine the level of activity. An estimated 150,000 to
200,000 tons of tailings had been distributed through Grand Junction
between 1953 and 1966. The tailings had been used primarily under
concrete slabs and around foundations. Other uses had been under
streets, driveways, swimming pools, water pipes, and sewer mains.
Radon levels exceeded the screening value in 42 percent of the resi-
dences and 62 percent of the businesses.
The study and evaluation of the problem has continued with involvement
of personnel from the Atomic Energy Commission, U.S. Public Health
Service, Environmental Protection Agency, and the Colorado Depart-
ment of Health. On July 27, 1970, the Surgeon General of the U .S.
Public Health Service made recommendations of action for radiation
levels in dwellings constructed on or with uranium mill tailings. The
recommendations were as follows:
74
-------
External Gamma Radiation Recommendation
Greater than 0.1 mR/hr. Remedial action indicated
From 0.05 to 0.1 mR/hr. Remedial action may be suggested
Less than 0.05 mR/hr. No action indicated
Indoor Radon Daughter Products Recommendation
Greater than 0.05 WL Remedial action indicated
From 0.01 to 0.05 WL Remedial action may be suggested
Less than 0.01 WL No action indicated
Of 534 Grand Junction locations sampled, 65 exceeded 0.05 working level
(WL) and 30 were higher than 0.1 mR/hr. The Surgeon General stated
that protracted exposure at the upper level rate of 0.1 mR/hr. and 0.05
WL could double .the risk of leukemia and lung cancer.
Remedial action studies are being conducted relating to use of tailings
o^
in construction projects . The average cost of removing the tailings
from under and around the structures has been estimated to be $3,220
per residence. Additionally, studies are under way to find methods of
controlling the diffusion of radon through structures.
Radon surveys are being undertaken in other locations where uranium
tailings have been utilized for construction purposes. Elevated levels
of radon-222 were found in some Uravan, Colorado homes and two families
were moved to other housing. Mobile gamma scanning operations are being
conducted around uranium milling areas by personnel from the Western
Environmental Research Laboratory in Las Vegas, Nevada, in an effort
to locate suspected areas. The problem of radon-222 gas emanating from
tailings material demonstrates the importance of utilizing effective
disposal and containment of tailings material.
One solution to the problem of long-term disposal would involve placement
of the tailings back into the abandoned mines . Open pit mines could be
filled and covered with topsoil. Some land owners in Texas have specified
in the lease that the pit be filled and topsoil replaced to restore land to
its original condition. This method may prove to be the most effective and
economical for the long term.
75
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SECTION XI
EFFECTS OF WASTES ON THE ENVIRONMENT
Radioactivity measurements of four types of samples—water, sediment,
biota, and crop—are useful in demonstrating the degree of pollution
resulting from uranium operations. The few mills discharging wastes
to rivers and streams at the present time treat the waste prior to dis-
charge; however, mine water containing pollutants is discharged in
several mining locations without chemical treatment. Surface water
monitoring will immediately indicate any pollution problems resulting
from the two types of discharge. The majority of the mills contain all
their wastes in tailings ponds with disposal by evaporation or seepage.
Seepage from ponds near rivers and streams can be detected by surface
water monitoring; however, many tailings ponds are far removed from
flowing rivers and streams . To demonstrate pollution in these areas,
activity of ground water samples must be measured.
Sediment samples reflect the accumulation of radioactivity over a period
of time depending on the flow history of the stream. During periods of
low flow, the concentration of activity increases in a polluted location
due to the accumulation of mill tailings . During periods of high flow,
the contaminated sediment is diluted by upstream sediment and distrib-
45
uted downstream. Radium-226 is leached from the sediment by the
scouring action of the water. Sediment samples from reservoirs reflect
the extent of pollution over a longer period since the sediments are
relatively undisturbed by the reservoir waters. Trends in levels of
radioactivity in reservoirs are gradual, but useful in demonstrating the
long-term effects from upstream pollution.
River biota (algae, bottom animals, and fish) accumulate and concentrate
radium-226; hence, serve as cumulative indicators of pollution. Due to
their concentration ability, the organisms are a more sensitive indicator
76
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of prolonged pollution than water samples collected intermittently. Plants
also accumulate and concentrate radium-226, and edible crops that have
been irrigated with contaminated water contribute to the total radioactive
intake of the population. Dairy cattle fed on alfalfa, a plant that concen-
trates radium to a high level, may contain the radionuclide in their milk.46
To determine the effect of wastes on the environment, background surveys
are extremely important. In many instances the mills producing waste
are located near mining areas where large quantities of ore are located
in the ground water table. Without knowledge of radiation levels prior
to milling operations, the degree of pollution is difficult to assess. Radium
and uranium levels may be quite high in ground waters from natural leach-
47
ing of ore bodies. Levels of natural radioactivity in ground waters in
excess of 3 picocuries of radium-226 per liter have been found in several
48 4Q
areas of the United States. ' 7
In the following discussion, data from previous surveys and ongoing moni-
toring programs for both radioactive and inorganic pollutants resulting
from uranium mining and milling operations will be grouped by sample
types. In many instances, data for a particular area are extremely limited.
GROUND WATER
The Gas Hills region of Wyoming is an arid, sparsely populated area. Four
uranium mills operate in the region with the mill effluent contained in tail-
ings ponds and disposed of by natural evaporation and seepage. The
mills monitor water wells in the vicinity of the tailings ponds to detect
radioactive and inorganic pollution. Levels of radium-226 have been
detected as high as 50 picocuries per liter; however, the majority of
levels are less than 10 picocuries per liter. Seepage has been noted
near some tailings ponds by the appearance of surface ponds in low areas
near the tailings pond. The seepage water is checked for contaminants
by the company and pumped to restricted areas if the concentration of
radioactivity is above the mill discharge limit of 30 picocuries per liter
of radium-226.
77
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The Dawn Mining Company at Ford, Washington, discharges waste into
an evaporation pond located near a river. The pond is not sealed against
seepage and is often dry. Company analyses of water from a monitor .well
located down-gradient from the pond have not shown contamination of the
ground water.
The Cotter Corporation mill at Canon City, Colorado, retains all effluent
in tailings ponds with all loss of liquid resulting from evaporation or
seepage. Seepage has been noted and well waters of high mineral con-
tent unfit for livestock consumption have been reported by residents, of
the area. Contamination from molybdenum is suspected and is under
investigation by the Colorado State Health Department. The company
operates monitoring wells and sampling stations on the Arkansas River.
