CHAPTER ONE—
INTRODUCTION

The single most important challenge facing the nuclear field (commercial and defense) is what to do with the nuclear waste.

The Nuclear Waste Policy Act of 1982 commits the United States to geologic isolation as the best long-term solution to the final disposition of waste. Twelve years and billions of dollars later, there remain numerous institutional and technical questions concerning our ability to develop public confidence in full reliance on a geologic solution to the waste management problem. The result is the need to consider alternatives that either would stimulate progress towards a geologic solution in which this public has confidence, or to inspire other solutions that would reduce the dependency on any single approach to radioactive waste management. Concepts such as the separation and transmutation (S&T) of nuclear wastes that either eliminates or reduces their radioactive inventories are recognized alternatives. These alternatives were studied for many years prior to the Nuclear Waste Policy Act. With continuing difficulties, including the high costs, of demonstrating the long-term safety over thousands of years of geologic isolation, it is time to examine them with greater intensity. That is the purpose of this study. Many believe that nuclear energy is not an acceptable option until its waste products can be disposed of in a demonstrably acceptable manner.

Wastes are generated in the production of nuclear weapons and by the operation of the more than 100 nuclear power producing plants. The former are generally referred to as "defense wastes"; the latter as "light-water reactor (LWR) spent fuel." (Because there are potentially useful amounts of plutonium, uranium, and rare metals in LWR spent fuel, there is justification in considering LWR spent fuel as an energy and materials resource rather than waste.)

In the United States, most civilian nuclear power has been produced by the once-through LWR fuel cycle. The spent fuel is stored predominantly at the sites of the power reactors from which it has been discharged. This material cannot remain safely where it is in its present form for an indefinite period, but it might be stored at these locations long enough to reduce significantly the decay heat of the 137Cs and 90Sr radionuclides that have about 30-year half-lives. Defense wastes are located at Department of Energy (DOE) sites throughout the country. Many of the defense wastes are stored as liquids in underground tanks and so are not yet in a stable, well-contained form. This must be treated, or better controlled in place, to diminish their risk to the public.

A variety of approaches to achieving the goal of safe and ultimate disposal of nuclear waste are being considered. One of these involves "separations and transmutation" (S&T) to separate the hazardous long-lived radionclides from the wastes and transmute them either by fission or by neutron absorption to generate shorter-lived or stable isotopes. In general, it is considered that safe disposal for short times (times of the order of 1,000 years) will be much easier to achieve and to guarantee than long times (times of the order of 100,000 years or more).

COMMITTEE MISSION AND OPERATION

Committee Formation and Mandate

In 1991, the Secretary of Energy, Admiral James D. Watkins, Jr., requested the National Research Council to conduct a broad systems review of the application of separations technology and transmutation systems to radioactive waste disposal. To implement this request, in June 1991 the NRC formed a 19-member multidisciplinary committee on Separations Technology and Transmutation Systems (STATS) under the direction of the Board on Radioactive



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Nuclear Wastes: Technologies for Separations and Transmutation CHAPTER ONE— INTRODUCTION The single most important challenge facing the nuclear field (commercial and defense) is what to do with the nuclear waste. The Nuclear Waste Policy Act of 1982 commits the United States to geologic isolation as the best long-term solution to the final disposition of waste. Twelve years and billions of dollars later, there remain numerous institutional and technical questions concerning our ability to develop public confidence in full reliance on a geologic solution to the waste management problem. The result is the need to consider alternatives that either would stimulate progress towards a geologic solution in which this public has confidence, or to inspire other solutions that would reduce the dependency on any single approach to radioactive waste management. Concepts such as the separation and transmutation (S&T) of nuclear wastes that either eliminates or reduces their radioactive inventories are recognized alternatives. These alternatives were studied for many years prior to the Nuclear Waste Policy Act. With continuing difficulties, including the high costs, of demonstrating the long-term safety over thousands of years of geologic isolation, it is time to examine them with greater intensity. That is the purpose of this study. Many believe that nuclear energy is not an acceptable option until its waste products can be disposed of in a demonstrably acceptable manner. Wastes are generated in the production of nuclear weapons and by the operation of the more than 100 nuclear power producing plants. The former are generally referred to as "defense wastes"; the latter as "light-water reactor (LWR) spent fuel." (Because there are potentially useful amounts of plutonium, uranium, and rare metals in LWR spent fuel, there is justification in considering LWR spent fuel as an energy and materials resource rather than waste.) In the United States, most civilian nuclear power has been produced by the once-through LWR fuel cycle. The spent fuel is stored predominantly at the sites of the power reactors from which it has been discharged. This material cannot remain safely where it is in its present form for an indefinite period, but it might be stored at these locations long enough to reduce significantly the decay heat of the 137Cs and 90Sr radionuclides that have about 30-year half-lives. Defense wastes are located at Department of Energy (DOE) sites throughout the country. Many of the defense wastes are stored as liquids in underground tanks and so are not yet in a stable, well-contained form. This must be treated, or better controlled in place, to diminish their risk to the public. A variety of approaches to achieving the goal of safe and ultimate disposal of nuclear waste are being considered. One of these involves "separations and transmutation" (S&T) to separate the hazardous long-lived radionclides from the wastes and transmute them either by fission or by neutron absorption to generate shorter-lived or stable isotopes. In general, it is considered that safe disposal for short times (times of the order of 1,000 years) will be much easier to achieve and to guarantee than long times (times of the order of 100,000 years or more). COMMITTEE MISSION AND OPERATION Committee Formation and Mandate In 1991, the Secretary of Energy, Admiral James D. Watkins, Jr., requested the National Research Council to conduct a broad systems review of the application of separations technology and transmutation systems to radioactive waste disposal. To implement this request, in June 1991 the NRC formed a 19-member multidisciplinary committee on Separations Technology and Transmutation Systems (STATS) under the direction of the Board on Radioactive

