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

Page Abstract 1 Introduction ------­ 1 Acknowledginents ------_------2 Quantity and location of the tailings ------­ 2 Radioactivity in tailings ------­ 4 Sources of potential human radiation exposure from uranium mill tailings ------6 Radon emanation ------6 VVind transport ------6 Surface water transport and leaching ------7 External gamma radiation ------­ 8 Contamination of terrestrial and aquatic vegetation ------8 Seepage ------~------9 Environmental factors ------9 Ore factors ------­ 10 Process factors ------10 Use of tailings as a construction material ------10 Leaching behavior of radium, thorium, and uranium ------11 Radium ------11 Thorium 16 Uranium ------17 VVater qualuy studies ------­ 18 Grants Mineral Belt in New Mexico ------18 Elliot Lake, Ontario ______------18 Other areas ------19 Uranium mill tailings disposal options ------­ 19 Surface stabilization and near surface burial of tailings ------­ 19 Radium removal from tailings ------­ 22 Preconcentrationof uranium ore------­ 23 Deep burial in underground cavities ------­ 24 Thick unsaturated zone storage· ------­ 25 Fixation and agglomeration of buried tailings ------­ 25 In-situ leach mining ------25 Conclusions ------­ 26 References ------26

ILLUSTRATIONS

FIGURE 1. Map showing the location of active and inactive conventional uranium 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 Biosphere­ Some Earth Science Perspectives

By Edward Landa

ABSTRACT "technologically enhanced natural radiation 1 U rani urn mining and milling is an expanding activ·ity exposure" to the surrounding population. in the Western United States. Although the milling The philosophy expressed by Lush and others process yields a uranium concentrate, the large volume ( 1978) is worth considering with regard to the of tailings remaining centains about 85 percent of the long-term storage of uranium mill tailings: radioactivity-originally associated with the ore. By vir­ tue of the physical and chemical processing of the ore The development of a long-term waste management and the redistribution of the contained radionuclides at philosophy require,s. the acceptance of a basic set of the Earth's surface, these tailings constitute a technolog­ management criteria. Our societies' approach has, as ically enhanced source of natural radiation exposure. its basic tenets, that the present generation of waste Sources of potential human radiation exposure from managers should l•eave the wastes in such a manner uranium mill tailings include the emanation of radon that there is no foreseeable threat to future generations gas, the transport of particles by wind and water, and and future generations will not have to be involved the transport of soluble radionuclides, seeping from dis­ in the care of the wastes. Implied is that the future posal areas, by ground water. Due to the 77,000 year bleed rate of contaminants from waste management half-life of thorium-230, the parent of radium-226,. the sites should not exce,ed present regulatory levels, and environmental effects associated with radionuclides con­ not rely on continued monitoring to demonstrate that tained in these tailings must be conceived of within the fact * * *. Any acceptable long term solutions must framework of geologic processes operating over geologic not rely solely on a social management system, but time. The magnitude of erosion of cover materials and rather on a management controlled by those basic tailings and the extent of geochemical mobilization of geochemical and biochemical cycles which have bezn the contained radionuclides to the atmosphere and hydro­ determining the flux rates of radionuclides through the sphere should be considered in the evaluation of the open environment dur.ing the evolution of life· on potential, long-term cons·equences of all proposed ura­ Earth. nium mill tailings management plans. In order to develop a management system which meets these criteria, a basic knowledge is needed of (a) those geochemical and biochemical reactions affect­ INTRODUCTION ing the mobility· of radionuclides, (b) the form into which those radionuc>Lides ane transformed during the Uranium mill tailings represent a unique milling and waste treatment operation, and (c) the type of radioactive waste. Rather than man­ conseque;n.ces of this transformation as related to their mobility within and the flux rate from the waste man~ made materials containing fission products, agement area over geological time. Only through an activation products, and (or) transuranic ele­ understanding of these processes and their interac.. ments, these tailings are earth materials con­ tions with th~ waste management environment .can we taining radionuclides naturally present in the determine whether present or future management areas Earth's crust that have been brought to the sur­ face, subjected to physical and chemical proc­ 1 Gesell and Prichard ( 1975) have defined "technologically en­ hanced natural radiation exposures" as exposures to truly natural essing, and subsequently exposed to the action sources of radiation (naturally occurring isotopes and cosmic of surficial geologic processes. Thus redistrib­ radiation) which would not have occurred without (or would have been increased by) some technological activity not expressly uted, these radionuclides constitute a source of designed to produce radiation.

1 will transcend smoothly the cessation of active man­ and evolutionary perspective in mind. Exam­ agement and determine whether future passively­ ples from the past are presented as they are managed bleed rates acceptable under present day and useful in understanding the behavior of ura­ hopefully future standards are achieved. nium mill tailings in the environment. How­ The purpose of this report is to document ever, examples of past mismanagement should some of the existing information relevant to not be confused with current management environmental mobilization, and to discuss the practices. efficacy of various uranium mill tailings dis­ A discussion of potential health impacts posal options in light of potential mobilization from uranium mill tailings is beyond the scope mechanisms. While the emphasis here is on the of this report; the reader is referred to Sears potential, long-term consequences of tailings and others (1975), Ramsey (1976), Ford, disposal, this view is in no way meant to de­ Bacon, and Davis Utah, Inc. (1978), Travis and tract from the very major advances in uranium others (1979), and U.S. Nuclear Regulatory mill tailings management, fostered by both the Commission (1979a) for an overview of the uranium industry and regulatory authorities, subject. which have occurred in the past 2 decades. In the early years of uranium milling, only limited ACKNOWLEDGMENTS attention was paid to the now better-under­ The author wishes to acknowledge the efforts stood, environmental effects associated with of Elise Passentino, Isaac Winograd, and mem­ radioactivity in the residual materials. In the bers of the technical staffs of the U.S. Environ­ late 1950's and early 1960's, work by the U.S. mental Protection Agency, the U.S. Nuclear Pubic Health Service and others provided the Regulatory Commission, and the U.S. Depart­ impetus for controls on the discharge of mill ment of Energy and its contractors in review­ effluents and initiation of stabilization efforts ing this circular. at tailings piles. The Grand Junction experi­ ence with the use of tailings for construction purposes spurred renewed interest in tailings QUANTITY AND LOCATION OF THE TAILINGS management during the late 1960's and early 1970's. An examination of the environmental Most uranium ores being mined in the United reports and statements prepared by mill op­ States are sandstones, but limestones and lig­ erators and regulatory agencies over the last nites are also of importance (Reed and others, few years reflects the increasing awareness of 1976). Milling consists of the mechanical and the potential hazards associated with these chemical processes that concentrate the ura­ tailings and the application of technology to nium fraction from the ore. In conventional mitigate these effects. The past 2 years repre­ uranium milling, the ore is crushed and leached sent a period of intense effort in this area, with either alkali or acid. Ores with the lime­ as.-.seen with the promulgation by the U.S. Nu­ stone contents greater than 15 percent are gen­ cear Regulatory Commission of siting, design, erally leached under alkaline conditions using operation and reclamation criteria for the man­ sodium carbonate-bicarbonate, while most other agement of uranium mill tailings (U.S. Nuclear ores are leached with sulfuric acid. The ura­ Regulatory Commission, 1977a), and the Com­ nium extracted by the leaching solution is con­ mission's preparation of a generic environ­ centrated by solvent extraction or ion exchange, mental impact statement on the U.S. uranium and subsequent precipitation (generally with milling industry to the year 2000 (U.S. Nuclear ammonia) of a uranium concentrate (80-85 Regulatory Commission, 1979a) . Also, the 95th percent U30s) that is referred to as "yellow­ Congress enacted the U rani urn Mill Tailings cake." The leached ore residues, "tailings," are Radiation Control Act of 1978 (Public Law 95- slurried with mill waste solutions and pumped 604) providing for the reclamation of inactive to an earthen retention pond. uranium mill tailings areas, and the control of As the ores being exploited in the United tailings as a licensed by-product material. The State today generally contain only about 0.1- reader is thus cautioned to keep this historical 0.2 percent U30s, essentially all of the tonnage

2 of ore processed at the mill is deposited in the conventional ore sources; however, active op­ tailings pond. With current mill capacities rang­ erations in Texas and Wyoming produce yellow­ ing up to 7,000 metric tons of ore per day cake from in-situ uranium leach solutions. Also, (Reed and others, 1976), the magnitude of the uranium is, or soon will be, recovered from tailings thus generated is apparent. At pres- phosphoric acid plants in Florida and Louisi­ ent, there are in excess of 100 million metric ana and from copper dump leach operations in tons of uranium mill tailings in the United Utah (Anonymous, 1978). As our reserves of States. Dependent upon the growth pattern pro­ higher grade ores becomes depleted, the min­ jected for the United States nuclear industry, ing and milling of lower grade and refractory and its reliance on domestic uranium sources, materials such as described by Mutschler and this s·olid waste inventory is estimated to in­ others (1976) and Maysilles and others (1978) crease to between 0.9 and 1. 7 billion metric will undoubtedly increase. Also, the nationwide tons by the year 2000 (Argonne National Lab­ exploration activities associated with the U.S. oratory, 1978; Adam and Rogers, 1978). As­ Department of Energy's National Uranium suming a bulk density for the tailings of Resource Evaluation (NURE) program may 1.7 g/cm3 (Adam and Rogers, 1978), this latter uncover new deposits. Thus, the areal extent quantity amounts to a volume of about one bil­ of uranium mining and milling activities in the lion cubic meters. This volume would cover United States might be expected to increase Washington, D.C., to a depth of about 5.8 m in the coming decades. (19ft). The tailings disposal sites may be broadly Most uranium mining and milling to date grouped into inactive and active milling cate­ has been in the Western States, especially in gories. The tailings at the inactive sites gen­ New Mexico, Colorado, Wyoming, Utah, and erally exist as piles atop the land surface which Texas (fig. 1). The bulk of these mills use are either exposed or covered by 0.15-0.6 m

! )( I ---- ~ I I ---.!_

I I I

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 people, where disruption and dispersion by Utah, Inc. 1976; 1977). Under the provisions natural forces are eliminated or reduced to the of the Uranium Mill Tailings Radiation Con­ maximum extent reasonably achievable (U.S. trol Act of 1978, the majority of thes·e inactive Nuclear Regulatory Commission, 1977a). Lin­ sites will be subject to remedial action under ing of disposal zones with compacted soil, the direction of the U.S. Department of Energy. asphalt, clay, or synthetic polymeric mem­ Based on the finding that uranium mill tailings branes may be required to reduce seepage of may pose a potential and significant radiation waste solutions. Disposal of tailings in open health hazard to the public, this legislation pit mines or specially excavated pits ("below calls for the stabilization and control of such grade") is now generally... favored over im­ tailings in a safe and environmentally sound poundment behind a dam, the common disposal manner in order to minimize or eliminate radi­ practice of the past. To date, there have been ation health hazards to the public. The exact no uranium mill tailings piles stabilized in a nature of this remedial action will be prescribed manner consistent with current NRC licensing on a site-specific basis, in accordance with requirements. Such activities are likely to begin health and environmental criteria to be devel­ in about 15 to 25 years, following the comple­ oped by the U.S. Environmental Protection tion of active milling and after a postopera­ Agency. Remedial-action options that were tional drying period, at sites being licensed considered in engineering assessments of these today. sites prepared for the U.S. Department of En­ ergy (Ford, Bacon, and Davis Utah, Inc., 1976; RADIOACTIVITY IN TAILINGS 1977) include on-site stabilization of the piles Naturally-occurring uranium contains with 0.15 to 5.5 m (0.5 to 18 ft) of cover earth, 99.2830 percent (by weight) uranium-238, and removal of tailings from their present loca­ 0.7110 percent uranium-235, and 0.0054 per­ tions, and stabilization at alternative sites cent uranium-234 (Hammond, 1970). Uranium nearby. Remedial action at the inactive sites ores commonly mined in the Un-ited States is likely to begin in the early 1980s. contain little thorium-232 (Haywood and At the present time, the U.S. Nuclear Regu­ others, 1977). Thus the bulk of the radioac­ latory Commission (NRC) regulates the de­ tivity in the ore, and hence in the yellowcake sign and siting of uranium mill tailings and tailings, is associated with uranium-238 disposal areas at active milling sites in non­ and its progeny. The decay scheme of ura­ Agreement States as part of its licensing and nium-238 is shown in figure 2. The long-lived regulation of source material milling under the components of the decay chain, and hence those National Environmental Policy Act of 1969 and the Atomic Energy Act of 1954 (Hendrie, TABLE 1.-Water quality standards associated with 1978). The Uranium Mill Tailings Radiation uranium-238 decay series radionuclides Control Act of 1978 amends the Atomic Energy [Concentrations (reported in picocuries/liter) as stipulated by in­ Act of 1954 by designation of uranium mill dicated Federal agencieS) tailings as a by-product material, and author­ u.s. u.s. Environmental izes the NRC to insure that the management Nuclear Protecteon Regulatory Agency of these tailings is carried out in such a man­ Radionuclide Commission Interim (MPCw Primary ner as deemed appropriate to protect the public -unrestricted Drinking areas 1 ) Water health and safety, and the environment from Regulations 2 associated radiological and non-radiological hazards. Applicants for the issuance of a li­ U-238 40,000 U-234 30,000 cense to construct and operate a uranium mill Th-230 2,000 are generally required to have a reclamation Ra-226 30 plan that includes a cover of at least 3 m (10 P~210 100 ft) of earth over the tailings. Waste manage­ 1 Maximum permissible concentrations in water for unrestricted areas; Code of Federal Regulations, Title 10, pt. 20, Jan. 1, 1977. ment criteria call for siting the tailings dis­ 2 Federal Register, v. 41, no. 133, July 9, 1976. Title 40, cb. 1, pt. 141-Radionuclides. ' posal areas in locations which are remote from s Maximum of 5 pCi/L of combined Ra-226 and Ra-228.