A monitoring well below the tailings pond area at Uravan, Colorado, has
shown slightly higher radium-226 concentrations and a high mineral
content compared to a well up-gradient from the ponds. Two abandoned
mines on Mesa Creek have a high radium-226 concentration in the drain-
age water that seeps into the ground and drains into the river. No data
on ground water is available for the area. Several large trees have died
down-gradient from the tailings area at Rifle, Colorado, indicative of a
high mineralization in the ground water.
Mill operations at Monticello, Utah, have been terminated and the tailings
pile stabilized against erosion. Ground water samples taken in the area
in 1967 showed radium concentrations as high as 17 picocuries per liter
possibly due to leaching of radioactivity from the pile.
Three uranium mills are located in the Grants, New Mexico area. The
area is semi-desert and the creeks and washes are usually dry except
during flash floods . Rio San Jose, the nearest river, is intermittent in
flow. Studies indicate that the background concentration of radium-226
in the Grants area ranges from 0.1 to 0.4 picocuries per liter. Two wells
78
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runs
near San Mateo Creek, which receives mine water discharges and
near the milling areas, had levels of radium-226 greater than background
in 1962. Mine drainage water contained 345 picocuries per liter of radium-
226.
An investigation was made in 1956 to determine whether the ground water
in the Grants-Bluewater area was being polluted by uranium waste stored
in a tailings pond. From a total waste discharge of 4.3 million gallons
per day, seepage losses were calculated to be 0.3 million gallons. The
loss required a seepage rate of 0.17 feet per day from the 70 acre pond.
The pond had been in use for three years at the time of the survey and
mill personnel anticipated that slimes in the waste would eventually seal
the pond. The investigation revealed that all inorganic constituents other
than nitrates tended to be fairly constant. Nitrates increased the nearer
the ground water was sampled to the tailings area with the highest value
being 16.9 milligrams per liter of nitrate-N. Findings elsewhere have
shown that nitrates travel more rapidly in soils than do other constituents
due to the selective nature of the ion exchange capacity of the soil. As the
ion exchange capacity of the soils is exhausted, the other constituents,
both inorganic and radioactive, may be found at greater distances from
the source of pollution.
The company has changed the milling process to eliminate the use of
nitrate compounds and has begun disposing of the greater part of the
effluent by injection to a deep well. It was believed that this disposal
method would reduce contaminants to a minimum in the ground water
system. The company operates monitor wells on the property and samples
wells in the surrounding area to detect any changes in the water quality.
Analyses of monitoring well samples by the company from 1964 through
1969, showed radium-226 concentration greater than two picocuries per
liter at only four locations. The highest radium-226 concentration was
5.2 picocuries per liter, demonstrating an upward trend at the location
from a concentration of less than two in 1964, to 5.2 in 1969. Nine
79
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sampling locations showed a gross alpha concentration somewhat above
background levels, but no definite trend over the six-year period was
established.
The other two mills in the Grants area operate monitoring wells at depths
of 75 to 100 feet near the tailings pond areas. All three mills are located
in close proximity, making pollutant source identification difficult. The
radium-226 concentration has ranged from 1 to 25 picocuries per liter in
one company's well.
Texas Gulf Coastal Plain operations employ open pit mining in which the
ground water is pumped from the mine continuously and mill wastes are
totally contained in tailings ponds. The uranium mills and the Texas
State Health Department have sampled wells in the mining and milling
area for radioactivity. Results from well to well have varied widely in
radium-226 concentration. In the majority of instances, the concentrations
were in excess of ten picocuries per liter with some values considerably
higher. Background data is not available to assess pollution from the
mining and milling operations. It is difficult to determine whether ele-
vated levels of contaminants are a result of mine and milling activities
or natural leaching of ore bodies in the area. The Continental Oil Company
is collecting and analyzing surface water and soil samples from a future
milling area to establish a background data for determining normal varia-
tions .
SURFACE WATER
Since 1950 river water samples have been analyzed from the Colorado
River Basin to detect the presence of radium-226 in the environment
resulting from uranium milling operations. At that time the radioactive
pollution of the water was extensive, but the degree of hazard to the
public was not fully realized. Radium concentrations ranged from a
background level of 0.2 picocuries per liter to 43 picocuries per liter
80
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in mining and milling areas. Most surface waters affected by the
uranium mill discharges were located in the Colorado River Basin.
In September, 1955, a preliminary field study was made to evaluate the
extent of stream pollution by waste discharges from uranium mills. The
effluents from the mills contained soluble radium-226 ranging from 4.5
to 920 picocuries per liter and large quantities of suspended tailings
solids high in radium-226. Water samples taken from below the mills had
radium concentrations up to 86 picocuries per liter compared to average
background levels of 0.3 picocuries per liter. A more detailed survey
was made in 1956 that substantiated the earlier findings. Leaching of
radium-226 from river muds and mill tailings solids by stream water and
uptake of the radionuclide by the stream biota was noted. Further work
on the ultimate fate of radium-226 in the stream environment was
recommended.
The serious nature of the problem was realized in 1957 when the standards
for exposure were revised downward and the U.S. Atomic Energy Com-
mission published regulations for waste discharge by licensees. As a
result of a conference held in 1958, a one-year fact-finding survey was
performed to assess the interstate pollution of the Animas River by uranium
mill waste discharge.
The Animas River survey showed the dissolved radium-226 content of
mill waste discharge to range from 44 to 822 picocuries per liter. An
estimated 30 to 40 milligrams of undissolved radium-226 was being dis-
charged daily in 15 tons of tailings solids. At locations of 2, 23, 28, and
59 miles below the mill, radium-226 concentrations were 12.6, 7.2, 7.6,
and 2.9 picocuries per liter, respectively. The radium-226 concentration
in raw water supplies of Aztec and Farmington, New Mexico, averaged
3.6 and 2.8 picocuries per liter, Treated water from the municipalities
averaged 3.6 and 2.6 picocuries per liter. At times treated water samples
contained more radium-226 than the raw water. The apparent anomaly was
81
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explained by the leaching effect of the water on water treatment plant lill«-i
sands polluted with radium-226. Concentrations of radium-226 ranghif/
from 25 to 30 picocuries per gram were found in the Aztec, New Mexico,
water treatment plant filter sands. The radium-226 was present in the
form of suspended solids or as a consequence of adsorption of dissolved
radium-226 on the sands. An average radium-226 concentration of 7.6
picocuries per liter in raw water was being used by New Mexico residents
during the survey.