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Nuclear Wastes: Technologies for Separations and Transmutation Waste Management. The committee was assisted by a subcommittee on Separations, under the Board on Chemical Sciences and Technology, and a subcommittee on Transmutation, under the Energy Engineering Board. These subcommittees included 10 additional experts to support and report to the STATS committee. The expertise of the STATS committee and its subcommittees included chemical, nuclear, and fuel-cycle engineering, separation science, accelerator physics, radioactive and hazardous waste disposal technologies, exposure assessment, economics, public policy, regulatory policy and procedures, nuclear reactor safety, and plant operations. A third STATS subcommittee on Integration functioned until May 1992. Biographies of the committee members are given in Appendix M. The proposed statement of work of the STATS study sent to DOE in May 1991 is given in Appendix A. The objective of the committee was to prepare a report covering its terms of reference as mutually agreed on between Admiral Watkins, Secretary of Energy, and Frank Press, Chairman, National Research Council, as elaborated in the Statement of Work given in Appendix A. In summary, STATS was requested to perform an independent review of both mature and developing separations technologies available in the United States and in other countries; evaluate the application of separations technology to DOE's radioactive defense waste management program; review the potential for application of separations and transmutation technologies to commercial spent nuclear fuel and potential impacts of successful waste separation and transmutation processes on the design and licensing of a deep geologic repository; this includes review and evaluation of potential life-cycle costs, benefits, ramifications, and program linkages between chemical separations and actinide or fission product transmutation in liquid metal reactors, accelerators, or other devices for the long-term management of high-level wastes; and recommend options that are economically and technically feasible and in compliance with all applicable regulations. To initiate the study, an international workshop was held in January 1992 where the committee was briefed by a number of people representing a wide cross section of disciplines. To facilitate the work of the committee, selected members made site visits. Committee and subcommittee meetings were held as necessary (see Appendix B). In May 1992, in response to a request by the Secretary of Energy, an interim report of the committee was submitted that summarized the committee's information at that time concerning actinide burning in advanced liquid metal reactors and the possible impacts on the repository program (see Appendix L). Why Actinide Burning is Being Reconsidered The resolution of the nuclear waste disposal problem is a crucial factor for the future of nuclear power in the United States. It is perceived to be one of the most important elements in establishing public confidence for continued or expanded nuclear electricity generation. Further, it plays a major role in the efforts to successfully manage and clean up the by-products from the nuclear weapons production complex. Consequently, any proposal for alternate approaches can easily capture the attention of numerous scientific and public constituencies. For both institutional and technical reasons, actinide burning is now being reconsidered. Institutional Incentives The apparent lack of progress on developing a nuclear waste repository has heightened public awareness and concern about achieving a solution to nuclear waste disposal. After two decades of federal programs and one decade after focused congressional action, an operating repository for civilian reactor wastes is still at least 15 years away. Cost estimates indicate that almost $10 billion will be expended before a decision to select a site and begin licensing actions will be made. Regulatory complexity and uncertainty is likewise affecting the progress toward and confidence about a final solution. Isolation standards are being reformulated and the associated regulatory structure is continuing to evolve. Finally, no significant progress has been made to establish broad-based political support for either a civilian waste repository or a monitored retrieval storage facility. Public perception appears focused on the long-lived radioactive elements and those that do not occur naturally. For this reason, the actinides, especially plutonium, are of special concern. Consequently, any mechanism to reduce or eliminate these elements will draw attention as an alternative to the seemingly stalemated approach to nuclear waste disposal. Similarly, the complex regulatory requirements for disposal imply that any mechanism to simplify the licensing process or make the contents of a repository more benign would be attractive. Further, if the nuclear waste in a repository could be shown to pose a threat for a significantly reduced period of time, it is perceived by many that proof of ultimate safety would be easier to provide. Subsequent discussion in the report will indicate, however, that while actinides and their reduction may be a big factor in evaluating transmutation concepts, separations and transmutation of long-lived fission products may represent an equally significant concern. Technical Incentives Recent technical progress in several areas has been proposed as justification to reconsider transmutation. Repro-

