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Cleaning Up Sites Contaminated with Radioactive Materials: International Workshop Proceedings 11 Uranium Recovery and Remediation of Uranium Mill Tailings: Russian and U.S. Experience James H. Clarke and Frank L. Parker, Vanderbilt University INTRODUCTION Recovery of uranium using conventional mining—open pit and underground—to excavate the ore and chemical processing to extract the uranium from the ore generates large volumes of solid and liquid material (uranium mill tailings, or UMT). These wastes are typically collected and stored in ponds, although there has been some effort to replace them in the excavated areas. If left uncovered, UMT constituents can be released to the atmosphere and transported to surface waters and groundwater through erosion and leaching, respectively. Remediation-reclamation approaches either keep the tailings covered with water, leave the dewatered tailings in the ponds or piles, or place them in prepared near-surface or surface pits with drainage and covers to reduce the erosion, resuspension, and leaching of the tailings. Until the mid-1970s, uranium was recovered exclusively through conventional mining approaches (underground mines and open-pit mining) in the United States. The first commercial application of in situ recovery and in situ leach (ISL) techniques that used chemical agents to extract the uranium through an array of injection and recovery wells was in 1975. Use of this technology increased as it gained a cost advantage, and now most uranium in the United States is recovered using ISL. In situ approaches have the advantage of eliminating large volumes
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Cleaning Up Sites Contaminated with Radioactive Materials: International Workshop Proceedings of tailings. However, it is typically impossible to restore groundwater quality to its initial state when uranium recovery is done in situ or to totally contain all of the leachate material (Davis and Curtis, 2007). However, most uranium mining wastes in the United States have come from conventional mining operations, both surface and underground, from 1957 to 1989 (World Nuclear Association, 2007). URANIUM RECOVERY AND MILL TAILINGS IN RUSSIA AND THE FORMER SOVIET UNION Uranium recovery in Russia and the former Soviet Union is done through both ISL and conventional mining. In the early 1990s, approximately 38 percent of uranium mined in the former Soviet Union came from ISL (Bradley, 1997). For the Russian Federation, on the basis of metric tons of uranium in the concentrate, the distribution of the 3,281 metric tons of uranium obtained from conventional mining and ISL in 2004 was as follows (OECD-IAEA, 2005): Open-pit and underground mining: 2,880 metric tons ISL: 200 metric tons Heap leaching: approximately 190 metric tons In-place leaching (slope or block): 11 metric tons During the workshop, it was stated that Russia intends to increase its production of uranium from 4,900 metric tons in 2010 to 18,000 metric tons by 2020 (Shatalov, 2007). Conventional mining of uranium has left large areas (several square kilometers) of land contaminated with mill tailings. For example, Uzbekistan has 2.8 km2 of such land; Tajikistan, 3 km2; Kyrgyzstan, 6.5 km2; Kazakhstan, 2.5 km2; and Russia, 2 km2 (Karamushka and Ostroborodov, 2008). As of 1990 the former Soviet Union had generated approximately 5 billion metric tons of mill tailings (Bradley, 1997). THE WISMUT SITE IN FORMER EAST GERMANY The major source of uranium for the Soviet Union was the mines, collectively now known as Wismut, in Saxony and Thuringia in the German Democratic Republic (GDR). More than 400,000 people have worked at Wismut, with peak employment reaching 130,000 people in 1950. The total output of the mines was 231,000 metric tons, with peak production of 7,100 metric tons in 1967. During the Cold War, very little was known about uranium mining in the Soviet Union. However, in 1954 a joint Soviet-GDR company, Wismut, was formed. After German reunification, production ceased and Wismut became the property of the Federal Republic of Germany. When this transfer occurred, much previously unavailable data became public. Wismut is responsible for the remediation
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Cleaning Up Sites Contaminated with Radioactive Materials: International Workshop Proceedings program to safely isolate and control the enormous quantity of uranium production residue, 312 × 106 m3 of waste rock, 1,518 ha of waste rock pile area, 161 × 106 m3 of tailings volume, and a tailings pond area of 724 ha. The estimated cost of cleanup is U.S. $6 billion over 15 years. (More recent information says that the cost will be “in the order of 6.2 billion euros” [Hagen, 2007].) Although working conditions were extremely poor and the environmental contamination was severe, the doses to the critical group were surprisingly small, 0.26 mSv/a, although approximately 5,500 cases of occupational