The dissolved radium-226 released in the mill effluent discharged to the
river could not account for all the dissolved radium-226 at a station two
miles below the mill. The bulk of the mill solids discharged settled on
the river bottom to serve as a source for continued leaching into the
water. Periods of high river flow carried the solids downstream.
As a result of the survey data which implicated solid waste tailings
discharged to the river as a major source of dissolved radium, laboratory
investigations were performed to define the degree and conditions assoc-
iated with leaching . ' ' Conclusions from these investigations
were as follows:
1. No appreciable amount of radium-226 leaching occurred after
30 minutes with periods of time up to six days.
2. The liquid to solid ratio was one of the more important variables.
Little increase in leaching occurred at ratios greater than 1,000,: 1,-but up
to this ratio, the leaching rate increased rapidly.
3. The amount of radium-226 leached is dependent on the quantity
of radium-bearing solids (or total radium reservoir) after a liquid-solid
ratio greater than 1000:1 is reached.
4. Subsequent leachings of mill tailings were not effective as seen
by Table 26. Storing solids under wet conditions for a period of time prior
to releaching did not result in increased radium leaching.
5. The fine ore particles contained the greater quantity of radium-226.
82
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6. Barium chloride greatly enhanced the removal of radium from
tailings. After maximum leaching with water, a 0.01 molar barium chloride
solution leached about 35 percent additional radium-226. Barium was the
only common inorganic element tested that caused significant leaching.
7, The sulfate and barium content of the solids influences the amount
of leached radium-226 that will remain in the dissolved state. Dissolved
radium-226 co-precipitates as a barium-radium sulfate when sulfate and
barium ions are present in sufficient quantities.
8. The leaching effect is greater for uranium mill waste solids than
for river sediments and for acid leached waste solids than for alkaline
leached solids.
A followup survey was made in November, 1959, after treatment facilities
were installed in the Durango uranium mill. The treatment procedures
reduced toxic chemicals by 76 percent, dissolved radium by 80 percent,
and removed 89 percent of the suspended ore solids. Substantial improve-
ment in stream water quality was made by the installation of the treatment
procedures.
Table 26. REPETITIVE LEACHING OF MILL TAILINGS
Time Percent radium-226 leached
30-min. initial leaching 1.61
1st additional hour 0.17
2nd additional hour 0.05
3rd additional hour 0.07
60-min. initial leaching 1-55
1st additional hour 0.14
2nd additional hour 0.09
3rd additional hour 0.24
120-min. initial leaching 1-24
1st additional hour 0.23
2nd additional hour 0.13
3rd additional hour 0.05
83
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As a result of the previous field and laboratory studies, the Colorado
River Basin Water Quality Control Project was established in 1960.
Figure 11 illustrates the location of the Radium Monitoring Network
sampling stations, while Table 27 lists the mean annual concentrations
of radium-226 in water at these stations from 1961 through 1970.
The Durango mill operated from 1959 to 1963; following closure of the
mill in March, 1963, the radium-226 concentration at Station 12 below
the mill decreased to near background levels by 1965. Effects from the
Uravan milling operations are shown by the elevated and fluctuating
radium-226 concentrations at Station 20 located immediately below the
mill. Concentrations at Station 20 ranged from 3 to 30 times higher than
above the mill. Individual sample values varied widely from 26.0 to
0.5 picocuries per liter for a 3.94 average during one 6-month time
interval in 1968-69.
Radium-226 polluted water from the San Miguel River and mine drainage
from Mesa Creek enters the Dolores River upstream from Station 26, thus
accounting for the elevated values measured at that station.
Concentrations of radium-226 at Station 9 below the confluence of the
Dolores and Colorado Rivers are consistently higher than at Station 6
upstream. Also, values at Station 10 downstream from the Moab Mill are
higher than at Station 9 upstream from the mill. The greatest concentra-
tion difference between Stations 9 and 10 was 0.65 picocuries per liter.
Radium-226 concentration in Lake Mead and Lake Havasu, Stations 32 and
33, are consistently higher than at Station 31 upstream and Station 30
downstream. Leaching of naturally-occurring uranium ore bodies in the
lake areas may contribute to the elevated values found.
Other uranium mining areas have not been studied to the extent of the
Colorado River Basin. All the uranium mills conduct monitoring pro-
grams to satisfy the requirements of their license. State and government
agencies have performed limited investigations in the Shirley Basin of
84
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RMN 26
RMN 9
RMN 29
f» J
Ui ARIZONA
RMN 30
Uranium Mill
Figure 11. COLORADO RIVER BASIN RADIUM MONITORING NETWORK
85
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Table 27. MEAN ANNUAL CONCENTRATIONS OF RADIUM-226
IN WATER AT MONITORING NETWORK STATIONS, 1961-1970
(values in picograms per liter [1.02 picograms = 1 picocurie])
No.
1
4
5
6
9
10
11
12
13
14
14S
15
16
17
18
20
21
22
24
25
26
28
29
30
31
32
33
RMN Station
Location
Colorado River at Silt, Colorado
Colorado River above DeBeque, Colorado
Gunnison River above Grand Junction, Colorado
Colorado River near Fruita, Colorado
Colorado River above Moab, Utah
Colorado River below Moab, Utah
Animas River at Durango, Colorado
Animas River at Colorado-New Mexico State Line
San Juan River above Farmington, New Mexico
San Juan River at Fruitland, New Mexico
San Juan River below Shiprock, New Mexico
San Juan River above Mexican Hat, Utah
San Juan River below Mexican Hat, Utah
San Miguel River above Naturita, Colorado
San Miguel River above Uravan, Colorado
San Miguel River below Uravan, Colorado
Dolores River at Bedrock, Colorado
Tomichi Creek above Gunnison, Colorado
Gunnison River above Gunnison, Colorado
Gunnison River below confluence of Tomichi Creek,
Gunnison, Colorado
Dolores River at Gateway, Colorado
Yampa River below Maybell, Colorado
Green River below Green River City, Utah
Colorado River at United States-Mexican Border
Colorado River at Page, Arizona
Colorado River at (Lake Mead) Boulder City, Nevada
Colorado River at Metropolitan Water District , .