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Nuclear Wastes: Technologies for Separations and Transmutation cessing technology has advanced in many countries, offering the promise of highly efficient and selective separation operations. Likewise, the advance of robotics and remote handling gives support to cleaner, more efficient processing of radioactive materials. Advanced reactor designs, specifically liquid-metal reactors, which have the potential to consume actinides and incorporate integrated reprocessing facilities, are reaching a conceptual development and demonstration stage. Further, the possibility of neutron production, using high-energy accelerators, has been enhanced by recent advances in accelerator technology. Proponents argue that such neutron production can be used to drive subcritical reactor assemblies, providing high neutron fluxes capable of transmuting actinides and fission products while providing some safety advantages. Scope of Study The scope of the study was to prepare a reviewed report evaluating the relative effects, costs, and feasibility of employing separations and transmutation technologies in the Department of Energy's programs for managing (1) spent nuclear fuel from civilian power reactors, and (2) radioactive wastes from selected existing defense production reactor sites. This final report of the STATS Committee is a peer-reviewed evaluation of the separations technology and transmutation systems application to radioactive waste management and disposal, with conclusions and recommendations. The report covers in detail the current status and potential applications of separations and transmutation technologies and systems. These include critical reactors and subcritical assemblies driven by accelerators, in conjunction with aqueous and/or nonaqueous separation processes for separating actinides to be transmuted. The report further examines whether practical implementation of feasible separations and transmutation (hereinafter referred to as S&T) concepts can contribute to a safer and more economical waste disposal method than what is now being considered. The report also assesses a time frame for such implementation. Time-Frame If there is a justification for the introduction of S&T, the time required for development and project implementation is important. The development phase is envisaged by the various proponents of the S&T concepts to end by the first decade of the next century and the implementation phase to start thereafter. The report reviews whether these dates are realistic, taking into consideration the following important factors: achievable separation efficiencies and actinide reduction factors over time; consideration of whether the S&T systems are to be developed solely for waste management needs or also for power production; realistic assessment of the time required to develop the concepts to achieve practicality; health and safety issues; economics; policy and public acceptance considerations; and licensing and regulatory issues. S&T Areas Current and Future Waste Management Programs. Assessment of the current waste management programs, future needs, and associated issues can indicate whether the present fuel cycle (see Appendix C) needs any change. If changes are needed, it would be necessary to identify the reasons for and the timing of such changes. Answers to these questions lead the scope of this study to include: (1) separations-only and storage/disposal concepts; (2) integrated systems consisting of S&T; and (3) impacts, positive and negative, of S&T technologies on waste inventories, management and disposal over the entire fuel cycle. Major considerations such as risk reductions, cost implications with cost-to-benefit analyses, and institutional feasibility and stability will be important for decision-making. Since most of the S&T proposals are based on concepts and paper studies, full details of the processes and systems are not available. The conclusions of the report are based on current national and, where relevant, international knowledge and status of S&T work. Impact on National Energy Strategy. The National Energy Strategy (U.S. DOE, 1991/1992), projects that a substantial amount of new generating capacity—from 190 to more than 275 gigawatts—would be added through nuclear power between 1991 and 2010. It concludes that nuclear power is best utilized for "base-load" capacity. This strategy undoubtedly depends on the strategy's conservation actions. A projected 195 to 290 gigawatts of nuclear capacity could be on line by the year 2030 if (1) favorable economics exist, (2) the public and the regulators deem the new plants to be safe, and (3) a solution to the disposal of nuclear waste can be found. Reducing uncertainties, assuring safety, and promoting stability in the licensing process can lead to more predictable construction times and costs. Implications of the nuclear energy component of the National Energy Strategy are important in determining S&T's role. In this report, two example cases, the declining power

