Tailings and Their 

Component Radionuclides 

From the Biosphere-Some 

Earth Science Perspectives 

Isolation of Uranium Mill Tailings 

and Their Component Radionuclides 

From the Biosphere-Some Earth 

Science Perspectives 

By Edward Landa 

GEOLOGICAL SURVEY CIRCULAR 814 

A critical review of the literature dealing with 

uranium mill tailings, with emphasis on the 

geologic and geochemical processes affecting 

the long-term containment of radionuclides 

1980 
United States Department of the Interior 

CECIL D. ANDRUS, Secretary 

Geological Survey 

H. William Menard, Director 

Library of Congress catalog-card No. 79-600148 

Free on application to Branch of Distribution, U.S. Geological Survey 

1200 South Eads Street, Arlington, VA 22202 
CONTENTS 

Abstract 

Introduction ------------------------------------------------------------- Acknowledginents --------- _ -----------------------------------------------

Quantity and location of the tailings ---------------------------------------

Radioactivity in tailings ---------------------------------------------------

Sources of potential human radiation exposure from uranium mill tailings ------

Radon emanation -----------------------------------------------------

VVind transport ------------------------------------------------------- Surface water transport and leaching -----------------------------------

External gamma radiation --------------------------------------------

Contamination of terrestrial and aquatic vegetation ----------------------

Seepage ----------------------------------------------------~--------

Environmental factors --------------------------------------------

Ore factors ------------------------------------------------------

Process factors --------------------------------------------------- Use of tailings as a construction material -------------------------------

Leaching behavior of radium, thorium, and uranium --------------------------

Radium ------------------------------------------------------------- Thorium 

Uranium ------------------------------------------------------------

VVater qualuy studies ----------------------------------------------------- Grants Mineral Belt in New Mexico ------------------------------------ Elliot Lake, Ontario _______________________ ---------------------------

Other areas ----------------------------------------------------------

Uranium mill tailings disposal options --------------------------------------

Surface stabilization and near surface burial of tailings ------------------

Radium removal from tailings -----------------------------------------

Preconcentrationof uranium ore----------------------------------------

Deep burial in underground cavities ------------------------------------

Thick unsaturated zone storage· ----------------------------------------

Fixation and agglomeration of buried tailings ---------------------------

In-situ leach mining --------------------------------------------------

Conclusions --------------------------------------------------------------

References ---------------------------------------------------------------

ILLUSTRATIONS 

FIGURE 1. Map showing the location of active and inactive conventional uranium 

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milling sites in the United States ----------------------------- 3 

2. Diagram showing the radioactive· decay scheme of uranium-238 ____ 5 

TABLES 

TABLE 1. VVat.er quality standards associated with uranium-238 decay series 

radionuclides ---------------------------------------------- 4 

2. Proportion of radium-226 leached from uranium ore, uranium mill 

tailings, and river bottom sediments in laboratory tests -------- 13 

Til 

Isolation of Uranium Mill Tailings and Their 

Component Radionuclides From the BiosphereSome Earth Science Perspectives 

By Edward Landa 

ABSTRACT 

U rani urn mining and milling is an expanding activ·ity 

in the Western United States. Although the milling 

process yields a uranium concentrate, the large volume 

of tailings remaining centains about 85 percent of the 

radioactivity-originally associated with the ore. By virtue of the physical and chemical processing of the ore 

and the redistribution of the contained radionuclides at 

the Earth's surface, these tailings constitute a technologically enhanced source of natural radiation exposure. 

Sources of potential human radiation exposure from 

uranium mill tailings include the emanation of radon 

gas, the transport of particles by wind and water, and 

the transport of soluble radionuclides, seeping from disposal areas, by ground water. Due to the 77,000 year 

half-life of thorium-230, the parent of radium-226,. the 

environmental effects associated with radionuclides contained in these tailings must be conceived of within the 

framework of geologic processes operating over geologic 

time. The magnitude of erosion of cover materials and 

tailings and the extent of geochemical mobilization of 

the contained radionuclides to the atmosphere and hydrosphere should be considered in the evaluation of the 

potential, long-term cons·equences of all proposed uranium mill tailings management plans. 

INTRODUCTION 

Uranium mill tailings represent a unique 

type of radioactive waste. Rather than manmade materials containing fission products, 

activation products, and (or) transuranic elements, these tailings are earth materials containing radionuclides naturally present in the 

Earth's crust that have been brought to the surface, subjected to physical and chemical processing, and subsequently exposed to the action 

of surficial geologic processes. Thus redistributed, these radionuclides constitute a source of 

1 

"technologically enhanced natural radiation 

exposure" 1 to the surrounding population. 

The philosophy expressed by Lush and others 

( 1978) is worth considering with regard to the 

long-term storage of uranium mill tailings: 

The development of a long-term waste management 

philosophy require,s. the acceptance of a basic set of 

management criteria. Our societies' approach has, as 

its basic tenets, that the present generation of waste 

managers should l•eave the wastes in such a manner 

that there is no foreseeable threat to future generations 

and future generations will not have to be involved 

in the care of the wastes. Implied is that the future 

bleed rate of contaminants from waste management 

sites should not exce,ed present regulatory levels, and 

not rely on continued monitoring to demonstrate that 

fact * * *. Any acceptable long term solutions must 

not rely solely on a social management system, but 

rather on a management controlled by those basic 

geochemical and biochemical cycles which have bezn 

determining the flux rates of radionuclides through the 

open environment dur.ing the evolution of life· on 

Earth. 

In order to develop a management system which 

meets these criteria, a basic knowledge is needed of 

(a) those geochemical and biochemical reactions affecting the mobility· of radionuclides, (b) the form into 

which those radionuc>Lides ane transformed during the 

milling and waste treatment operation, and (c) the 

conseque;n.ces of this transformation as related to their 

mobility within and the flux rate from the waste man~ 

agement area over geological time. Only through an 

understanding of these processes and their interac .. 

tions with th~ waste management environment .can we 

determine whether present or future management areas 

1 Gesell and Prichard ( 1975) have defined "technologically enhanced natural radiation exposures" as exposures to truly natural 

sources of radiation (naturally occurring isotopes and cosmic 

radiation) which would not have occurred without (or would 

have been increased by) some technological activity not expressly 

designed to produce radiation. 
will transcend smoothly the cessation of active management and determine whether future passivelymanaged bleed rates acceptable under present day and 

hopefully future standards are achieved. 

The purpose of this report is to document 

some of the existing information relevant to 

environmental mobilization, and to discuss the 

efficacy of various uranium mill tailings disposal options in light of potential mobilization 

mechanisms. While the emphasis here is on the 

potential, long-term consequences of tailings 

disposal, this view is in no way meant to detract from the very major advances in uranium 

mill tailings management, fostered by both the 

uranium industry and regulatory authorities, 

which have occurred in the past 2 decades. In 

the early years of uranium milling, only limited 

attention was paid to the now better-understood, environmental effects associated with 

radioactivity in the residual materials. In the 

late 1950's and early 1960's, work by the U.S. 

Pubic Health Service and others provided the 

impetus for controls on the discharge of mill 

effluents and initiation of stabilization efforts 

at tailings piles. The Grand Junction experience with the use of tailings for construction 

purposes spurred renewed interest in tailings 

management during the late 1960's and early 

1970's. An examination of the environmental 

reports and statements prepared by mill operators and regulatory agencies over the last 

few years reflects the increasing awareness of 

the potential hazards associated with these 

tailings and the application of technology to 

mitigate these effects. The past 2 years represent a period of intense effort in this area, 

as.-.seen with the promulgation by the U.S. Nucear Regulatory Commission of siting, design, 

operation and reclamation criteria for the management of uranium mill tailings (U.S. Nuclear 

Regulatory Commission, 1977a), and the Commission's preparation of a generic environmental impact statement on the U.S. uranium 

milling industry to the year 2000 (U.S. Nuclear 

Regulatory Commission, 1979a) . Also, the 95th 

Congress enacted the U rani urn Mill Tailings 

Radiation Control Act of 1978 (Public Law 95-

604) providing for the reclamation of inactive 

uranium mill tailings areas, and the control of 

tailings as a licensed by-product material. The 

reader is thus cautioned to keep this historical 

2 

and evolutionary perspective in mind. Examples from the past are presented as they are 

useful in understanding the behavior of uranium mill tailings in the environment. However, examples of past mismanagement should 

not be confused with current management 

practices. 

A discussion of potential health impacts 

from uranium mill tailings is beyond the scope 

of this report; the reader is referred to Sears 

and others (1975), Ramsey (1976), Ford, 

Bacon, and Davis Utah, Inc. (1978), Travis and 

others (1979), and U.S. Nuclear Regulatory 

Commission (1979a) for an overview of the 

subject. 

ACKNOWLEDGMENTS 

The author wishes to acknowledge the efforts 

of Elise Passentino, Isaac Winograd, and members of the technical staffs of the U.S. Environmental Protection Agency, the U.S. Nuclear 

Regulatory Commission, and the U.S. Department of Energy and its contractors in reviewing this circular. 

QUANTITY AND LOCATION OF THE 

TAILINGS 

Most uranium ores being mined in the United 

States are sandstones, but limestones and lignites are also of importance (Reed and others, 

1976). Milling consists of the mechanical and 

chemical processes that concentrate the uranium fraction from the ore. In conventional 

uranium milling, the ore is crushed and leached 

with either alkali or acid. Ores with the limestone contents greater than 15 percent are generally leached under alkaline conditions using 

sodium carbonate-bicarbonate, while most other 

ores are leached with sulfuric acid. The uranium extracted by the leaching solution is concentrated by solvent extraction or ion exchange, 

and subsequent precipitation (generally with 

ammonia) of a uranium concentrate (80-85 

percent U30s) that is referred to as "yellowcake." The leached ore residues, "tailings," are 

slurried with mill waste solutions and pumped 

to an earthen retention pond. 

As the ores being exploited in the United 

State today generally contain only about 0.1-

0.2 percent U30s, essentially all of the tonnage 
of ore processed at the mill is deposited in the 

tailings pond. With current mill capacities ranging up to 7,000 metric tons of ore per day 

(Reed and others, 1976), the magnitude of the 

tailings thus generated is apparent. At present, there are in excess of 100 million metric 

tons of uranium mill tailings in the United 

States. Dependent upon the growth pattern projected for the United States nuclear industry, 

and its reliance on domestic uranium sources, 

this s·olid waste inventory is estimated to increase to between 0.9 and 1. 7 billion metric 

tons by the year 2000 (Argonne National Laboratory, 1978; Adam and Rogers, 1978). Assuming a bulk density for the tailings of 

1.7 g/cm3 (Adam and Rogers, 1978), this latter 

quantity amounts to a volume of about one billion cubic meters. This volume would cover 

Washington, D.C., to a depth of about 5.8 m 

(19ft). 

Most uranium mining and milling to date 

has been in the Western States, especially in 

New Mexico, Colorado, Wyoming, Utah, and 

Texas (fig. 1). The bulk of these mills use 

---- ~ 

I 

I 

I 

I 

! )( I 

I ---.!_ 

conventional ore sources; however, active operations in Texas and Wyoming produce yellowcake from in-situ uranium leach solutions. Also, 

uranium is, or soon will be, recovered from 

phosphoric acid plants in Florida and Louisiana and from copper dump leach operations in 

Utah (Anonymous, 1978). As our reserves of 

higher grade ores becomes depleted, the mining and milling of lower grade and refractory 

materials such as described by Mutschler and 

others (1976) and Maysilles and others (1978) 

will undoubtedly increase. Also, the nationwide 

exploration activities associated with the U.S. 

Department of Energy's National Uranium 

Resource Evaluation (NURE) program may 

uncover new deposits. Thus, the areal extent 

of uranium mining and milling activities in the 

United States might be expected to increase 

in the coming decades. 

The tailings disposal sites may be broadly 

grouped into inactive and active milling categories. The tailings at the inactive sites generally exist as piles atop the land surface which 

are either exposed or covered by 0.15-0.6 m 

FIGURE !.-Location of active and inactive conventional uranium milling sites in the United States. 

3 
(0.5-2 ft) of soil (Ford, Bacon, and Davis 

Utah, Inc. 1976; 1977). Under the provisions 

of the Uranium Mill Tailings Radiation Control Act of 1978, the majority of thes·e inactive 

sites will be subject to remedial action under 

the direction of the U.S. Department of Energy. 

Based on the finding that uranium mill tailings 

may pose a potential and significant radiation 

health hazard to the public, this legislation 

calls for the stabilization and control of such 

tailings in a safe and environmentally sound 

manner in order to minimize or eliminate radiation health hazards to the public. The exact 

nature of this remedial action will be prescribed 

on a site-specific basis, in accordance with 

health and environmental criteria to be developed by the U.S. Environmental Protection 

Agency. Remedial-action options that were 

considered in engineering assessments of these 

sites prepared for the U.S. Department of Energy (Ford, Bacon, and Davis Utah, Inc., 1976; 

1977) include on-site stabilization of the piles 

with 0.15 to 5.5 m (0.5 to 18 ft) of cover earth, 

and removal of tailings from their present locations, and stabilization at alternative sites 

nearby. Remedial action at the inactive sites 

is likely to begin in the early 1980s. 

At the present time, the U.S. Nuclear Regulatory Commission (NRC) regulates the design and siting of uranium mill tailings 

disposal areas at active milling sites in nonAgreement States as part of its licensing and 

regulation of source material milling under the 

National Environmental Policy Act of 1969 and 

the Atomic Energy Act of 1954 (Hendrie, 

1978). The Uranium Mill Tailings Radiation 

Control Act of 1978 amends the Atomic Energy 

Act of 1954 by designation of uranium mill 

tailings as a by-product material, and authorizes the NRC to insure that the management 

of these tailings is carried out in such a manner as deemed appropriate to protect the public 

health and safety, and the environment from 

associated radiological and non-radiological 

hazards. Applicants for the issuance of a license to construct and operate a uranium mill 

are generally required to have a reclamation 

plan that includes a cover of at least 3 m (10 

ft) of earth over the tailings. Waste management criteria call for siting the tailings disposal areas in locations which are remote from 

4 

people, where disruption and dispersion by 

natural forces are eliminated or reduced to the 

maximum extent reasonably achievable (U.S. 

Nuclear Regulatory Commission, 1977a). Lining of disposal zones with compacted soil, 

asphalt, clay, or synthetic polymeric membranes may be required to reduce seepage of 

waste solutions. Disposal of tailings in open 

pit mines or specially excavated pits ("below 

grade") is now generally ... favored over impoundment behind a dam, the common disposal 

practice of the past. To date, there have been 

no uranium mill tailings piles stabilized in a 

manner consistent with current NRC licensing 

requirements. Such activities are likely to begin 

in about 15 to 25 years, following the completion of active milling and after a postoperational drying period, at sites being licensed 

today. 

RADIOACTIVITY IN TAILINGS 

Naturally-occurring uranium contains 

99.2830 percent (by weight) uranium-238, 

0.7110 percent uranium-235, and 0.0054 percent uranium-234 (Hammond, 1970). Uranium 

ores commonly mined in the Un-ited States 

contain little thorium-232 (Haywood and 

others, 1977). Thus the bulk of the radioactivity in the ore, and hence in the yellowcake 

and tailings, is associated with uranium-238 

and its progeny. The decay scheme of uranium-238 is shown in figure 2. The long-lived 

components of the decay chain, and hence those 

TABLE 1.-Water quality standards associated with 

uranium-238 decay series radionuclides 

[Concentrations (reported in picocuries/liter) as stipulated by indicated Federal agencieS) 

Radionuclide 

U-238 

U-234 

Th-230 

Ra-226 

P~210 

u.s. 

Nuclear 

Regulatory 

Commission 

(MPCw 

-unrestricted areas 1 ) 

40,000 

30,000 

2,000 

30 

100 

u.s. 

Environmental Protecteon 

Agency 

Interim 

Primary 

Drinking 

Water Regulations 2 

1 Maximum permissible concentrations in water for unrestricted areas; Code of Federal Regulations, Title 10, pt. 20, Jan. 1, 1977. 2 Federal Register, v. 41, no. 133, July 9, 1976. Title 40, cb. 1, 

pt. 141-Radionuclides. ' s Maximum of 5 pCi/L of combined Ra-226 and Ra-228. 
..... 

:a: 

(.) 

226 

~ 222 

u 

~ 0 

..... 

<( 218 

214 

210 

206 

~ ~ :::> :::> 2 i2 

<( 0 (k: :a: :::> ..... 

~ 

:::> 

2 

i= ~ u :::> ~ 

~ 2 :::> 

0 i= 0 (k: u <( a. <( (k: 

86 85 ' 

~ w :::> 2 

u 2 i= 2 0 <( 

<( 0 t; (k: <( 

LL (k: <( 

EXPLANATION 

NUCLIDE 

half-life(secs., 

mins., days 

or years) 

MODE OF DECAY L__!_ 

Major 

r -radiation 

Emitter 

~ 

:::> 

2 

0 

...J 

0 

a. 

:a: 

..... 

:::> 

~ Ul 

ill 

0 

<( 

w 

...J 

FIGURE 2.-The radioactive decay scheme of uranium-238. Only- dominant decay- modes are shown. (Adapted 

from U.S. Department of Health, Education and Welfare, 1970, and Motica, 1977). 

of environmental concern (table 1) , are uranium-238, uranium-234, thorium-230, radium226, and lead-210. Because the drinking water 

standards for radium-226 are the most restrictive (table 1), most monitoring and research 

efforts on the radiological impact of uranium 

mill tailings on surface- and ground-water 

quality have focused on this radionuclide. Assuming secular equilibrium, an ore containing 

0.2 percent U aOs will contain 0.00056 g of 

5 

radium-226/metric ton of ore (U.S. Environmental Protection Agency, 1973). As in both 

acid and alkaline leaching, greater than 98 percent of the radium-226 remains with the tailings (Moffett, 1976) ; the tailings from such 

an ore will contain about 560 picocuries (pCi) 

of radium-226/g. 