4 EXPLANATION NUCLIDE half-life(secs., mins., days or years) L__!_MODE OF DECAY

Major r -radiation 226 Emitter ..... :a: (.) ~ 222 u ~ 0..... <( 218

214

210

206

86 85'

~ :::> 2 ~ ~ i= ~ ~ w ~ u :::> :::> 2 :::> :a: :::> :::> ~ ..... :::> u 2 i= 2 2 i2 ~ 2 0 <( :::> <( 0 i= 2 0 0 (k: 0 0 <( 0 ...J ~ <( :a: (k: u <( (k: <( t; Ul :::> <( (k: 0 w ..... a. LL (k: <( a. ill ...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 ura­ radium-226/metric ton of ore (U.S. Environ­ nium-238, uranium-234, thorium-230, radium- mental Protection Agency, 1973). As in both 226, and lead-210. Because the drinking water acid and alkaline leaching, greater than 98 per­ standards for radium-226 are the most restric­ cent of the radium-226 remains with the tail­ tive (table 1), most monitoring and research ings (Moffett, 1976) ; the tailings from such efforts on the radiological impact of uranium an ore will contain about 560 picocuries (pCi) mill tailings on surface- and ground-water of radium-226/g. quality have focused on this radionuclide. As­ While about 90-95 percent of the uranium suming secular equilibrium, an ore containing in the ore is extracted in the milling process, 0.2 percent U aOs will contain 0.00056 g of most of the uranium-daughter products, com-

5 prising about 85 percent of the total radio­ SOURCES OF POTENTIAL HUMAN RADIATION EXPOSURE FROM activity in the ore, remain with the tailings, URANIUM MILL TAILINGS which thus constitute a low-level radioactive RADON EMANATION waste material. The tailings are often classified Radon-222 is the radioactive noble gas daugh­ into a coarse- and a fine-size fraction referred ter product of Ra-226. Tailings from several to as "sand" and "slime," respectively. The acid-leach uranium mills in the United States uranium-bearing minerals are generally softer have an emanating power (defined as that frac­ than the bulk components of the· host rock. tion of radon produced in a mineral matrix Thus, crushing of the ore tends to concentrate which escapes the matrix and is free to diffuse the uranium and uranium-daughter products in the pore spaces) of about 10-20 percent in the slime fractions. Borrowman and Brooks (Ryon and others, 1977; Macbeth and others, (1975) examined acid- and alkali-processed 1978) . Because of the short half-life of radon tailings and found that while the slime fraction and the resultant radioactive decay of a por­ made up only 25-27 percent by weight of the tion of the radon released from the tailings tailings, it contained 77-94 percent of the ra­ particles during its diffusion through the pore dium inventory. Slimes from the processing of spaces within the pile, the radon flux at the ores from the Western United States may con­ surface of the pile also depends upon the thick­ tain up to 3,000 pCi of radium-226/g (Hay­ ness, porosity, permeability, and moisture con­ wood and others, 1977) . tent of the tailings and any cover material. The relaxation length :2 for radon diffusing Besides radionuclides, non-radioactive sub­ through a dry sand is about 1.5 m (Tanner, stances potentially detrimental to water quality 1964a; Schiager, 1974; Macbeth and others, may also be introduced into the surficial en­ 1978). vironment by activities associated with. ura­ Most assessments of the radiological impact nium milling. These substances may be pres­ of uranium mill tailings have concluded that ent in the ore or in the process reagents. The the inhalation of radon daughter products is process reagents may contribute chloride, ni­ the major source of radiation exposure asso­ trate, and sulfate (West, 1972; Clark, 1974), ciated with these materials (U.S. Environmen­ while the ores may contribute elements such as tal Protection Agency, 1973; Haywood and others, 1977; Adam and Rogers, 1978). As selenium, arsenic, molybdenum, and vanadium radon release from inactive, dry tailings piles (U.S. Environmental Protection Agency, 1971; may be 4 to 25 times greater than that from Clark, 197 4) . wet tailings ponds (Goldsmith and others, Besides the leached ore residues, 1nilling 1978; U.S. Environmental Protection Agency, waste solutions (barren liquor from leach proc­ 1973) , the maximum radiological impact from ess with small amounts of entrained or soluble this source may occur after mill operation ceases,· but prior to burial. Radon emanation organic solvents) also enter the tailings reten­ will persist for a period governed by decay of tion pond. These waste streams contain soluble thorium-230 (half-life of 77,000 years), the radionuclides that (1) may persist in solution longest-lived uranium-238 daughter product and migrate in ground water, (2) may precipi­ that remains with the tailings and that decays tate by interacting with components from other to radium-226, the parent of radon-222 (fig. 2). waste solutions or as a result of liming or other amendments, or (3) may be sorbed by the tail­ WIND TRANSPORT ings or underlying soil in the retention pond. Ore crushing and yellowcake drying and At the Bluewater uranium mill in New Mexico, packaging lead to the atmospheric suspension waste effluents have in the past been disposed 2 The relaxation length is defined as the distance required to re­ of by injection into a deep Permian aquifer duce the radon concentratfon by a factor of "e", where "e" is the base of the natural logarithm system and has the approximate containing non-potable water (West, 1972). value of 2. 72.

6 of radioactive dusts, which create inhalation came in the late 1950's with the finding of high hazards locally, and are subject to wind move­ levels of soluble and suspended radium-226 in ment to off-site areas. With available dust con­ reaches of rivers in the Colorado River basin trol technology such exposure pathways can be downstream from uranium mills. Prior to this minimized (U.S. Environmental Protection time, one of the mills in the area discharged Agency, 1973; Sears and others, 1975). waste solutions and tailings to a neighboring Tailings exposed to the wind prior to burial, water course. Photographs from the 1950's and or as a result of the erosion of cover materials, 1960's of several of the mill sites (Sigler and will also be subject to wind transport. The others, 1966) show the proximity of the un­ quantity of the tailings thus mobilized will de­ stabilized tailings piles to the banks of major pend upon the characteristics of the wind ( ve­ rivers in the area. Such tailings are very sus­ locity, duration, and direction), the character­ ceptible to soil erosion processes and down­ istics of the tailings (particle size and moisture stream transport in the watershed. Laboratory content), and the location of the tailings within (see table 2) and field studies (Tsivoglou and or upon the landscape. Final burial of tailings others, 1960; Havlik and others, 1968b) sug­ in pits below at least 3m of earth, as presently gest that uranium mill tailings and radium­ recommended by the NRC, should greatly ex­ contaminated river sediments occurring in pand the period of protection of the tailings streambeds can act as sources of dissolved ra­ from wind transport as compared with that dium to the flowing water. Corrective action offered by the exposed or thinly-covered "above­ to eliminate the discharge of liquid and solid grade" 3 piles resulting from earlier operations. mill effluents to the river were taken in 1959 Breslin and Glauberman (1970) have shown (see page 8). Efforts at controlling erosion dramatic photographs. of "dust devils" moving of the piles, begun in the late 1960's under the across such exposed tailings piles. Recent studies regulatory authority of the Colorado Depart­ on bare, inactive tailings piles in western New ment of Health, will undoubtedly be addressed Mexico (Dreesen, 1978) have demonstrated by the remedial action program mandated by that large quantities of tailings sands may be the Uranium Mill Tailings Radiation Control caried downwind by particle creep and salta­ Act of 1978. The siting of tailings disposal tion, particularly during strong· spring winds. areas on streambanks would not be permitted Windblown tailings from inactive, unstabilized under present licensing criteria for uranium tailings piles in the Western States are respon­ mill tailings management (U.S. Nuclear Regu­ sible for dose rates greater than 25 mRem/yr latory Commission, 1977a). Nevertheless, the ( millirem per year) 4 at distances up to 1 mile leaching of tailings by surface waters should from the pile (U.S. Environmental Protection be considered as the potential result of long­ Agency, 1976b). Under present NRC mill li­ term erosional processes. censing criteria, applicants must have a pro­ 4 For a discussion of ionizing radiation exposure, dose, and dose gram that minimizes the dispersal of airborne equivalent measurements, see Shapiro ( 1972) or other health physics particulates from tailings disposal areas aur­ texts. The mean annual whole body background radiation doses from natural sources of external ionizing radiation in Albuquerque, ing mill operations and in the interim period N. Mex.; Grand Junction, Colo.; and Cheyenne, Wyo., are about prior to reclamation. Control measures gener­ 132, 159, and 164 milli,rads respectively (Eisenbud, 1963). The maximum permissible organ (excluding the thyroid) or whole body ally include keeping the tailings moist and (or) c:!ose equivalent for persons in· the general public as the result of using chemical binding agents (Martin, 1978; expo3ures to planned discharges of radioactive materials to the general environment from uranium fuel cycle activities, and to U.S. Nuclear Regulatory Commission, 1978e). radiation from these operations, will be 25 mRem/yr ( 0.025 Rem/ yr). Th!s standard (effective date for operations associated with SURFACE WATER TRANSPORT AND LEACHING milling of uranium ore is December 1, 1980), however, excludes dose equivalents attributable to radon and its daughter products First awareness of the environmental prob­ (U.S. Environmental Protection Agency, 1976a, p. A17-A18; Fed­ eral Register, v. 42, no. 9, January 13, 1977, Part VII, p. 2858- lems associated with uranium mill tailings 2861). While the standard excludes operations at waste di,sposal sites, windblown tailings at activity licensed millng sites are con­ 3 In this report, "above grade" and "below grade" refer to NRc" sidered. The standard, however, does not apply retroactively to off­ terminology (U.S. Nuclear Regulatory Commission, 1979a) and in­ site, windblown tailings. At the inactive mill sites, remedial ac­ dicate positions above or below the surrounding land surface. Other tion to correct such ground contaminat:on will likely be part of meanings associated with the term "grade" (see Gary and others, the program initiated under the Uranium Mill Tailings Radiation 1972, p. 3·05) are not implied. Control Act of 1978.

7 In the past, there have been tailings dike commun., R. H. Kennedy, 1979). Translocation failures, and ess·entially instantaneous releases of radium, or perhaps radon (Hendricks, 1977), of up to 15,000 tons of tailings from an im­ to foliage may result in enhanced radon exhala­ poundment area (U.S. Atomic Energy Com­ tion from buried tailings. Ingestion of con­ mission, 1974). Present design, construction taminated vegetation by humans, either directly and inspection criteria for earth and rockfill or by consumption of livestock or game ani­ embankments used for retaining tailings at mals, which have grazed upon such vegetation, newly-licensed uranium mills using above­ represents a potential source of human radia­ ground impoundments (U.S. Nuclear Regula­ tion exposure. tory Commission, 1977b) should reduce the Water quality studies on the Animas River probability of such failures. in the vicinity of the now inactive uranium mill in Durango, Colo., by the U.S. Public EXTERNAL GAMMA RADIATION Health Service and Utah State University in Primarily because of gamma radiation the late 1950's and early 1960's showed that emited by bismuth-214 (see fig. 2, p. 5), aquatic algae may be radium accumulators. a uranium mill tailings pile constitutes a source In 1958, essentially all of the liquid wastes for external radiation exposure. The exposure from the mill were discharged to the river rate at the surface of an uncovered tailings along with about 13.6 metric tons/day (15 pile may be estimated by the relationship de­ tons/day) of solid tailings (Tsivoglou and veloped by Schiager (1974) as follows: others, 1960). Early in 1959, impoundment and X=2.4 CRa treatment of liquid effluents from the mill be­ gan and radium levels in the river water were where observed to decine (Sigler and others, 1966). X= exposure rate at the surface of the pile, The mill closed in 1963 (Ford, Bacon, and in microroentgens per hour, and Davis Utah, Inc., 1977; GJT-6). A 1958 sam­ CRa =concentration of radium-226 in the tail- pling of the aquatic biota in .the river by the ings in picocuries per gram. U.S. Public Health Service at locations 2, 23, Thus for an exposed tailings pile containing and 59 river-miles below the mill showed 560 pCi of radium-226/g, the gamma exposure radium-226 concentrations in the algae to be rate at the surface is estimated to be about about 80, 30, and 5 times greater, respectively, 1,340 pR/hr, or about 12 R/yr. than the concentrations observed in algae col­ lected 1 mile upstream of the mill. The highest CONTAMINATION OF TERRESTRIAL AND algal concentration of radium-226 observed AQUATIC VEGETATION was apparently 880 pCi/g (ashed weight), Vegetation growing atop or adjacent to a measured in the spring of 1959. This compares uranium mill tailings disposal area may ex­ with radium levels in algae sampled upstream hibit elevated levels of contaminants such as of the mill of about 3 to 6 pCi/g. With the radium-226 as a result of either root uptake initiation of pollution control measures at the and translocation or surficial contamination of mill, radium levels in the river water declined, foliage by airborne particulates (Moffett and and radium-226 concentrations in algae sam­ Tellier, 1977; Dreesen and otl)ers, 1978; Kelley, pled in the downstream zone during 1960-1963 1978; Whicker, 1978). Thick soil covers will averaged about 2 to 4 times that of the up­ mitigate both pathways. However, many plants, stream samples (Sigler and others, 1963). Pilot especially selected species native to arid zones studies are underway at one location in the are deep-rooted, and may penetrate the under­ Grants Mineral Belt of New Mexico on the lying tailings (Kelley, 1978; Whicker, 1978; use of algal uptake of radium as a pollution Wullstein, 1978). Researchers, sponsored by control measure for uranium mine and mill the U.S. Department of Energy, are examin­ effluents (Eadie and Kaufmann, 1977). The ing the uptake of radionuclides by plant sp·ecies uptake by algae of radium-226 entering sur­ that may be involved in the vegetative stabili­ face waters can eventually also lead to incor­ zation of uranium mill tailings (written poration into the human food chain.