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Nuclear Wastes: Technologies for Separations and Transmutation and the continuing constant power, are given to illustrate the effects of S & T. Technologies Separations technology employing PUREX has been used to obtain plutonium and uranium from production reactor fuel in the weapons program for many years from the beginning of the nuclear industry using the plutonium and uranium extraction (PUREX) aqueous processing of spent thermal reactor fuels. Although dozens of other promising separation methods have been studied in the laboratory and in pilot plants, including nonaqueous reprocessing, none has been developed to the same level for practical application as the PUREX process. The report reviews the existing PUREX process and other aqueous and nonaqueous processes under development, including studies on the chemistry of solvents. The advanced liquid metal reactor (ALMR) program includes the integral fast reactor (IFR) under development by Argonne National Laboratory (ANL) and the Power Reactor, Innovative, Small Module (PRISM) modular reactor concept under development by General Electric (GE). The primary aim of the ALMR is power production as a breeder. However, the ALMR can be modified for transmutation of transuranic wastes (TRU). The LWRs could be used as plutonium burners, as transmuters of actinides, and transmutation of fission products 99TC and 129I. Existing LWRs are in an advanced stage of development, the proposed next generation being advanced light-water reactors (ALWRs). The Clean Use of Reactor Energy (CURE) concept proposed by Westinghouse Hanford Co. envisions the use of both ALMRs and LWRs in a system transmuting actinides as well as fission products. Finally, Brookhaven National Laboratory (BNL) proposes the modification of their conceptual space particle bed reactor (PBR) to recycle uranium as well as unburned plutonium. The information on these latter two concepts is so meager that no analysis of their performance has been possible. High neutron fluxes can be attained by the use of accelerators for fast burn-up of the actinides and certain fission products. Los Alamos National Laboratory (LANL) and BNL have undertaken several conceptual studies for achieving accelerator-based transmutation. The accelerator scheme envisions the production of electricity—part of it used to power the accelerator and the rest for sale—an important element in paying at least part of the cost of transmutation. Development of the concepts described above to achieve practical S&T realities—economic and technical factors taken into account—will have to overcome many problems. The report highlights and analyzes these problem areas and assesses the options that have potential for further development. BACKGROUND ON SPENT REACTOR FUEL AND HIGH-LEVEL WASTE DISPOSAL History The final disposal of spent reactor fuel and high-level radioactive waste (HLW) from nuclear reactors in the United States was initially addressed early in the development of nuclear power. It was recognized that the waste from civilian power reactors and atomic energy defense activities was sufficiently hazardous as to require long-term isolation from human populations. In a 1957 study for the U.S. Atomic Energy Commission (AEC), the National Academy of Sciences recommended that high-level waste be buried in deep underground repositories and suggested bedded salt deposits as a likely host rock. Generic engineering tests were performed in the mid-1960s to see the effects of emplacement of spent fuel on salt and vice versa in a salt mine near Lyons, Kansas. Shortly thereafter, conceptual designs were developed for a repository at that location. The high-level waste program at that time focused on technical issues, principally the interactions between waste forms and the host rock and the geologic and hydrologic integrity of the site. However, it soon became clear that public and institutional involvement would play an important role in the progress of the high-level waste program. In 1972, after encountering some technical difficulties and institutional issues, the AEC abandoned the Lyons' project and sought to identify another site in salt deposits. In addition, the AEC announced a program to employ retrievable surface storage as an interim measure until a repository could be developed. Site investigations began in southeastern New Mexico in the early 1970s to identify potential repository locations in the western part of the Permian basin. In 1975, the Energy Research and Development Administration (ERDA) identified a location in salt approximately 30 miles east of Carlsbad, New Mexico, that ultimately became the site for the Waste Isolation Pilot Plant (WIPP). At the same time, ERDA gave up plans for early construction of a retrievable surface storage facility. Evaluation of other locations around the United States for a nuclear waste repository began in 1976. In 1980, ERDA's successor agency, the Department of Energy, issued a generic environmental impact statement that examined numerous strategies, including transmutation of radionuclides to a more benign form, and selected mined geologic disposal as the approach for waste isolation in the United States. This action and a concurrent government policy also confirmed that spent fuel from civilian nuclear power reactors would not be reprocessed but disposed of directly in a repository (The Nuclear Waste Policy Act was silent on the question of spent-fuel reprocessed waste disposal). The following year the U.S. Con-