Intake, Lake Havasu, California-Arizona
Years
1961
0.18
0.20
—
—
0.34
0.41
0.05
0.37
—
—
—
0.18
0.34
0.02
0.14
0.98
0.85
0.02
0.03
0.04
0.42
0.11
—
—
—
—
—
1962
0.15
0.16
0.07
0.17
0.24
0.33
0.05
0.37
0.08
0.12
0.11
0.15
0.24
0.04
0.21
0.84
0.39
—
0.05
0.04
1.38
0.09
0.06
0.15
—
—
—
1963
0.23
0.23
0.11
0.21
0.29
0.54
0.06
0.23
0.07
0.12
0.12
0.13
0.16
0.04
0.33
1.34
0.45
—
0.05
0.05
1.03
0.09
0.10
0.17
0.25
0.33
0.35
1964
0.25
0.22
0.12
0.18
0.27
0.32
0.05
0.13
0.04
0.07
0.09
0.14
0.09
0.05
0.14
0.86
0.61
—
0.05
0.04
1.13
0.09
0.09
0.18
0.25
0.31
0.36
1965
0.16
0.17
0.07
0.17
0.19
0.27
0.04
0.09
—
0.06
0.06
0.07
0.07
0.05
0.16
0.46
0.28
—
0.04
0.03
0.67
0.06
—
0.16
0.17
0.41
0.36
1966
0.20
0.18
0.09
0.16
0.26
0.39
0.05
0.09
—
0.05
0.05
0.08
0.07
0.05
0.13
1.92
0.33
—
—
—
1.20
—
—
0.16
0.15
0.41
0.39
1967
0.20
0.19
0.08
0.17
0.28
0.93
0.05
0.09
—
0.06
—
0.08
0.08
0.04
0.12
1.57
0.50
—
—
—
1.22
—
—
0.17
0.14
0.32
0.34
1968
0.19
0.18
0.08
0.14
0.24
0.45
0.05
0.07
-r-
0.06
—
0.09
0.07
0.04
0.11
3.37
0.30
—
—
—
1.78
—
—
0.14
0.16
0.22
0.26
1969
0.17
0.14
0.07
0.11
0.17
0.20
0.05
0.05
—
0.06
0.06
0.08
0.08
0.04
0.07
1.54
0.28
—
—
—
1.71
—
—
0.13
0.15
0.19
—
1970
0.17
0.11
0.05
0.10
0.15
0.18
0.08
0.05
—
—
0.06
0.05
0.04
0.04
0.09
0.42
0.36
—
—
—
0.59
—
—
0.11
0.13
0.16
--
-------
Wyoming and the Texas Gulf Coastal Plains. Surface water drainage from
Shirley Basin, Wyoming, drains to Spring Creek, Little Medicine Bow
River, Seminoe Reservoir, and the North Platte River system. An esti-
mated 1,500 to 3,000 gallons per minute of water from open pit mines
and dewatering wells is pumped into Spring Creek. Radium-226 concen-
trations of 35 picocuries per liter have been detected below the conflu-
ence of Spring Creek and the Little Medicine Bow River. Uranium was
detected in concentrations of 1,000 rnicrograms per liter at the same
location. Radioactivity in Seminoe Reservoir has remained at back-
ground levels. Elevated selenium concentrations have also been found
in water samples from the area.
In the Texas Gulf Coastal Plains area mine water was discharged to a
creek draining to a river and a lake. Radium-226 and uranium analyses
of creek water indicated elevated levels below the discharge point. The
chloride content was also above normal. To remedy the problem, the
company began discharging the mine water to an abandoned mine.
RIVER SEDIMENT
River sediment is polluted with radioactivity from the uranium industry
by the direct discharge of solid waste tailings, by smaller amounts of
suspended fines in the discharged effluent, and by chemical precipita-
tion of dissolved radioactive substances by sulfates in the water. River
sediments serve as cumulative indicators of long-term contamination of
the environment. Removal of radioactive sediments from a specific stream
location is slow; in one instance, four years was estimated for concentra-
tions to return to normal background levels following termination of
45
solids discharge to the river.
As a result of the Animas River survey, background levels of normal river
sediments were established in the range of two picocuries of radium-226
per gram. Levels of radium-226 in the sediment directly below the point
of solids discharge to the river measured 115 picocuries per gram.
The levels of activity in the sediment are higher during periods of low
87
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flow due to the lack of scouring action of the water. Radioactivity is
leached from sediments while the sediment is being transported down-
stream to become eventually deposited in lakes or reservoirs. Due to the
high radium-226 content of the waste solids and the leaching effect of the
river water, a significant portion of the dissolved radium has as its
source the deposited solids on the river bed. Direct discharge of tail-
ings materials by mills to waterways was banned in 1959.
Fine suspended solids in the mill waste effluent represents the current
major source of radium-226 in river sediments. Table 23 lists suspended
solids content of mill effluents. Radium-226 values as great as 3,500
picocuries per gram and 190 picocuries per liter of effluent may be seen.
Laboratory studies have shown that radium-226 may be leached from
solids in amounts as high as 50 percent. Using the above values, 50
percent leaching would produce 95 picocuries per liter dissolved
radium-226, an amount considerably greater than is normally present
in an effluent following treatment. Removal of suspended solids is
necessary to minimize the radium-226 concentration in water.
RESERVOIR SEDIMENT
The ultimate destination of contaminated waste solids is in the bottom
sediments of lakes and reservoirs. In an effort to obtain background
concentrations of radium-226 in Lake Mead, two core samples of sedi-
59
ment deposited over the years 1935-1949 were analyzed. Radium-226
concentrations ranging from 1.5 to 2.0 picograms per gram were obtained
from the core samples according to the year of deposition. After develop-
ment of the uranium industry, concentrations in surface sediments ranged
up to 5.9 picograms per gram. An average of 2.9 picograms per gram
was calculated for all sediment samples analyzed for the period from
45
1960 to 1964. Lake Mohave and Lake Havasu sediments averaged 1.3
and 2.2 picograms per gram, respectively, for the same period. Lake
Mead, located upstream from the other reservoirs, has been the primary
collecting area for contaminated sediments.
88
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Lake Powell, in southern Utah, replaced Lake Mead as the recipient of
sediments from the Colorado River in 1964. Lake Powell sediments were
analyzed in 1965, and found to be near background levels. Water
samples ranging from 0.18 to 0.26 picograms of radium-226 per liter
showed lower concentrations of radioactivity than Lake Mead. At the
time of sampling, the lake had not had time to accumulate contaminated
sediments. Unfortunately, more recent data are not available.