radiation-induced cancer of the lung were identified (Kirchmann and Cigna, 2003). Some doubt has been expressed about the necessity of such large remediation costs. For example, Jiri Hulka has stated: “In my view, a great deal of remediation work is unnecessary on radiological grounds; it is carried out for political, aesthetic or other reasons. For example, I do not think it was necessary, on radiological grounds, to spend over 10 million euros on the remediation of uranium tailings at Wismut, in Germany” (Hulka, 2003). At a conference in 2004, I also expressed similar reservations about the benefits relative to the cost of the U.S. mill tailings program: “I was recently in Wyoming with Chinese colleagues to visit uranium mining and milling remediation sites. I was struck by the hundreds of millions of dollars being spent to protect a population that might be there in 200 to up to 1,000 years in the future from statistical deaths. I wondered if our intergenerational concerns had not blinded us to our intra-generational concerns…. I was further struck by the fact that because of the long term buildup of thorium and radium daughter products that the maximum doses would not occur for hundreds of thousands of years. Does it make sense to spend those amounts of money now to protect these future generations while allowing so many local members of the population to live below the poverty level?” (Parker, 2004). Some appreciation of the magnitude of the Wismut properties can be gained from Figure 11-1, which shows a small portion of the mining area. URANIUM RECOVERY IN THE UNITED STATES Most mines that produced uranium as a primary commodity are, or were, located in Colorado, Utah, Wyoming, New Mexico, and Arizona. They are typically on federal and tribal lands. The number of locations associated with uranium, as identified in the U.S. Environmental Protection Agency (EPA) database, is around 15,000. Of these uranium locations, more than 4,000 are mines having documented production (EPA, 2006). Figure 11-2 shows where most of the uranium mining activities were located in the West. Currently, 80 percent of mined uranium in the United Stated comes from ISL. Uranium mining in the United States had decreased significantly since the 1970s. However, the price of uranium has soared from $29 per pound in June 2005 to $138 per pound as of June 18, 2007 (Uranium Miner, 2007). While the actual numbers might change, the U.S. Nuclear Regulatory Com-
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Cleaning Up Sites Contaminated with Radioactive Materials: International Workshop Proceedings FIGURE 11-1 A view of a portion of the Wismut facilities. FIGURE 11-2 Location of uranium mines in the western United States.
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Cleaning Up Sites Contaminated with Radioactive Materials: International Workshop Proceedings mission (NRC) is currently expecting 25 licensing actions for uranium recovery in the 2008-2009 time frame. Specifically, these licensing actions include 14 new operations (11 ISL and 3 conventional mines) and 11 restarts, of which 9 are ISL and 2 are conventional mines (USNRC, 2007). URANIUM MILL TAILINGS REMEDIATION IN THE UNITED STATES: THE URANIUM MILL TAILINGS RADIATION CONTROL ACT (UMTRCA) OF 1978 While UMTs typically contain relativity low activity, they are perceived by many to constitute a serious hazard based on their very large volume. The Uranium Mill Tailings Radiation Control Act (UMTRCA) of 1978 was passed in response to a perceived need for the implementation of engineered controls to prevent releases from UMT sites. Title I of the act addresses active and inactive facilities at the time the act was passed that had recovered uranium for the federal government. The U.S. Department of Energy (DOE) was given the responsibility of remediating these sites under a general license from the NRC, and the EPA was charged with developing protective standards for UMT sites. Title II of UMTRCA addressed UMT remediation at commercial facilities active in 1978 and future facilities licensed by the NRC. As of 2007, there are 16 uranium recovery facilities licensed by the NRC—12 conventional mines and 4 ISL. Closure and remediation of Title II sites are the responsibility of the licensee (USNRC, 2006). Table 11-1 provides information about Title II sites currently undergoing decommissioning. TABLE 11-1 Title II Sites Undergoing Decommissioning Name Location Estimated Decommissioning Costs ($) American Nuclear Corporation Casper, WY 3.2 million Bear Creek Converse County, WY 900,000 COGEMA Mining Inc. Mills, WY 12.1 million ExxonMobil Highlands Converse County, WY Homestake Grants, NM 55.5 million Pathfinder-Lucky MC Gas Hills WY Pathfinder-Shirley Basin Shirley Basin, WY Rio Algom-Ambrosia Lake Grants, NM 18 million Sequoyah Fuels Corporation Gore, OK Umetco Minerals Corp. East Gas Hills, WY United Nuclear Corporation Church Rock, NM 3.7 million Western Nuclear Inc.-Split Rock Jeffrey City, WY SOURCE: USNRC, no date.