While about 90-95 percent of the uranium 

in the ore is extracted in the milling process, 

most of the uranium-daughter products, com-
prising about 85 percent of the total radioactivity in the ore, remain with the tailings, 

which thus constitute a low-level radioactive 

waste material. The tailings are often classified 

into a coarse- and a fine-size fraction referred 

to as "sand" and "slime," respectively. The 

uranium-bearing minerals are generally softer 

than the bulk components of the· host rock. 

Thus, crushing of the ore tends to concentrate 

the uranium and uranium-daughter products 

in the slime fractions. Borrowman and Brooks 

(1975) examined acid- and alkali-processed 

tailings and found that while the slime fraction 

made up only 25-27 percent by weight of the 

tailings, it contained 77-94 percent of the radium inventory. Slimes from the processing of 

ores from the Western United States may contain up to 3,000 pCi of radium-226/g (Haywood and others, 1977) . 

Besides radionuclides, non-radioactive substances potentially detrimental to water quality 

may also be introduced into the surficial environment by activities associated with. uranium milling. These substances may be present in the ore or in the process reagents. The 

process reagents may contribute chloride, nitrate, and sulfate (West, 1972; Clark, 1974), 

while the ores may contribute elements such as 

selenium, arsenic, molybdenum, and vanadium 

(U.S. Environmental Protection Agency, 1971; 

Clark, 197 4) . 

Besides the leached ore residues, 1nilling 

waste solutions (barren liquor from leach process with small amounts of entrained or soluble 

organic solvents) also enter the tailings retention pond. These waste streams contain soluble 

radionuclides that (1) may persist in solution 

and migrate in ground water, (2) may precipitate by interacting with components from other 

waste solutions or as a result of liming or other 

amendments, or (3) may be sorbed by the tailings or underlying soil in the retention pond. 

At the Bluewater uranium mill in New Mexico, 

waste effluents have in the past been disposed 

of by injection into a deep Permian aquifer 

containing non-potable water (West, 1972). 

6 

SOURCES OF POTENTIAL HUMAN 

RADIATION EXPOSURE FROM 

URANIUM MILL TAILINGS 

RADON EMANATION 

Radon-222 is the radioactive noble gas daughter product of Ra-226. Tailings from several 

acid-leach uranium mills in the United States 

have an emanating power (defined as that fraction of radon produced in a mineral matrix 

which escapes the matrix and is free to diffuse 

in the pore spaces) of about 10-20 percent 

(Ryon and others, 1977; Macbeth and others, 

1978) . Because of the short half-life of radon 

and the resultant radioactive decay of a portion of the radon released from the tailings 

particles during its diffusion through the pore 

spaces within the pile, the radon flux at the 

surface of the pile also depends upon the thickness, porosity, permeability, and moisture content of the tailings and any cover material. 

The relaxation length :

2 for radon diffusing 

through a dry sand is about 1.5 m (Tanner, 

1964a; Schiager, 1974; Macbeth and others, 

1978). 

Most assessments of the radiological impact 

of uranium mill tailings have concluded that 

the inhalation of radon daughter products is 

the major source of radiation exposure associated with these materials (U.S. Environmental Protection Agency, 1973; Haywood and 

others, 1977; Adam and Rogers, 1978). As 

radon release from inactive, dry tailings piles 

may be 4 to 25 times greater than that from 

wet tailings ponds (Goldsmith and others, 

1978; U.S. Environmental Protection Agency, 

1973) , the maximum radiological impact from 

this source may occur after mill operation 

ceases,· but prior to burial. Radon emanation 

will persist for a period governed by decay of 

thorium-230 (half-life of 77,000 years), the 

longest-lived uranium-238 daughter product 

that remains with the tailings and that decays 

to radium-226, the parent of radon-222 (fig. 2). 

WIND TRANSPORT 

Ore crushing and yellowcake drying and 

packaging lead to the atmospheric suspension 

2 The relaxation length is defined as the distance required to reduce the radon concentratfon by a factor of "e", where "e" is the 

base of the natural logarithm system and has the approximate 

value of 2. 72. 
of radioactive dusts, which create inhalation 

hazards locally, and are subject to wind movement to off-site areas. With available dust control technology such exposure pathways can be 

minimized (U.S. Environmental Protection 

Agency, 1973; Sears and others, 1975). 

Tailings exposed to the wind prior to burial, 

or as a result of the erosion of cover materials, 

will also be subject to wind transport. The 

quantity of the tailings thus mobilized will depend upon the characteristics of the wind ( velocity, duration, and direction), the characteristics of the tailings (particle size and moisture 

content), and the location of the tailings within 

or upon the landscape. Final burial of tailings 

in pits below at least 3m of earth, as presently 

recommended by the NRC, should greatly expand the period of protection of the tailings 

from wind transport as compared with that 

offered by the exposed or thinly-covered "abovegrade" 3 piles resulting from earlier operations. 

Breslin and Glauberman (1970) have shown 

dramatic photographs. of "dust devils" moving 

across such exposed tailings piles. Recent studies 

on bare, inactive tailings piles in western New 

Mexico (Dreesen, 1978) have demonstrated 

that large quantities of tailings sands may be 

caried downwind by particle creep and saltation, particularly during strong· spring winds. 

Windblown tailings from inactive, unstabilized 

tailings piles in the Western States are responsible for dose rates greater than 25 mRem/yr 

( millirem per year) 4 at distances up to 1 mile 

from the pile (U.S. Environmental Protection 

Agency, 1976b). Under present NRC mill licensing criteria, applicants must have a program that minimizes the dispersal of airborne 

particulates from tailings disposal areas auring mill operations and in the interim period 

prior to reclamation. Control measures generally include keeping the tailings moist and (or) 

using chemical binding agents (Martin, 1978; 

U.S. Nuclear Regulatory Commission, 1978e). 

SURFACE WATER TRANSPORT AND LEACHING 

First awareness of the environmental problems associated with uranium mill tailings 

3 In this report, "above grade" and "below grade" refer to NRc" 

terminology (U.S. Nuclear Regulatory Commission, 1979a) and indicate positions above or below the surrounding land surface. Other 

meanings associated with the term "grade" (see Gary and others, 

1972, p. 3·05) are not implied. 

7 

came in the late 1950's with the finding of high 

levels of soluble and suspended radium-226 in 

reaches of rivers in the Colorado River basin 

downstream from uranium mills. Prior to this 

time, one of the mills in the area discharged 

waste solutions and tailings to a neighboring 

water course. Photographs from the 1950's and 

1960's of several of the mill sites (Sigler and 

others, 1966) show the proximity of the unstabilized tailings piles to the banks of major 

rivers in the area. Such tailings are very susceptible to soil erosion processes and downstream transport in the watershed. Laboratory 

(see table 2) and field studies (Tsivoglou and 

others, 1960; Havlik and others, 1968b) suggest that uranium mill tailings and radiumcontaminated river sediments occurring in 

streambeds can act as sources of dissolved radium to the flowing water. Corrective action 

to eliminate the discharge of liquid and solid 

mill effluents to the river were taken in 1959 

(see page 8). Efforts at controlling erosion 

of the piles, begun in the late 1960's under the 

regulatory authority of the Colorado Department of Health, will undoubtedly be addressed 

by the remedial action program mandated by 

the Uranium Mill Tailings Radiation Control 

Act of 1978. The siting of tailings disposal 

areas on streambanks would not be permitted 

under present licensing criteria for uranium 

mill tailings management (U.S. Nuclear Regulatory Commission, 1977a). Nevertheless, the 

leaching of tailings by surface waters should 

be considered as the potential result of longterm erosional processes. 

4 For a discussion of ionizing radiation exposure, dose, and dose 

equivalent measurements, see Shapiro ( 1972) or other health physics 

texts. The mean annual whole body background radiation doses 

from natural sources of external ionizing radiation in Albuquerque, 

N. Mex.; Grand Junction, Colo.; and Cheyenne, Wyo., are about 

132, 159, and 164 milli,rads respectively (Eisen bud, 1963). The 

maximum permissible organ (excluding the thyroid) or whole body 

c:!ose equivalent for persons in· the general public as the result of 

expo3ures to planned discharges of radioactive materials to the 

general environment from uranium fuel cycle activities, and to 

radiation from these operations, will be 25 mRem/yr ( 0.025 Rem/ 

yr). Th!s standard (effective date for operations associated with 

milling of uranium ore is December 1, 1980), however, excludes 

dose equivalents attributable to radon and its daughter products 

(U.S. Environmental Protection Agency, 1976a, p. A17-A18; Federal Register, v. 42, no. 9, January 13, 1977, Part VII, p. 2858-

2861). While the standard excludes operations at waste di,sposal 

sites, windblown tailings at activity licensed millng sites are considered. The standard, however, does not apply retroactively to offsite, windblown tailings. At the inactive mill sites, remedial action to correct such ground contaminat:on will likely be part of 

the program initiated under the Uranium Mill Tailings Radiation 

Control Act of 1978. 
In the past, there have been tailings dike 

failures, and ess·entially instantaneous releases 

of up to 15,000 tons of tailings from an impoundment area (U.S. Atomic Energy Commission, 1974). Present design, construction 

and inspection criteria for earth and rockfill 

embankments used for retaining tailings at 

newly-licensed uranium mills using aboveground impoundments (U.S. Nuclear Regulatory Commission, 1977b) should reduce the 

probability of such failures. 

EXTERNAL GAMMA RADIATION 

Primarily because of gamma radiation 

emited by bismuth-214 (see fig. 2, p. 5), 

a uranium mill tailings pile constitutes a source 

for external radiation exposure. The exposure 

rate at the surface of an uncovered tailings 

pile may be estimated by the relationship developed by Schiager (1974) as follows: 

X=2.4 CRa 

where 

X= exposure rate at the surface of the pile, 

in microroentgens per hour, and 

CRa =concentration of radium-226 in the tailings in picocuries per gram. 

Thus for an exposed tailings pile containing 

560 pCi of radium-226/g, the gamma exposure 

rate at the surface is estimated to be about 

1,340 pR/hr, or about 12 R/yr. 

CONTAMINATION OF TERRESTRIAL AND 

AQUATIC VEGETATION 

Vegetation growing atop or adjacent to a 

uranium mill tailings disposal area may exhibit elevated levels of contaminants such as 

radium-226 as a result of either root uptake 

and translocation or surficial contamination of 

foliage by airborne particulates (Moffett and 

Tellier, 1977; Dreesen and otl)ers, 1978; Kelley, 

1978; Whicker, 1978). Thick soil covers will 

mitigate both pathways. However, many plants, 

especially selected species native to arid zones 

are deep-rooted, and may penetrate the underlying tailings (Kelley, 1978; Whicker, 1978; 

Wullstein, 1978). Researchers, sponsored by 

the U.S. Department of Energy, are examining the uptake of radionuclides by plant sp·ecies 

that may be involved in the vegetative stabilization of uranium mill tailings (written 

8 

commun., R. H. Kennedy, 1979). Translocation 

of radium, or perhaps radon (Hendricks, 1977), 

to foliage may result in enhanced radon exhalation from buried tailings. Ingestion of contaminated vegetation by humans, either directly 

or by consumption of livestock or game animals, which have grazed upon such vegetation, 

represents a potential source of human radiation exposure. 

Water quality studies on the Animas River 

in the vicinity of the now inactive uranium 

mill in Durango, Colo., by the U.S. Public 

Health Service and Utah State University in 

the late 1950's and early 1960's showed that 

aquatic algae may be radium accumulators. 

In 1958, essentially all of the liquid wastes 

from the mill were discharged to the river 

along with about 13.6 metric tons/day (15 

tons/day) of solid tailings (Tsivoglou and 

others, 1960). Early in 1959, impoundment and 

treatment of liquid effluents from the mill began and radium levels in the river water were 

observed to decine (Sigler and others, 1966). 

The mill closed in 1963 (Ford, Bacon, and 

Davis Utah, Inc., 1977; GJT-6). A 1958 sampling of the aquatic biota in .the river by the 

U.S. Public Health Service at locations 2, 23, 

and 59 river-miles below the mill showed 

radium-226 concentrations in the algae to be 

about 80, 30, and 5 times greater, respectively, 

than the concentrations observed in algae collected 1 mile upstream of the mill. The highest 

algal concentration of radium-226 observed 

was apparently 880 pCi/g (ashed weight), 

measured in the spring of 1959. This compares 

with radium levels in algae sampled upstream 

of the mill of about 3 to 6 pCi/g. With the 

initiation of pollution control measures at the 

mill, radium levels in the river water declined, 

and radium-226 concentrations in algae sampled in the downstream zone during 1960-1963 

averaged about 2 to 4 times that of the upstream samples (Sigler and others, 1963). Pilot 

studies are underway at one location in the 

Grants Mineral Belt of New Mexico on the 

use of algal uptake of radium as a pollution 

control measure for uranium mine and mill 

effluents (Eadie and Kaufmann, 1977). The 

uptake by algae of radium-226 entering surface waters can eventually also lead to incorporation into the human food chain. 
SEEPAGE 

The movement of both mill effluents through 

active tailings ponds and precipitation through 

inactive piles creates the potential for groundwater contamination. Some of the environmental, ore, and process factors that may influence 

the migration of radionuclides and other potentially toxic elements through the soil and 

subsurface materials are outlined as follows. 

Environmental Factors 

The arid and semi-arid climate in the Western States where most of the active and inactive mills in the United States are situated 

mitigates against extensive leaching of the tailings by percolating rainwater. At the model 

mill considered in the generic environmental 

impact statement on uranium milling (U.S. 

Nuclear Regulatory Commission, 1979a), the 

long-term rate at which water would seep 

through the tailings into the subsoil, following 

the cessation of mill operations and the accompanying discharge of waste solutions to the 

tailings pond, is estimated to be 5 percent of 

the rate of seepage during the period of operation. There are, however, uranium deposits 

and (or) mills located in areas of the Nation 

which have greater annual precipitation such 

as the Texas Gulf Coastal Plain and southeastern Alaska (Reed and others, 1976). Also, 

over the course of geologic time, a future shift 

to pluvial 5 conditions in the now arid Western 

States is certainly a possibility. For example, 

the present-day Chihuahuan, Sonoran, and 

Mohave Deserts of the Southwestern United 

States were woodlands less than 10,000 years 

ago, indicating a period of higher rainfall 

(Van Devender, 1977), or of lower temperature accompanied by lower evaporation rates 

(Brakenridge, 1978). 

The rate of movement of a dissolved species 

through a porous medium is a function of the 

relative affinity of the solute for the solution 

phase, as compared to the solid phase, as well 

as the bulk velocity of the fluid. Thus, the permeability and sorptive properties of the soil 

and rock underlying the disposal zone, and the 

pH, Eh, ionic strength, and composition of the 

a "Pluvial" refers to an episode of time or climate, especially 

one corresponding to a glacial age, characterized by abundant 

rainfall. 

9 

ground water influences the rate of subsurface 

transport of radionuclides. Factors influencing 

the mobilization or retardation of specific nuclides are discussed in the leaching section 

below. 

Lining of the tailings ponds with low permeability materials may inhibit the movement 

of radionuclides into the ground water. These 

materials may be chemically-inert, synthetic 

polymers such as polyvinyl chloride whose retarding effect is purely physical, or surfaceactive, natural materials such as bentonite, 

which may limit the movement of radionuclides 

by chemical as well as physical means. The 

use of liners is becoming more common at 

newly-licensed mills in the United States, in 

response to NRC guidelines (U.S. Nuclear Regulatory Commission, 1977a) cal1ing for minimization of seepage of toxic materials from 

tailings disposal areas into the ground-water 

system. At the Madawaska mill site near Bancroft, Ontario, a slurry of bentonite, local clay, 

and cement was injected into the alluvium to 

the bed-rock surface through slotted pipes in an 

attempt to form a "grout curtain" to reduce 

the amount of radium-226 and other contaminants, seeping from a tailings pond, that will 

reach a nearby lake (Dodds and others, 1978). 

When mill operations cease and waste solutions are no longer pumped to the tailings retention ponds, the liquid will eventually evaporate, leaving a pile of sand, slime, neutralization and BaS04 sludges, and process reagents. 

The recharge to local ground-water systems 

from the tailings retention system will be less 

after milling operations end than during operations owing to the cessation of input of process 

effluents. In the presently arid and semi-arid 

zones of the United States where most of the 

mill tailings are located, ground-water recharge 

by precipitation is low, thereby restricting the 

movement of radionuclides. 

Digital modeling studies of water movement 

in uncovered, inactive uranium mill tailings 

profiles suggest that under precipitation and 

evaporation conditions occurring in north-central Utah, long-term recharge to underlying 

shallow (water table at about 3 m) ground 

water can, however, occur (Hendricks, 1978; 

Klute and Heermann, 1978). Cover materials, 

vegetation, profile layering, intensity, duration, 
and character of evaporation and precipitation 

(rain and snow) events, and depth to the 

ground-water table may influence water flow 

in the profile and the extent of recharge (Klute 

and Heermann, 1978). These early results, however, suggest that tailing management schemes, 

which rely on the maintenance of moist conditions in cover materials and near-surface tailings to provide for radon-flux attenuation 

(Argonne National Laboratory, 1978) should 

be evaluated in light of the potential for increased recharge (Hendricks, 1978). In uranium mihing and milling areas with relatively 

high rainfall, for example, the Elliot Lake area 

of Ontario, Canada, such recharge through the 

tailings may be appreciable even after mill 

operations cease. 