Only limited sampling has been conducted in other reservoirs located
downstream from uranium mining and milling operations. The reservoirs
include: Boysen Reservoir, downstream from the Gas Hills operations;
Seminoe Reservoir, downstream from the Shirley Basin operations;
Angostura Reservoir, downstream from the Edgemont, South Dakota
operations; and Lake Corpus Christi, downstream from the Texas Gulf
Coastal Plains operations.
AQUATIC BIOTA
Detailed studies of the effects of waste discharge from uranium mills on
the aquatic biota of the Animas, Dolores, and San Miguel Rivers were
conducted during 1958-63.46> 55> 56> 6° Prior to the installation of
waste treatment processes, essentially all of the benthic organisms were
eliminated immediately below the uranium mills, and greatly reduced 35
to 40 miles downstream. Reductions in fish populations were also noted.
Release of the raffinate solution from the solvent extraction process in the
waste discharge was found to be primarily responsible for the toxicities
noted. Installation of treatment facilities resulted in a significant
improvement in benthic populations .
Selected benthic invertebrates and attached algae serve as useful cumula-
tive indicators of radioactivity, since both concentrate radium-226 from
the surrounding aqueous environment to approximately the same degree.
Concentration factors may be calculated from the following formula:
radium-226 per gram of live 0
radium-226 per gram of water
radium-226 per gram of live (wet) weight
89
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Algae were found to concentrate radium-226 within a range of 500 to
1,000. In the Animas River survey, background levels of radium-226
from unpolluted areas were found to be 4.5 picograms per gram of ash
weight for algae, 3.5 picocuries for aquatic insects, and 0.44 picocuries
for fish. The ash weight comprises 4 to 5 percent of the live weight. At
a sampling station located approximately 15 miles downstream from milling
operations, specimens taken revealed radium-226 concentrations as great
as 152 picograms per gram ash weight for algae, 230 picograms for
insects, and 24 picograms for fish. These values represent concentra-
'r •
tion factors of 844 for algae, 1,280 for insects, and 133 for fish; hence,
graphically illustrate the accumulative abilities of algae and invertebrates.
Attached algae and selected benthic invertebrates have additional advan-
tages over other stream organisms with regard to their selection as
practical, long-term indicators of radioactivity pollution. Such advan-
tages include ease of collection under field conditions and immobility.
CROPS
The effects on farm crops grown in radium-226 contaminated soils and/or
irrigated with radium-226 polluted waters have been investigated. ' '
In control studies, vegetables and fruits grown in soils having background
radium-226 concentrations of 1.4 picograms per gram and irrigated with
uncontaminated water, contained 2.0 picograms per kilogram wet weight.
By contrast, produce grown on soils containing as high as 17 picograms
per gram radium and irrigated with radium-polluted water, contained
concentrations as great as 11 picograms per kilogram wet weight.
Of the plants studied, alfalfa samples concentrated radium-226 to a much
greater degree when grown in the presence of radium-contaminated soil
and water. In one area alfalfa had radium-226 concentrations ranging
from 12.0 to 27.5 picograms per kilogram wet weight. In another area
the concentration in two samples was 210 and 320 picograms radium-226
per kilogram wet weight. Milk samples from cows fed contaminated
alfalfa were found to contain radium-226 concentrations as high as 5.0
picograms per liter.
90
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Phosphate fertilizers contain trace amounts of natural radioactivity and
were possible contributors to the radium-226 content of the crops. Investi-
gations showed fertilizers to contain radium-226 concentrations as high
as 21 picograms per gram. Alfalfa analysis showed that crops fertilized
with radium-226 contaminated fertilizer contained somewhat higher
amounts of radium-226 than those fertilized with uncontaminated ferti-
lizer; however, a stronger effect was observed in crops irrigated with
water containing radioactive elements.
With present day waste treatment practices it is unlikely that crop samples
would be found to contain levels of radioactivity as high as previously
mentioned. No crop samples have been analyzed in recent years, how-
ever , to substantiate a decrease in contamination as a result of waste
treatment processes.
At the present time cattle are grazing near waste tailings areas in several
locations where wind and water erosion has carried tailings material into
pastures. The effect of ingesting contaminated pasture grass is unknown.
Uptake of radioactivity by cattle may pass on to the general population
through milk and meat consumption.
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SECTION XII
STANDARDS FOR RADIOLOGICAL PROTECTION
Small amounts of a large variety of naturally-occurring radionuclides
are always present in the environment, and are responsible for normal
background radioactivity. Other radioactive materials are produced
artificially through nuclear weapons testing and nuclear power reactors.
Water and comestibles normally contain an amount of radioactivity
dependent upon their contact with radionuclides in the environment.
On ingestion, radioactive substances are absorbed and become lodged
in bones or other organs. The radionuclides emit alpha, beta, and
gamma radiations that are injurious to body tissue above certain levels.
The most hazardous of the radionuclides are naturally-occurring
radium-226 and artificially-produced strontium-90. The maximum
permissible standards for these elements are significantly lower than
for other radionuclides.
The amount of strontium-90 in the environment is the result of past nuclear
explosions and relatively constant; therefore, any reduction in the hazard-
ous radioactive materials present must be from a reduction in radium-226
concentration. A significant amount of radium-226 released to the environ-
ment is a consequence of uranium milling and refining operations. The
amount of radium-226 permitted in the environment is dependent on the
amount of strontium-90 present. The ratio of radium-226 concentration to
the maximum permissible concentration plus the ratio of strontium-90 to
the maximum permissible concentration should not be greater than one.
Several guidance documents on radiation exposure for various radio-
nuclides have been issued through the years. The trend in allowable
exposure levels has been downward and will probably be further
lowered in a document soon to be released. All of the documents con-
tain maximum permissible concentrations or ranges for radium-226 and
strontium-90.
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INTERNATIONAL COMMISSION ON RADIOLOGICAL PROTECTION REPORT
For continuous occupational exposure, the ICRP report lists the maxi-
mum permissible concentration for dissolved radium-226 in water as
100 picocuries per liter and 300,000 picocuries per liter for suspended
radium-226. The concentrations are based on the assumption that an
average person consumes 2.2 liters of water per day or its food
equivalent.
The levels are reduced by a factor of 10 to give the maximum permis-
sible concentration for an individual of 10 picocuries radium-226 per
liter (22 picocuries per day). A factor of 30 is used to give the maxi-
mum permissible concentrations for the general public of 3.3 picocuries
radium-226 per liter (7.3 picocuries per day) . The limits apply only
in the absence of other bone-seeking radionuclides such as strontium-90.
In their presence the limits should be reduced accordingly. The report
sets the limits of strontium-90 for the general public at 33 picocuries
per liter—10 times higher than the limit for radium-226.