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Cleaning Up Sites Contaminated with Radioactive Materials: International Workshop Proceedings Information about the status of Title I sites is maintained by DOE through the Office of Legacy Management in Grand Junction, Colorado (DOE, 2001). The NRC Uranium Recovery Licensing Branch, Decommissioning and Uranium Recovery Licensing Directorate, Division of Waste Management and Environmental Protection, Office of Federal and State Materials and Environmental Programs, maintains records on Title II sites. UMTRCA designated the federal government (DOE) as the long-term custodian for all sites remediated under Title I. For Title II sites, the host state could assume the role of long-term custodian. As of 2007, no host states have come forward, and DOE has taken the responsibility for custodial care of all sites regulated under UMTRCA. At this time, all but 2 of the approximately 20 Title I sites have been remediated. At one location (the Moab, Utah, site), the tailings are close to the banks of the Colorado River, and DOE has agreed to move them to a safer location at a cost of several hundred million U.S. dollars. The remaining site at Grand Junction, Colorado, will remain open to receive additional tailings for several more years. All but two of these sites are in semiarid climates. Canonsburg and Burrell, Pennsylvania, are in humid environments. Surveillance and monitoring of closed UMT sites are conducted through the DOE Office of Legacy Management in Grand Junction, Colorado, for both Title I and Title II sites. Inspection reports are available through the DOE Office of Legacy Management (DOE, 2005b, no date [b]). Through 1999 the total cost of activities for the Title I sites was approximately $1.5 billion (DOE, no date [a]). Costs for the remediation of Title I sites had been estimated by DOE, prior to the passage of UMTRCA in 1978, to be in the range of $150 million-200 million (GAO, 1995). RISKS ASSOCIATED WITH UMT SITES As indicated above, the sheer volume of waste at UMTs, despite the relatively low activity associated with the tailings wastes, has engendered a perception that UMT sites pose a serious hazard and potential risk to human health and the environment. The actual risk, of course, depends upon the nature and amount of radioactive materials to which the public can be exposed. The U.S. National Research Council examined the scientific basis for risk assessment at UMT sites in 1986. Although there are many National Research Council reports on topics that deal with aspects of management of uranium mill tailings, this is the only report that approaches the problem holistically (National Research Council, 1986). In its report the authoring committee states the following: Surveillance should be maintained to take necessary corrective action if needed.