Ore Factors 

The mineralogy of the host rock will influence the chemical properties of the water percolating through a tailings pile. The oxidation 

of pyrite contained in uranium mill tailings 

may result in the production of sulfuric acid. 

Some Canadian uranium ores contain from 4 

to 8 percent pyrite, and the inactive tailings 

piles at Elliot Lake, Ontario, exhibit pH values 

of 1.9 to 2.3 (Watkin and Winch, 1973; Moffett, 

1976). As thorium is soluble under acid leaching conditions (see below), seepage from an 

inactive tailings pile at Elliot Lake containing 

only 12 pCi of radium-226/L, had 7,500 pCi 

of thorium-230/L and 1,800 pCi of thorium232/L (Moffett, 1976). Uranium ores mined 

in the United States generally have lower pyrite contents. The Ambrosia Lake, New Mexico 

(Bell, 1963; Hilpert, 1969), Saguache County, 

Colorado (U.S. Forest Service, 1978), and 

Shirley Basin, Wyo., (Harshman, 1972), deposits contain significant amounts of pyrite, the 

latter containing about 1 percent pyrite in the 

unaltered sandstone host rock and from about 

0.2 to 18 percent pyrite in the ore. 

Process Factors 

The leaching solution, alkali or acid, will influence the chemical form, carbonates or sulfates, of the radionuclides in the tailings, and 

the pH of the tailings. At the Tuba City, Ariz., 

uranium mill site, the inactive acid-leached 

tailings piles have a pH as low as 2.3, while 

the inactive alkali-leached tailings piles have 

a pH as high as 9.5 (Havens and Dean, 1969). 

The neutralization of acidic mill effluents 

with lime and (or) limestone to about pH 8 

will precipitate most soluble thorium-230 and 

lead-210 as hydroxide and (or) carbonate 

phases, and reduce soluble radium-226 levels 

from about 1,000 pCi/L to about 100 pCi/L. 

The dissolved Ra-226 concentration in the neutralized effluent may subsequently be reduced 

to about 3 pCi/L by the coprecipitation of 

radium with BaS04 following the addition (to 

the neutralized, settled effluent) of BaCl2 in the 

presence of excess sulfate (International 

Atomic Energy Agency, 1976). Such procedures remove radionuclides from the liquid 

phase and transfer them to a solid phase where 

they are less likely to be environmentally 

mobile. 

USE OF TAILINGS AS A CONSTRUCTION 

MATERIAL 

Before the radiological hazards associated 

with uranium mill tailings were recognized, 

the desirable mechanical properties of the tailings sands, and the low cost of the material to 

local contractors, encouraged its use as a fill 

material in construction projects. The radiological hazards to occupants of structures constructed using these tailings sands involve: 

• External radiation exposure associated with 

gamma-emitting radionuclides in the tailings. 

• Inhalation of radon daughter products, and 

the resultant radiation dose to lung tissue. 

An estimated 300,000 tons of tailings were 

used in the Grand Junction area of Colorado, 

with about 50,000 tons of this going into home, 

business, and school construction, such as bedding for concrete slabs, water lines, and sewer 

lines. The use of tailings at Grand Junction 

continued from 1952 to 1966 when work by the 

Colorado State Department of Health and the 

U.S. Public Health Service showed elevated 

radiation levels in structures where tailings had 

been used. In 1972, a remedial action program 

(now about half completed) aimed at about 700 

such structures, and involving tailings removal 

and backfill with uncontaminated material, was 

begun under the management of the Colorado 

State Department of Health and the U.S. 

10 
Department of Energy (Hendricks, 1977; 

Comptroller General of the United States, 

1978). 

While the Grand Junction case appears to 

have been the most extensive, and has been the 

subject of the most documentation and public 

attention, the use of uranium mill tailings for 

construction purposes has apparently occurred 

to a limited extent in other communities where 

nearby piles existed, including Salt Lake City, 

Utah (Ford, Bacon, and Davis Utah, Inc., 

1978, table 1-1). In the Cane Valley area of 

southeastern Utah and northeastern Arizona, 

uranium mill tailings and ore had been used 

through 1975 for the construction of about 16 

residential structures on the Navajo Reservation. These materials were incorporated directly into the floor, foundation materials, and 

exterior stucco, in contrast to their usage at 

Grand Junction, primarily as bedding material 

for floors and foundations (Hans and Douglas, 

1975). The 1975 U.S. Environmental Protection Agency study which documented this practice at Cane Valley has presumably resulted in 

its cessation, and the remedial action and control measures at inactive and active mills mandated by the Uranium Mill Tailings Radiation 

Control Act of 1978 is likely to further curtail 

the use of tailings as a contruction material 

in the near future. 

LEACHING BEHAVIOR OF RADIUM, 

THORIUM, AND URANIUM 

RADIUM 

Radium exhibits only the (2+) oxidation 

state in solution, and its chemistry resembles 

that of barium. Radium forms water-soluble 

chloride, bromide, and nitrate salts. The phosphate, carbonate, selenate, fluoride, and oxalate 

salts of radium are slightly soluble in water, 

while radium sulfate is relatively insoluble in 

water [Ksp=4.25 x 10-n at 20°C (Sedlet, 1966)]. 

This solubility product for RaS04, the presumed chemical form of radium in sulfuric 

acid-leached tailings, corresponds to a radium 

concentration of 1.5 x 10- 3 g/L of pure water, 

and of 4.6 X 10- 6 g/L of water containing 200 

ppm sulfate. The latter concentration of radium, while only a few parts-per-billion, is still 

about six orders of magnitude greater than 

that permitted in drinking water (table 1). 

The hydrated ion of radium is the smallest 

in the alkaline earth series, and hence it would 

tend to be preferentially retained by ion exchange surfaces (Kirby and Salutsky, 1964; 

Sedlet, 1966). Radium has the least tendency 

of all the alkaline earths to form complex ions. 

Like the other alkaline earths, radium forms 

few complexes in acidic solutions. In alkaline 

solutions, anionic complexes of radium with 

organic ligands, such as EDT A ( ethylenediamine tetraacetic acid) and citric acid, are 

known to occur (Sedlet, 1966). Means and 

others (1978) suggest that EDTA-mobilization 

may be responsible for apparently elevated levels of radium seen in water and soil sampled 

around a radioactive waste disposal trench at 

the Oak Ridge National Laboratory burial 

ground. The possible complexation by natural 

chelating agents, such as fulvic acid, has apparently not been studied. Complexes with inorganic ligands, such as bicarbonate or chloride, are not reported to occur. Radium compounds have low solubilities in organic solvents 

(Kirby and Salutsky, 1964). 

Radium apparently does not form discrete 

minerals, but can coprecipitate with tannin and 

gelatin (Vdovenko and Dubasov, 1975), calcium carbonate, hydrous ferric oxides (Tanner, 

1964b), barite (BaS04), celestite (SrS04) and 

angelsite (PbS04) (Austin and Droullard, 

1978), tricalcium phosphate, thorium oxalate, 

and phosphate (Sedlet, 1966), and aluminum 

phosphate (Koide and Bruland, 1975). Associations of radium with barium sulfate are 

known in uranium ore deposits (Granger and 

others, 1961) and in nodules in cattle thyroids 

(Middlesworth, 1978) . These associations may 

11 

be due either to coprecipitation or the adsorption of radium onto existing barium sulfate 

crystals. Tanner (1964) cites Russian workers 

who report radium not to coprecipitate with 

gypsum [CaS04 ·2H20]. However, by-product 

gypsum from phosphoric acid production in 

central Florida contains about 20 to 30 pCi/ g 

of radium-226 (Kaufmann and Bliss, 1977). 

Radium may be sorbed by clay minerals, colloidal silicic acid (Vdovenko and Dubasov, 

1975), manganese oxides (Moore and Reid, 

1973), and organic matter (Titayeva, 1967; 

Morse, 1970; Titayeva and others, 1977). 

Ground waters dominated by chloride and (or) 
bicarbonate, low in sulfate, with high ionic 

strengths and high contents of calcium and 

barium are conducive to the transport of radium (Tanner, 1964b; Kagan, 1967; Perel'man, 

1972; Cadigan and others, 1976; Felmlee and 

Cadigan, 1978a). While, unlike uranium, only 

a single valence state exists for radium, the 

influence of oxidation-reduction conditions on 

the mobility of elements, such as iron, manganese, and sulfur, which may be involved in 

the coprecipitation and sorption of radium 

should be considered. 

In table 2, the results of several studies on 

the leachability of radium from uranium ores 

and mill tailings are listed. These data suggest the following generalizations: 

• Radium in uranium ore is only slightly soluble in H2S04, but highly soluble in HCl 

and HNOa, presumably because of the 

greater solubility of RaCl2 and Ra (N03 ) 2 

as compared to RaS04. 

• Radium in acid-processed tailings is leachable with EDTA, HCl, HN03 and distilled 

water. The solubility in distilled water is 

highly dependent upon the liquid-to-solid 

ratio used in the test, suggesting a limiting solubility product or suspension pH 

effect. The water leaching data presented 

in table 2 suggest that uranium mill tailings 

in the environment may constitute a longterm source for radium contamination of 

contacting surface and ground waters. Indeed some tailings in Canada that have 

been exposed to weathering forces for several years apparently do show evidence of 

radium depletion (Moffett and Tellier, 

1977; Skeaff, 1977). 

• The data on salt extraction (table 2) confuse, 

as well as clarify, the picture of how radium exists in the tailings. The differences 

in tailings materials and leaching conditions (time, temperature, solute concentrations ,solid-solution ratio) makes a comparison of the extraction-yield data difficult, as is an extrapolation of these data 

to natural environments. There are many 

apparent contradictions ; most notable is 

the effect of barium chloride leaching on 

radium removal. The recent work of Seeley 

(1976) on radium removal from real and 

simulated acid-leached uranium mill tail12 

ings slimes suggests that both adsorption 

and coprecipitation reactions may be involved in the retention of radium by the 

tailings. Radium may be sorbed on active 

sites of silicate minerals, as well as coprecipitated with several alkaline earth sulfate compounds of widely differing solubilities, for example, CaS04, SrS04, and 

BaS04. Hence, radium release from the 

tailings probably involves both surface 

desorption mechanisms, as well as multicomponent solubility considerations. By 

analogy to Seeleys work on acid leached 

tailings, alkaline earth carbonates are 

probably involved in the immobilization 

of radium in alkaline-leached uranium mill 

tailings. 

Shearer and Lee (1964) suggest that in 

acid-leached uranium mill tailings, radium 

exists as a coprecipitate with barium sulfate. Work by Levins and others (1978) 

on the leaching of alkaline earth elements 

from Australian-ore uranium mill tailings 

with varying strengths of sodium chloride solution showed a parallel increase 

in barium and radium-226 concentration 

in the leachate witp increasing salt molarity, while calcium and strontium concentrations iii the leachate varied little 

with salt molarity, thereby supporting an 

association of radium with a barium phase. 

However, other investigatons (Seeley, 

1976; Ryon and others, 1977; Kaiman, 

1977, 1978) suggest that radium may show 

more association with the far more soluble calcium sulfate mineral, gypsum. Also, 

a member of the jarosite family, a group 

of hydrous iron sulfate minerals, containing 80,000 pCi/g of radium-226 has been 

found in weathering pyritic tailings from 

Elliot Lake, Ontario (Moffett and others, 

1977). This jarosite-material may have 

precipitated during the acid-leaching process as suggested by Kaiman (1977, 1978), 

or may have been formed during the weathering of the ore or the tailings. The latter 

mechanism is suggested by the work of 

I varson and others ( 1978) on the synthesis 

of jarosite [KFea (S04) 2 (0H)6] in the presence of glauconite, illite, and microcline, 

and natrojarosite [NaFea (804) 2 (0H)6] in 
TABLE 2.-Proportion of radium-226 leached from uranium ore, uranium mill tailings, and river bottom sediments in laboratory tests 

Material 

Uranium 

ore. 

Acid-leached 

uranium 

mill tailings. 

Leaching conditions 

Distilled water, 25oC, 1 percent solids, 

65 min. 

Distilled water, room temperature, 10 percent 

solids, 3 hr. 

1N KCl, room temperature, 10 percent solids, 

0.25-5.0 hr. 

0.01N KCl, room temperature, 10 percent 

solids, 0.25 hr. 

1N NaCl, room temperature, 10 percent 

solids, 0.25-5 hr. 

1N CaCl2, room temperature, 10 percent solids, 

1-5 hr. 

1N BaCl2, room temperature, 10 percent solids, 

0.25 hr. 

N a-carbonate/bicarbonate, in-mill alkalineleaching conditions. 

HzS04, in-mill leaching acid conditions ______ _ 

0.1N HCl, room temperature, 5-8 hr ---------

1.5M HCl, 60°C, 25 percent solids, 3X30 min __ 

3M, HCl, 85·°C, 25 percent solids, 1 hr -------

3M HNOa, 85°C, 25 percent solids, 1 hr _____ _ 

Distilled water, 25°C, 3 percent solids, 15-

90 hr. 

Distilled water, 25°C, 3 percent solids, 380 

hr, 10 succ~ssive leaches of 15-90 hr each. 

DistiHed water, 25oC, 1 percent solids, 1 hr __ 

Distilled water, 25°C, 0.1 percent solids, 1 hr __ 

Distilled water, 25oC, 0.01 percent solids, 

1 hr. 

Distilled water, room temperature, 10 percent 

solids, 5-15 hrs. 

1N KCl, room temperature, 10 percent solids, 

l hr. 

1N KaP04, room temperature, 10 percent solids, 

6 hr. 

0.1N KCl, room temperature, 10 percent solids, 

1 hr. 

0.01N KCl, room temperature, 10 percent 

solids 15 min. 

1N NaCl, room temperature, 10 percent 

solids, 6 hr. 

1N NaaP04, room temperature, 10 percent 

solids, 6 hr. 

1N (NH4hS04, room temperature, 10 percent 

solids, 1 hr. 

1N CaCl2, room temp.erature, 10 percent solids, 

3 hr. 

13 

Proportion of 

Ra-226 

extracted 

(in percent) 

0.42 

2.3- 2.7 

22 -31 

2.6- 9 

14 -17 

3.1 - 5.3 

0.1 - 0.3 

1.5 - 2 .. 2 

0.4 - 0.7 

2.9 - 4.5 

86 -98 

90 

94 

0.2 - 1.0 

4.4 

1.2 

23.2 

40 

3.5- 4.7 

100 

2.4 

54 

10 

95 

6.6 

12 

48 

Reference 

Shearer, 1962 (table 17). 

Havlik and others, 1968b. 

Havlik and others, 1968b. 

Havlik and others, 1968b. 

Havlik and others, 1968b. 

Havlik and others, 1968b. 

Havlik and others, 1968b. 

Moffett, 1976. 

Moffett, 1976. 

Havlik and others, 1968a. 

Borrowman and Brooks, 

1975. 

Seeley, 1976. 

Seeley, 1976. 

Ryon and others, 1977. 

Ryon and others, 1977. 

Shearer, 1962 (table 20). 

Shearer, 1962 (table 20). 

Shearer, 1962 (table 20). 

Havlik and others, 

1968a, b. 

Havlik and others, 1968b. 

Havlik and others, 1968b. 

Havlik and others, 1968b. 

Havlik and others, 1968b. 

Havlik and others, 1968b. 

Havlik and others, 1968b. 

Havlik and others, 1968b. 

Havlik and others, 1968b. 
TABLE 2.-Proportion of radium-226 leached from uranium ore, uranium mill tailings, and river bottom sediments in laboratory tests-Continued 

Proportion of 

Material Leaching conditions Ra-226 Reference extracted 

(in percent) 

Acid-leached lN BaCl2, room temperature, 10 percent solids, 0.9 Havlik and others, 1968b. 

uranium 1 hr. 

mill tail- O.OlM, BaCl2, 25oC, 1 percent solids, 1 hr ---- 35 -37 Shearer, 1962 (table 29). 

ings. lN MgCl2, room temperature, 10 percent solids, 9.3 Shearer, 1962 (table 29). 

5h~ ' 

lN MgCOa, room temperature, 10 percent 2.0 Shearer, 1962 (table 29). 

solids, 5 hr. 

0.15M EDTA, 60°C, 15 percent solids, 5 hr ___ 80 Borrowman and Brooks, 

1975. 

1.5M HCI, 60oC, 25 percent solids, 3 X 30 min_ 92, Borrowman and Brooks, 

1975. 

O.lN HCl, room temperature, 10 percent 22.4 Havlik and others., 1968a. 

solids, 0.25-5 hr. 

O.OOlN HOI, room tempera.t.ure, 10 percent 9.6 Havlik and others, 1968a. 

solids, 0.25-5 hr. 

lO~N HaB04 (pH 6), room temperature, 10 5.0 Havlik and others, 1968a. 

percent solids, 0.25-5 hr. 

10-5M NaHCOa (pH 9), room temperature·, 10 2.8 Havlik and others, 1968. 

percent solids. 

O.lN NaOH, room temperature, 10 percent 4.9 Havlik and others, 1968a. 

solids, 0.25-5 hr. 

Acid-leached 3M HNOa, 85°C, 25 percent solids, 1 hr ------ 94 Seeley, 1976. 

uranium 

mill tailings 

(sand fraction only). 

Acid-leached 3M HNOa 85°C, 25 percent solids, 1 hr ------- 72 Seeley, 1976. 

uranium H20, room tem.perature!, 3 percent solids, 11 Seeley, 1976. 

mill tailings 16 hr. 

(slime frac- H20, room temperature, 0.01 percent solids, 20 -54 Skeaff, 1977. tion only). 15 min (in cyclosizer, wet particle size 

analyzer). 

lM LiCl, room temperature, 3 percent solids, 11 Seeley, 1976. 