8 SEEPAGE ground water influences the rate of subsurface The movement of both mill effluents through transport of radionuclides. Factors influencing active tailings ponds and precipitation through the mobilization or retardation of specific nu­ inactive piles creates the potential for ground­ clides are discussed in the leaching section water contamination. Some of the environmen­ below. tal, ore, and process factors that may influence Lining of the tailings ponds with low per- the migration of radionuclides and other po­ meability materials may inhibit the movement tentially toxic elements through the soil and of radionuclides into the ground water. These subsurface materials are outlined as follows. materials may be chemically-inert, synthetic polymers such as polyvinyl chloride whose re­ Environmental Factors tarding effect is purely physical, or surface­ The arid and semi-arid climate in the West­ active, natural materials such as bentonite, ern States where most of the active and inac­ which may limit the movement of radionuclides tive mills in the United States are situated by chemical as well as physical means. The mitigates against extensive leaching of the tail­ use of liners is becoming more common at ings by percolating rainwater. At the model newly-licensed mills in the United States, in mill considered in the generic environmental response to NRC guidelines (U.S. Nuclear Reg­ impact statement on uranium milling (U.S. ulatory Commission, 1977a) cal1ing for mini­ Nuclear Regulatory Commission, 1979a), the mization of seepage of toxic materials from long-term rate at which water would seep tailings disposal areas into the ground-water through the tailings into the subsoil, following system. At the Madawaska mill site near Ban­ the cessation of mill operations and the accom­ croft, Ontario, a slurry of bentonite, local clay, panying discharge of waste solutions to the and cement was injected into the alluvium to tailings pond, is estimated to be 5 percent of the bed-rock surface through slotted pipes in an the rate of seepage during the period of opera­ attempt to form a "grout curtain" to reduce tion. There are, however, uranium deposits the amount of radium-226 and other contami­ and (or) mills located in areas of the Nation nants, seeping from a tailings pond, that will which have greater annual precipitation such reach a nearby lake (Dodds and others, 1978). as the Texas Gulf Coastal Plain and south­ When mill operations cease and waste solu­ eastern Alaska (Reed and others, 1976). Also, tions are no longer pumped to the tailings re­ over the course of geologic time, a future shift tention ponds, the liquid will eventually evapo­ to pluvial 5 conditions in the now arid Western rate, leaving a pile of sand, slime, neutraliza­ States is certainly a possibility. For example, tion and BaS04 sludges, and process reagents. the present-day Chihuahuan, Sonoran, and The recharge to local ground-water systems Mohave Deserts of the Southwestern United from the tailings retention system will be less States were woodlands less than 10,000 years after milling operations end than during opera­ ago, indicating a period of higher rainfall tions owing to the cessation of input of process (Van Devender, 1977), or of lower tempera­ effluents. In the presently arid and semi-arid ture accompanied by lower evaporation rates zones of the United States where most of the (Brakenridge, 1978). mill tailings are located, ground-water recharge The rate of movement of a dissolved species by precipitation is low, thereby restricting the through a porous medium is a function of the movement of radionuclides. relative affinity of the solute for the solution Digital modeling studies of water movement phase, as compared to the solid phase, as well in uncovered, inactive uranium mill tailings as the bulk velocity of the fluid. Thus, the per­ profiles suggest that under precipitation and meability and sorptive properties of the soil evaporation conditions occurring in north-cen­ and rock underlying the disposal zone, and the tral Utah, long-term recharge to underlying pH, Eh, ionic strength, and composition of the shallow (water table at about 3 m) ground water can, however, occur (Hendricks, 1978; a "Pluvial" refers to an episode of time or climate, especially Klute and Heermann, 1978). Cover materials, one corresponding to a glacial age, characterized by abundant rainfall. vegetation, profile layering, intensity, duration,

9 and character of evaporation and precipitation the inactive alkali-leached tailings piles have (rain and snow) events, and depth to the a pH as high as 9.5 (Havens and Dean, 1969). ground-water table may influence water flow The neutralization of acidic mill effluents in the profile and the extent of recharge (Klute with lime and (or) limestone to about pH 8 and Heermann, 1978). These early results, how­ will precipitate most soluble thorium-230 and ever, suggest that tailing management schemes, lead-210 as hydroxide and (or) carbonate which rely on the maintenance of moist con­ phases, and reduce soluble radium-226 levels ditions in cover materials and near-surface tail­ from about 1,000 pCi/L to about 100 pCi/L. ings to provide for radon-flux attenuation The dissolved Ra-226 concentration in the neu­ (Argonne National Laboratory, 1978) should tralized effluent may subsequently be reduced be evaluated in light of the potential for in­ to about 3 pCi/L by the coprecipitation of creased recharge (Hendricks, 1978). In ura­ radium with BaS04 following the addition (to nium mihing and milling areas with relatively the neutralized, settled effluent) of BaCl2 in the high rainfall, for example, the Elliot Lake area presence of excess sulfate (International of Ontario, Canada, such recharge through the Atomic Energy Agency, 1976). Such proce­ tailings may be appreciable even after mill dures remove radionuclides from the liquid operations cease. phase and transfer them to a solid phase where they are less likely to be environmentally Ore Factors mobile. The mineralogy of the host rock will influ­ ence the chemical properties of the water per­ USE OF TAILINGS AS A CONSTRUCTION MATERIAL colating through a tailings pile. The oxidation of pyrite contained in uranium mill tailings Before the radiological hazards associated may result in the production of sulfuric acid. with uranium mill tailings were recognized, Some Canadian uranium ores contain from 4 the desirable mechanical properties of the tail­ to 8 percent pyrite, and the inactive tailings ings sands, and the low cost of the material to piles at Elliot Lake, Ontario, exhibit pH values local contractors, encouraged its use as a fill of 1.9 to 2.3 (Watkin and Winch, 1973; Moffett, material in construction projects. The radio­ 1976). As thorium is soluble under acid leach­ logical hazards to occupants of structures con­ ing conditions (see below), seepage from an structed using these tailings sands involve: inactive tailings pile at Elliot Lake containing • External radiation exposure associated with only 12 pCi of radium-226/L, had 7,500 pCi gamma-emitting radionuclides in the tail­ of thorium-230/L and 1,800 pCi of thorium- ings. 232/L (Moffett, 1976). Uranium ores mined • Inhalation of radon daughter products, and in the United States generally have lower py­ the resultant radiation dose to lung tissue. rite contents. The Ambrosia Lake, New Mexico An estimated 300,000 tons of tailings were (Bell, 1963; Hilpert, 1969), Saguache County, used in the Grand Junction area of Colorado, Colorado (U.S. Forest Service, 1978), and with about 50,000 tons of this going into home, Shirley Basin, Wyo., (Harshman, 1972), depos­ business, and school construction, such as bed­ its contain significant amounts of pyrite, the ding for concrete slabs, water lines, and sewer latter containing about 1 percent pyrite in the lines. The use of tailings at Grand Junction unaltered sandstone host rock and from about continued from 1952 to 1966 when work by the 0.2 to 18 percent pyrite in the ore. Colorado State Department of Health and the U.S. Public Health Service showed elevated Process Factors radiation levels in structures where tailings had The leaching solution, alkali or acid, will in­ been used. In 1972, a remedial action program fluence the chemical form, carbonates or sul­ (now about half completed) aimed at about 700 fates, of the radionuclides in the tailings, and such structures, and involving tailings removal the pH of the tailings. At the Tuba City, Ariz., and backfill with uncontaminated material, was uranium mill site, the inactive acid-leached begun under the management of the Colorado tailings piles have a pH as low as 2.3, while State Department of Health and the U.S.

10 Department of Energy (Hendricks, 1977; The hydrated ion of radium is the smallest Comptroller General of the United States, in the alkaline earth series, and hence it would 1978). tend to be preferentially retained by ion ex­ While the Grand Junction case appears to change surfaces (Kirby and Salutsky, 1964; have been the most extensive, and has been the Sedlet, 1966). Radium has the least tendency subject of the most documentation and public of all the alkaline earths to form complex ions. attention, the use of uranium mill tailings for Like the other alkaline earths, radium forms construction purposes has apparently occurred few complexes in acidic solutions. In alkaline to a limited extent in other communities where solutions, anionic complexes of radium with nearby piles existed, including Salt Lake City, organic ligands, such as EDTA ( ethylenedia­ Utah (Ford, Bacon, and Davis Utah, Inc., mine tetraacetic acid) and citric acid, are 1978, table 1-1). In the Cane Valley area of known to occur (Sedlet, 1966). Means and southeastern Utah and northeastern Arizona, others (1978) suggest that EDTA-mobilization uranium mill tailings and ore had been used may be responsible for apparently elevated lev­ through 1975 for the construction of about 16 els of radium seen in water and soil sampled residential structures on the Navajo Reserva­ around a radioactive waste disposal trench at tion. These materials were incorporated di­ the Oak Ridge National Laboratory burial rectly into the floor, foundation materials, and ground. The possible complexation by natural exterior stucco, in contrast to their usage at chelating agents, such as fulvic acid, has ap­ Grand Junction, primarily as bedding material parently not been studied. Complexes with in­ for floors and foundations (Hans and Douglas, organic ligands, such as bicarbonate or chlo­ 1975). The 1975 U.S. Environmental Protec­ ride, are not reported to occur. Radium com­ tion Agency study which documented this prac­ pounds have low solubilities in organic solvents tice at Cane Valley has presumably resulted in (Kirby and Salutsky, 1964). its cessation, and the remedial action and con­ Radium apparently does not form discrete trol measures at inactive and active mills man­ minerals, but can coprecipitate with tannin and dated by the Uranium Mill Tailings Radiation gelatin (Vdovenko and Dubasov, 1975), cal­ Control Act of 1978 is likely to further curtail cium carbonate, hydrous ferric oxides (Tanner, the use of tailings as a contruction material 1964b), barite (BaS04), celestite (SrS04) and in the near future. angelsite (PbS04) (Austin and Droullard, 1978), tricalcium phosphate, thorium oxalate, LEACHING BEHAVIOR OF RADIUM, and phosphate (Sedlet, 1966), and aluminum THORIUM, AND URANIUM phosphate (Koide and Bruland, 1975). Asso­ RADIUM ciations of radium with barium sulfate are Radium exhibits only the (2+) oxidation known in uranium ore deposits (Granger and state in solution, and its chemistry resembles others, 1961) and in nodules in cattle thyroids that of barium. Radium forms water-soluble (Middlesworth, 1978) . These associations may chloride, bromide, and nitrate salts. The phos­ be due either to coprecipitation or the adsorp­ phate, carbonate, selenate, fluoride, and oxalate tion of radium onto existing barium sulfate salts of radium are slightly soluble in water, crystals. Tanner (1964) cites Russian workers while radium sulfate is relatively insoluble in who report radium not to coprecipitate with water [Ksp=4.25 x 10-n at 20°C (Sedlet, 1966)]. gypsum [CaS04 ·2H20]. However, by-product This solubility product for RaS04, the pre­ gypsum from phosphoric acid production in sumed chemical form of radium in sulfuric central Florida contains about 20 to 30 pCi/g acid-leached tailings, corresponds to a radium of radium-226 (Kaufmann and Bliss, 1977). concentration of 1.5 x 10-3 g/L of pure water, Radium may be sorbed by clay minerals, col­ and of 4.6 X 10-6 g/L of water containing 200 loidal silicic acid (Vdovenko and Dubasov, ppm sulfate. The latter concentration of ra­ 1975), manganese oxides (Moore and Reid, dium, while only a few parts-per-billion, is still 1973), and organic matter (Titayeva, 1967; about six orders of magnitude greater than Morse, 1970; Titayeva and others, 1977). that permitted in drinking water (table 1). Ground waters dominated by chloride and (or)