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Cleaning Up Sites Contaminated with Radioactive Materials: International Workshop Proceedings Risk management strategies must be site specific. The health risks posed by radon differ widely depending upon distance of potential receptors from the site. ENGINEERED APPROACHES TO THE CLOSURE OF UMT SITES Closures of inactive UMT sites in the United States have employed the use of engineered barriers (surface covers) whose primary functions are the prevention of the release of radon gas to the atmosphere, the infiltration of precipitation and subsequent leaching of the waste and transport of waste constituents to groundwater, and the transport of waste materials to surface water through runoff. These covers typically include a primary radon release and infiltration prevention barrier of compacted clay soils, with other layers included to protect the primary barrier. Figure 11-3 shows the cover design employed at Durango, Colorado. The function of the cover is described for the 360-acre Cheney site, which contains the 98-acre disposal cell and is located about 18 miles southeast of Grand Junction. The cell is about 80 feet deep from lowest to highest points and is capped with an engineered, 7-foot-thick multicomponent cover. The cover is composed of a 1.5-foot-thick transition layer placed directly on the radioactive materials; a 2-foot-thick clay layer serving as the radon barrier and minimizing water infiltration; a 2-foot-thick layer of clay above the radon-infiltration barrier minimizing freeze-thaw damage; a 6-inch-thick coarse-grained bedding layer covering the freeze-thaw barrier to minimize capillary movement of fluids and FIGURE 11-3 Mill tailings cover design, Durango, Colorado.
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Cleaning Up Sites Contaminated with Radioactive Materials: International Workshop Proceedings provide surface drainage; and a 12-inch-thick riprap erosion protection layer (DOE, 2005a). Several Title I sites also had existing groundwater contamination, and groundwater management measures were necessary as well. PERFORMANCE ISSUES AND MONITORING When considering the design approach for an engineered cover at a UMT site, local climate and environmental factors are important, as the cover design is dependent upon rainfall and infiltration rates. At some sites, however, the engineered covers are experiencing degradation as a result of natural processes, especially erosion and root intrusion (biointrusion). For example, at the Title I site in Burrell, Pennsylvania, Japanese knotwood trees penetrated the primary barrier just a few years after the site was closed and increased the hydraulic conductivity of the barrier by two orders of magnitude over the design value. A risk assessment, however, revealed that the biointrusion process had increased evapotranspiration and that corrective action was not required (Waugh, 1999). Examples of erosion have also been seen on rock-covered side slopes, for instance, at the Durango, Colorado, site. Maintenance has not yet been deemed necessary but may be required in the future (DOE, 2006). In its report on the potential hazards associated with UMT sites and their closure, the International Atomic Energy Agency (IAEA, 1997) stated the following: In the long term, typical scenarios or occurrences needing attention are intrusion and erosion (i.e., human or natural-caused degradation of engineered barriers, etc.). Maintaining institutional control for long time periods. Upgrading long-term confinement systems (e.g., upgraded near-surface barriers, disposal into a lake, or by backfill into an underground mine). Implementing advanced solutions where practicable and economically feasible, such as extracting selected radioisotopes from the tailings. Selecting dispersion instead of containment if a safety assessment case allows it. Comparing “enhanced activity” conditions with site or local “natural activity.” Adopting less conservative or probabilistic scenarios or assumed occurrences. Effects of radioactive and non-radioactive substances on the environment. Recently, another National Research Council committee examined issues concerning the long-term performance of engineered barriers (National Research Council, 2007). The following comments and recommendations are taken from its report:
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Cleaning Up Sites Contaminated with Radioactive Materials: International Workshop Proceedings “Given that development of optimal designs for lifetimes of thousands of years is likely to be both infeasible and prohibitively expensive, designs that allow for recovery, repair, and/or replacement are to be encouraged” (p. S2). “Tomographic imaging and seismic velocity surveys …. Multispectral imaging …. Interferomagnetic synthetic aperture radar, light detection, and ranging and other airborne/satellite techniques …. However, to date, these technologies have yielded little data that can be used to quantitatively and reliably monitor barrier systems” (p. S3). “The estimated service lives of geomembranes decrease from 1,000 years at 10°C to only about 15 years at 60°C” (p. S3). “Cover systems are effective at isolating waste, as long as periodic maintenance is performed” (p. S4). “Recommendation 5: Regulatory agencies and research sponsors should support the validation, calibration, and improvement of models to predict the behavior of containment system components and the composite system over long periods of time. These models should be validated and calibrated using the results of field observations and measurements.” Closed UMT sites in the United States are monitored annually, including physical inspections of cover integrity and access restrictions such as signs and fences. While a requirement for perpetual monitoring and maintenance of these sites is unrealistic, it is noted that the general NRC license contains no expiration date. Research is ongoing to develop improved designs that can better accommodate natural processes and environmental change. A summary of the conventional sites being remediated and their costs is presented in Table 11-2, and the costs for decommissioning nonconventional sites, ISL, are given in Table 11-3.