16 hr. 

lM KCl, room temperature, 3 percent solids, 12 Seeley, 1976. 

16 hr. 

lM NH4Cl, room temperature, 3 percent solids, 15 Seeley, 1976. 

16 hr. 

lM AlCla, room temperature, 3 percent soHds, 20 Seeley, 1976. 

16 hr. 

lM HCI, room temperature, 3 percent solids, 34 Seeley, 1976. 

16 hr. 

lM NaCI, room temperature, 3 percent solids, 36 Seeley, 1976. 

16 hr. 

lM FeCla, room temperature, 3 percent solids, 59 Seeley, 1976. 

16 hr. 

lM BaCI2, room temperature, 3 percent solids, 65 Seeley, 1976. 

16 hr. 

lM CaCl2, room temperature, 3 percent solids, 73 Seeley, 1976. 

16 hr. 

14 
TABLE 2.-Proportion of radium-226 leached from uranium ore, uranium mill tailings, and river bottom sediments in laboratory tests-Continued 

Proportion of 

Mattrial Leaching conditions Ra-226 Reference extracted 

(in percent) 

Acid-leached 

uranium mill 

tailings. 

(Slime fraction only.) 

1M Na4 EDTA, room temperature, 3 percent 

solids, 16 hr. 

93 Seeley, 1976. 

1M Na2 DTPA, room temperature, 3 percent 

solids, 16 hr. 

94 Seeley, 1976. 

Alakali-leached 

uranium 

Distilled water, 25·°C, 1 percent solids, 1 hr __ 0.14 Shearer, 1962 (table 18). 

56 Borrowman and Brooks, 

mill tailings. 

0.15M EDTA, 60°C, 15 percent solids, 2 hr __ _ 

1975. 

River bottom 1 

sediment. 

Distilled water, 25oC, 1 percent solids 1 hr __ 

0.01M HCl, 25°C, 1 percent solids, 1 hr ------

0.07 Shearer, 1962 (table 32). 

0.30 Shearer, 1962 (table 32). 

0.01M NaCl, 25oC, 1 percent solids, 1 hr ____ _ 0.07 Shearer, 1962 (table 32). 

0.01M KCl, 25°C, 1 percent solids, 1 hr _____ _ 0.12 Shearer, 1962 (table 32). 

O.OlM MgCl2, 25oC, 1 percent solids, 1 hr ___ _ 0.07 Shearer, 1962 (table 32). 

0.01M CaCl2 25°C, 1 percent solids, 1 hr ------ 0.40 Shearer, 1962 (table 32). 

0.01M SrCl2, 25oC, 1 percent solids, 1 hr ___ _ 2.12 Shearer, 1962 (table 32). 

0.015M BaCl2, 25°C, 1 percent solids, 1 hr ___ _ 16.5 Shearer, 1962 (table 33). 

0.01M BaCl2, 25°C, 1 percent solids, 1 hr ____ _ 10.1 -12.8 Shearer, 1962 (tables 

32, 33). 

0.001MBaC12, 25oC, 1 percent solids, 1 hr ____ _ 6.4 Shearer, 1962 (table 33). 

0.0001MBaCI2, 25°C, 1 percent solids, 1 hr ___ _ 0.13 Shearer, 1962 (table 33). 

1 Collected at site 1-2 miles below a uranium mill waste discharge source. 

the presence of albite, during the oxidation of ferrous iron in solution by Thiobacillus ferrooxidans, an acidophilic bacterium found frequently in oxidizing pyritic environments. Indeed, the bacterium 

T. ferrooxidans and the mineral jarosite 

were isolated earlier by Ivarson (1973) 

from a yellow-brown sediment sampled at 

the bottom of a pool of highly-acidic water 

in an underground Elliot Lake mine, yielding pyrite- and pyrrhotite-bearing uranium ore. The possible redistribution and 

concentration of radium by this or other 

weathering-associated mechanisms may be 

of importance. in determining the mobility 

of radium. 

• The observation of a sorption-ion exchange 

type pattern of radium-226 displacement 

seen with the river sediments is more easily 

explained as these materials have presumably been chemically contaminated with 

soluble radium that has sorbed to the clays. 

and organic matter of the river bottom, 

as well as physically contaminated by tailings discharged by or eroded from the mill 

area. The replacing power relationship 

seen here: 

Ba>Sr>Ca>Mg 

follows that which might be predicted on 

the basis of hydrated ionic radii (Grim, 

1968) .• 

The geochemical controls on radium mobilization to, and removal from, natural waters 

has been little studied. Distribution coefficients 

measured for radium for soil and rock materials at three mill sites in Wyoming, Utah, and 

Washington range from 8 to 650 mL/g (U.S. 

Nuclear Regulatory Commission, 1978a). 

Whether these differences refl·ect technique dependency or actual differences in sorptive capacities is not clear. 

Some environmental analyses of subsurface 

radium migration from uranium mill tailings 

piles (Sears and others, 1975; U.S. Nuclear 

Regulatory Commission, 1978a) have assumed 

that because of the lack of significant groundwater recharge following the end of mill effiu15 
ent inputs to the tailings pond, and the sorption 

of radium by earth materials, no significant 

movement of radium will occur after mill operations cease. The analyses by Sears and others 

(1975) acknowledges the possible mobilization 

of radium by ground water as a result of climatic changes that increase leaching by infiltrating precipitation and by inundation by a 

rising water table. A study of radium and uranium concentrations in ground water samples 

from the Ogallala formation of the High Plains 

of Texas and New Mexico showed radium to be 

present in less than its radioactive equilibrium 

magnitude (Barker and Scott, 1958); Dyck 

(1978) indicates that in surficial environments, 

uranium is more readily leached from soil and 

rock than thorium-230 and radium-226. The 

preferential leaching of radium, with respect 

to uranium, by ground waters (Granger, 1963; 

Cadigan and Felmlee, 1977 ; Felmlee and Cadigan, 1978b), and in fossil bones ( Charalambous 

and Papastefanou, 1977; Papastefanou and 

Charalambous, 1978) has been noted in other 

studies. Differences in the relative mobilities 

of uranium and radium, as reflected in radioactive disequilibria studies, may be a reflection 

of local oxidation-reduction conditions affecting 

the solubility of uranium. However, the fact 

that high radium ground waters exist around 

uranium ore bodies ( Germanov and others, 

1958; Cook, 1978; U.S. Nuclear Regulatory 

Commission, 1978b,c) suggests that natural 

ground water can mobilize radium from the 

precursor of the tailings. While it is acknowledged that uranium mill tailings differ physically and chemically from uranium ore, detailed 

studies of the hydrogeochemical controls on the 

migration of radium from orebodies may provide valuable information for the assessment 

of long-term migration of radium from the 

tailngs deposits, which have histories of only 

about 30 years or less. This information may 

also have application to geologic disposal of 

high-level radioactive waste (spent reactor 

fuel), as radium-226 is the most hazardous 

nuclide for exposure by ingestion in such waste 

aged more than 50,000 years ( Gera, 1975) . 

The character of seepage water draining out 

of the tailings pile is difficult to predict over 

the long-term (U.S. Nuclear Regulatory Commission, 1979a). While the waste solutions discharged to the tailings pond at a conventional 

acid-leach mill will be high in sulfates, after 

the end of milling operations, only natural 

waters (precipitation and runoff) will be infiltrating the tailings. With time, the sulfate 

content of the seepage might be expected to 

decrease, and this may contribute to greater 

radium mobilization from the tailings. 

THORIU)1 

In aqueous systems, only the Th4 + oxidation 

state is known to exist. The tetravalent ion 

undergoes hydrolysis in aqueous solutions above 

pH 2 to 3 and is subject to extensive sorption 

by clay minerals and humic acid at near neutral 

pH (Bondietti, 1974; Ames and Rai, 1978). 

In near-neutral pH and alkaline soils, precipitation of thorium as a highly insoluble hydroxide (Hyde, 1960, indicates Ksp of Th ( OH) 4 = 

10- 39 ) or hydrated oxide phase (Ames and Rai, 

1978) and coprecipitation with hydrated ferric 

oxides (Kluge and others, 1977) may, in addition to adsorption reactions, be important 

mechanisms for the removal for thorium from 

solution. Because of sorption and precipitation 

reactions and the slow solution rate of thoriumbearing resistate minerals thorium levels in 

natural waters are generally low. 

Because of its high charge density, thorium, 

like uranium, in aqueous solution is susceptible 

to complex formation. Inorganic and organic, 

cationic, neutral and anionic, simple and polymeric complexes are known (Cotton and Wilkinson, 1966; Herman and Langmuir, 1978). 

Studies of soil profiles developed in the glacial 

moraines of the High Sierra area of California 

have shown evidence for thorium complexation 

by, and translocation with, soluble soil organic 

matter (Hansen and Huntington, 1969). Among 

the common inorganic anions that form strong 

complexes with thorium are fluoride, sulfate, 

phosphate, chloride, and nitrate (Ames and 

Rai, 1978). Centrifugation, dialysis, and ion 

exchange studies of thorium in ground waters 

from granitic terranes (Dement'yev and Syromyatnikov, 1965) suggest its occurrence and 

transport perodminantly as either a colloidal 

phase, or as a soluble, anionic complex. The 

principal chemical characteristics of the ground 

waters found to contain the most thorium were 

low pH, low salinity and hardness, and high 

16 
organic content (Dement'yev and Syromyatnikov, 1965). Thus, it would appear that some 

of the chemical properties of ground water 

th~t appear to favor the transport of thorium 

(high concentration of sulfate, low concentration of calcium, and low ionic strength) may 

inhibit the ground water transport of radium. 

The liquid effluents discharged to the tailings 

pond may contain a variety of organic compounds from the solvent extraction circuit or 

other stages in the milling process. Also, carbonaceous materials in uranium ores, which 

may be dissolved in the milling process (Dreesen and others, 1978), are discharged with the 

tailings. As organic complexes of thorium have 

been shown to be of importance in natural 

water systems, the influence of both natural 

and process-reagent organic species on the environmental mobility of thorium-230 should 

be evaluated. The presence of complexing 

agents in these effluents has been offered as a 

partial exp_lanation for the low distribution 

coefficients observed for thorium-230 on subsoil materials equilibrated with tailings pond 

water from a Wyoming millsite (D' Appolonia 

Consulting Engineers, Inc., 1977). 

The waste stream (pH 10) at the Humeca 

uranium mill contains about 110 pCi/L of 

thorium-230 (U.S. Environmental Protection 

Agency, 1976b). At lower pH's, thorium becomes more soluble. Acid-leach milling may 

dissolve from 30 to 90 percent of the thorium 

in the ore (Robertson, 1962; Moffet, 1976; 

Ryon and others, 1977; Levins and others, 

1978). Acidic effluents (pH 2.5) from uranium 

mills in the Grants Mineral Belt of New Mexico contain from 150,000 to 170,000 pCi/L of 

thorium-230 (Kaufmann and others, 1976). 

The solubilized thorium can be subsequently 

precipitated if the acidic effluent is neutralized, 

either by contact with natural media or by 

process additions of lime and (or) limestone 

to the waste solutions. At Elliot Lake, Ontario, 

current practice involves raising the pH of the 

tailings slurry to about pH 10.5 with lime upon 

impoundment (Raicevic, 1978). At the Sherwood uranium mill (acid-leach) in eastern 

Washington, the tailings slurry is neutralized 

(from an initial pH of about 1 to a final pH 

of about 7) by the addition of lime prior to 

discharge to the tailings pond (U.S. Depart17 

ment of the Interior, 1976); however, at most 

active mills in the United States, the waste 

stream is not neutralized. Neutralization of the 

waste solutions by contact with the alkaline 

subsoils which underlie the tailings ponds at 

most western sites will likely result in the 

precipitation or coprecipitation of thorium as 

noted above. 

URANIUM 

The dominant uranium valence states, which 

are stable in geologic environments, are the 

uranous (U4+) and uranyl (U6+) states, the 

former being far less soluble. The U4 + = U6 + 

transition has a redox potential within the 

normal range for geologic environments (Langmuir, 1978), 

U4 + + 2Hz0 = U0z2+ + 4H + + 2e-. 

The standard oxidation potential (25° C) is 

Eo= +0.27 volts. Uranium transport generally 

occurs in oxidizing surface and ground waters 

as the uranyl ion, U02

2+, or as uranyl floride-, 

phosphate-, or carbonate-complexes. These complex ions include neutral, cationic-, and anionicspecies. The uranyl ion and uranyl fluoride 

complexes dominate in oxidizing, acidic waters, 

while the phosphate- and carbonate- complexes 

dominate in near-neutral and alkaline oxidizing waters, respectively. Hydroxyl-, silicate-, 

organic-, and sulfate-complexes may also be 

of importance, the latter especially in mining 

and milling operations using sulfuric acid as 

a leaching agent (Langmuir, 1978). In weakly 

acid waters high in dissolved organic matter, 

uranium may be transported as a pseudocolloidal phase (Kochenov and others, 1965). 

Soils and related materials have been shown 

to sorb significant quantities of uranium. Masuda and Yamamoto (1971) showed that 10-g 

soil samples (pH 5.4-5.8) were able to sorb 

all of the uranium (supplied as uranyl nitrate) 

from 100 mL of aqueous solutions containing 

1 to 100 p.g/mL of uranium. The quantity of 

uranium adsorbed was not related to the soils' 

cation exchange capacities. Szalay (1964) 

showed peats to sorb up to 2-3 meq U0z2 + /g 

and suggests the sorption is a cation exchange 

process. Dement'yev and Syromyatnikov 

(1968) showed maximal sorption of hexavalent 

uranium by colloidal humic acid, fulvic acid, 
coal, and iron oxides to occur at pH 5 to 6. 

Langmuir ( 1978) reports maximal sorption of 

uranyl ions on natural materials (organic matter, iron-, manganese-, and titanium-oxyhydro:xides, zeolites, and clays) to occur at pH 5.0 

to 8.5. The sorption of uranyl ions by such 

natural media appears to be reversible, and for 

uranium to be "fixed" and thereby accumulate, 

it requires reduction to U4 + by the substrate or 

by a mobile phase such as H2S (Kochenov and 

others, 1965; Langmuir, 1978). 

WATER QUALITY STUDIES 

GRANTS MINERAL BELT IN NEW MEXICO 

The most extensive study to date on the 

effects of uranium mining and milling operations on ground water quality was done by the 

U.S. Environmental Protection Agency (EPA) 

in the Grants Mineral Belt area of northwestern New Mexico in 1975 (U.S. Environmental 

Protection Agency, 1975; Kaufmann and 

others, 1976; Eadie and Kaufmann, 1977). 

This area contains about 40 percent of the 

Nation's uranium reserves and presently has 

five inactive tailings piles, five active mills and 

seven mills in the proposal, design, or construction phase. Ground-water contamination in 

these milling areas can occur as a result of 

seepage from active tailings ponds, or inactive 

tailings piles, or from leakage out of the zone 

of injection from disposal well operations. 

Seepage from the tailings ponds in the Bluewater Valley and the Ambrosia Lake areas 

amounted to about 180,000 and 491,000 m3 /yr, 

respectively, for the period 1973-1974. These 

quantities represent about 8 and 29 percent, 

respectively, of the inflow to the ponds. 

While mill effluents (sampled at the Bluewater mill over the period 1960-1975) contained from 40 to 292 pCi/L of radium-226, 

only one of the· 71 existing wells sampled in 

the region (well depths ranging from 8.2 to 

299 m) showed radium-226 concentrations in 

excess of 5 pCi/L. This sample contained 6.6 

pCi/L of radium-226 and was obtained from 

a shallow (8.2 m) well adjacent to an active 

tailings pond in the Ambrosia Lake area. 

While the active mills discharge no waste 

solutions to the surface waters, mine drainage 

waters do enter surface water courses, and as 

shallow ground waters in these areas most 

commonly occur in valley fills, which may be 

recharged by surface water, the potential for 

ground-water contamination from this source 

exists. The radium content of mine drainage 

waters varies greatly with the stage of development of the mine, that is, the degree of exposure of the orebody. Mine drainage waters 

samples during the period 1970-1975 in the 

Churchrock and J ackpile-Paguate areas had 

radium-226 contents ranging from 8 to 190 

pCi/L. However, the EPA study failed to reveal ground-water contamination as a result 

of mining operations. 

Non-radioactive constituents in the mine and 

mill effluents can lead to elevated levels of 

total dissolved solids, ammonia, nitrate, selenium, and vanadium in surface and ground 

waters. Selenium probably occurs as the selenite 

anion in oxidizing, alkaline waters (Hem, 

1970), and is an element of concern in the 

vicinity of an alkaline-leach mill in the region. 

Shallow, downgradient, off-site, domestic wells 

containing up to 3.9 mg/ of selenium (EPA 

Interim Primary Drinking Water Standard is 

0.01 mg Se/L) have been observed here, the 

contaimination of the shallow aquifer presumably caused by seepage through the sandy soil 

from the adjacent tailings pond. Periodic resampling of selected wells in the EPA study 

is advisable to provide a data base for future 

evaluation of the environmental effects of mining and milling in the Grants area. 

ELLIOT LAKE, ONTARIO 

Important uranium deposits exist in the 

Elliot Lake area of southeastern Ontario, Canada. In contrast to the Grant Mineral Belt's 

mean annual precipitation of 25 em and evaporation potential of 180 em (Ford, Bacon, and 

Davis Utah, Inc., 1977, GJT-13), the wettemperate Elliot Lake area is characterized by 

~a mean annual precipitation of 80 em and 

evaporation of about 60 em (Hare and Thomas, 

1974). The uranium ore contains about 3-8 

percent pyrite, and hence upon oxidation, there 

exists the opportunity for extensive sulfuric 

acid leaching of the tailings. 