11 bicarbonate, low in sulfate, with high ionic ings slimes suggests that both adsorption strengths and high contents of calcium and and coprecipitation reactions may be in­ barium are conducive to the transport of ra­ volved in the retention of radium by the dium (Tanner, 1964b; Kagan, 1967; Perel'man, tailings. Radium may be sorbed on active 1972; Cadigan and others, 1976; Felmlee and sites of silicate minerals, as well as copre­ Cadigan, 1978a). While, unlike uranium, only cipitated with several alkaline earth sul­ a single valence state exists for radium, the fate compounds of widely differing solu­ influence of oxidation-reduction conditions on bilities, for example, CaS04, SrS04, and the mobility of elements, such as iron, manga­ BaS04. Hence, radium release from the nese, and sulfur, which may be involved in tailings probably involves both surface the coprecipitation and sorption of radium desorption mechanisms, as well as multi­ should be considered. component solubility considerations. By In table 2, the results of several studies on analogy to Seeleys work on acid leached the leachability of radium from uranium ores tailings, alkaline earth carbonates are and mill tailings are listed. These data sug­ probably involved in the immobilization gest the following generalizations: of radium in alkaline-leached uranium mill • Radium in uranium ore is only slightly solu­ tailings. ble in H2S04, but highly soluble in HCl Shearer and Lee (1964) suggest that in and HNOa, presumably because of the acid-leached uranium mill tailings, radium

greater solubility of RaCl2 and Ra (N03 ) 2 exists as a coprecipitate with barium sul­ as compared to RaS04. fate. Work by Levins and others (1978) • Radium in acid-processed tailings is leach­ on the leaching of alkaline earth elements

able with EDTA, HCl, HN03 and distilled from Australian-ore uranium mill tailings water. The solubility in distilled water is with varying strengths of sodium chlo­ highly dependent upon the liquid-to-solid ride solution showed a parallel increase ratio used in the test, suggesting a limit­ in barium and radium-226 concentration ing solubility product or suspension pH in the leachate witp increasing salt mo­ effect. The water leaching data presented larity, while calcium and strontium con­ in table 2 suggest that uranium mill tailings centrations iii the leachate varied little in the environment may constitute a long­ with salt molarity, thereby supporting an term source for radium contamination of association of radium with a barium phase. contacting surface and ground waters. In­ However, other investigatons (Seeley, deed some tailings in Canada that have 1976; Ryon and others, 1977; Kaiman, been exposed to weathering forces for sev­ 1977, 1978) suggest that radium may show eral years apparently do show evidence of more association with the far more solu­ radium depletion (Moffett and Tellier, ble calcium sulfate mineral, gypsum. Also, 1977; Skeaff, 1977). a member of the jarosite family, a group • The data on salt extraction (table 2) confuse, of hydrous iron sulfate minerals, contain­ as well as clarify, the picture of how ra­ ing 80,000 pCi/g of radium-226 has been dium exists in the tailings. The differences found in weathering pyritic tailings from in tailings materials and leaching condi­ Elliot Lake, Ontario (Moffett and others, tions (time, temperature, solute concen­ 1977). This jarosite-material may have trations ,solid-solution ratio) makes a com­ precipitated during the acid-leaching proc­ parison of the extraction-yield data diffi­ ess as suggested by Kaiman (1977, 1978), cult, as is an extrapolation of these data or may have been formed during the weath­ to natural environments. There are many ering of the ore or the tailings. The latter apparent contradictions ; most notable is mechanism is suggested by the work of the effect of barium chloride leaching on I varson and others ( 1978) on the synthesis radium removal. The recent work of Seeley of jarosite [KFea (S04) 2(0H) 6] in the pres­ (1976) on radium removal from real and ence of glauconite, illite, and microcline, simulated acid-leached uranium mill tail- and natrojarosite [NaFea (804) 2(0H)6] in

12 TABLE 2.-Proportion of radium-226 leached from uranium ore, uranium mill tailings, and river bottom sedi­ ments in laboratory tests

Proportion of Material Ra-226 Leaching conditions extracted Reference (in percent) Uranium Distilled water, 25oC, 1 percent solids, 0.42 Shearer, 1962 (table 17). ore. 65 min. Distilled water, room temperature, 10 percent 2.3- 2.7 Havlik and others, 1968b. solids, 3 hr. 1N KCl, room temperature, 10 percent solids, 22 -31 Havlik and others, 1968b. 0.25-5.0 hr. 0.01N KCl, room temperature, 10 percent 2.6- 9 Havlik and others, 1968b. solids, 0.25 hr. 1N NaCl, room temperature, 10 percent 14 -17 Havlik and others, 1968b. solids, 0.25-5 hr. 1N CaCl2, room temperature, 10 percent solids, 3.1 - 5.3 Havlik and others, 1968b. 1-5 hr. 1N BaCl2, room temperature, 10 percent solids, 0.1 - 0.3 Havlik and others, 1968b. 0.25 hr. N a-carbonate/bicarbonate, in-mill alkaline- 1.5 - 2.. 2 Moffett, 1976. leaching conditions. HzS04, in-mill leaching acid conditions ______0.4 - 0.7 Moffett, 1976. 0.1N HCl, room temperature, 5-8 hr ------2.9 - 4.5 Havlik and others, 1968a. 1.5M HCl, 60°C, 25 percent solids, 3X30 min __ 86 -98 Borrowman and Brooks, 1975. 3M, HCl, 85·°C, 25 percent solids, 1 hr ------90 Seeley, 1976. 3M HNOa, 85°C, 25 percent solids, 1 hr ______94 Seeley, 1976. Acid-leached Distilled water, 25°C, 3 percent solids, 15- 0.2 - 1.0 Ryon and others, 1977. uranium 90 hr. mill tail­ Distilled water, 25°C, 3 percent solids, 380 4.4 Ryon and others, 1977. ings. hr, 10 succ~ssive leaches of 15-90 hr each. DistiHed water, 25oC, 1 percent solids, 1 hr __ 1.2 Shearer, 1962 (table 20). Distilled water, 25°C, 0.1 percent solids, 1 hr __ 23.2 Shearer, 1962 (table 20). Distilled water, 25oC, 0.01 percent solids, 40 Shearer, 1962 (table 20). 1 hr. Distilled water, room temperature, 10 percent 3.5- 4.7 Havlik and others, solids, 5-15 hrs. 1968a, b. 1N KCl, room temperature, 10 percent solids, 100 Havlik and others, 1968b. l hr. 1N KaP04, room temperature, 10 percent solids, 2.4 Havlik and others, 1968b. 6 hr. 0.1N KCl, room temperature, 10 percent solids, 54 Havlik and others, 1968b. 1 hr. 0.01N KCl, room temperature, 10 percent 10 Havlik and others, 1968b. solids 15 min. 1N NaCl, room temperature, 10 percent 95 Havlik and others, 1968b. solids, 6 hr. 1N NaaP04, room temperature, 10 percent 6.6 Havlik and others, 1968b. solids, 6 hr. 1N (NH4hS04, room temperature, 10 percent 12 Havlik and others, 1968b. solids, 1 hr. 1N CaCl2, room temp.erature, 10 percent solids, 48 Havlik and others, 1968b. 3 hr.

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

Proportion of Material Ra-226 Leaching conditions extracted Reference (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 frac- tion 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 sedi­ ments in laboratory tests-Continued

Proportion of Mattrial Ra-226 Leaching conditions extracted Reference (in percent) Acid-leached 1M Na4 EDTA, room temperature, 3 percent 93 Seeley, 1976. uranium mill solids, 16 hr. tailings. (Slime frac­ 1M Na2 DTPA, room temperature, 3 percent 94 Seeley, 1976. tion only.) solids, 16 hr. Alakali-leached Distilled water, 25·°C, 1 percent solids, 1 hr __ 0.14 Shearer, 1962 (table 18). uranium 0.15M EDTA, 60°C, 15 percent solids, 2 hr __ _ 56 Borrowman and Brooks, mill tailings. 1975. River bottom 1 Distilled water, 25oC, 1 percent solids 1 hr __ 0.07 Shearer, 1962 (table 32). sediment. 0.01M HCl, 25°C, 1 percent solids, 1 hr ------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 oxida­ ings discharged by or eroded from the mill tion of ferrous iron in solution by Thio­ area. The replacing power relationship bacillus ferrooxidans, an acidophilic bac­ seen here: terium found frequently in oxidizing py­ Ba>Sr>Ca>Mg ritic environments. Indeed, the bacterium T. ferrooxidans and the mineral jarosite follows that which might be predicted on were isolated earlier by Ivarson (1973) the basis of hydrated ionic radii (Grim, from a yellow-brown sediment sampled at 1968) .• the bottom of a pool of highly-acidic water The geochemical controls on radium mobili­ in an underground Elliot Lake mine, yield­ zation to, and removal from, natural waters ing pyrite- and pyrrhotite-bearing ura­ has been little studied. Distribution coefficients nium ore. The possible redistribution and measured for radium for soil and rock mate­ concentration of radium by this or other rials at three mill sites in Wyoming, Utah, and weathering-associated mechanisms may be Washington range from 8 to 650 mL/g (U.S. of importance. in determining the mobility Nuclear Regulatory Commission, 1978a). of radium. Whether these differences refl·ect technique de­ • The observation of a sorption-ion exchange pendency or actual differences in sorptive ca­ type pattern of radium-226 displacement pacities is not clear. seen with the river sediments is more easily Some environmental analyses of subsurface explained as these materials have presum­ radium migration from uranium mill tailings ably been chemically contaminated with piles (Sears and others, 1975; U.S. Nuclear soluble radium that has sorbed to the clays. Regulatory Commission, 1978a) have assumed and organic matter of the river bottom, that because of the lack of significant ground­ as well as physically contaminated by tail- water recharge following the end of mill effiu-

15 ent inputs to the tailings pond, and the sorption charged to the tailings pond at a conventional of radium by earth materials, no significant acid-leach mill will be high in sulfates, after movement of radium will occur after mill oper­ the end of milling operations, only natural ations cease. The analyses by Sears and others waters (precipitation and runoff) will be in­ (1975) acknowledges the possible mobilization filtrating the tailings. With time, the sulfate of radium by ground water as a result of cli­ content of the seepage might be expected to matic changes that increase leaching by infil­ decrease, and this may contribute to greater trating precipitation and by inundation by a radium mobilization from the tailings. rising water table. A study of radium and ura­ nium concentrations in ground water samples THORIU)1 from the Ogallala formation of the High Plains In aqueous systems, only the Th4 + oxidation of Texas and New Mexico showed radium to be state is known to exist. The tetravalent ion present in less than its radioactive equilibrium undergoes hydrolysis in aqueous solutions above magnitude (Barker and Scott, 1958); Dyck pH 2 to 3 and is subject to extensive sorption (1978) indicates that in surficial environments, by clay minerals and humic acid at near neutral uranium is more readily leached from soil and pH (Bondietti, 1974; Ames and Rai, 1978). rock than thorium-230 and radium-226. The In near-neutral pH and alkaline soils, precipi­ preferential leaching of radium, with respect tation of thorium as a highly insoluble hydrox­ to uranium, by ground waters (Granger, 1963; ide (Hyde, 1960, indicates Ksp of Th ( OH) 4 = 39 Cadigan and Felmlee, 1977 ; Felmlee and Cadi­ 10- ) or hydrated oxide phase (Ames and Rai, gan, 1978b), and in fossil bones ( Charalambous 1978) and coprecipitation with hydrated ferric and Papastefanou, 1977; Papastefanou and oxides (Kluge and others, 1977) may, in addi­ Charalambous, 1978) has been noted in other tion to adsorption reactions, be important studies. Differences in the relative mobilities mechanisms for the removal for thorium from of uranium and radium, as reflected in radio­ solution. Because of sorption and precipitation active disequilibria studies, may be a reflection reactions and the slow solution rate of thorium­ of local oxidation-reduction conditions affecting bearing resistate minerals thorium levels in the solubility of uranium. However, the fact natural waters are generally low. that high radium ground waters exist around Because of its high charge density, thorium, uranium ore bodies ( Germanov and others, like uranium, in aqueous solution is susceptible 1958; Cook, 1978; U.S. Nuclear Regulatory to complex formation. Inorganic and organic, Commission, 1978b,c) suggests that natural cationic, neutral and anionic, simple and poly­ ground water can mobilize radium from the meric complexes are known (Cotton and Wil­ precursor of the tailings. While it is acknowl­ kinson, 1966; Herman and Langmuir, 1978). edged that uranium mill tailings differ physi­ Studies of soil profiles developed in the glacial cally and chemically from uranium ore, detailed moraines of the High Sierra area of California studies of the hydrogeochemical controls on the have shown evidence for thorium complexation migration of radium from orebodies may pro­ by, and translocation with, soluble soil organic vide valuable information for the assessment matter (Hansen and Huntington, 1969). Among of long-term migration of radium from the the common inorganic anions that form strong tailngs deposits, which have histories of only complexes with thorium are fluoride, sulfate, about 30 years or less. This information may phosphate, chloride, and nitrate (Ames and also have application to geologic disposal of Rai, 1978). Centrifugation, dialysis, and ion high-level radioactive waste (spent reactor exchange studies of thorium in ground waters fuel), as radium-226 is the most hazardous from granitic terranes (Dement'yev and Sy­ nuclide for exposure by ingestion in such waste romyatnikov, 1965) suggest its occurrence and aged more than 50,000 years ( Gera, 1975) . transport perodminantly as either a colloidal The character of seepage water draining out phase, or as a soluble, anionic complex. The of the tailings pile is difficult to predict over principal chemical characteristics of the ground the long-term (U.S. Nuclear Regulatory Com­ waters found to contain the most thorium were mission, 1979a). While the waste solutions dis- low pH, low salinity and hardness, and high