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Nuclear Wastes: Technologies for Separations and Transmutation gress established the WIPP project in New Mexico as a demonstration project for disposal of defense transuranic waste. Congress precluded licensing of WIPP by the Nuclear Regulatory Commission (NRC) and did not require WIPP to demonstrate compliance with Environmental Protection Agency (EPA) standards prior to emplacement of waste. Faced with significant controversy and regional concern, in 1982 Congress enacted PL 97-425, the Nuclear Waste Policy Act (NWPA). The act provided the basis to select and develop sites for two nuclear waste repositories sufficient to accommodate the high-level radioactive waste produced by both the civilian and defense sectors. The NWPA also provided for the establishment by the EPA of standards for protection of the general environment from off-site releases of radioactive material in repositories. In the case of civilian HLW and spent fuel, the NRC's role is as the repository licensing authority in compliance with these standards. The NWPA also mandated that the fuel costs of the HLW management program be paid through a nuclear waste fee. A fee of one mil ($0.001) per kilowatt hour of nuclear-generated electricity is paid into the Nuclear Waste Fund and currently provides about $800 million a year (One mil per kilowatt is the initial value of the fee that is required to be charged as necessary to ensure full cost recovery). Total income and earnings to the Fund since its inception in 1983 is approximately $6 billion through 1992 and $8 billion through 1994. While this fund is generated entirely by ratepayers using nuclear electricity, and may only be used to support storage and disposal activities specified in the NWPA, it is still subject to congressional appropriations and deficit controls to establish annual allowable expenditures for the program. Through 1992, approximately $3.5 billion has been spent from the Nuclear Waste Fund. For the disposal of defense HLW, the NWPA specifies that fees be paid by the federal government via congressional appropriation. In 1983, the National Academy of Sciences completed a system study on the geologic disposal of HLW that reviewed alternative technologies available for the isolation of radioactive waste in mined geologic repositories, evaluated the need for and possible performance benefits from those technologies, and identified appropriate technical criteria for selecting the appropriate technology. In 1983, the NRC issued regulations (10CFR60) to guide its licensing process, and in 1985 the EPA promulgated the environmental standards (40CFR191). In 1987, the EPA standard was remanded by a U.S. federal court, and the EPA was required to evaluate and reissue a revised standard addressing the concerns of the court on the containment and isolation provisions in the EPA standard. In 1992 Congress required the EPA to develop a new standard for Yucca Mountain based on recommendations from a study by the National Academy of Sciences. In addition, the WIPP Land Withdrawal Act directed EPA to promulgate a standard specifically for WIPP and gave EPA authority for its implementation. In 1985, President Reagan concluded that defense HLW would be disposed of in the repository being developed for civilian waste. During this same time frame, and consistent with the schedule laid out in the NWPA, DOE concluded that a monitored retrievable storage (MRS) facility was required for spent fuel from commercial nuclear power reactors. This facility would provide temporary storage and subsequent shipment to a repository. The following year, three candidate sites were recommended to be fully characterized for potential use as the nation's first HLW repository. These sites were located in Hanford, Washington; Yucca Mountain, Nevada; and Deaf Smith County, Texas. All three sites were to be characterized in parallel and a preferred site identified for repository development. In 1987, after significant public and institutional controversy, and faced with significant costs for characterization, Congress amended the NWPA. The Nuclear Waste Policy Amendments Act (NWPAA) eliminated the program to identify a site for a second repository, pending reconsideration in 2007, and provided for the characterization for only one site, Yucca Mountain, Nevada, for the first repository. The NWPAA also allowed for an MRS facility but tied its development and construction to that of the first repository. Current Waste Disposal Situation Spent Reactor Fuel After significant institutional and political controversy, the Yucca Mountain Project is proceeding with the characterization of the volcanic tuff for development as a repository. The project schedule has a goal of submitting a license application to the NRC in 2001. Allowing 3 years for licensing and 6 years for construction, operation of the repository is currently scheduled to begin in 2010. The repository at Yucca Mountain would contain a total of 70,000 metric tons uranium (MTU) equivalent of nuclear waste, of which about 62,000 MTU would be spent fuel from civilian power reactors. This capacity is the statutory limit imposed by the NWPA and does not necessarily represent physical limits at the Yucca Mountain site. This spent-fuel content for Yucca Mountain is approximately equal to what will be discharged by U.S. reactors through the year 2010. The projected discharge of spent fuel from current reactors in the U.S. during their lifetime (by the year 2040) will be about 90,000 MTU, necessitating a second repository or congressional action to increase the limit on capacity in the first repository. Since the TRU content of spent fuel is