Moffett and Tellier (1978) have examined 

the tailings solids and ground water contained 

within the pile at a 17 -year old abandoned 

uranium mill tailings area at Elliot Lake. 

18 
Thorium, originally present in the ore at 170 

p.g/g, was reduced to 4-6 p.g/g in the upper 15-

20 em of the weathering tailings. It should be 

recognized that the concentration of thorium in 

the ore-feed may have varied during the life of 

the tailings pond. Also, some of the thorium 

solubilized during the acid milling of the ore 

may not, due to incomplete neutralization of the 

mill effluent, have been precipitated and deposited with the tailings solids sampled. Nevertheless, it would appear that much of the thorium present in the tailings solids at the time 

of deposition has since been lost to surface and 

ground waters. These tailings also show evidence of the leaching loss of uranium and 

radium-226, although again, the apparently 

diminished levels may reflect changes in the 

ore grade having gone through the mill, and 

sampling variations associated with the heterogeneity of the tailings pile. 

The ground waters sampled within the tailings pile are grouped into two acidity classes. 

The low acidity group samples (acidity <1000 

mg/L as CaC03) were all obtained from the 

slime-rich zones of the pile (where pyrite oxidation is restricted owing to a lack of dewatering) and were generally lower in total dissolved solids, iron, zinc, uranium, lead-210, and 

gross a and f3 activity than those samples in 

the high acidity group. While the low acidity 

waters showed no detectable thorium, the high 

acidity waters showed up to 2,100 pCi/L of 

thorium-228, 4,200 pCi/L of thorium-232, and 

52,000 pCi/L of thorium-230. In contrast to 

the trend observed for the other radioisotopes, 

radium-226 levels were generally higher in the 

low acidity (mean= 113 pCi/L) as compared 

to the high acidity (mean=59 pCi/L) waters 

(Moffett and Tellier, 1978). This may be due 

to the suppression of RaS04 dissolution in the 

zones of active pyrite oxidation caused by the 

high sulfate concentrations in the interstitial 

waters. 

The leaching of radionuclides from abandoned Elliot Lake tailings has been studied in 

laboratory columns by Schmidtke and others 

( 1978) . These tailings initially contained 122 

pCi/g of radium-226 and 3.2 pCi/g of thorium-230. Using water application rates of 49 

mm/yr, the leachate contained 81 pCi radium226/L initially, decreasing in 2.3 years to 5 

pCi/L, and 1565 pCi/L of thorium-230, initially, decreasing in 2.3 years to 693 pCi/L. 

OTHER AREAS 

The U.S. Department of Energy has recently 

issued a series of 20 reports prepared by Ford, 

Bacon, and Davis Utah, Inc., dealing with inactive uranium mill tailings piles in eight 

Western States (Ford, Bacon, and Davis Utah, 

Inc., 1976, 1977). These reports are engineering assessments of possible methods and costs 

of cleanup of these sites, and include sitespecific information on tailings characteristics 

and ground water and soil contamination. 

The tailings sampled at the various piles 

were found to have a maximum radium-226 

concentration ranging from about 100 to 5,000 

pCi/g .The depth of leaching of radium into 

the soil beneath most of the tailings (generally 

defined in these reports as the depth at which 

the soil radium-226 levels fall to twice background levels) ranged up to about 8 feet. At 

several of the sites (Monument Valley and 

Tuba City in Arizona, Durango, Naturita, and 

Rifle in Colorado, Ambrosia Lake in New Mexico, and Falls City in Texas) there were indications of local ground and surface water contamination with respect to Ra-226, presumably 

caused by seepage and runoff from the tailings 

piles, although with the exception of the Ambrosia Lake and Falls City sites, EPA drinking water standards were generally not exceeded at the time of sampling (Ford, Bacon, 

and Davis Utah, Inc., 1977, GJT-4,6,8,10,13, 

16). At the Naturita, Grand Junction, Old 

Rifle, and Gunnison sites, the water table 

within the alluvium on which the tailings piles 

rest is very shalow, and at times may rise 

within the tailings, thereby creating the potential for unconfined ground water to leach the 

tailings (Ford, Bacon, and Davis Utah, Inc., 

1977, GJT-8,9,10,12). 

URANIUM MILL TAILINGS TREATMENT 

AND DISPOSAL OPTIONS 

SURFACE STABILIZATION OF TAILINGS AND 

NEAR SURFACE BURIAL 

The tailings are non-cohesive, small rock 

fragments, and thus highly susceptible to erosive forces. They generally do not have the 

physical and chemical properties required to 

19 
sustain plant growth, and therefore will not 

be amenable to direct stabilization by vegetation. To date, many inactive tailings piles remain uncovered and unvegetated, and thereby 

subject to severe wind and water erosion. Stabilization efforts to date have generally involved contouring of the pile, application of a 

thin earth cover (topsoil, gravel, riprap on 

steep slopes), vegetation, and construction of 

drainage ditches to divert surface runoff water 

from neighboring land from reaching and eroding the piles. 

Climatic considerations, such as lack of adequate rainfall for plant growth, and the low 

fertility of cover materials often require the 

use of mulches, fertilizer, and irrigation water 

in order to establish a vegetation stand. While 

it is certainly possible, with human intervention and application of soil amendments, to 

establish vegetation on these tailings and 

cover materials, at present there has been insufficient research and time to evaluate whether 

or not permanent, maintenance-free vegetative stabilization can be successfully achieved. 

The record to date is spotty. While at some 

locations thick vegetation stands have been 

achieved, these have often required repeated 

irrigation. Visible erosion following stabilization attempts have been reported (Ford, Bacon, 

and Davis Utah, Inc., 1977, GJT-18). 

In areas where stabilization with vegetation 

is not feasible because of lack of sufficient 

rainfall, chemical stabilization methods have 

been proposed and (or) tried. The use of a 

water-soluble, elastom~ric polymer tailingsbinding agents was tested on the Tuba City, 

Ariz., uranium mill tailings in Se·ptember 1968 

(Havens and Dean, 1968). A May 1974 inspection of the site showed extensive disintegration of the initially indurated crust (Ford, 

Bacon, and Davis Utah, Inc., 1977, GJT-5). 

Decomposition of the stabilization crust within 

2 to 3 years was observed following the test 

application of a tar-like agent to the surface 

of a portion of the tailings at the inactive mill 

site in Salt Lake City, Utah (Ford, Bacon, and 

Davis Utah, Inc., 1976). A major loss of the 

radon-flux attenuating abilities of a plasticized 

sulfur compound was observed in 2 years at 

uranium mill tailings test plots near Las Vegas, 

Nev. (Bernhardt and others, 1975; Macbeth 

20 

and others, 1978) . The placement of a coarse 

rock cover over the soil cap in order to approximate a natural "desert pavement," and 

thereby armor the soil cap has been suggested 

as a means of prolonging the period of tailings 

burial (Nelson and Shepard, 1978). A coarse 

rock cover has been used with some success 

in minimizing wind and water erosion of tailings at the inactive mill site near Shiprock, 

N.Mex. (Nelson and Shepard, 1978). A gravel 

cover will apparently be used in the final stabilization of the tailings derived from a mill 

in southeastern Utah, which was recently considered for relicensing (U.S. Nuclear Regulatory Commission, 1979b) . 

The use of "below -grade" burial of tailings 

in pits, and the use of 3 m or more of cover 

earth, as advocated by the NRC (U.S. Nuclear 

Regulatory Commission, 1979a), will provide 

for a longer period of erosional stability than 

that associated with "above-grade" impoundment of tailings, the common disposal method 

at the inactive sites and older active sites. 

"Below-grade" disposal will not result in remnant tailings piles above the land Sll;rface, and 

thus the component cover materials and tailings 

will be less susceptible to wind and water erosion than those in "above-grade" structures. 

However, cover materials and tailings in 

"below-grade" disposal systems, as well as the 

surrounding land surface, are, nevertheless, 

subject to erosion. 

"Stability" is a time-dependent concept. A 

concept whose time-focus is that of human life 

spans and the life spans of man-made structures is inadequate in assessing the fate of 

materials whose radioactive character persists 

over hundreds of thousands of years. Schumm 

(1963) reports average denudation rates of 9 

to 20 cm/1,000 yr for arid/semi-arid terranes 

[average annual precipitation of 25 to 38 em 

(10-15 inches)]. Using the lower end of this 

range, earthen covers of 0.6 m (2ft) and 3m 

(10ft) in thickness would be removed in about 

6,700 and 33,000 years, respectively. During 

these time periods about 6 and 26 percent, 

respectively, of the thorium-230 will have decayed, and without subsequent reburial, the 

tailings, with the bulk of their radioactive complement, thus may be exposed to wind and 

water erosion. 
The rates of disinterment presented require 

qualification. The regional denudation rates 

used do not consider local conditions such as 

position in drainage basin and topographic features providing wind breaks (U.S. Nuclear 

Regulatory Commission, 1979a), which may 

cause local erosion rates to deviate considerably in either direction from the regional mean. 

Neither do the disinterment rates consider 

climatic changes in the future that can alter 

erosion rates. Manipulated soil covers are likely 

to be more susceptible to erosion than natural 

soils or bedrock. Grazing and burrowing activities of animals may increase the erosion rates 

(Whicker, 1978). On the other hand, newlydesigned tailings disposal areas (U.S. Nuclear 

Regulatory C~mmission, 1978d) will probably 

be covered and contoured to yield a low relieflength ratio; hence the regional denudation 

rates presented above may overestimate the rate 

of disinterment. Also, the consideration of regional denudation rates emphasizes erosional 

processes to the exclusion of depositional processes that may be of local importance in a given 

area. Indeed, siting of tailings disposal areas 

in aggrading portions of landscape may be beneficial as depositional processes would tend to 

maintain a cover above the tailings, and thus 

attenuate dispersal as well as radon exhalation and gamma radiation exposure (U.S. Nuclear Regulatory Commission, 1979a). These 

potential benefits associated with an aggrading 

geomorphic surface may, however, be offset if 

the area is also a ground-water recharge zone. 

Radon emanation can be controlled by covering the tailings with either liquids or solids, 

thereby decreasing the diffusion rate of the 

radon and allowing for its decay (half-life of 

radon-222 is 3.8 days) prior to atmospheric 

emergence. A water cover of 60 em (2ft) can 

reduce radon emanation by about 96 percent 

(U.S. Environmental Protection Agency, 1973). 

However, long-term maintenance of a ponded 

situation may not be possible after mill operation ceases, nor is it a desirable situation from 

the standpoint of seepa.ge of radium and other 

contaminants into the subsurface. 

Two feet of earth will theoretically reduce 

radon emanation, with respect to the bare tailings, by about 25-60 percent (U.S. Environmental Protection Agency, 1973; Sears and 

21 

others, 1975) .

6 A recent NRC position paper 

(U.S. Nuclear Regulatory Commission, 1977a) 

indicates that a major goal of uranium mill 

tailings management programs should be the 

reduction of radon emanation rates from inactive tailings impoundment areas to about 

twice that of the emanation rate in the surrounding environs. 7 Assuming an average background radon emanation rate of about 1 pCi 

m- 2 s- 1 (Wilkening, 1974; Martin and Miller, 

1978) and a radon flux from a typical exposed 

tailings pile of about 500 pCi m- 2 s- 1 (Clements and others, 1978), the NRC goals require 

about a 99.6 percent reduction in radon emanation. Depending upon the cover materials 

particle size distribution, bulk density, moisture content, and other properties affecting the 

permeability to radon migration, a thickness 

of about 3 to 12m (10-40 ft) or more of earth 

will be required for a 99 percent reduction in 

radon emanation from the underlying tailings 

(U.S. Environmental Protection Agency, 1973; 

Sears and others, 1975; Macbeth and others, 

1978; Nelson and Shepard, 1978). Thus to reduce radon emanation to a maximum extent, 

particularly in view of the erosion rates previously cited, burial of the tailings in a deep 

excavation or cavity would be most effective. 

While concrete, asphalt, and organic binding 

agents may provide marked reductions in radon 

0 Radon measurements were made in the atmosphere above the 

uranium mill tailings pile at Grand Junction, Colo., in 1967-68, 

during the active life of the mill, and again in 1974-75, following 

the stabilization of the inactive tailings pile with a 6-inch soil cover 

in 1970 (Duncan and others, 1977). Although the comparative data 

is limited to only two stations, it suggests that the mean annual 

radon concentration measured above the tailings pile after stabilization was about three times that measured before stabilization. This 

result is probably associated with the differing mo:sture contents 

of the pile at the different sampling times. In 1967-68 portions of 

the pile were ponded as a result of the input of mill effluents, 

while in 1974-75 the tailings were much drier, the only moisture 

inputs to the pile being the natural precipitation and occasional 

irrigation waters. This decreased moisture content would allow 

radon to diffuse more rapidly within the tailings pile and thus 

more radon would reach the atmospheric interface before its 

radioactive decay. Other possibly contributing factors in the poststabilization increase in atmosphere radon concentratons include: 

( 1) The redistribution of tailings during contouring operations 

p~rformed as part of the stabilization program and the resultant 

changes in pile depth, surface area and relative position, with respect to the surface, of high-radium slime zones and ( 2) The action of plant roots, burrowing animals, and dessication and settling 

cracks in penetrat:.ng the soil cap and tailings, and thereby creating channels for radon movement. 7 The proposed radon flux limit in the draft generic environmental impact statement on uranium milling prepared by the U.S. 

Nuclear Regulatory Commission (1979a) is given as 2 pCi m-2 s-1 

rather than as an increment of background. 
flux in laboratory and short-term field trials, 

their long-term physical and chemical stability 

in the weathering environment should be considered. 

Cover rna terials will also affect levels of 

gamma radiation exposure from the pile. The 

cover, by virtue of its shielding character, will 

produce a net attenuation of the exposure rate. 

Each 30 em ( 1 ft) of packed earth will theoretically reduce the exposure rate by a factor 

of about ten (Swift and others, 1976). Thus, 

for a typical pile (see pg. 8}, a 120 em (4-ft) 

earthen cover should reduce the surface exposure rate on the pile to about 1 n1R/year. 

Current NRC licensing guidelines (U.S. Nuclear Regulatory Commission, 1977a) call for 

the reduction of direct gamma radiation from 

reclaimed tailings impoundment areas to essentially background levels ( about 150 mR/yr in 

Western States where most uranium is mined). 

While the relatively thick covers, 3-5m (10-15 

feet) , proposed for new mill tailings reclamation projects will certainly achieve such control levels, their removal by erosion over geologic time will progressively restore both the 

radon flux and gamma exposure rate to thefr 

uncovered values. 

RADIUM REMOVAL FROM TAILINGS 

An alternative to the controlled storage of 

radioactive mill tailings would be the removal 

of the uranium daughter products, either initially from the ore at the time of milling, or 

from the tailings subsequently, to produce a 

radiologically-innocuous crushed-rock material, 

and a radioactive concentrate. Borrowman and 

Brooks (1975) showed that from 92 to 96 percent of the radium in uranium ores was leached 

(25 percent solids slurry) by two, 30-minute, 

60°C treatments with 1.5 M HCI. More than 

99 percent of the uranium present in the ore 

was leached by this treatment. Following uranium removal, the leach liquor was lime-neutralized and dosed with barium chloride and 

sodium sulfate to coprecipitate the leached 

radium with barium sulfate. Greater than 99 

percent radium removal was achieved thereby 

in a BaS04 precipitate having 4 percent of the 

weight of the ore treated .As thorium-230 is 

the long-lived parent isotope of radium-226, 

thorium removal would be an essential component of any adopted milling process aimed at 

radium removal from the tailings. Thorium, 

like radium, forms acid-soluble chloride salts 

(Rogers and Adams, 1969), and hence its removal from the tailings by an HCl leaching 

process would also appear possible. Concentration of thorium in solution by coprecipitation 

with barium sulfate may be possible (Ambe 

and Lieser, 1978). For this reason, the radium 

concentrate proposed above may also contain 

much of the thorium. Alternate procedures for 

the concentration of the thorium-230 from 

uranium mill effluents by a combination of ion 

exchange, coprecipitation, and solvent extraction procedures, followed by precipitation of 

thorium hydroxide have been proposed by 

Kluge and others (1977). 

Borrowman and Brooks (1975) also found 

92-95 percent radium removal by 1.5-3.0 M 

HCl from acid-processed uranium mill tailings. 

Thus "detoxification" of existing tailings would 

appear possible. The remilling of tailings for 

recovery of residual uranium offers an opportunity for such a radium removal. The inactive uranium mill tailings examined by Ford, 

Bacon, and Davis Utah, Inc. (1976, 1977) had 

residual uranium contents of from 0.005 to 

0.049 percent (by weight) U30s, and with 

present-day technology it appears economically feasible to reprocess tailings with greater 

than about 0.02 to 0.03 percent U 30s. 

Work at Oak Ridge National Laboratory 

focusing on nitric acid leaching of uranium 

ores and tailings has shown removals of 85-98 

percent of the radium-226 by a two-stage leach 

with 3M HN03 at 33 percent solids for 5 hours 

at 70°C (Ryon and others, 1977). Thorium-230 

removals from these ores and tailings under 

identical leaching conditions were 92-99 percent, and uranium removals from the ores were 

greater than 99.5 percent. Conversion of the 

extracted radium- and thorium-nitrates to an 

oxide form by heating and fixation of this oxide 

concentrate, in asphalt for example, prior to 

burial may be a possible disposal technique 

(U.S. Nuclear Regulatory Commission, 1979a). 