16 organic content (Dement'yev and Syromyatni­ ment of the Interior, 1976); however, at most kov, 1965). Thus, it would appear that some active mills in the United States, the waste of the chemical properties of ground water stream is not neutralized. Neutralization of the th~t appear to favor the transport of thorium waste solutions by contact with the alkaline (high concentration of sulfate, low concentra- subsoils which underlie the tailings ponds at tion of calcium, and low ionic strength) may most western sites will likely result in the inhibit the ground water transport of radium. precipitation or coprecipitation of thorium as The liquid effluents discharged to the tailings noted above. pond may contain a variety of organic com­ pounds from the solvent extraction circuit or URANIUM other stages in the milling process. Also, car­ The dominant uranium valence states, which bonaceous materials in uranium ores, which are stable in geologic environments, are the may be dissolved in the milling process (Dree­ uranous (U4 +) and uranyl (U6 +) states, the sen and others, 1978), are discharged with the former being far less soluble. The U4 + = U6 + tailings. As organic complexes of thorium have transition has a redox potential within the been shown to be of importance in natural normal range for geologic environments (Lang­ water systems, the influence of both natural muir, 1978), and process-reagent organic species on the en­ U4 + + 2Hz0 = U0z2 + + 4H + + 2e-. vironmental mobility of thorium-230 should be evaluated. The presence of complexing The standard oxidation potential (25° C) is agents in these effluents has been offered as a Eo= +0.27 volts. Uranium transport generally partial exp_lanation for the low distribution occurs in oxidizing surface and ground waters 2 coefficients observed for thorium-230 on sub­ as the uranyl ion, U02 +, or as uranyl floride-, soil materials equilibrated with tailings pond phosphate-, or carbonate-complexes. These com­ water from a Wyoming millsite (D' Appolonia plex ions include neutral, cationic-, and anionic­ Consulting Engineers, Inc., 1977). species. The uranyl ion and uranyl fluoride The waste stream (pH 10) at the Humeca complexes dominate in oxidizing, acidic waters, uranium mill contains about 110 pCi/L of while the phosphate- and carbonate- complexes thorium-230 (U.S. Environmental Protection dominate in near-neutral and alkaline oxidiz­ Agency, 1976b). At lower pH's, thorium be­ ing waters, respectively. Hydroxyl-, silicate-, comes more soluble. Acid-leach milling may organic-, and sulfate-complexes may also be dissolve from 30 to 90 percent of the thorium of importance, the latter especially in mining in the ore (Robertson, 1962; Moffet, 1976; and milling operations using sulfuric acid as Ryon and others, 1977; Levins and others, a leaching agent (Langmuir, 1978). In weakly 1978). Acidic effluents (pH 2.5) from uranium acid waters high in dissolved organic matter, mills in the Grants Mineral Belt of New Mex­ uranium may be transported as a pseudocol­ ico contain from 150,000 to 170,000 pCi/L of loidal phase (Kochenov and others, 1965). thorium-230 (Kaufmann and others, 1976). Soils and related materials have been shown The solubilized thorium can be subsequently to sorb significant quantities of uranium. Ma­ precipitated if the acidic effluent is neutralized, suda and Yamamoto (1971) showed that 10-g either by contact with natural media or by soil samples (pH 5.4-5.8) were able to sorb process additions of lime and (or) limestone all of the uranium (supplied as uranyl nitrate) to the waste solutions. At Elliot Lake, Ontario, from 100 mL of aqueous solutions containing current practice involves raising the pH of the 1 to 100 p.g/mL of uranium. The quantity of tailings slurry to about pH 10.5 with lime upon uranium adsorbed was not related to the soils' impoundment (Raicevic, 1978). At the Sher­ cation exchange capacities. Szalay (1964) wood uranium mill (acid-leach) in eastern showed peats to sorb up to 2-3 meq U0z2 + /g Washington, the tailings slurry is neutralized and suggests the sorption is a cation exchange (from an initial pH of about 1 to a final pH process. Dement'yev and Syromyatnikov of about 7) by the addition of lime prior to (1968) showed maximal sorption of hexavalent discharge to the tailings pond (U.S. Depart- uranium by colloidal humic acid, fulvic acid,

17 coal, and iron oxides to occur at pH 5 to 6. commonly occur in valley fills, which may be Langmuir ( 1978) reports maximal sorption of recharged by surface water, the potential for uranyl ions on natural materials (organic mat­ ground-water contamination from this source ter, iron-, manganese-, and titanium-oxyhy­ exists. The radium content of mine drainage dro:xides, zeolites, and clays) to occur at pH 5.0 waters varies greatly with the stage of devel­ to 8.5. The sorption of uranyl ions by such opment of the mine, that is, the degree of ex­ natural media appears to be reversible, and for posure of the orebody. Mine drainage waters uranium to be "fixed" and thereby accumulate, samples during the period 1970-1975 in the it requires reduction to U4 + by the substrate or Churchrock and J ackpile-Paguate areas had by a mobile phase such as H2S (Kochenov and radium-226 contents ranging from 8 to 190 others, 1965; Langmuir, 1978). pCi/L. However, the EPA study failed to re­ veal ground-water contamination as a result WATER QUALITY STUDIES of mining operations. GRANTS MINERAL BELT IN NEW MEXICO Non-radioactive constituents in the mine and The most extensive study to date on the mill effluents can lead to elevated levels of effects of uranium mining and milling opera­ total dissolved solids, ammonia, nitrate, sele­ tions on ground water quality was done by the nium, and vanadium in surface and ground U.S. Environmental Protection Agency (EPA) waters. Selenium probably occurs as the selenite in the Grants Mineral Belt area of northwest­ anion in oxidizing, alkaline waters (Hem, ern New Mexico in 1975 (U.S. Environmental 1970), and is an element of concern in the Protection Agency, 1975; Kaufmann and vicinity of an alkaline-leach mill in the region. others, 1976; Eadie and Kaufmann, 1977). Shallow, downgradient, off-site, domestic wells This area contains about 40 percent of the containing up to 3.9 mg/ of selenium (EPA Nation's uranium reserves and presently has Interim Primary Drinking Water Standard is five inactive tailings piles, five active mills and 0.01 mg Se/L) have been observed here, the seven mills in the proposal, design, or construc­ contaimination of the shallow aquifer presum­ tion phase. Ground-water contamination in ably caused by seepage through the sandy soil these milling areas can occur as a result of from the adjacent tailings pond. Periodic re­ seepage from active tailings ponds, or inactive sampling of selected wells in the EPA study tailings piles, or from leakage out of the zone is advisable to provide a data base for future of injection from disposal well operations. evaluation of the environmental effects of min­ Seepage from the tailings ponds in the Blue­ ing and milling in the Grants area. water Valley and the Ambrosia Lake areas amounted to about 180,000 and 491,000 m 3 /yr, ELLIOT LAKE, ONTARIO respectively, for the period 1973-1974. These Important uranium deposits exist in the quantities represent about 8 and 29 percent, Elliot Lake area of southeastern Ontario, Can­ respectively, of the inflow to the ponds. ada. In contrast to the Grant Mineral Belt's While mill effluents (sampled at the Blue­ mean annual precipitation of 25 em and evapo­ water mill over the period 1960-1975) con­ ration potential of 180 em (Ford, Bacon, and tained from 40 to 292 pCi/L of radium-226, Davis Utah, Inc., 1977, GJT-13), the wet­ only one of the· 71 existing wells sampled in temperate Elliot Lake area is characterized by the region (well depths ranging from 8.2 to ~a mean annual precipitation of 80 em and 299 m) showed radium-226 concentrations in evaporation of about 60 em (Hare and Thomas, excess of 5 pCi/L. This sample contained 6.6 1974). The uranium ore contains about 3-8 pCi/L of radium-226 and was obtained from percent pyrite, and hence upon oxidation, there a shallow (8.2 m) well adjacent to an active exists the opportunity for extensive sulfuric tailings pond in the Ambrosia Lake area. acid leaching of the tailings. While the active mills discharge no waste Moffett and Tellier (1978) have examined solutions to the surface waters, mine drainage the tailings solids and ground water contained waters do enter surface water courses, and as within the pile at a 17 -year old abandoned shallow ground waters in these areas most uranium mill tailings area at Elliot Lake.

18 Thorium, originally present in the ore at 170 pCi/L, and 1565 pCi/L of thorium-230, ini­ p.g/g, was reduced to 4-6 p.g/g in the upper 15- tially, decreasing in 2.3 years to 693 pCi/L. 20 em of the weathering tailings. It should be recognized that the concentration of thorium in OTHER AREAS the ore-feed may have varied during the life of The U.S. Department of Energy has recently the tailings pond. Also, some of the thorium issued a series of 20 reports prepared by Ford, solubilized during the acid milling of the ore Bacon, and Davis Utah, Inc., dealing with in­ may not, due to incomplete neutralization of the active uranium mill tailings piles in eight mill effluent, have been precipitated and de­ Western States (Ford, Bacon, and Davis Utah, posited with the tailings solids sampled. Never­ Inc., 1976, 1977). These reports are engineer­ theless, it would appear that much of the tho­ ing assessments of possible methods and costs rium present in the tailings solids at the time of cleanup of these sites, and include site­ of deposition has since been lost to surface and specific information on tailings characteristics ground waters. These tailings also show evi­ and ground water and soil contamination. dence of the leaching loss of uranium and The tailings sampled at the various piles radium-226, although again, the apparently were found to have a maximum radium-226 diminished levels may reflect changes in the concentration ranging from about 100 to 5,000 ore grade having gone through the mill, and pCi/g .The depth of leaching of radium into sampling variations associated with the hetero­ the soil beneath most of the tailings (generally geneity of the tailings pile. defined in these reports as the depth at which The ground waters sampled within the tail­ the soil radium-226 levels fall to twice back­ ings pile are grouped into two acidity classes. ground levels) ranged up to about 8 feet. At The low acidity group samples (acidity <1000 several of the sites (Monument Valley and mg/L as CaC03) were all obtained from the Tuba City in Arizona, Durango, Naturita, and slime-rich zones of the pile (where pyrite oxi­ Rifle in Colorado, Ambrosia Lake in New Mex­ dation is restricted owing to a lack of dewater­ ico, and Falls City in Texas) there were indi­ ing) and were generally lower in total dis­ cations of local ground and surface water con­ solved solids, iron, zinc, uranium, lead-210, and tamination with respect to Ra-226, presumably gross a and f3 activity than those samples in caused by seepage and runoff from the tailings the high acidity group. While the low acidity piles, although with the exception of the Am­ waters showed no detectable thorium, the high brosia Lake and Falls City sites, EPA drink­ acidity waters showed up to 2,100 pCi/L of ing water standards were generally not ex­ thorium-228, 4,200 pCi/L of thorium-232, and ceeded at the time of sampling (Ford, Bacon, 52,000 pCi/L of thorium-230. In contrast to and Davis Utah, Inc., 1977, GJT-4,6,8,10,13, the trend observed for the other radioisotopes, 16). At the Naturita, Grand Junction, Old radium-226 levels were generally higher in the Rifle, and Gunnison sites, the water table low acidity (mean= 113 pCi/L) as compared within the alluvium on which the tailings piles to the high acidity (mean=59 pCi/L) waters rest is very shalow, and at times may rise (Moffett and Tellier, 1978). This may be due within the tailings, thereby creating the poten­ to the suppression of RaS04 dissolution in the tial for unconfined ground water to leach the zones of active pyrite oxidation caused by the tailings (Ford, Bacon, and Davis Utah, Inc., high sulfate concentrations in the interstitial 1977, GJT-8,9,10,12). waters. The leaching of radionuclides from aban­ URANIUM MILL TAILINGS TREATMENT doned Elliot Lake tailings has been studied in AND DISPOSAL OPTIONS laboratory columns by Schmidtke and others SURFACE STABILIZATION OF TAILINGS AND ( 1978) . These tailings initially contained 122 NEAR SURFACE BURIAL pCi/g of radium-226 and 3.2 pCi/g of tho­ The tailings are non-cohesive, small rock rium-230. Using water application rates of 49 fragments, and thus highly susceptible to ero­ mm/yr, the leachate contained 81 pCi radium- sive forces. They generally do not have the 226/L initially, decreasing in 2.3 years to 5 physical and chemical properties required to