NATIONAL BUREAU OF STANDARDS HANDBOOK 69
An abridgement of the ICRP report, the handbook gives the recommenda-
tions of a group of experts, the National Committee on Radiation Protec-
tion and Measurements, on limits of radiation exposure. The
publication contains the same table of maximum permissible concentra-
tions as the ICRP report and refers to the report for factors to reduce
the occupational limits to levels considered safe for the general public.
Body burdens and concentrations of radionuclides may be averaged
over a period of one year.
FEDERAL RADIATION COUNCIL STANDARDS
The Federal Radiation Council was established to advise the President
regarding radiation matters affecting health, to give guidance to all
Federal agencies in the formulation of radiation standards, and to
establish and execute programs of cooperation with states. The initial
93
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recommendations of the council were published in the Federal Register
on May 18, 1960. A second report offered specific guidance concern-
ing exposure of population groups to four radionuclides, including
63
radium-226 and strontium-90.
The council deviated from the use of a single intake value for maximum
permissible concentrations of radionuclides, and established three
ranges of concentration with a graded scale of action for each range.
It was reasoned that a single numerical concentration does not provide
adequate guidance for taking appropriate action in all situations. The
three ranges of intake are shown in Table 28. The ranges of transient
rates of intake for the graded scale of action are shown in Table 29.
The upper limit of Range II (Table 29) is based on an annual concentra-
tion considered as an acceptable risk for a lifetime.
Compared to the ICRP and NCRP recommended standard for radium-226
of 7.3 picocuries per day, an average of Range II (2 to 20 picocuries per
day) is not greatly different. Use of the range concept prevents an
alarmist interpretation of transient levels of exposure. The range allows
a higher level of concentration without cause for concern, but also
recommends surveillance and control at a level of two picocuries of
radium-226, lower than the ICRP and NCRP recommendations.
USPHS DRINKING WATER STANDARDS—1962
The standards, guided by the Federal Radiation Council recommendations,
state that water supplies shall be approved without further consideration
of other sources of radioactivity when radium-226 and strontium-90 con-
centrations do not exceed three and 10 picocuries per liter, respectively.
Should the concentrations be exceeded, a water supply shall be approved
after surveillance of total intakes of radioactivity from all sources indicates
that such intakes are within the Range II limits of 2 to 20 picocuries per
day of radium-226.
94
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Table 28. GRADED SCALE OF ACTION
Ranges of transient rates
of daily intake Graded scale of action
Range I Periodic confirmatory surveillance as
necessary.
Range II Quantitative surveillance and routine
control.
Range III Evaluation and application of additional
control measures as necessary.
Table 29. RANGES OF TRANSIENT RATES OF INTAKE
FOR USE IN GRADED SCALE OF ACTION
(picocuries per day)
Radionuclide Range I Range II Range III
Radium-226 0- 2 2- 20 20- 200
Strontium-90 0-20 20-200 200-2,000
95
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WATER QUALITY CRITERIA—FWPCA
The National Technical Advisory Committee on Water Quality Criteria,
established February 27, 1967, assembled a comprehensive document
on water quality requirements to be used as a basic reference by groups
and agencies engaged in water quality studies and standard-setting
activities. The committee established standards for surface water
criteria for public water supplies in two groupings. The first, per-
missible criteria, included those characteristics and concentrations of
substances in raw surface water that allow for the production of a safe,
clear, potable, aesthetically pleasing, and acceptable public water
supply meeting the limits of the Public Health Service Drinking Water
Standards of 1962 after treatment. The second, desirable criteria,
included those characteristics and concentrations of substances in raw
surface waters that represent high quality water in all respects for use
as public water supplies. The standards for radioactivity and also for
the most probable inorganic contaminants present in uranium mining
and milling wastes are given in Table 30.
Table 30. SURFACE WATER CRITERIA FOR PUBLIC WATER SUPPLIES
Constituent
Permissible
criteria
Desirable
criteria
Radioactivity:
Gross beta
Radium-226
Strontium-90
(pi'cocuries per liter)
1,000
3
10
Inorganic chemicals: (milligrams per liter)
Chloride 250.00
Sulfate 250.00
Nitrates 10.00
Arsenic 0.05
Selenium 0.01
Uranyl Ion 5.00
(picocuries per liter)
<100
<1
<2
(milligrams per liter)
<25
<50
virtually absent
absent
absent
absent
96
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During 1970, a number of questions were raised regarding the adequacy
of radiation protection standards. To provide satisfactory answers to
the queries, the National Academy of Sciences was asked to thoroughly
review all pertinent, available scientific data and recommend changes
deemed necessary. A report of findings by the organization has not
been released. Additionally, an EPA working group reviewing drinking
water standards is expected to publish revised standards with lowered
radioisotope levels.
In summary, all documents concerning water quality standards for
radioactive wastes are in relatively close agreement. The continuing
trend in maximum permissible concentrations is downward. The limits
of standards are considered to be maximums and every effort should be
made by the uranium industry in pollution abatement programs to reduce
the concentrations of pollutants released to the environment to as low a
level as is possible, rather than discharging wastes to the preselected
level of the standard. Abatement procedures have demonstrated that
the level of concentration of radium-226 in river water can be maintained
at less than one picocurie per liter.
97
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SECTION XIII
TESTING AND MONITORING PROGRAMS
Although considerable testing and monitoring for pollution caused by
uranium mining and milling activities has been conducted in the Colorado
River Basin, other uranium-producing areas have received scant atten-
tion . The information gained in the Colorado River Basin studies has
been invaluable in identifying problem areas within the industry.
To adequately define pollution due to radioactivity, analysis for radium-
226 is necessary since this radionuclide is considered to be the most
hazardous of the naturally-occurring radionuclides and has been given
the lowest maximum permissible concentration. As a general rule, when
radium-226 concentrations are found to be below the standard limit, all
other radionuclide concentrations will be below their standard limit.
Uranium analysis should also be performed. In addition to the specific
analyses mentioned, gross alpha and gross beta activity should be
measured to insure that other radionuclide concentrations are low. In
instances of higher gross alpha or gross beta activities than would be
expected from the radium-226 and uranium content, analyses for other
specific radionuclides are indicated: thorium isotopes, lead-210,
polonium-210, and strontium-90 .
1
While radiological pollution has been the major concern from thet uranium
industry wastes, analyses for other inorganic elements should not be
neglected. The frequency of analysis for chlorides, sulfates, nitrates,
arsenic, selenium, and molybdenum should depend on the levels found
in previously analyzed samples.