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Cleaning Up Sites Contaminated with Radioactive Materials: International Workshop Proceedings TABLE 11-2 Remediation of UMTRCA Title I Uranium Mill Sites Under the UMTRA Project Summary Table: Uranium Ore Processed, Disposal Cell Material, and Cost for Remediation as of December 31, 1999 Remediation Project (Mill Site Name, State) Uranium Ore Processed Disposal Cell Remediation Project Cost Ore (Million Short Tons) Uranium Production (Million Pounds U3O8) Remediated Material Volume (Million Cubic Yards) Total Cost (Thousand U.S. Dollars) Per Pound Produced (Dollars per Pound U3O8) Per Unit of Remediated Material (Dollars per Cubic Yard) Per Unit of Radiation Avoided (Dollars per Curie, Ra-226) Minimum Cost per Curie Avoided Edgemont, SD 1.98 6.86 3.00 5,411 0.79 1.80 10,267.55 Maximum Cost per Curie Avoided Lowman, ID 0.20 0.37 0.13 18,434 50.47 142.46 1,536,166.67 Totala and Averages 27.17 116.53 46.07 1,476,340 12.67 32.04 105,249.88 aFor 24 sites. SOURCE: DOE, 2005a.
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Cleaning Up Sites Contaminated with Radioactive Materials: International Workshop Proceedings TABLE 11-3 Estimated Decommissioning Costs for U.S. Nonconventional Uranium Production Facilities (in 1994 dollars) Name and Costs Well Field Restoration Costs ($, thousands) Groundwater Restoration Costs ($, thousands) Other Costs ($, thousands) Total Costs ($, thousands) Groundwater Restoration Costs (% of Total) Maximum: Burns Ranch/Clay West 3,808 15,994 15,211 35,013 46 Minimum: Tex-1 201 176 199 576 31 Average 931 2,819 3,233 7,032 Totalsa 13, 027 39, 460 45, 961 98, 448 40 aFor 14 sites. SOURCE: DOE, 1995, p. 38; Davis and Curtis, 2007, p. 15. REFERENCES Bradley, Don J. 1997. Behind the Nuclear Curtain: Radioactive Waste Management in the Former Soviet Union. Columbus, Ohio: Battelle Press. Davis, J. A., and G. P. Curtis. 2007. Consideration of Geochemical Issues in Groundwater Restoration at Uranium In-Situ Leach Mining Facilities, NUREG/CR-6870, U.S. Nuclear Regulatory Commission, January. DOE (Department of Energy). No date (a). Energy Information Administration. Uranium Mill Sites under the Uranium Mill Tailings Remedial Action (UMTRA) Project. Available online at www.eia.doe.gov/cneaf/nuclear/page/umtra/title1sum.html. DOE. No date (b). Office of Legacy Management in Grand Junction, Colorado. Available online at www.lm.doe.gov/land/sites/co/gj/gjo/gjo.htm. DOE. 1995. Energy Information Administration. Decommissioning of U.S. Uranium Production Facilities. DOE/EIA-0592. Available online at tonto.eia.doe.gov/ftproot/nuclear/0592.pdf. DOE. 2001. Grand Junction Office. Guidance for Implementing the Long-Term Surveillance Program for UMTRCA Title I and Title II Disposal Sites. GJO-2001-TAR, April. DOE. 2005a. Energy Information Administration. Grand Junction (Climax Uranium) Mill Site. Available online at www.eia.doe.gov/cneaf/nuclear/page/umtra/grandjunction_title1.html. DOE. 2005b. Office of Legacy Management. Annual Site Inspection and Monitoring for Uranium Mill Tailings. Radiation Control Act Title I Disposal Sites, DOE Office of Legacy Management DOE-LM/GJ1015—2005, December. DOE. 2006. Office of Legacy Management. Durango, Colorado, Processing and Disposal Sites. Available online at www.lm.doe.gov/documents/sites/co/dur_d/fact_sheet/Durango.pdf. EPA (Environmental Protection Agency). 2006. Office of Radiation and Indoor Air Radiation Protection Division. Uranium LocationDatabase Compilation, EPA 402-R-05-009. Available online at www.epa.gov/radiation/docs/tenorm/402-r-05-009.pdf. GAO (General Accounting Office). 1995. Uranium Mill Tailings: Cleanup Continues, but Future Costs are Unknown, GAO/RCED-96-37. Washington, D.C.: GAO. Available online at www.gao.gov/archive/1996/rc96037.pdf.