19 sustain plant growth, and therefore will not and others, 1978) .The placement of a coarse be amenable to direct stabilization by vegeta­ rock cover over the soil cap in order to ap­ tion. To date, many inactive tailings piles re­ proximate a natural "desert pavement," and main uncovered and unvegetated, and thereby thereby armor the soil cap has been suggested subject to severe wind and water erosion. Sta­ as a means of prolonging the period of tailings bilization efforts to date have generally in­ burial (Nelson and Shepard, 1978). A coarse volved contouring of the pile, application of a rock cover has been used with some success thin earth cover (topsoil, gravel, riprap on in minimizing wind and water erosion of tail­ steep slopes), vegetation, and construction of ings at the inactive mill site near Shiprock, drainage ditches to divert surface runoff water N.Mex. (Nelson and Shepard, 1978). A gravel from neighboring land from reaching and erod­ cover will apparently be used in the final sta­ ing the piles. bilization of the tailings derived from a mill Climatic considerations, such as lack of ade­ in southeastern Utah, which was recently con­ quate rainfall for plant growth, and the low sidered for relicensing (U.S. Nuclear Regula­ fertility of cover materials often require the tory Commission, 1979b) . use of mulches, fertilizer, and irrigation water The use of "below-grade" burial of tailings in order to establish a vegetation stand. While in pits, and the use of 3 m or more of cover it is certainly possible, with human interven­ earth, as advocated by the NRC (U.S. Nuclear tion and application of soil amendments, to Regulatory Commission, 1979a), will provide establish vegetation on these tailings and for a longer period of erosional stability than cover materials, at present there has been in­ that associated with "above-grade" impound­ sufficient research and time to evaluate whether ment of tailings, the common disposal method or not permanent, maintenance-free vegeta­ at the inactive sites and older active sites. tive stabilization can be successfully achieved. "Below-grade" disposal will not result in rem­ The record to date is spotty. While at some nant tailings piles above the land Sll;rface, and locations thick vegetation stands have been thus the component cover materials and tailings achieved, these have often required repeated will be less susceptible to wind and water ero­ irrigation. Visible erosion following stabiliza­ sion than those in "above-grade" structures. tion attempts have been reported (Ford, Bacon, However, cover materials and tailings in and Davis Utah, Inc., 1977, GJT-18). "below-grade" disposal systems, as well as the In areas where stabilization with vegetation surrounding land surface, are, nevertheless, is not feasible because of lack of sufficient subject to erosion. rainfall, chemical stabilization methods have "Stability" is a time-dependent concept. A been proposed and (or) tried. The use of a concept whose time-focus is that of human life water-soluble, elastom~ric polymer tailings­ spans and the life spans of man-made struc­ binding agents was tested on the Tuba City, tures is inadequate in assessing the fate of Ariz., uranium mill tailings in Se·ptember 1968 materials whose radioactive character persists (Havens and Dean, 1968). A May 1974 inspec- over hundreds of thousands of years. Schumm tion of the site showed extensive disintegra­ (1963) reports average denudation rates of 9 tion of the initially indurated crust (Ford, to 20 cm/1,000 yr for arid/semi-arid terranes Bacon, and Davis Utah, Inc., 1977, GJT-5). [average annual precipitation of 25 to 38 em Decomposition of the stabilization crust within (10-15 inches)]. Using the lower end of this 2 to 3 years was observed following the test range, earthen covers of 0.6 m (2ft) and 3m application of a tar-like agent to the surface (10ft) in thickness would be removed in about of a portion of the tailings at the inactive mill 6,700 and 33,000 years, respectively. During site in Salt Lake City, Utah (Ford, Bacon, and these time periods about 6 and 26 percent, Davis Utah, Inc., 1976). A major loss of the respectively, of the thorium-230 will have de­ radon-flux attenuating abilities of a plasticized cayed, and without subsequent reburial, the sulfur compound was observed in 2 years at tailings, with the bulk of their radioactive com­ uranium mill tailings test plots near Las Vegas, plement, thus may be exposed to wind and Nev. (Bernhardt and others, 1975; Macbeth water erosion.

20 The rates of disinterment presented require others, 1975) .6 A recent NRC position paper qualification. The regional denudation rates (U.S. Nuclear Regulatory Commission, 1977a) used do not consider local conditions such as indicates that a major goal of uranium mill position in drainage basin and topographic fea­ tailings management programs should be the tures providing wind breaks (U.S. Nuclear reduction of radon emanation rates from in­ Regulatory Commission, 1979a), which may active tailings impoundment areas to about cause local erosion rates to deviate consider­ twice that of the emanation rate in the sur­ ably in either direction from the regional mean. rounding environs.7 Assuming an average back­ Neither do the disinterment rates consider ground radon emanation rate of about 1 pCi climatic changes in the future that can alter m- 2 s-1 (Wilkening, 1974; Martin and Miller, erosion rates. Manipulated soil covers are likely 1978) and a radon flux from a typical exposed to be more susceptible to erosion than natural tailings pile of about 500 pCi m- 2 s-1 (Clem­ soils or bedrock. Grazing and burrowing activi­ ents and others, 1978), the NRC goals require ties of animals may increase the erosion rates about a 99.6 percent reduction in radon ema­ (Whicker, 1978). On the other hand, newly- nation. Depending upon the cover materials designed tailings disposal areas (U.S. Nuclear particle size distribution, bulk density, mois­ Regulatory C~mmission, 1978d) will probably ture content, and other properties affecting the be covered and contoured to yield a low relief­ permeability to radon migration, a thickness length ratio; hence the regional denudation of about 3 to 12m (10-40 ft) or more of earth rates presented above may overestimate the rate will be required for a 99 percent reduction in of disinterment. Also, the consideration of re­ radon emanation from the underlying tailings gional denudation rates emphasizes erosional (U.S. Environmental Protection Agency, 1973; processes to the exclusion of depositional proc­ Sears and others, 1975; Macbeth and others, esses that may be of local importance in a given 1978; Nelson and Shepard, 1978). Thus to re­ area. Indeed, siting of tailings disposal areas duce radon emanation to a maximum extent, in aggrading portions of landscape may be bene­ particularly in view of the erosion rates pre­ ficial as depositional processes would tend to viously cited, burial of the tailings in a deep maintain a cover above the tailings, and thus excavation or cavity would be most effective. attenuate dispersal as well as radon exhala­ While concrete, asphalt, and organic binding tion and gamma radiation exposure (U.S. Nu­ agents may provide marked reductions in radon clear Regulatory Commission, 1979a). These potential benefits associated with an aggrading 0 Radon measurements were made in the atmosphere above the geomorphic surface may, however, be offset if uranium mill tailings pile at Grand Junction, Colo., in 1967-68, the area is also a ground-water recharge zone. 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 Radon emanation can be controlled by cover­ in 1970 (Duncan and others, 1977). Although the comparative data ing the tailings with either liquids or solids, is limited to only two stations, it suggests that the mean annual radon concentration measured above the tailings pile after stabiliza­ thereby decreasing the diffusion rate of the tion was about three times that measured before stabilization. This radon and allowing for its decay (half-life of result is probably associated with the differing mo:sture contents of the pile at the different sampling times. In 1967-68 portions of radon-222 is 3.8 days) prior to atmospheric the pile were ponded as a result of the input of mill effluents, emergence. A water cover of 60 em (2ft) can while in 1974-75 the tailings were much drier, the only moisture inputs to the pile being the natural precipitation and occasional reduce radon emanation by about 96 percent irrigation waters. This decreased moisture content would allow (U.S. Environmental Protection Agency, 1973). radon to diffuse more rapidly within the tailings pile and thus more radon would reach the atmospheric interface before its However, long-term maintenance of a ponded radioactive decay. Other possibly contributing factors in the post­ situation may not be possible after mill opera­ stabilization increase in atmosphere radon concentratons include: ( 1) The redistribution of tailings during contouring operations tion ceases, nor is it a desirable situation from p~rformed as part of the stabilization program and the resultant the standpoint of seepa.ge of radium and other changes in pile depth, surface area and relative position, with re­ spect to the surface, of high-radium slime zones and ( 2) The ac­ contaminants into the subsurface. tion of plant roots, burrowing animals, and dessication and settling Two feet of earth will theoretically reduce cracks in penetrat:.ng the soil cap and tailings, and thereby creat­ ing channels for radon movement. radon emanation, with respect to the bare tail­ 7 The proposed radon flux limit in the draft generic environ­ ings, by about 25-60 percent (U.S. Environ­ mental impact statement on uranium milling prepared by the U.S. Nuclear Regulatory Commission (1979a) is given as 2 pCi m-2 s-1 mental Protection Agency, 1973; Sears and rather than as an increment of background.

21 flux in laboratory and short-term field trials, nent of any adopted milling process aimed at their long-term physical and chemical stability radium removal from the tailings. Thorium, in the weathering environment should be con­ like radium, forms acid-soluble chloride salts sidered. (Rogers and Adams, 1969), and hence its re- Cover rna terials will also affect levels of moval from the tailings by an HCl leaching gamma radiation exposure from the pile. The process would also appear possible. Concentra­ cover, by virtue of its shielding character, will tion of thorium in solution by coprecipitation produce a net attenuation of the exposure rate. with barium sulfate may be possible (Ambe Each 30 em ( 1 ft) of packed earth will theo­ and Lieser, 1978). For this reason, the radium retically reduce the exposure rate by a factor concentrate proposed above may also contain of about ten (Swift and others, 1976). Thus, much of the thorium. Alternate procedures for for a typical pile (see pg. 8}, a 120 em (4-ft) the concentration of the thorium-230 from earthen cover should reduce the surface ex­ uranium mill effluents by a combination of ion posure rate on the pile to about 1 n1R/year. exchange, coprecipitation, and solvent extrac­ Current NRC licensing guidelines (U.S. Nu­ tion procedures, followed by precipitation of clear Regulatory Commission, 1977a) call for thorium hydroxide have been proposed by the reduction of direct gamma radiation from Kluge and others (1977). reclaimed tailings impoundment areas to essen­ Borrowman and Brooks (1975) also found tially background levels ( about 150 mR/yr in 92-95 percent radium removal by 1.5-3.0 M Western States where most uranium is mined). HCl from acid-processed uranium mill tailings. While the relatively thick covers, 3-5m (10-15 Thus "detoxification" of existing tailings would feet) , proposed for new mill tailings reclama­ appear possible. The remilling of tailings for tion projects will certainly achieve such con­ recovery of residual uranium offers an oppor­ trol levels, their removal by erosion over geo­ tunity for such a radium removal. The inac­ logic time will progressively restore both the tive uranium mill tailings examined by Ford, radon flux and gamma exposure rate to thefr Bacon, and Davis Utah, Inc. (1976, 1977) had uncovered values. residual uranium contents of from 0.005 to 0.049 percent (by weight) U30s, and with RADIUM REMOVAL FROM TAILINGS present-day technology it appears economi­ An alternative to the controlled storage of cally feasible to reprocess tailings with greater radioactive mill tailings would be the removal than about 0.02 to 0.03 percent U 30s. of the uranium daughter products, either ini­ Work at Oak Ridge National Laboratory tially from the ore at the time of milling, or focusing on nitric acid leaching of uranium from the tailings subsequently, to produce a ores and tailings has shown removals of 85-98 radiologically-innocuous crushed-rock material, percent of the radium-226 by a two-stage leach and a radioactive concentrate. Borrowman and with 3M HN03 at 33 percent solids for 5 hours Brooks (1975) showed that from 92 to 96 per­ at 70°C (Ryon and others, 1977). Thorium-230 cent of the radium in uranium ores was leached removals from these ores and tailings under (25 percent solids slurry) by two, 30-minute, identical leaching conditions were 92-99 per­ 60°C treatments with 1.5 M HCI. More than cent, and uranium removals from the ores were 99 percent of the uranium present in the ore greater than 99.5 percent. Conversion of the was leached by this treatment. Following ura­ extracted radium- and thorium-nitrates to an nium removal, the leach liquor was lime-neu­ oxide form by heating and fixation of this oxide tralized and dosed with barium chloride and concentrate, in asphalt for example, prior to sodium sulfate to coprecipitate the leached burial may be a possible disposal technique radium with barium sulfate. Greater than 99 (U.S. Nuclear Regulatory Commission, 1979a). percent radium removal was achieved thereby Thus, nitric acid leaching offers another pos­ in a BaS04 precipitate having 4 percent of the sible method for producing a radium- and weight of the ore treated .As thorium-230 is thorium-depleted tailings material, although the long-lived parent isotope of radium-226, problems related to ground-water contamina­ thorium removal would be an essential compo- tion by nitrates from waste solutions would

22 probably exist with such a system. Neither the McCready. As radium in sulfuric acid-leached HCl nor HN03 milling of ores or tailings has mill tailings may also exist as a mixed alkaline yet been commercially-adopted, probably be­ earth-sulfate precipitate (Seeley, 1976), these cause of a combination of concerns, including same microbial and chemical processes may those regarding the field-scale feasibility and also be operative in conventional tailings the higher projected capital and operating costs disposal systems. of such processes as compared to conventional The level of control required for the residual sulfuric acid milling and the disposal of radio­ material will depend upon the degree of decon­ active concentrates and residual materials. tamination achieved. Neither research nor reg­ Levins and others (1978) have studied the use ulatory efforts to date have clearly established of low-cost sodium chloride for the leaching of a "safe" level of radium-226 in earth mate­ radium from uranium mill tailings. While over rials destined for unrestricted environmental 90 percent removal is achieved by four-stage disposal. A radium-226 concentration of about leaching of acid-milled tailings in 5 M N aCl 20 pCijg has been suggested as a goal for the solutions at 25°C, the process does not remove unrestricted storage of tailings by Borrow­ thorium-230, hence, the long-term source for man and Brooks (1975) and Schiager (1977). radium-226 remains in the tailings. The U.S. Environmental Protection Agency Raicevic (1978) has developed a flotation (1978a,b) has proposed a radium concentra­ procedure which removes about 60-75 percent tion of 5 pCi of radium-226/g as the lower of the uranium, thorium and radium-226, as limit for designation of uranium and phos­ well as about 95 percent of the pyrite in sam­ phate milling and processing solid wastes as ples of Elliot Lake tailings, and concentrates "hazardous," and thereby requiring regulated them in a fraction of about 25 percent the disposal and ground-water monitoring. In con­ weight of the original tailings. Flotation tests trast, the State of Louisiana has adopted a by the U.S. Bureau of Mines on acid-leached regulation establishing 0.1 pCi/g as the maxi­ tailings from the inactive, Salt Lake City site, mum allowable concentration of radioactive like th{Jse of Raicevic (1978), yielded a radium­ material (nuclides not specified) in mineral rich gypsum concentrate (Borrowman and tailings not subject to radiation safety disposal Brooks, 1975). However, the flotation tech­ requirements (Conference of Radiation Con­ niques tried were less effective than sand-slime trol Program Directors, 1978). Such a stand­ separation by simple sedimentation, the latter ard would appear to be untenable with respect process achieving a concentration of 94 percent to radium-226 as its average crustal abun­ of the radium-226 into a slime fraction repre­ dance is about 1 pCi/g (Rankama and Sahama, senting 25 weight-percent of the original tail­ 1950; Borrowman and Brooks, 1975). How­ ings. ever, work at Elliot Lake, Ontario (Mooney Because of their higher radionuclide levels, and Scott, 1978; Dilworth, Secord, Meagher the concentrates derived from the physical or and Associates Ltd., 1979) suggests that glacial chemical separation of the radium-226 and other sands with a total radium concentration of radionuclides from the tailings will probably only 1pCi/g and an emanation coefficient of require a higher level of control than the orig­ 20 percent may produce unacceptable radon inal tailings. Recent work sponsored by the daughter concentrations in overlying dwellings. Canada Centre for Mineral and Energy Tech­ nology focused on the -chemical and biological PRECONCENTRATION OF URANIUM ORE stability of the Ba/RaS04 sludges. While radon The pre-milling sorting or beneficiation of emanation from such precipitates is reported the uranium ore into a high- and a low-activity to be low (Hahn, 1936), radium may be re­ fraction has been suggested by Canadian work­ leased from them as a result of chemical leach­ ers (Lush and others, 1978) as a means of ing by natural water and (or) as a result of reducing the quantity of radioactive tailings the microbial metabolism of the precipitate generated. The high activity fraction contain­ by anaerobic, sulfate-reducing bacteria present ing most of the uranium and uranium-daughter in soils and waters (pers. commun., R. G. L. products would be milled, and yield a tailings