Thus, nitric acid leaching offers another possible method for producing a radium- and 

thorium-depleted tailings material, although 

problems related to ground-water contamination by nitrates from waste solutions would 

22 
probably exist with such a system. Neither the 

HCl nor HN03 milling of ores or tailings has 

yet been commercially-adopted, probably because of a combination of concerns, including 

those regarding the field-scale feasibility and 

the higher projected capital and operating costs 

of such processes as compared to conventional 

sulfuric acid milling and the disposal of radioactive concentrates and residual materials. 

Levins and others (1978) have studied the use 

of low-cost sodium chloride for the leaching of 

radium from uranium mill tailings. While over 

90 percent removal is achieved by four-stage 

leaching of acid-milled tailings in 5 M N aCl 

solutions at 25°C, the process does not remove 

thorium-230, hence, the long-term source for 

radium-226 remains in the tailings. 

Raicevic (1978) has developed a flotation 

procedure which removes about 60-75 percent 

of the uranium, thorium and radium-226, as 

well as about 95 percent of the pyrite in samples of Elliot Lake tailings, and concentrates 

them in a fraction of about 25 percent the 

weight of the original tailings. Flotation tests 

by the U.S. Bureau of Mines on acid-leached 

tailings from the inactive, Salt Lake City site, 

like th{Jse of Raicevic (1978), yielded a radiumrich gypsum concentrate (Borrowman and 

Brooks, 1975). However, the flotation techniques tried were less effective than sand-slime 

separation by simple sedimentation, the latter 

process achieving a concentration of 94 percent 

of the radium-226 into a slime fraction representing 25 weight-percent of the original tailings. 

Because of their higher radionuclide levels, 

the concentrates derived from the physical or 

chemical separation of the radium-226 and other 

radionuclides from the tailings will probably 

require a higher level of control than the original tailings. Recent work sponsored by the 

Canada Centre for Mineral and Energy Technology focused on the -chemical and biological 

stability of the Ba/RaS04 sludges. While radon 

emanation from such precipitates is reported 

to be low (Hahn, 1936), radium may be released from them as a result of chemical leaching by natural water and (or) as a result of 

the microbial metabolism of the precipitate 

by anaerobic, sulfate-reducing bacteria present 

in soils and waters (pers. commun., R. G. L. 

McCready. As radium in sulfuric acid-leached 

mill tailings may also exist as a mixed alkaline 

earth-sulfate precipitate (Seeley, 1976), these 

same microbial and chemical processes may 

also be operative in conventional tailings 

disposal systems. 

The level of control required for the residual 

material will depend upon the degree of decontamination achieved. Neither research nor regulatory efforts to date have clearly established 

a "safe" level of radium-226 in earth materials destined for unrestricted environmental 

disposal. A radium-226 concentration of about 

20 pCijg has been suggested as a goal for the 

unrestricted storage of tailings by Borrowman and Brooks (1975) and Schiager (1977). 

The U.S. Environmental Protection Agency 

(1978a,b) has proposed a radium concentration of 5 pCi of radium-226/g as the lower 

limit for designation of uranium and phosphate milling and processing solid wastes as 

"hazardous," and thereby requiring regulated 

disposal and ground-water monitoring. In contrast, the State of Louisiana has adopted a 

regulation establishing 0.1 pCi/ g as the maximum allowable concentration of radioactive 

material (nuclides not specified) in mineral 

tailings not subject to radiation safety disposal 

requirements (Conference of Radiation Control Program Directors, 1978). Such a standard would appear to be untenable with respect 

to radium-226 as its average crustal abundance is about 1 pCi/g (Rankama and Sahama, 

1950; Borrowman and Brooks, 1975). However, work at Elliot Lake, Ontario (Mooney 

and Scott, 1978; Dilworth, Secord, Meagher 

and Associates Ltd., 1979) suggests that glacial 

sands with a total radium concentration of 

only 1pCi/g and an emanation coefficient of 

20 percent may produce unacceptable radon 

daughter concentrations in overlying dwellings. 

PRECONCENTRATION OF URANIUM ORE 

The pre-milling sorting or beneficiation of 

the uranium ore into a high- and a low-activity 

fraction has been suggested by Canadian workers (Lush and others, 1978) as a means of 

reducing the quantity of radioactive tailings 

generated. The high activity fraction containing most of the uranium and uranium-daughter 

products would be milled, and yield a tailings 

23 
having an estimated mass of about 20-50 percent that of conventional milling, while containing two to five times more radium and 

other uranium daughter products per unit 

mass. This smaller quantity of more concentrated tailings would presumably be more 

amenable to waste management. The fate of 

the non-milled, low activity fraction is not 

discussed. 

Preconcentration of certain types of uranium 

ores by high speed lump sorting machines 

equipped with radiometric detectors would appear to be technically attainable and economically desirable (Smith and White, 1969). A 

gravity-flotation technique tested on a quartzpebble conglomerate, Elliot Lake ore achieved 

a bulk reduction of 2 or 3:1 with a 90 percent 

recovery of uranium (Honeywell and Kaiman, 

1966). 

The bulk of the uranium ores presently 

milled in the United States are low grade 

(about 0.1-0.2 percent U30s) sandstone deposits in which the uranium coats the sand grains 

and fills the interstices (Harshman, 1970), 

and thus would not appear to be amenable to 

upgrading by lump sorting. The physical upgrading of these ores by other mineral beneficiation methods may be possible, although no 

such research- or commercial-scale operations 

are known to the author. Preconcentration by 

sizing had been used at several, now-inactive 

upgrading plants and mills in the United States 

with such sandstone ores. This process yielded 

a slime concentrate high in uranium and its 

daughter products, and a sandy fraction which 

was discharged to a tailings pond (M·erritt, 

1971). Such efforts were aimed at producing 

an acceptable mill feed from low-grade ores 

and (or) at reducing the cost of shipping ore 

to the mill. They did not influence the overall 

waste management problem, as the tailings 

from such upgrader operations, and similarly 

the segregated sand fractions of tailings at 

conventional mills, contain too much radium 

and other potentially detrimental elements for 

unrestricted disposal. Preconcentration of ore 

and the segregation for disposal of the lowactivity fraction may be of value in the waste 

management area, but only if that reject fraction is sufficiently low in radioactive and toxic 

elements as to justify a lesser degree of environmental control than the tailings from the 

processing of the high-activity fraction. 

DEEP BURIAL IN UNDERGROUND CAVITIES 

Deep burial provides for longer periods of 

isolation prior to disinterment by erosive 

forces, as well as greater long-term attenuation 

of radon exhalation and gamma radiation exposure, than shallow burial. Underground excavation is expensive and with the large volume 

of tailings to be buried, the construction of 

cavities solely for such disposal is highly unlikely. For this reason, emplacement in abandoned mine shafts and drifts is the most likely 

option for deep disposal of tailings. While 

cavities from various mining operations may 

potentially be available, proximity to mill sites 

makes those associated with underground uranium mining the most likely candidates. At 

present, about 50 percent of the uranium 

(based on quantity of U30s) produced in the 

United States is associated with underground 

mining. About 56-70 percent of the presentlyestimated $30-uranium ore reserves 8 lie at 

depths greater than 90-150 m (300-500 ft), 

allowing for recovery largely by underground, 

and perhaps solution mining, as opposed to 

open pit mining (U.S. Department of Energy, 

1978). Because of the large volume of tailings 

generated by the milling of open pit-mined ores, 

as well as the bulking (the increase in volume 

of material owing to manipulation of the tailings as compared to the in-place ore) and the 

collapse of cavities at depth owing to the mining of pillars, the volume of underground space 

associated with uranium mining available for 

the potential disposal of tailings is obviously 

inadequate to handle all of the tailings that 

will be produed. 

Deep burial may put tailings in contact with 

aquifers and thereby introduce radioactive and 

non-radioactive contaminants into the ground 

water. Whether such disposal is environmentally-acceptable will be dependent upon many 

factors including the chemical form and quantity of the elements of concern in the tailings, 

the ability of the ground water to leach these 

constituents from the tailings, th~ chemical 

8 Ore that is estimated to be recoverable by mining at costs 

equal to or less than $3<0 per pound of UsOs. 

24 
form of the leached constituents (anions, cations, uncharged species, or colloids), the sorptive capacity of the aquifer for the species of 

concern, the rate of ground-water flow, the 

distance from the disposal zone to discharge 

areas, the initial water quality in the aquifer, 

and the present and projected usage of the 

ground water. 

THICK-UNSATURATED ZONE STORAGE 

Unsaturated zones of 100 m thickness are 

common in Southwestern United States beneath the upper reaches of piedmont alluvial 

fans, and zones 100-600 m thick may occur 

beneath selected mesas, plateaus, and sometimes eve~r beneath valley floors. Even if the 

climate of a future pluvial time should approach subhumid conditions, a major rise in 

the water table would appear to be unlikely 

at such sites provided there is moderate to 

high relief, relatively permeable rocks occur 

within the unsaturated zone, and regional aquifers with topographically low outlets underlie 

the sites (Winograd, 1974). It has been suggested that burial of high level radioactive 

wastes in such thick unsaturated zones be 

evaluated (Winograd, 1974). Such a proposal 

may also have merit for the storage of uranium 

mill tailings or tailings concentrates. Buriai of 

tailings in an excavation at a depth of about 

30-40 m in a thick unsaturated zone should 

reduce radon emanation to near background 

levels, limit the potential for inundation of the 

tailings by a rising ground-water table, and 

provide for radioactive decay over the course 

of at least two to three half-lives of thorium-230 prior to disinterment by erosion. 

The excavation of such burial pits, unaccompanied by ore recovery, will undoubtedly 

be quite expensive. The transport of tailings 

to such burial sites from distant mills would 

have to involve pipeline or rail transfer, and 

thus would be both costly and introduce new 

potential avenues for environmental contamination. 

FIXATION AND AGGLOMERATION OF BURIED 

TAILINGS 

Incorporation of tailings into an asphaltic or 

concrete matrix has been considered in several 

conceptual evaluations of uranium mill tailings 

storage options (Sears and others, 1975; 

Martin and Miller, 1978), although apparently 

there have been no published reports on the experimental evaluation of such procedures. The 

costs for such a venture would appear to be 

high, and the long-term stability of the binding 

between tailings and cement or asphalt is not 

known (Martin and Miller, 1978). The decomipos,ition of a tar-like, surfa0e-stabilizing agent 

within 2 to 3 years after application was observed in a 1969 field test at the inactive uranium mill tailings site in Salt Lake ·City, Utah 

(Ford, Bacon, and Davis Utah, Inc., 1976). 

Koehmstedt and others (1977) have studied the 

use of 3 to 6 mm (0.12-0.24 in) thickness of 

asphalt emulsion appHed to uranium mill tailings as a m·eans of limiting radon emanation. 

While quite effective in short-t·erm laboratory 

studies, such sealants are acknowledged to be 

susceptible to degradation by physical (freeze 

and thaw, ultra-violet radiation), chemical (by 

action of oxygen, ozone, salts, adds and alkalies), and mic'!'obiological reactions, and thus 

their application would not appear to provide 

a long-term solution to the tailings problem. 

Wiles (1978) has found that the pelletizing, 

firing and glazing (by incorporation of 5-10 

percent powdered glass, CaF 2 or Fe203) can reduce the leaching of radium from uranium mill 

tailings in tests of up to 20 days by up to three 

orders of magnitude. Again, long-term mechanical and chemical stability of these pelletized 

materials in the natural environment is not 

known. 

IN-SITU LEACH MINING 

In-situ leach mining refers to a selective extraction technique whereby ore minerals in 

their natural geologic setting are preferentially 

dissolved from the surrounding host rock by 

specific leach solutions and the mineral value 

recovered. In-situ operations for uranium recovery presently exist at about 20 sites; most 

are in Wyoming and Texas. The general procedure consists of injecting a leach solution 

("lixiviant"-generally ammonium carbonate, 

sodium carbonate or sulfuric acid) into the ore 

zone below the water table, oxidizing, complexing, and mobilizing the uranium, recovering the 

pregnant solution at production wells, and 

pumping this solution to the surface for ura25 
nium extraction (Larson, 1978). This surface 

processing may generate some radioactive 

sludges (U.S. Nuclear Regulatory Commission, 

1978b); however, the bulk of the radium-bearing residual orebody remains underground. To 

be suitable for in-situ leach mining, the ore deposit must be located in the saturated zone, 

be confined both above and below by impervious 

layers, have adequate permeability, and be 

amenable to chemical leaching (U.S. Nuclear 

Regulatory Commission, 1978b). 

While such techniques do not generate tailings deposits at the surface, they are not without potential environmental hazards. Substances injected into the aquifer, and elements, 

both radioactive and non-radioactive, mobilized 

from the ore zone by these substances represent 

potential ground-water contaminants both during mining and after such operations cease. A 

recent report by Thompson and others (1978) 

discusses techniques aimed at the post-mining 

restoration of water quality in the affected portions of the aquifer to acceptable levels and presents results from several pilot restoration 

operations. 

CONCLUSIONS 

This report has not attempted to specifically 

address the question: What degree of containment is required for the storage of uranium 

mill tailings? An answer to this question must 

take into account what society regards as an 

acceptable risk for itself and future generations. The issue of "acceptable risk" is complex, transcending the boundaries of science 

and technology, and is beyond the scope of this 

report. What has been attempted is an outline 

of the pathways for environm·ental radiation 

exposure from uranium mill tailings and some 

of the potential long-term hydrologic and geologic consequences of various c·ontainment 

schemes. 

Because of the 77,000 year half-life of 

thorium-230, the diminution of environmental 

effects associated with radionuclides contained 

in these tailings must be conceived of within 

the framework of geologic processes operating 

over geologic time. The magnitude of erosion of 

cover materials and tailings, and the extent of 

geochemical mobilization of the contained 

radionuclides to the atmosphere and hydro26 

sphere should be considered in the evaluation of 

the potential, long-term consequences of all 

proposed uranium mill tailings management 

plans. The period and extent of containment of 

radionuclides will depend upon: 

( 1) The technology involved in tailings' processing and in the siting and design of 

disposal sites. 

(2) The nature of the interaction between the 

radionuclides and the components of the 

confining natural media. 

(3) The rates of environmental processes such 

as erosion, aggradation, precipitation 

and evapotranspiration. 

All of these factors will influence the flux of 

radion uclides through the environment. While 

the radon source term to the atmosphere will 

largely be a function of the depth of burial with 

time, the mobilization of long-lived radionuclides from the tailings by surface and 

ground waters and the retention of these radio-

;nuclides by soils and rocks is more complex and 

appears worthy of additional study. 

REFERENCES 

Adam, J. A., and Rogers, V. L., 1978 A classification 

system for radioactive waste dispos:al-What waste 

goes where: U.S. Nuclear Regulatory Commission 

Report NUREG-0456, 416 p. 

Ambe, S., and Lieser, K. H., 1978, Coprecipitation of 

thorium with barium sulfate: Radiochimica Acta, 

v. 25, no. 2, p. 93-98. 

Ames, L. L., and Rai, Dhanpat, 1978, Radionuclide interactions with soil and rock media: U.S. Environmental Protection Agency, Office of Radiation Programs Report EPA 520/6-78-007A, v. 1, 306 p. 

Anonymous, 1978, Formidable challenges await uranium 

mining: Mining Engineering, v. 30, no. 10, p. 1423. 

Argonne National Laboratory, 1978, Final report of the 

Task Force on Uranium Mill Tailings Waste Management: Argonne National Laboratory, Environmental Impact Studies Division (June 1978), 261 p. 

Austin, S. R., and Droullard, R. F., 1978, Radon emanation from domestic urani urn ores determine·d by 

modifications of the clos·ed can, gamma-only assay 

method: U.S. Bureau of Mines Report of Investigations no. 8264, 7 4 p. 

Barker, F. B., and Scott, R. C., 1958, Uranium and radium in the ground water of the Llano Estacado, 

Texas and New Mexico: American Geophysical 

Union Transactions, v. 39, no. 3, p. 459-466. 

Bell, K. G., 1963, Uranium in carbonate rocks: U.S. Geological Survey Professional Paper 474-A, 29 p. 

Bernhardt, D. E., Johns, F. B., and Kaufmann, R. F., 

1978, Radon exhalation from uranium mill tailings 

piles-description and verification of the measurement method: U.S. Environmental Protection 
Agency, Office of Radiation Programs, Technical 

Note ORP/LV-75-7(A), 39 p. 

Bondietti, E. A., 1974, Adsorption of plutonium (IV) 

and thorium (IV) by soil colloids: Abstracts of Annual Meeting American Society of Agronomy, p. 23. 

Borrowman, S. R., and Brooks, P. T., 1975, Radium removal from uranium ores and mill tailings: U.S. 

Bureau of Mines Report of Investigations no. 8099, 

12 p. 

Brakenridge, G. R., 1978, Evidence for a cold, dry fullglacial climate in the American southwest: Quaternary Research, v. 9, p. 22-40. 

Breslin, A. J., and Glauberman, H., 1970, Investigation 

of radioactive dust dispersed from uranium tailings 

piles, in, Reinig, W. C., ed., Environmental Surveillance in the Vicinity of Nuclear Facilities: 

Charles C. Thomas, Publisher; Springfield, Ill., p. 

249-253. 

Cadigan, R. A., and Felmlee, J. K., 1977, Radioactive 

springs geochemical data related to uranium exploration: Journal of Geochemic-al Exploration, v. 8, 

p. 381-395. 

Cadigan, R. A., Felmlee, J. K., and Rosholt, J. N., 1976. 

Radioactive mineral springs in Delta County, Colorado: U.S. Geological Survey Open-File Report 76-

223, 39 p. 

Charalambous, Stef., and Papastefanou, Const., 1977, 

On the radioactivity of fossil bones: Nuclear Instruments and Methods, v. 142, p. 581-588. 