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Cleaning Up Sites Contaminated with Radioactive Materials: International Workshop Proceedings Hagen, M. 2007. The Wismut uranium mining rehabilitation project running for 15 years—lessons learned and achievements. Advanced Materials Research (20-21):243-247. Hulka, J. 2003. Issues and Trends in Radioactive Waste Management. Proceedings of an International Conference, Vienna, December 9-13, 2002. Vienna: International Atomic Energy Agency, pp. 405-406. Available online at www-pub.iaea.org/MTCD/publications/PDF/Pub1175_web/Book/Pub1175_web.pdf. IAEA (International Atomic Energy Agency). 1997. Waste Technology Section. Closeout of Uranium Mines and Mills: A Review of Current Practices, IAEA-TECDOC-939. Vienna: IAEA. Karamushka, V. P., and V. V. Ostroborodov. 2008. Lands Damaged as a Result of Uranium Ore Mining Operations in the Russian Federation. Pp. 61-68 in Cleaning Up Sites Contaminated with Radioactive Materials: International Workshop Proceedings. Washington, D.C.: The National Academies Press. Presented at the International Workshop on Cleaning Up Sites Contaminated with Radioactive Materials, Moscow, Russian Federation, June 4-6, 2007. Kirchmann, R. J. C., and A. A. Cigna. 2003. Radioactivity from Military Installations Sites and Effects on Population Health, SCOPE-RADSITE. Authors of the Wismut section were K. Wichterey and P. Schmidt. National Research Council. 1986. Scientific Basis for Risk Assessment and Management of Uranium Mill Tailings. Washington, D.C.: National Academy Press. National Research Council. 2007. Assessment of the Performance of Engineered Waste Containment Barriers. Washington, D.C.: The National Academies Press. OECD-IAEA. 2005. Uranium 2005: Resources, Production and Demand. Paris: Organization for Economic Cooperation and Development. Parker, F. L. 2004. “Rethinking” low-level radioactive waste disposal. Proceedings of the WM’04 Conference, Abstract no. 46151, February 29-March 4, 2004. Shatalov, V. V. 2007. Environmental Protection Aspects of the Federal Target Program: The Uranium of Russia. Presented at the International Workshop on Cleaning Up Sites Contaminated with Radioactive Materials, Moscow, Russian Federation, June 4-6, 2007. Uranium Miner. 2007. Available online at www.uraniumminer.net. Accessed June 18, 2007. USNRC (U.S. Nuclear Regulatory Commission). No date. Locations of Uranium Recovery Sites Undergoing Decommissioning. Available online at www.nrc.gov/info-finder/decommissioning/uranium. USNRC. 2006. Fact Sheet on Uranium Mill Tailings. Available online at www.nrc.gov/reading-rm/doc-collections/fact-sheets/mill-tailings.html. USNRC. 2007. National Mining Association. Uranium Recovery Workshop, Denver, Colorado, May 14-16, 2007. Waugh, W. J. 1999. Plant Encroachment on the Burrell, Pennsylvania, Disposal Cell: Evaluation of Long-Term Performance and Risk, DOE Grand Junction Office, GJO-99-96-TAR. World Nuclear Association. 2007. Available online at www.world-nuclear.org/education/mining.htm.