23 having an estimated mass of about 20-50 per­ ronmental control than the tailings from the cent that of conventional milling, while con­ processing of the high-activity fraction. taining two to five times more radium and other uranium daughter products per unit DEEP BURIAL IN UNDERGROUND CAVITIES mass. This smaller quantity of more concen­ Deep burial provides for longer periods of trated tailings would presumably be more isolation prior to disinterment by erosive amenable to waste management. The fate of forces, as well as greater long-term attenuation the non-milled, low activity fraction is not of radon exhalation and gamma radiation ex­ discussed. posure, than shallow burial. Underground ex­ Preconcentration of certain types of uranium cavation is expensive and with the large volume ores by high speed lump sorting machines of tailings to be buried, the construction of equipped with radiometric detectors would ap­ cavities solely for such disposal is highly un­ pear to be technically attainable and economi­ likely. For this reason, emplacement in aban­ cally desirable (Smith and White, 1969). A doned mine shafts and drifts is the most likely gravity-flotation technique tested on a quartz­ option for deep disposal of tailings. While pebble conglomerate, Elliot Lake ore achieved cavities from various mining operations may a bulk reduction of 2 or 3:1 with a 90 percent potentially be available, proximity to mill sites recovery of uranium (Honeywell and Kaiman, makes those associated with underground ura­ 1966). nium mining the most likely candidates. At The bulk of the uranium ores presently present, about 50 percent of the uranium milled in the United States are low grade (based on quantity of U30s) produced in the (about 0.1-0.2 percent U30s) sandstone depos­ United States is associated with underground its in which the uranium coats the sand grains mining. About 56-70 percent of the presently­ and fills the interstices (Harshman, 1970), estimated $30-uranium ore reserves 8 lie at and thus would not appear to be amenable to depths greater than 90-150 m (300-500 ft), upgrading by lump sorting. The physical up­ allowing for recovery largely by underground, grading of these ores by other mineral bene­ and perhaps solution mining, as opposed to ficiation methods may be possible, although no open pit mining (U.S. Department of Energy, such research- or commercial-scale operations 1978). Because of the large volume of tailings are known to the author. Preconcentration by generated by the milling of open pit-mined ores, sizing had been used at several, now-inactive as well as the bulking (the increase in volume upgrading plants and mills in the United States of material owing to manipulation of the tail­ with such sandstone ores. This process yielded ings as compared to the in-place ore) and the a slime concentrate high in uranium and its collapse of cavities at depth owing to the min­ daughter products, and a sandy fraction which ing of pillars, the volume of underground space was discharged to a tailings pond (M·erritt, associated with uranium mining available for 1971). Such efforts were aimed at producing the potential disposal of tailings is obviously an acceptable mill feed from low-grade ores inadequate to handle all of the tailings that and (or) at reducing the cost of shipping ore will be produed. to the mill. They did not influence the overall Deep burial may put tailings in contact with waste management problem, as the tailings aquifers and thereby introduce radioactive and from such upgrader operations, and similarly non-radioactive contaminants into the ground the segregated sand fractions of tailings at water. Whether such disposal is environmen­ conventional mills, contain too much radium tally-acceptable will be dependent upon many and other potentially detrimental elements for factors including the chemical form and quan­ unrestricted disposal. Preconcentration of ore tity of the elements of concern in the tailings, and the segregation for disposal of the low­ the ability of the ground water to leach these activity fraction may be of value in the waste constituents from the tailings, th~ chemical management area, but only if that reject frac­ tion is sufficiently low in radioactive and toxic 8 Ore that is estimated to be recoverable by mining at costs elements as to justify a lesser degree of envi- equal to or less than $3<0 per pound of UsOs.

24 form of the leached constituents (anions, ca­ storage options (Sears and others, 1975; tions, uncharged species, or colloids), the sorp­ Martin and Miller, 1978), although apparently tive capacity of the aquifer for the species of there have been no published reports on the ex­ concern, the rate of ground-water flow, the perimental evaluation of such procedures. The distance from the disposal zone to discharge costs for such a venture would appear to be areas, the initial water quality in the aquifer, high, and the long-term stability of the binding and the present and projected usage of the between tailings and cement or asphalt is not ground water. known (Martin and Miller, 1978). The decom­ ipos,ition of a tar-like, surfa0e-stabilizing agent THICK-UNSATURATED ZONE STORAGE within 2 to 3 years after application was ob­ Unsaturated zones of 100 m thickness are served in a 1969 field test at the inactive ura­ common in Southwestern United States be­ nium mill tailings site in Salt Lake ·City, Utah neath the upper reaches of piedmont alluvial (Ford, Bacon, and Davis Utah, Inc., 1976). fans, and zones 100-600 m thick may occur Koehmstedt and others (1977) have studied the beneath selected mesas, plateaus, and some­ use of 3 to 6 mm (0.12-0.24 in) thickness of times eve~r beneath valley floors. Even if the asphalt emulsion appHed to uranium mill tail­ climate of a future pluvial time should ap­ ings as a m·eans of limiting radon emanation. proach subhumid conditions, a major rise in While quite effective in short-t·erm laboratory the water table would appear to be unlikely studies, such sealants are acknowledged to be at such sites provided there is moderate to susceptible to degradation by physical (freeze high relief, relatively permeable rocks occur and thaw, ultra-violet radiation), chemical (by within the unsaturated zone, and regional aqui­ action of oxygen, ozone, salts, adds and alka­ fers with topographically low outlets underlie lies), and mic'!'obiological reactions, and thus the sites (Winograd, 1974). It has been sug­ their application would not appear to provide gested that burial of high level radioactive a long-term solution to the tailings problem. wastes in such thick unsaturated zones be Wiles (1978) has found that the pelletizing, evaluated (Winograd, 1974). Such a proposal firing and glazing (by incorporation of 5-10 may also have merit for the storage of uranium percent powdered glass, CaF2 or Fe203) can re­ mill tailings or tailings concentrates. Buriai of duce the leaching of radium from uranium mill tailings in an excavation at a depth of about tailings in tests of up to 20 days by up to three 30-40 m in a thick unsaturated zone should orders of magnitude. Again, long-term mechan­ reduce radon emanation to near background ical and chemical stability of these pelletized levels, limit the potential for inundation of the materials in the natural environment is not tailings by a rising ground-water table, and known. provide for radioactive decay over the course of at least two to three half-lives of tho­ IN-SITU LEACH MINING rium-230 prior to disinterment by erosion. In-situ leach mining refers to a selective ex­ The excavation of such burial pits, unac­ traction technique whereby ore minerals in companied by ore recovery, will undoubtedly their natural geologic setting are preferentially be quite expensive. The transport of tailings dissolved from the surrounding host rock by to such burial sites from distant mills would specific leach solutions and the mineral value have to involve pipeline or rail transfer, and recovered. In-situ operations for uranium re­ thus would be both costly and introduce new covery presently exist at about 20 sites; most potential avenues for environmental contami­ are in Wyoming and Texas. The general pro­ nation. cedure consists of injecting a leach solution ("lixiviant"-generally ammonium carbonate, FIXATION AND AGGLOMERATION OF BURIED sodium carbonate or sulfuric acid) into the ore TAILINGS zone below the water table, oxidizing, complex­ Incorporation of tailings into an asphaltic or ing, and mobilizing the uranium, recovering the concrete matrix has been considered in several pregnant solution at production wells, and conceptual evaluations of uranium mill tailings pumping this solution to the surface for ura-

25 nium extraction (Larson, 1978). This surface sphere should be considered in the evaluation of processing may generate some radioactive the potential, long-term consequences of all sludges (U.S. Nuclear Regulatory Commission, proposed uranium mill tailings management 1978b); however, the bulk of the radium-bear­ plans. The period and extent of containment of ing residual orebody remains underground. To radionuclides will depend upon: be suitable for in-situ leach mining, the ore de­ ( 1) The technology involved in tailings' proc­ posit must be located in the saturated zone, essing and in the siting and design of be confined both above and below by impervious disposal sites. layers, have adequate permeability, and be (2) The nature of the interaction between the amenable to chemical leaching (U.S. Nuclear radionuclides and the components of the Regulatory Commission, 1978b). confining natural media. While such techniques do not generate tail­ (3) The rates of environmental processes such ings deposits at the surface, they are not with­ as erosion, aggradation, precipitation out potential environmental hazards. Sub­ and evapotranspiration. stances injected into the aquifer, and elements, All of these factors will influence the flux of both radioactive and non-radioactive, mobilized radion uclides through the environment. While from the ore zone by these substances represent the radon source term to the atmosphere will potential ground-water contaminants both dur­ largely be a function of the depth of burial with ing mining and after such operations cease. A time, the mobilization of long-lived radio­ recent report by Thompson and others (1978) nuclides from the tailings by surface and discusses techniques aimed at the post-mining ground waters and the retention of these radio­ restoration of water quality in the affected por­ ;nuclides by soils and rocks is more complex and tions of the aquifer to acceptable levels and pre­ appears worthy of additional study. sents results from several pilot restoration operations. REFERENCES Adam, J. A., and Rogers, V. L., 1978 A classification CONCLUSIONS system for radioactive waste dispos:al-What waste goes where: U.S. Nuclear Regulatory Commission This report has not attempted to specifically Report NUREG-0456, 416 p. address the question: What degree of contain­ Ambe, S., and Lieser, K. H., 1978, Coprecipitation of ment is required for the storage of uranium thorium with barium sulfate: Radiochimica Acta, v. 25, no. 2, p. 93-98. mill tailings? An answer to this question must Ames, L. L., and Rai, Dhanpat, 1978, Radionuclide in­ take into account what society regards as an teractions with soil and rock media: U.S. Environ­ acceptable risk for itself and future genera­ mental Protection Agency, Office of Radiation Pro­ tions. The issue of "acceptable risk" is com­ grams Report EPA 520/6-78-007A, v. 1, 306 p. plex, transcending the boundaries of science Anonymous, 1978, Formidable challenges await uranium mining: Mining Engineering, v. 30, no. 10, p. 1423. and technology, and is beyond the scope of this Argonne National Laboratory, 1978, Final report of the report. What has been attempted is an outline Task Force on Uranium Mill Tailings Waste Man­ of the pathways for environm·ental radiation agement: Argonne National Laboratory, Environ­ exposure from uranium mill tailings and some mental Impact Studies Division (June 1978), 261 p. of the potential long-term hydrologic and geo­ Austin, S. R., and Droullard, R. F., 1978, Radon emana­ tion from domestic urani urn ores determine·d by logic consequences of various c·ontainment modifications of the clos·ed can, gamma-only assay schemes. method: U.S. Bureau of Mines Report of Investiga­ Because of the 77,000 year half-life of tions no. 8264, 74 p. thorium-230, the diminution of environmental Barker, F. B., and Scott, R. C., 1958, Uranium and ra­ dium in the ground water of the Llano Estacado, effects associated with radionuclides contained Texas and New Mexico: American Geophysical in these tailings must be conceived of within Union Transactions, v. 39, no. 3, p. 459-466. the framework of geologic processes operating Bell, K. G., 1963, Uranium in carbonate rocks: U.S. Geo­ over geologic time. The magnitude of erosion of logical Survey Professional Paper 474-A, 29 p. cover materials and tailings, and the extent of Bernhardt, D. E., Johns, F. B., and Kaufmann, R. F., 1978, Radon exhalation from uranium mill tailings geochemical mobilization of the contained piles-description and verification of the measure­ radionuclides to the atmosphere and hydro- ment method: U.S. Environmental Protection