The major problems encountered in testing and monitoring programs are
the lack of sufficient data, the intermittance of data, and the reliability
of data obtained. Background data are not available for many areas to
utilize in assessing the degree of pollution. Split samples analyzed by
98
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different laboratories have shown discrepancies, indicating the need for
improved quality control measures to assure the validity of the results.
All companies involved in milling and refining of radioactive materials
must meet certain requirements. The companies are licensed by the
Atomic Energy Commission or by states designated as agreement states.
Agreement states have assumed all licensing, record keeping, and
inspection responsibilities from the Atomic Energy Commission. Of
the seven states in which milling activities are presently being conducted,
Colorado, Texas, and Washington are agreement states.
The licensing requirements are set forth in the Code of Federal Regulations,
Title 10, Part 20 (10 CFR 20). One requirement of the regulations is that
the company conduct a continuous sample monitoring program to verify
that the mill is operating within defined limits set forth in the license.
The records must be kept available for periodic inspection by the Atomic
Energy Commission or the agreement states.
The 10 CFR 20 limit for soluble radium-226 that may be discharged to an
unrestricted area is 30 picocuries per liter and for insoluble or suspended
radium-226, 30,000 picocuries per liter. The section further states, "In
addition to limiting concentrations in effluent streams, the Commission
may limit quantities of radioactive materials released in air or water
during a specified period of time if it appears that the daily intake of
radioactive material from air, water, or food by a suitable sample of an
exposed population group, averaged over a period not exceeding one
year, would otherwise exceed the daily intake resulting from continuous
exposure to air or water containing one-third the concentration of radio-
active materials specified . . . ." For soluble radium-226, the amount
would be one-third of 30, or 10 picocuries per liter.
The State of Colorado operates a radiochemistry laboratory and conducts
a monitoring program.. The State has cooperated through meetings and
sampling surveys with Federal agencies to assess pollution effects on
stream waters. Other states perform alpha and beta analyses on samples
99
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and occasionally gamma scans. Most states are not equipped to perform
radioactive analyses of the radionuclides in the uranium mill waste
discharge. As laboratory apparatus and equipment needed for the
analyses are quite expensive for the number of analyses required in
a monitoring program, the states often enlist the aid of a Federal agency.
Federal agencies have been involved in testing and monitoring activities
concerned with the uranium industry since the 1950's. Both short-term
(one year or less) and continuous long-term monitoring activities have
been carried out in the Colorado River Basin. ' ' A Radium
Monitoring Network was established for the basin and samples for
analysis collected periodically throughout the basin by the Colorado
River Basin Laboratory in Salt Lake City, Utah. The first monitoring
station was established in January, 1961, with the number eventually
increasing to a maximum of 27 stations. The network was discontinued
in September, 1969, with 19 sampling stations. Data from the sampling
stations were assembled in 16 Radium Monitoring Network Data Releases.
In October, 1969, many network stations were transferred into a Water
Quality Surveillance System along with new stations. The frequency of
collection at the 25 stations varied from one week to semi-annually. Data
from the stations are stored by computer in the Storet system.
Sample analyses for the Colorado River Basin Project consisted of gross
alpha, gross beta, gross gamma scans, radium-226, natural uranium,
thorium, lead-210, polonium-210, and strontium-90. Not all parameters
were measured on every sample; however, gross alpha, gross beta,
radium-226, and natural uranium were routinely performed. Some of
the analytical methods were developed or perfected in the Colorado
zy £Q /Q
River Basin Laboratory; ' ' others were taken from Standard
JQ
Methods. In addition to long-term sampling programs, special surveys
were conducted. To obtain a comprehensive overview of the effects of
uranium milling waste products on the environment, many types of
100
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samples other than water were analyzed, including river and reservoir
sediments, topsoil, water treatment plant filter sands, aquatic biota,
crops, and milk.
101
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SECTION XIV
TECHNOLOGICAL ADVANCES IN THE URANIUM INDUSTRY
No major advancements have been made in uranium mining, milling,
and waste treatment during the past thirteen years; however, research
has produced new and improved methods that may eventually be used in
the uranium industry. The methods will be discussed in detail below.
PHYSICAL UPGRADING OF LOW GRADE ORES
As the demand for uranium increases, processing of lower grade ores
will be required. Processing of larger quantities of ore will result in
excessive consumption of leaching reagents to produce the same amount
of uranium concentrate. The leaching and neutralization process is the
71
most costly phase of the milling processes as seen in Table 31. Reduc-
tion of the volume of ore required to produce the same amount of uranium
would result in a tremendous cost savings and prevent a larger waste
disposal problem.
Table 31. DIRECT OPERATING COSTS OF
URANIUM EXTRACTION IN THE U.S.A.
Process Percent of cost
Crushing 6
Grinding and thickening 5
Leaching and neutralization 43
Liquid/solid separation 6
Extraction and purification 8
Precipitation, drying, and packaging 9
Services (effluent treatment, 23
administration, etc.)
alntermediate-sized mill (1,500-2,000 ton/day) operating on 5 Ib/ton ore,
with solvent extraction.
102
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Methods of lump-ore sorting by machines may prove useful in reducing
the bulk of ore processed fivefold with a uranium recovery rate of 90 to
95 percent. Radiometric, conductimetric, and optical detection systems
have been used for ore sorting. Another promising method is high-
intensity wet magnetic separation utilizing superconducting magnets.
• t '
More automation of equipment in the ore separation and grinding proc-
esses would prevent exposure of employees to areas of high dust concen-
tration . Automation in the uranium concentrate packaging process would
also eliminate another source of high dust exposure.
IMPROVED URANIUM EXTRACTION PROCESSES
An improved Eluex process has been developed that differs from existing
ones in that a stage of uranium solvent extraction is coupled with each
stage of resin elution rather than the elution and solvent extraction
72
operations being conducted separately. The improved system will
reduce the number of stages, retention time, and resin inventory to
about one-fourth or one-fifth that in existing circuits. Such improve-
ments in circuit design may influence the design of milling processes in
mills constructed in the future. From a waste treatment standpoint,
processes involving maximum recycle of tailings solution should be one
of the major goals.
Extraction of uranium from mine water by ion exchange techniques has
been in use in some uranium mining areas since 1963. Mine water con-
tains sufficient uranium to warrant recovery from an economical stand-
point. An improved countercurrent ion exchange process has been
27
developed for recovery of uranium from natural mine waters. The
improved technique reduced resin inventory requirements by 70 percent.