Clark, D. A., 1974, State-of-the-art: Uranium mining, 

milling, and refining industry: U.S. Environmental 

Protection Agency Report EPA-660/2-74-038, 113 

p. 

Clements, W. E., Barr, S., and Marple, M. L., 1978, 

Uranium mill tailings piles as sources of atmosphe·ric 222Rn: Los Alamos Scientific Lab Report LAUR 78-828 ( preprint from Natural Radiation Environment III Symposium, Houston, Texas, April 

23-28, 1978)' 34 p. 

Comptroller General of the United States, 1978, The 

uranium mill tailings cleanup: Federal leadership 

at last, U.S. General Accounting Office, (Re·pt.) 

EMD-78-90; June 20, 1978. 

Conference of Radiation Control Program Directors, 

1978, Natural radioactivity contamination problems-A report of the task force: U.S. Environmental Protection Agency (Rept.) EPA-520/4-77-

015. 

Cook, L. M., 1978, The uranium district of the Texas 

Gulf Coastal Plain (Summary Paper) Inte·rnational 

Symposium on the Natural Radiation Environment 

III; Houston, Texas: April 23-28, 1978, p. 249-

250. 

Cotton, F. A., and Wilkinson, G., 1966, Advanced inorganic chemistry: Wiley, New York, 1136 p. 

D' Appolonia Consulting Engineers, Inc., 1977, Environmental effects of present and proposed tailings disposal practices, Split Rock Mill, Jeffrey City, 

Wyoming; Report 3, v. 1 and 2. Prepared for Western Nuclear, Inc. (project no. RM77-419, Oct. 

1977). 

27 

Dement'yev, V. S., and Syromyatnikov, N. G., 1965, 

Mode of occurrence of thorium isotopes in ground 

waters: Geochemical International, v. 2, no. 1, p. 

141-147. 

Dement'yev, V. S., and Syromyatnikov, N. G., 1968, 

Conditions of formation of a sorp·tion barrier to 

the migration of uranium in an oxidizing environment: Geochemical International, v. 5, p. 394-400. 

Dilworth, Secord, Meagher and Associates Ltd., 1979, 

Radon production rate of Elliot Lake Soil.s, Report 

4-DetVelopment program for radon reduction. 

DSMA Report 1012/102'4. Prepared for Atomic 

Energy Control Board of Canada, 26 p. 

Dodds, R. B., Jurgens, E. I., and Freitag, C. A., 1978, 

Retention of radioactive wastes at an operating uranium mill site: in Proceedings of Seminar on Management, Stabilisation and Environmental Impact 

of Uranium Mill Tailings, Albuquerque, New Mexico: July 24-28, 1978; Organisation fOT Economic 

Co-Operation and Development, Nuclear Energy 

Agency, Paris, France. p. 227-243. 

Douglas, R. L., and Hans, J. M., Jr., 1975, Gamma 

radiation surveys at inactive uranium mill sites: 

U.S. Environmental Protection Agency-Office of 

Radiation Programs, Technical Note ORP/LV-75-

5, 97 p. 

Drees·en, D. R., 1978, Uranium mill tailings--environmental implications : Los Alamos Scientific Laboratory, LASL Mini-Review, LASL 77-37, Feb. 1978, 

4 p. 

Dreesen, D. R., Marple, M. L., and Kelley, N. E., 1978, 

Contaminant transport, revegetation and trace element studies at inactive uranium mill tailings piles, 

in Proceedings Symposium on Uranium Mill Tailings Disposal: Colorado Sta·te Uni:versity, Ft. Collins, Colo., Nov. 20-21, 1978, p. 111-139. 

Duncan, D. L., Boysen, G. A., Grossman, L., and Franz, 

G. A., Ill, 1977, Outdoor radon study (1974-

1975)-An evaluation of ambient radon-222 concentrations in Grand Junction, Colorado: U.S. Environmental Protection Agency, Office of Radiation 

Pl'lograms, Technical Note ORP/LV-77-1, 68 p. 

Dyck, W., 1978, The mobility and concentration of uranium and its decay products in temperate surficial 

environments, in M. M. Kimberly, ed Short course 

handbook-Uranium deposits, their mineralogy and 

origin: Mineralogical Association of Canada (Toronto, Oct. 2'7-29, 1978) University of Toronto 

Press, p. 57-100. 

Eisenbud, M., 1963, Environmental radioactivity: McGraw-Hill, New York, 430 p. 

Eadie, G. G., and Kaufmann, R. F., 1977, Radiological 

evaluation of the effects of uranium mining and 

milling operations on selected ground water supplies 

in the· Grants Mineral Belt, New Mexico: Health 

Physics, v. 3.2', p. 231-2:41. 

Felmlee, J. K., and Cadigan, R. A., 1978a, Radium and 

uranium data for mineral springs in eight western 

states: U.S. Geological Su:rvey Open-File· Report 

78-561, 45 p. 

Felmlee, J. K., and Cadigan, R. A., 1978b, Determination 

of uranium in source· rocks by using radiutp in 
Crystal Springs, Great Salt Lake area, Utah: U.S. 

Geological Survey Open-File Report 78-102, 29 p. 

Ford, Bacon, and Davis Utah, Inc., 1976, Phase II-Title 

I, Engineerirlg assessments of inactive uranium mill 

tailings: Vitro site; Salt Lake City, Utah. Pre·pared 

for the U.S. Energy Research and Development Administration, Grand Junction, Colo. 

Ford, Bacon, and Davis Utah, Inc., 1977, Phase II-Title 

I, Engineering assessments of inactive· uranium mill 

tailings.: Prepared for the U.S. Department of 

Energy (:£ormerly U.S. Energy Research and Development Administration) Grand Junction, Colorado. 

GJT-2 

GJT-3 

GJT-4 

GJT-5 

GJT-6 

GJT-7 

GJT-8 

GJT-9 

GJT-10 

GJT-11 

GJT-12 

GJT-13 

Shiprock site, New Mexico 

Mexican Hat site, Utah 

Monument Valley site, Arizona 

Tuba City site, Arizona 

Durango site, Colorado 

Slick Rock site, Colorado 

Naturita site, Colorado 

Grand Junction site, Colorado 

New and Old Rifle sites, Colorado. 

Maybell site, Colorado 

Gunnison site, Colorado 

Phillips/United Nuclear site; 

Ambrosia Lake, New Mexico 

GJT-14 Green River site, Utah 

GJT-15 Spook site, Converse Co., Wyoming 

GJT-16 Falls City site, Texas 

GJT-17 Lowman site, Idaho 

GJT-18 Lakeview site, Oregon 

GJT-19 Riverton site, Wyoming 

GJT-20 Ray Point site, Texas 

Ford, Bacon, and Davis Utah, Inc., 1978, Radiation 

pathways and potential health impacts from inactive 

uranium mill tailings: Prepared for U.S. Department of Energy Report GJT-22, p. 

Gary, Margaret, McAfee, Robert, Jr., and Wolf, C. L., 

eds., 1972, Glossa:ry of Geology: Washington, 

American Geological Institute, 805 p. 

Gera, Ferrucdo, 1975, Geochemical behavior of longlived radioactive wastes: Oak Ridge National Laboratory Report ORNL-TM-4481, 99 p. 

G€'rm.anov, A. 1., Batulin, S. G., Volkov, G. A., Lisitsin, 

A. K., and Serebrennikov, V. S., 1958, Some· regularities of uranium distribution in underground 

waters, Proc. Second U.N. International Confe'rence 

Peaceful Uses of Atomic Energy, Geneva, 2: p. 

161-177. 

Gesell, T. F., and Prichard, H. M., 1975, The technologically enhanced natural radiation environment: 

Health Physics, v. 28, p. 361-366. 

Goldsmith, W. A., Haywood, F. F., and Leggett, R. W., 

1978, Transport of radon which diffuse'S from uranium mill tailings (Summary Pap·er) International 

Symposium on the Natural Radiation Environment 

III: Houston, Tex., April 23-28, 1978, p. 242-245. 

Granger, H. C., 1963, Radium migration and its eff·ect 

on the apparent age of uranium deposits at Ambrosia Lake, New Mexico: U.S. Geological Survey 

Prof. Paper 475-B, p. 860-863. 

28 

Gran~·r, H. C., Santos, E. S., Dean, B. G., and Moore, 

F. B., 1961, Sandstone-type uranium deposits at 

Ambrosia Lake, New Mexico-an interim report: 

Economic Geology, v. 56, no. 7, p. 1179-12Q9. 

Grim, R. E., 1968, Clay mineralogy (2d ed.): McGraw 

Hill, New York, 596 p. 

Hahn, Otto, 1936, Ap,plied Radiochemistry: Cornell University Press, Ithaca, N.Y., 278 p. 

Hammond, C. R., 1970, The elements (uranium), in 

Weast, R. G., ed., Handbook of Chemistry and 

Physics (51st ed.) : The Chemical Rubber Co., 

Cleveland, Ohio, p. B-35. .,. 

Hans, J. M., Jr., and Douglas, R. L., 1975, Radiation 

survey of dwellings in Cane Valley, Arizona and 

Utah, for use of uranium mill tailings. U.S. Environmental Protection Agency~ Technical Note 

ORP/LV-75-2, 37 p. 

Hansen, R. 0., and Huntington, G. L., 1969, Th01rium 

movement in morainal soils of the· High Sierra, 

California: Soil Science, v. 108, no. 4, p. 257-265. 

Hare, F. K., and Thomas, M. K., 1974, Climate Canada. 

Wiley, Toronto, 256 p. 

Harshman, E. N., 1970, Uranium ore rolls in the United 

States, in Proceedings Panel on Uranium Exploration Geology, Vienna, April 13-17, 1978, International Atomic Energy Agency, p. 219-232. 

Harshman, E. N., 1972, Geology and uranium deposits, 

Shi<rley Basin Area, Wyoming: U.S. Geological 

Survey Professional Paper 7 45, 82 p. 

Havens, R., and Dean, K. C., 1969, Chemical stabilization of the uranium tailings at Tuba. City, Arizona: 

U.S. Bureau of Mines Report of Investigations no. 

7288, 12 p. 

Havlik, Borivoj, Grafova, Jaraslava, and Nycova, Bedris.ka,. 1968a, Radium liberation from uranium ore 

processing mill waste solids and uranium rocks into 

surface streams-(!) The effect of different pH of 

surface waters: Health Physics, v. 14, p. 417-422. 

Havlik, B., Nycova, B., and Grafova, J., 1968b, Radium 

liberation from uranium ore processing mill waste 

solids and uranium rocks into surface streams-(11) 

The effect of different chemical composition of surface wate·r: Health Physics, v. 14, p. 423-430. 

Haywood, F. F., Goldsmith, W. A., Perdue, P. T., Fox, 

W. F., and Shinpaugh, W. H., 1977, Assessment of 

radiological impact of the inactive uranium-mill 

tailings pile at Salt Lake City, Utah: Oak Ridge 

National Labo~atory Report ORNL/TM-5251. 

Hem, J. D., 1970, Study and interpretation of the chemical characteristics of natural water (second edition): U.S. Geological Survey Water Supply Paper 

1473, 363 p. 

Hendricks, D. W., 1977, Uranium mill tailings--storage, 

use and disposal problems, in Proceedings First 

Conference on Uranium Mining Technology, ed.: 

Kim, Y. S., University of Nevada, Reno, April 24-

29, 1977, Section XXI, 28 p. 

Hendricks, D. W., 1978, Forward to U.S. Environmental Protection Ag.ency Technical Note ORP/LV78-8 (A. Klute and D. F. Heermann, Water movement in uranium mill tailings profiles.) p. iii-iv. 
Hendrie, J. M., 1978, Statement before the Subcommittee on Energy and the Environment, Committee on 

Interior and Insular Affairs, U.S. House of Representatives, Ninety-fifth Congress (June 27, 1978) 

Hearings serial no. 95-30, p. 254-263. 

Herman, S. J., and Langmuir, D., 1978, Thorium comple·xes in natural waters: [Abs.], Geological Society 

of America Annual Meeting, Toronto, Canada, p. 

419. 

Hilpert, L. S., 1969, Uranium resources of northwestern 

New Mexico: U.S. Geological Survey Prof. Paper 

603, 166 p. 

Honeywell, W. R., and Kaiman, S., 1966, Flotation of 

uranium from Elliot Lake ores: Canadian Mining 

Metallurgy Bulletin, v. 69, p. 99-107. 

International Atomic Energy Agency, 1976, Management of wastes from the mining and milling of 

uranium and thorium ores-A code of practice and 

guide to the code. IAEA Safety Series No. 44, 

Vienna, 50 p. 

Ivarson, K. C., 19-73, Microbiological formation of basic 

ferric sulfates: Can. Journal of Soil Science, v. 53, 

p. 315-323. 

Ivarson, K. C., Ross, G. J., and Miles, N. M., 1978, Alterations of mi.ca•s and feldspars during microbial 

formation of basic ferric sulfates in the laboratory: 

Soil Science Society of America Journal, v. 42, no. 

3, p. 518-5·24. 

Kagan, M. S., 1967, Radon, radium, uranium and mesothorium I in mineral waters of the Rostov region: 

Geokhimiya Translations, pt. 2, p. 497-511. 

Kaiman, S., 1977, Mineralogical examination of old tailings from the Nordic Lake Mine, Elliot Lake, Ontario: Canada Centre for Mineral and Energy 

Technology, Energy Research Program, Mineral 

Science Laboratories Report ERP/MSL 77-190 

(IR), 12 p. 

Kaiman, S., 1978, Mineralogical examination of current 

Elliot Lake uranium tailings: Canada Cent:ve for 

Mineral and Energy Technology, Minerals Research 

Program, Mineral Sciences Laboratories, Report 

MRP/MSL 78-83 (IR), 9 p. 

Kaufmann, R. F., and Bliss, J. D., 1977, Effects of phosphate mineralization and the phosphate industry on 

radium-226 in gro\lnd water of central Florida: 

U.S. Environmental Protection Agency, Office of 

Radiation Programs Report EPA-520-6-77-010, 

125 p. 

Kaufmann, R. F., Eadie, G. G., and Russell, C. R., 1976, 

Effects of uranium mining and milling on ground 

water in the Grants Mineral Belt, New Mexico: 

Ground Water, v. 14, no. 5, p. 296-308. 

Kelley, N. E., 1978, Vegetational stabilization of uranium spoil areas, Grants, New Mexico: Ph.D. thesis, 

University of New Mexico, Los Alamos Scientific 

Laboratory Report LA-7624-T, 88 p. 

Kirby, H. W., and Salutsky, M. L., 1964, The radiochemistry of radium: National Academy of Sciences, N ationa! Research Council, NAS-NS 3057, 205 p. 

Kluge, E., Lieser, K. H., Loc. 1., and Quandt, S., 1977, 

Separation of ~Th (Ionium) from uranium ores in 

29 

sulfuric acid and nitric acid solutions: Radiochimica 

Acta, v. 24, no. 1, p. 21-26. 

Klute, A., and Heermann, D. F., 1978, Water movement 

in uranium mill tailings profile's: U.S. Environmental Protection Agency, Office of Radiation Programs, 

Las Vegas, Nev. Facility, Technical Note ORP/LV78-8, 82 p. 

Kochenov,, A. V., Zinev'yev, V. V., and Lovaleva, S. A., 

1965, Some features of the accumulation of uranium in peat bogs: Geochemical International, v. 2, 

p. 65-70. 

Koehmstedt, P. L., Harley, J. N., and Davis, D. K., 1967, 

Use of asphalt emulsion sealants to contain radon 

and radium in uranium tailings: Battelle Pacific 

Northwest Laboratories Report BNWL-2190, 73 p. 

Koide, Minoru, and Bruland, K. W., 1975, Electrodeposition and determination of radium by isotopic dilution in seawater and in s·ediments simultaneously 

with other natural radionuclides: Analytica 

Chimica Acta, v. 75·, no. 1, p. 1-19. 

Langmuir, Donald, 1978, Uranium solution-mineral equilibria at low temperatures with applications to 

sedimentary ore deposits: Geochimica Oosmochimica 

Acta, v. 42., p. 547-569. 

Larson, W. G., 1978, Uranium in situ leach mining in 

the United States: U.S. Bure·au of Mines Informa· 

tion Circular no. 8777, 68 p. 

Levins, D. M., Ryan, R. K., and Strong, K. P., 1978, 

Leaching of radium from uranium tailings, in Proc. 

Seminar on Management, Stabilisation and Environmental Impact of Uranium Mill Tatilings., Albuquerque, N. Mex., July 24-28, 1978: Organisation 

for Economic Co.Operation and Development, Nuclear Energy Agency, Paris, France, p. 271-286. 

Lush, D., Brown, J., Fletcher, R., Goode, J., and 

Jurgens, T., 1978, An assessment of the long-term 

interaction of uranium ta.iling:s. with the natural 

environment, in Proc. Seminar on Management, 

Stabilization and Environmental Impact of Uranium Mill Tailings, Albuquerque, N. Mex., July 24-

28, 1978: OECD Nuclear Energy Agency, Paris, 

France, p. 373-398. 

Macbeth, P. J., Jensen, C. M., Rogers, V. C., and Overmeyer, R. F., 1978, Laboratory research on tailings 

stabilization methods and their effectiveness in radiation containment: Pre·pared by Ford, Bacon, and 

Davis Utah, Inc. for U.S. Department of Energy, 

Grand Junction, Colo. Report GJT-21. 

Martin, J. B., 1978, Update of NRG mill Jic.ensing activities: Proceedings of Uranium Industry Seminar, Grand Junction, Colo.; Oct. 17-18, 1978, U.S. 

Department of Energy, Grand Junction, Colo., 

GJ0-108 (78), p. 219-229. 