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27 Crystal Springs, Great Salt Lake area, Utah: U.S. Gran~·r, H. C., Santos, E. S., Dean, B. G., and Moore, Geological Survey Open-File Report 78-102, 29 p. F. B., 1961, Sandstone-type uranium deposits at Ford, Bacon, and Davis Utah, Inc., 1976, Phase II-Title Ambrosia Lake, New Mexico-an interim report: I, Engineerirlg assessments of inactive uranium mill Economic Geology, v. 56, no. 7, p. 1179-12Q9. tailings: Vitro site; Salt Lake City, Utah. Pre·pared Grim, R. E., 1968, Clay mineralogy (2d ed.): McGraw for the U.S. Energy Research and Development Ad­ Hill, New York, 596 p. ministration, Grand Junction, Colo. Hahn, Otto, 1936, Ap,plied Radiochemistry: Cornell Uni­ Ford, Bacon, and Davis Utah, Inc., 1977, Phase II-Title versity Press, Ithaca, N.Y., 278 p. I, Engineering assessments of inactive· uranium mill Hammond, C. R., 1970, The elements (uranium), in tailings.: Prepared for the U.S. Department of Weast, R. G., ed., Handbook of Chemistry and Energy (:£ormerly U.S. Energy Research and De­ Physics (51st ed.) : The Chemical Rubber Co., velopment Administration) Grand Junction, Colo­ Cleveland, Ohio, p. B-35. .,. rado. Hans, J. M., Jr., and Douglas, R. L., 1975, Radiation GJT-2 Shiprock site, New Mexico survey of dwellings in Cane Valley, Arizona and GJT-3 Mexican Hat site, Utah Utah, for use of uranium mill tailings. U.S. En­ GJT-4 Monument Valley site, Arizona vironmental Protection Agency~ Technical Note GJT-5 Tuba City site, Arizona ORP/LV-75-2, 37 p. GJT-6 Durango site, Colorado Hansen, R. 0., and Huntington, G. L., 1969, Th01rium GJT-7 Slick Rock site, Colorado movement in morainal soils of the· High Sierra, GJT-8 Naturita site, Colorado California: Soil Science, v. 108, no. 4, p. 257-265. GJT-9 Grand Junction site, Colorado Hare, F. K., and Thomas, M. K., 1974, Climate Canada. GJT-10 New and Old Rifle sites, Colorado. Wiley, Toronto, 256 p. GJT-11 Maybell site, Colorado Harshman, E. N., 1970, Uranium ore rolls in the United GJT-12 Gunnison site, Colorado States, in Proceedings Panel on Uranium Explora­ GJT-13 Phillips/United Nuclear site; tion Geology, Vienna, April 13-17, 1978, Interna­ Ambrosia Lake, New Mexico tional Atomic Energy Agency, p. 219-232. GJT-14 Green River site, Utah Harshman, E. N., 1972, Geology and uranium deposits, GJT-15 Spook site, Converse Co., Wyoming ShiIdaho Havens, R., and Dean, K. C., 1969, Chemical stabiliza­ GJT-18 Lakeview site, Oregon tion of the uranium tailings at Tuba. City, Arizona: GJT-19 Riverton site, Wyoming U.S. Bureau of Mines Report of Investigations no. GJT-20 Ray Point site, Texas 7288, 12 p. 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28 Hendrie, J. M., 1978, Statement before the Subcommit­ sulfuric acid and nitric acid solutions: Radiochimica tee on Energy and the Environment, Committee on Acta, v. 24, no. 1, p. 21-26. Interior and Insular Affairs, U.S. House of Repre­ Klute, A., and Heermann, D. F., 1978, Water movement sentatives, Ninety-fifth Congress (June 27, 1978) in uranium mill tailings profile's: U.S. Environmen­ Hearings serial no. 95-30, p. 254-263. tal Protection Agency, Office of Radiation Programs, Herman, S. J., and Langmuir, D., 1978, Thorium com­ Las Vegas, Nev. Facility, Technical Note ORP/LV- ple·xes in natural waters: [Abs.], Geological Society 78-8, 82 p. of America Annual Meeting, Toronto, Canada, p. Kochenov,, A. V., Zinev'yev, V. V., and Lovaleva, S. A., 419. 1965, Some features of the accumulation of ura­ Hilpert, L. S., 1969, Uranium resources of northwestern nium in peat bogs: Geochemical International, v. 2, New Mexico: U.S. Geological Survey Prof. Paper p. 65-70. 603, 166 p. 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29 Masuda, Kuniyoshi, and Yamamoto, Takashi, 1971, Nelson, J. D., and Shepard, T. A., 1978, Evaluation of Studies on environmental contamination by ura­ long-term ·stability of uranium mill tailing disposal nium, (2) Adsorption of uranium on soil and its alternatives: Final report, contract no. 31-109-38- desorption: Journal Radiation Research, v. 12, p. 4199, Geotechnical Engineering Program, Colorado 94-99. State University for Argonne National Labora­ Maysilles, J. H., Nichols, I. L., and Seidel, D. C., 1978, tories, April 1978, 337 p. Extracting uranium from low grade ore from the Papastefanou, C., and Charalambous, SW., 1978, Ra- Coso Mountains, Calif.: U.S. Bureau of Mines Re­ 226 leaching from fossil bones: Nuclear Instru­ port of Investigations no. 8306, 14 p. ments and Methods, v. 141, p. 599-601. Means, J. L., Crerar, D. 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S., 1962, Thorium and uranium variations nology, Minerals Research Program, Mining Re­ in the Blind River ores: Economic Geology, v. 57, search Laboratories Report MRP/MRL 77-6 (J) p. 1175-1184. Revised, 15 p. Rogers, J. J. W., and Adams, J. A. S., 1969, Thorium, Moffett, D., and T·ellier, M., 1978, Radiological investiga­ in Wede,pohl, K. H., ed., Handbook of geochemistry: tions of an abandoned uranium tailings area: Jour­ v. II/1, chap. 90. nal of Environmental Quality, v. 7, no. 3, p. 310-314. Ryon, A. D., Hurst, F. J., and Seeley, F. G., 1977, Nitric Moffett, D., Zahary, G., Campbell, M. C., and Ingles, a.cid leaching of radium and other significant radio­ J. C., 1977, CANMET's environmental and process nuclides from uranium ores and tailings.: Oak Ridge research on uranium: Canada Centre for Mineral National Laboratory Re·port ORNL/TM-5944, 37 p. and Energy Technology, Minerals and Energy Re­ Schiager, K. J., 1974, Analysis of radiation exposures S8arch Programs, Mining Research Laboratories, on or near uranium mill tailings piles: Radiation Mineral Scienc.es Laboratories Report 77-53, 29 p. Data and Reports, U.S. Environmental Protection Mooney, B. L., and Scott, A. G., 1978, Radium content of Agency, Office of Radiation Programs, v. 15, no. 7, Elliot Lake sand deposits compared with other On­ p. 411-425. tario sands: Abstracts, Geological Society America S.chiager, K. J., 1977, Radwaste radium-radon risk, in Annual Meeting, Toronto, Canada, p. 459. Proceedings Workshop on Policy and Technical Is­ Moore, W. S., and Reid, D. F., 1973, Extraction of ra­ sues Pertinent to the Development of Environmen­ dium from natural waters using manganese-im­ tal Protection Criteria for Radioactive Waste, pregnated acrylic fibers: Jour. Geophys.. Research, Albuquerque, April 12-14, 1977: U.S. Environmen­ v. 78, no. 36, p. 8880-8886. tal Protection Agency, Office of Radiation Programs Morse, R. H., 1970, The surficial geochemistry of ra,.. Report ORP/GSD-77-2, p. 2-45 to 2-81. dium, radon and uranium near Bancroft, Ontario Schmidtke, N. W., Averill, D., Bryant, D. N., Wilkinson, with application to prospecting for uranium: Ph.D. P., and Schmidt, J. W., 1978, Removal of 226Ra from thesis, Queen's University, Kingston, Ontario, Can­ tailings pond effluents and ·s,tabilization of uranium ada, 154 p. mine tailings-bench and pilot plant studies, in Pro­ Motica, J. E., 1977, Uranium exploration, in Proc. First ceedings Seminar on Management, Stabilisation and Conf. on Uranium Mining Technology, ed. Kim, Environmental Impact of Uranium Mill Tailings, Y. S.: University of Nevada, Reno, April 214-29, Albuquerque, N. Mex., July 24-28, 1978, OECD 1977, Section II, 27 p. Nuclear Energy Agency, Paris, France, p. 299-315. Mutschler, P. H., Hill, J. J., and Williams, B. B., 1976, S.ehumm, S. 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30 Ryon, A. D., and Witherspoon, J. P., 1975, Correla­ Travis, C. C., Cotter, S. J., Watson, A. P., Randolph, tion of radioactive waste treatment costs and the M. L., McDowell-Boyer, L. M., and Fields, D. E., environmental impact of waste effluents in the nu­ 1979, A radiological assessment of Rn-222 released clear fuel cycle for use in establishing "as-low-as­ from uranium mills and other natural and techno­ practic.able" guides-milling of uranium ores: Oak logically enhanced sources: Prepared for the U.S. Ridge National Laboratory Report ORNL/TM-4903, Nuclear Regulatory Commission by Oak Ridge Na­ v. 1, 291 p. tional Laboratory, NUREG/CR-0573 (ORNL/ S.edlet, Jacob, 1966, Radon and Radium, in Kolthoff, NUREG-55), 216 p. I. M. and Elving, P. J., eds., Treatise on Analytical Tsivoglou, E. C., Shearer, S. D., Jr., Jones, J. D., and Chemistry, pt. 2: v. 4, Wiley-Interscience, New Clark, D. A., 1960, Estimating human radiation ex­ York, p. 219-366. posure on the Animas River: Journal American Seeley, F. G., 1976, Problems in the separation of ra­ Water Works Association, v. 52, p. 1271-1290. dium from uranium ore tailings: Hydrometallurgy, U.S. Atomic Energy Commission, 1974, Environmental v. 2, p. 249-263. survey of the uranium fuel cycl~Report: WASH- Shapiro, J., 1972, Radiation protection: Harvard Univ. 1248. Press, Cambridge·, Mass., 339 p. U.S. Department of Energy, 1978, Statistical data of Shearer, S. D., Jr., 1962, The leachability of radium- the uranium industry, Jan. 1, 1978-Report: GJ0- 22'6 from uranium mill waste solids and river sedi­ 100(78). ments: Ph.D. thesis, University of Wisconsin, 16·2 p. U.S. Department of Health, Education and Welfare, Shearer, S. D., Jr., and Lee, G. 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31 Resource Conservation and Recovery Act, Subtitle vironmental statement related to the operation of C-Haza:rdous waste management: U.S. Envirsewage :sludges, and rock phos.phate clear Regulatory Commission, for amelioration of acid uranium mill tailings, in U.S. Nuclear Regulatory Commission, 1977a, Branch Proc. International Conference on Land for Waste position-uranium mill tailings. management, Fuel Management, Ottawa, Canada, Oct. 1973: p. 48-56. Processing and Fabrication Branch: May 13, 1977, West, S. W., 1972, Disposal of uranium mill effluent by 3 p. well injection in the Grants area, Valencia County, U.S. Nuclear Regulatory Commission, 1977b, Design, New Mexico: U.S. Geological Survey Professional construction, and inspection of embankment reten­ Paper 386-D, 28 p. tion systems for uranium mills: Regulatory guide Whicker, F. W., 1978, Biological interactions and rec}a,.. 3.11, revision 2, Dec. 1977, 9 p. mation of uranium mill tailings, in Proc. Symp. on Uranium Mill Tailings Disposal: Colorado State U.S. Nuclear Regulatory Commission, 1978a, Final en­ University, Fort Collins, Colo., Nov. 20-21, 1978; vironmental statement related to the United Nu­ clear Corporation Morton Ranch, Wyoming uranium p. 141-153. Wiles, D. R., 1978, The leaching of radium from Beaver­ mill: NUREG-0532. lodge tailings, in Proc. Seminar on Management, U.S. Nuclear Regulatory Commission, 1978b, Final en­ Stabilisation and Environmental Impact of Ura­ vironmental statement related to operation of nium Mill Tailings, Albuquerque, N.Mex., July 24- Wyoming Mineral Corporation lrigaray solution 28, 1978: OECD Nuclear Energy Agency, Paris, mining project: NUREG-0481. France, p·. 245-257. U.S. Nuclear Regulatory Commission, 1978c, Final en­ Wilkening, M. H., 1974, Radon-222 from the island of vironmental statement related to operation of High­ Hawaii-Deep soils are more important than lava land uranium solution mining project: NUREG- fields or volcanoes: Science, v. 183, no. 4123, p. 413- 0489. 415. U.S. Nuclear Regulatory Commission, 1978d, Final en­ Winograd, I. J., 1974, Radioactive waste storage in the vironmental statement related to operation of Swe.et­ arid zone.: EOS, American Geophysical Union water uranium project: NUREG-0505. Transactions, v. 55, no. 10, p. 884_:-894. (Discussion U.S. Nuclear Regulatory Commission, 1978e, Draft en­ in EOS, v. 57, no. 4, p. 178, 215-216.) vironmental statement related to operation of White Wullstein, L. H., 1978, Vegetative stabilization report Mesa uranium project: NUREG-0494. (Appendix A in Macbeth, and others,1978, Labora­ U.S. Nuclear Regulatory Commission, 1979a, Draft tory research on tailings stabilization methods and generic environmental impact statement on uranium their effectiveness in radiation containment: Pre­ milling: NUREG-0511. pared for U.S. Department of Energy, Grand Junc­ U.S. Nuclear Regulatory Commission, 1979b, Final en- tion, Colo., Rept. GJT-21).

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