Additional savings in equipment and labor costs would be realized by
utilization of this process.
103
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EXTRACTION OF URANIUM FROM SEAWATER
Uranium is present in seawater in concentrations of 2.9 to 3.3 micrograms
per liter. Seawater is the lowest grade but the most abundant source of
uranium. Of the trace metals in seawater, uranium is considered to be
the only one present in sufficient quantities to warrant economic extrac-
2 73
tion in the foreseeable future. ' Studies have shown that 82 percent
of the uranium may be rapidly extracted by a flotation technique. While
it is unlikely that this source of uranium would be considered unless ore
reserves become depleted, the technology for extraction has been
developed.
f
Other studies of uranium recovery from seawater have been made that
consist of concentrating uranium on adsorber beds in a coastal lagoon
2
where a constant tidal flow can be maintained across the beds. Hydrous
titanium oxide was found to be a suitable adsorber. Ammonium carbonate
proved to be the best solvent for extraction of uranium from the beds,
resulting in an 80 percent removal from one pass of solution. The life of
the beds is estimated at less than ten years. Final estimated cost of proc-
essed material was in the range of $27 to $43 per pound of uranium oxide.
The cost is high for present uses of uranium, but in the event of a short-
age , or breeder reactors are placed into commercial use, the cost might
prove reasonable.
UNDERGROUND URANIUM EXTRACTION USING NUCLEAR EXPLOSIVES
Nuclear explosives have been used to increase the recovery of under-
ground resources. Underground nuclear explosions conducted under
the Plowshare program have increased the rate of gas production in
underground formations by increasing the porosity and permeability of
the formation. If nuclear explosive projects prove to be safe and econom-
ically competitive with conventional fracturing methods, the method
could possibly prove useful in combination with underground solution
74
mining of uranium ore bodies. The problem of radioactive contaminated
waste would be increased, however, due to the production of artificial
radionuclides.
104
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RADIUM REMOVAL FROM URANIUM MILL EFFLUENTS AND TAILINGS
SOLIDS
Ion exchange techniques for radium removal from acid waste liquors have
42
been studied. Of thirteen solids tested, ten adsorbed more than 75 per-
cent of the radium from a simulated lime-neutralized feed. The most
effective solid, a commercially synthetic zeolite, removed 96 percent of
the radium from solution. A brief study was made of the elution of radium
from the ion exchangers. Ammonium nitrate and ammonium chloride
proved to be the most efficient reagents with elution efficiencies as high
as 90 percent. Greater than 97 percent of the radium was removed from
the pregnant solution by barium sulfate precipitation. The eluted resin
was reused for another adsorption cycle of radium with the same
efficiency.
A study conducted by the Bureau of Mines indicated that 90 percent of the
radium could be removed from tailings solids by a versenate leaching
process, but the cost was estimated to double the price of uranium.
Radium is significantly leached from tailings solids by water or barium
chloride solution. Removal of radium from waste tailings solids would
make disposal much less of a problem.
105
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SECTION XV
REFERENCES
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and Problems. Bureau of Mines, Washington, D .C. Bulletin
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2. Low Grade Uranium Ore. Nucl. Eng. 13 (144): 436-438, May 1968.
3. An Assessment of the Economic Effects of Radiation Exposure
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4. Merritt, R. C. The Extractive Metallurgy of Uranium. Golden,
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106
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11. Farthing, G. 13th Annual Nuclear Report: Fuel. Electrical
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107
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Bacteria. Canada Department of Energy, Mines and Resources,
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108
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40. Lewis, C. J. Treatment of Uranium Mill Wastes. In: Proc. 14th
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1964.
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1957.
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pp. 237-240.
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49. Hickey, John L. S. and S. D. Campbell. High Radium-226
Concentrations in Public Water Supplies. Public Health Reports .
83^551-556, July 1968.
50. Report on an Investigation of Ground Water Pollution, Grants-
Bluewater, New Mexico. New Mexico Department of Public Health,
Santa Fe. August 1957. 12 pp.
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«us. OOVERNMfNT PRINTING OFFICE: 1974 546-319/430 1-3
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SELECTED WATER
RESOURCES ABSTRACTS
INPUT TRANSACTION FORM
1. Report No.
ion I
w
4. Title
STATE-OF-THE-ART: URANIUM MINING. MILLING.
AND REFINING INDUSTRY,
7. Aathor(s)
Clark, D.A.
9. Or anization
United States Environmental Protection Agency
Robert S. Kerr Environmental Research Laboratory
Ada, Oklahoma
5 RtpvefDate
t: :'"'''•'•'« ••':
8. f •.•rformiitg Organization
Report Ho.
tr>. Project No.
21AGF-02
11 Contract/ Grant V
1*3.* Tfpc ir! Rtpoft and
" Period Covered
75. Supplementary llotes
Environmental Protection Agency report number EPA-660/2-74-038, June 197k
16. Abstract
The report presents an overview of the uranium mining, milling, and refining industry
of the United States. Topics discussed include ore reserves, geographical locations,
production statistics, future requirements, processes for extraction and benefielating,
waste characteristics, including radioactive and other potential pollutants, current
treatment and disposal methods, effects of wastes on the environment, standards for
radiological protection, testing and monitoring programs, technological advances
within the uranium industry, anticipated future problems, and recommended areas
for further study. (Clark-EPA)
a*Waste"breatment, *Waste disposal, *Mine water, *Seepage, *Stabilization, *Research
and development, Surface water, Groundwater, Water pollution sources. Environmental
effects, Industrial plants. Chemical wastes. Radioactive wastes. Solid wastes, Chemical
precipitation. Neutralization, Water quality standards. Monitoring.
7b*Mningrwastes, Reachability of solids, Physical upgrading. Suspended solids.
17c. COWRR Field & Croup
05A, 05B, 05C, 05D, 05E
IS. Availability 19. Security cSs!E
(Repo^fT'V-fili *•'•'
"0. Se- rityCI>ss.
^ (Page)&-
A: .,,,... tor Don A. Clark
;$*•.. ^Fsir«f**p
% >/••«•: ;•••"•
Send To:
WATER RESOURCES SCIENTIFIC INFORMATION CENTER
US DEPARTMENT OF THE INTERIOR
WASHINGTON. D. C. 2O24O
i,»tii-.-fion Environmental Protection Agency
WRSIC 1O2 (RE.V. JUNE 1971)
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