Martin, J. B., and Miller, H. J., 1978, Generic environmental impact statement on U.S. uranium milling 

industry, in Proc. Seminar on Management, Stabilisation and Environmental Impact of Uranium Mill 

Tailings, Albuquerque, N. Mex., July 24-28, 1978: 

Organisation for Economic Co.Operation and Development, Nuclear Energy Agency, Paris, France, 

p. 453-468. 
Masuda, Kuniyoshi, and Yamamoto, Takashi, 1971, 

Studies on environmental contamination by uranium, (2) Adsorption of uranium on soil and its 

desorption: Journal Radiation Research, v. 12, p. 

94-99. 

Maysilles, J. H., Nichols, I. L., and Seidel, D. C., 1978, 

Extracting uranium from low grade ore from the 

Coso Mountains, Calif.: U.S. Bureau of Mines Report of Investigations no. 8306, 14 p. 

Means, J. L., Crerar, D. A., and Duguid, J. 0., 1978, 

M-igration of radioactive· wastes: radionuclide mobilization by complexing agents: Science, v. 200, no. 

4349, p. 1477-1481. 

Merritt, R. C., 1971, The extractive metallurgy of uranium: Colorado School of Mines Research Institute, 

Golden, 576 p. 

Middlesworth, L. V., 1978, Radium and thorium with 

barium in micronodul.e·s of cattle thyroids (Summary Paper) Inti. Symp. on the· Natural Radiation 

Environment III: Houston, Tex., April 23-28, 1978, 

p. 125-127. 

Moffett, D., 1976, The disposal of solid wastes and liquid 

effluents from the milling of uranium ores: Canada 

Centre for Mineral and Energy Te·chnology, Minerals Res·earch Program, Mining Research Laboratories Repoort 76-19, 76 p. 

Moffett, D., and Tellier, M., 1977, Uptake of radioisotopes by vegetation growing on uranium mill tailings: Canada Centre for Mineral and Energy Technology, Minerals Research Program, Mining Research Laboratories Report MRP/MRL 77-6 (J) 

Revised, 15 p. 

Moffett, D., and T·ellier, M., 1978, Radiological investigations of an abandoned uranium tailings area: Journal of Environmental Quality, v. 7, no. 3, p. 310-314. 

Moffett, D., Zahary, G., Campbell, M. C., and Ingles, 

J. C., 1977, CANMET's environmental and process 

research on uranium: Canada Centre for Mineral 

and Energy Technology, Minerals and Energy ReS8arch Programs, Mining Research Laboratories, 

Mineral Scienc.es Laboratories Report 77-53, 29 p. 

Mooney, B. L., and Scott, A. G., 1978, Radium content of 

Elliot Lake sand deposits compared with other Ontario sands: Abstracts, Geological Society America 

Annual Meeting, Toronto, Canada, p. 459. 

Moore, W. S., and Reid, D. F., 1973, Extraction of radium from natural waters using manganese-impregnated acrylic fibers: Jour. Geophys .. Research, 

v. 78, no. 36, p. 8880-8886. 

Morse, R. H., 1970, The surficial geochemistry of ra,.. 

dium, radon and uranium near Bancroft, Ontario 

with application to prospecting for uranium: Ph.D. 

thesis, Queen's University, Kingston, Ontario, Canada, 154 p. 

Motica, J. E., 1977, Uranium exploration, in Proc. First 

Conf. on Uranium Mining Technology, ed. Kim, 

Y. S.: University of Nevada, Reno, April 21

4-29, 

1977, Section II, 27 p. 

Mutschler, P. H., Hill, J. J., and Williams, B. B., 1976, 

Uranium from the Chattanooga Shale~Some problems involved in development: U.S. Bu:reau of Mines 

Information Circular no. 8700, 85 p. 

30 

Nelson, J. D., and Shepard, T. A., 1978, Evaluation of 

long-term ·stability of uranium mill tailing disposal 

alternatives: Final report, contract no. 31-109-38-

4199, Geotechnical Engineering Program, Colorado 

State University for Argonne National Laboratories, April 1978, 337 p. 

Papastefanou, C., and Charalambous, SW., 1978, Ra226 leaching from fossil bones: Nuclear Instruments and Methods, v. 141, p. 599-601. 

Perel'man, A. 1., 1972, Geochemistry of elements in the 

supergere zone: Translated from Russian, Israel 

Program for Scientific Translations, J erusaleni, 

1977. 

Raicevic, D., 1978, Decontamination of Elliot Lake uranium tailings: Canada Centre· for Mineral and 

Energy Technology, Minerals Research Program; 

Mining Research Laboratories Report MRP/MSL 

78-120 (OP & J), 26 p. 

Ramsey, William, 1976, Radon from uranium mill tailing~A source of significant radiation hazard?: Environmental Management, v. 1, no. 2, p. 139-145. 

Rankama, Kalervo, and Sahama, Th. G., 1950, Geochemistry: University of Chicago Press, 912 p. 

Reed, A. K., Meeks, H. C., Pomeroy, S. E., and Hale, 

V. Q., 1976, Assessment of the environmental aspects of uranium mining and milling: U.S. Environmental Protection Agency Report EPA..:.S00/7-76-

036, 59 p. 

Robertson, D. S., 1962, Thorium and uranium variations 

in the Blind River ores: Economic Geology, v. 57, 

p. 1175-1184. 

Rogers, J. J. W., and Adams, J. A. S., 1969, Thorium, 

in Wede,pohl, K. H., ed., Handbook of geochemistry: 

v. II/1, chap. 90. 

Ryon, A. D., Hurst, F. J., and Seeley, F. G., 1977, Nitric 

a.cid leaching of radium and other significant radionuclides from uranium ores and tailings.: Oak Ridge 

National Laboratory Re·port ORNL/TM-5944, 37 p. 

Schiager, K. J., 1974, Analysis of radiation exposures 

on or near uranium mill tailings piles: Radiation 

Data and Reports, U.S. Environmental Protection 

Agency, Office of Radiation Programs, v. 15, no. 7, 

p. 411-425. 

S.chiager, K. J., 1977, Radwaste radium-radon risk, in 

Proceedings Workshop on Policy and Technical Issues Pertinent to the Development of Environmental Protection Criteria for Radioactive Waste, 

Albuquerque, April 12-14, 1977: U.S. Environmental Protection Agency, Office of Radiation Programs 

Report ORP/GSD-77-2, p. 2-45 to 2-81. 

Schmidtke, N. W., Averill, D., Bryant, D. N., Wilkinson, 

P., and Schmidt, J. W., 1978, Removal of 226Ra from 

tailings pond effluents and ·s,tabilization of uranium 

mine tailings-bench and pilot plant studies, in Proceedings Seminar on Management, Stabilisation and 

Environmental Impact of Uranium Mill Tailings, 

Albuquerque, N. Mex., July 24-28, 1978, OECD 

Nuclear Energy Agency, Paris, France, p. 299-315. 

S.ehumm, S. A., 1963, The disparity between present 

rates of denudation and orogeny, U.S. Geological 

Survey Professional Paper 454-H, table 1, 13 p. 

Sears, M. B., Blanco, R. E., Dahlman, R. D., Hill, G. S., 
Ryon, A. D., and Witherspoon, J. P., 1975, Correlation of radioactive waste treatment costs and the 

environmental impact of waste effluents in the nuclear fuel cycle for use in establishing "as-low-aspractic.able" guides-milling of uranium ores: Oak 

Ridge National Laboratory Report ORNL/TM-4903, 

v. 1, 291 p. 

S.edlet, Jacob, 1966, Radon and Radium, in Kolthoff, 

I. M. and Elving, P. J., eds., Treatise on Analytical 

Chemistry, pt. 2: v. 4, Wiley-Interscience, New 

York, p. 219-366. 

Seeley, F. G., 1976, Problems in the separation of radium from uranium ore tailings: Hydrometallurgy, 

v. 2, p. 249-263. 

Shapiro, J., 1972, Radiation protection: Harvard Univ. 

Press, Cambridge·, Mass., 339 p. 

Shearer, S. D., Jr., 1962, The leachability of radium22'6 from uranium mill waste solids and river sediments: Ph.D. thesis, University of Wisconsin, 16·2 p. 

Shearer, S. D., Jr., and Lee, G. F., 1964, Leachability 

of radium-226 from uranium mill solids and river 

sediments: Health Physics, v. 10, p. 217-227. 

Sigler, W. F., Helm, W. T., Angelovic, J. W., Linn, 

D. W., and Martin, S. S., 1966, The effects. of uranium mill wastes on stream biota: Utah Agricultural Experimental Station Bulletin 462, Utah 

State University, Logan, Utah, 76 p. 

Skeaff, J. M., 1977, Distribution of radium-226 in uranium mill tailings : Canada Centre for Mineral and 

Energy Technology, Minerals Research Program, 

Mineral Sciences Laboratories Report MRP I MSL 

77-340, 20 p. 

Smith, S. E. and White, P. A., 1969, Review of uranium 

ore p·rocessing research : Canadian Mining Journal, 

v. 90, no. 5, p. 71-74. 

Szalay, A., 1964, Cation exchange properties of humic 

acids and their importance in the geochemical enrichment of U02++ and other cations: Geochimica et 

Cosmochimica Acta, v. 28, p. 1605-1614. 

Tanner, A. B., 1964a, Radon migration in the grounda review, in Adams, J. A. S., and Lowder, W. M., 

eds., The Natural Radiation Environment: University of Chicago Pres·s, p. 161-190. 

Tanner, A. B., 1964b, Physical and chemical controls on 

distribution of radium-226 and radon-2:22 in ground 

water near Great Salt Lake, Utah, in Adams, 

J. A. S. and Lowder, W. M., eds., The Natural Radiation Environment: Unive·rsity of Chicago Press, 

p. 253-276. 

Thomnson, W. E., Rouse, G. E., SwaT7enski, W. V., Carrington, 0. F., Warner, D. L., and Pyrih, R. Z., 1978, 

Ground-water elements of in situ leach mining of 

uranium: Prenared for U.S. Nuclear Regulatory 

Commission, NUREG/CR-0311, 173. 

Titayeva, N. A., 1967, Association of radium and uranium with peat: Geochemistry International, v. 4, 

no. 6,p. 1168-1174. 

Titayev.a, N. A., Taskayev, A. 1., Ovchenkov, V. Ya., 

Aleksakhin, R. M., and Shuktomova, I. 1., 1977, 

U, Th and Ra isotope compositions in soils in prolonged contact with radioactive stratal waters: 

Geochemistry International, v. 14, no. 5, p. 57-63. 

31 

Travis, C. C., Cotter, S. J., Watson, A. P., Randolph, 

M. L., McDowell-Boyer, L. M., and Fields, D. E., 

1979, A radiological assessment of Rn-222 released 

from uranium mills and other natural and technologically enhanced sources: Prepared for the U.S. 

Nuclear Regulatory Commission by Oak Ridge National Laboratory, NUREG/CR-0573 (ORNL/ 

NUREG-55), 216 p. 

Tsivoglou, E. C., Shearer, S. D., Jr., Jones, J. D., and 

Clark, D. A., 1960, Estimating human radiation exposure on the Animas River: Journal American 

Water Works Association, v. 52, p. 1271-1290. 

U.S. Atomic Energy Commission, 1974, Environmental 

survey of the uranium fuel cycl~Report: WASH1248. 

U.S. Department of Energy, 1978, Statistical data of 

the uranium industry, Jan. 1, 1978-Report: GJ0-

100(78). 

U.S. Department of Health, Education and Welfare, 

1970, Radiological Health Handbook: Bureau of 

Radiological Health; Rockville, Md, 458 p. 

U.S. Department of the Interior, 1976, Final environmental statement, Sherwood Uranium Project, 

Spokane Indian Reservation: Bureau of Indian Affairs, Portland, Oreg., v. 1-2. 

U.S. Environmental Protection Agency, 1971, Evaluation of the impact of the Mines Development, Inc., 

Mill on water quality conditions in the Cheyenne 

River: U.S. Environmental Protection Agency, Region VIII, Denver, Colo., S.ept. 1971, 46 p. 

U.S. Environmental Protection Agency, 1973, Environmental analysis of the uranium fuel cycle, pt. I, 

Fuel Supply: Office of Radiation Programs-Report EPA-520/9-73-003-B, 190 p. 

U.S. Environmental Protection Agency, 1975, Water 

quality impacts of uranium mining and milling activities in the Grants Mineral Belt, New Mexico: 

U.S. Environmental Protection Agency, Region VI, 

Dallas, Tex. Report EPA 906/9-75-002, 188 p. 

U.S. Environmental Protection Agency, 1976a, Environmental radiation protection requirements for normal 

operations of activities in the uranium fuel cycle 

(40 CFR 190) Final environmental statement: U.S. 

Environmental Protection Agency, Office of Radiation Programs-Report EPA-520/4-76-016, v. I, 

236 p. 

U.S. Environmental Protection Age·ncy, 1976b, Environmental analysis of the uranium fuel cycle, pt. IV, 

supplementary analysis, 1976: U.S. Environmental 

Protection Agency, Office of Radiation Program.s, 

Report EPA 5·20./ 4-76-017, 130 p. 

U.S. Environmental Protection Agency, 1977, Radiological quality of the environment in the United 

States, 1977: Office of Radiation Programs-Report EPA 520/1-77-009, 295 p. 

U.S. Environmental Protection Agency, 1978a, Hazardous wa.ste~proposed guidelines and regulations and 

proposal on ldentification and listing: Federal Register, v. 43, no. 243, Dec. 18, 1978, p. 58945-59028. 

U.S. Environmental Protection Agency, 1978b, Draft 

background document, radioactive waste (BD-6); 
Resource Conservation and Recovery Act, Subtitle 

C-Haza:rdous waste management: U.S. Envir<Ynmental Protection Agency, Office of Solid Waste, 

Dec. 15, 1978, 38 p. 

U.S. For,est S.ervice, 197'8, Draft environmental statement related to the operation of the Homestake 

Mining Company Pitch Project: Prepared jointly 

by U.S. Forest Service, Delta, Colo., and U.S. Nuclear Regulatory Commission, 

U.S. Nuclear Regulatory Commission, 1977a, Branch 

position-uranium mill tailings. management, Fuel 

Processing and Fabrication Branch: May 13, 1977, 

3 p. 

U.S. Nuclear Regulatory Commission, 1977b, Design, 

construction, and inspection of embankment retention systems for uranium mills: Regulatory guide 

3.11, revision 2, Dec. 1977, 9 p. 

U.S. Nuclear Regulatory Commission, 1978a, Final environmental statement related to the United Nuclear Corporation Morton Ranch, Wyoming uranium 

mill: NUREG-0532. 

U.S. Nuclear Regulatory Commission, 1978b, Final environmental statement related to operation of 

Wyoming Mineral Corporation lrigaray solution 

mining project: NUREG-0481. 

U.S. Nuclear Regulatory Commission, 1978c, Final environmental statement related to operation of Highland uranium solution mining project: NUREG0489. 

U.S. Nuclear Regulatory Commission, 1978d, Final environmental statement related to operation of Swe.etwater uranium project: NUREG-0505. 

U.S. Nuclear Regulatory Commission, 1978e, Draft environmental statement related to operation of White 

Mesa uranium project: NUREG-0494. 

U.S. Nuclear Regulatory Commission, 1979a, Draft 

generic environmental impact statement on uranium 

milling: NUREG-0511. 

U.S. Nuclear Regulatory Commission, 1979b, Final en32 

vironmental statement related to the operation of 

the Moab uranium mill: NUREG-0453. 

Van Devender, T. R., 1977, Holocene woodlands in the 

southwestern deserts: Science, v. 198, p·. 189-192. 

Vdovenko, V. M., and Dubasov, Yu. V., 1975, Analytical 

chemistry of radium: Wiley, New York, 198 p. 

Watkin, E. M., and Winch, J. E., 1973, Com posted organic wastes, sewage :sludges, and rock phos.phate 

for amelioration of acid uranium mill tailings, in 

Proc. International Conference on Land for Waste 

Management, Ottawa, Canada, Oct. 1973: p. 48-56. 

West, S. W., 1972, Disposal of uranium mill effluent by 

well injection in the Grants area, Valencia County, 

New Mexico: U.S. Geological Survey Professional 

Paper 386-D, 28 p. 

Whicker, F. W., 1978, Biological interactions and rec}a,.. 

mation of uranium mill tailings, in Proc. Symp. 

on Uranium Mill Tailings Disposal: Colorado State 

University, Fort Collins, Colo., Nov. 20-21, 1978; 

p. 141-153. 

Wiles, D. R., 1978, The leaching of radium from Beaverlodge tailings, in Proc. Seminar on Management, 

Stabilisation and Environmental Impact of Uranium Mill Tailings, Albuquerque, N.Mex., July 24-

28, 1978: OECD Nuclear Energy Agency, Paris, 

France, p·. 245-257. 

Wilkening, M. H., 1974, Radon-222 from the island of 

Hawaii-Deep soils are more important than lava 

fields or volcanoes: Science, v. 183, no. 4123, p. 413-

415. 

Winograd, I. J., 1974, Radioactive waste storage in the 

arid zone.: EOS, American Geophysical Union 

Transactions, v. 55, no. 10, p. 884_:-894. (Discussion 

in EOS, v. 57, no. 4, p. 178, 215-216.) 

Wullstein, L. H., 1978, Vegetative stabilization report 

(Appendix A in Macbeth, and others,1978, Laboratory research on tailings stabilization methods and 

their effectiveness in radiation containment: Prepared for U.S. Department of Energy, Grand Junction, Colo., Rept. GJT-21). 

-tr U.S. GOVERNMENT PRINTING OFFICE: 1980 0- 311-344/15