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Nuclear Wastes: Technologies for Separations and Transmutation approximately 1% by mass, 900 MTU of TRU will be generated by currently operating reactors, with approximately 600 MTU produced by the year 2010. The repository program is encountering considerable controversy. The characterization of the Yucca Mountain site does not enjoy political support in the state of Nevada. Program costs have risen significantly, and the program has been delayed more than a decade in light of the apparent complexity of characterizing a repository consistent with NRC licensing requirements. No firm estimates are available of the cost of characterization, which is expected to exceed $5 billion before a license application can be submitted. For its part, the MRS program will also require securing a site in the face of probable political opposition. Further, the development of the MRS is by statute linked directly to progress on the repository; it is therefore likely that an MRS cannot be brought into operation on a schedule to support DOE's commitment to begin accepting spent fuel in 1998. These factors have seriously eroded public and institutional confidence in the management and potential success of DOE's civilian radioactive waste management program. Concern has been expressed repeatedly with regard to an overly complex management system that places too little emphasis on the scientific and engineering evaluations to effectively determine the potential of the Yucca Mountain site on a timely basis. This apparent lack of progress and significant cost give rise to efforts to identify alternatives or simplifications to the development of a nuclear waste repository. Lack of progress in the development of nuclear waste repositories has also been attributed, in part, to the complexity of the environmental standards and the difficulty in demonstrating compliance with these standards. Concerns over the ability to comply with the standards and the apparently overstructured, inflexible programs being implemented by DOE resulted in strong recommendations by Congress that the standards, approach, and program be reevaluated. These concerns were legislatively addressed in 1992 by congressional requirements (PL 102-486) that public health and safety standards be promulgated by the Administrator of the Environmental Protection Agency for a repository at the Yucca Mountain site. These standards must be based on findings and recommendations of the National Academy of Sciences. The standards were required to address the maximum annual effective dose equivalent to individual members of the public. The National Academy of Sciences was asked to provide findings and recommendations that addressed the appropriateness of a standard based on dose to an individual, impact of postclosure institutional control on repository risk, and the validity of scientific predictions regarding the probability of human intrusion over a 10,000-year period. Requirements were also place on the U.S. NRC to modify its technical requirements and criteria to be consistent with the new standards of the EPA. The legislation provided that the National Academy of Sciences committee issue a report. The National Academy of Sciences report entitled Technical Bases for Yucca Mountain Standards was issued in 1995. Defense High-Level Waste The production of nuclear weapons and naval propulsion systems has resulted in an accumulation of radioactive wastes at several locations around the United States. These wastes are typically classified as high-level radioactive waste (HLW), transuranic wastes (TRU), low-level radioactive wastes (LLW), and, more recently, mixed wastes. Liquid HLWs are the direct products resulting from the reprocessing of spent reactor fuel and irradiated targets. As generated, the wastes are highly acidic, but almost all of them have been neutralized with sodium hydroxide to prevent unacceptable corrosion of mild steel tanks. The wastes are stored primarily in large metal tanks containing various mixtures of liquids, sludges, salt cake, and solids (calcines). The locations and approximate amounts of HLWs in storage (U.S. DOE, 1991) are as follows: Savannah River Site 132,000 m3 Hanford Site 254,000 m3 Idaho Chemical Processing Site 12,000 m3 West Valley Demonstration Project 1,230 m3 The composition of wastes at each site varies as a result of the specific processing and storage techniques used. The Idaho site, for example, has acidic liquids stored in tanks and a large volume of waste converted into a solid (calcine). The West Valley project has relatively smaller volumes of alkaline and acidic wastes that are intended for subsequent processing into a glass waste form for disposal. At Savannah River, significant quantities of wastes have been generated from the application of the PUREX process to fuel and targets from production reactors. A vitrification facility to convert these HLWs into a stable glass form is in final stages of completion. The largest quantity of HLW is stored in 149 single shell tanks and 28 double-shell tanks at the Hanford site. These wastes, while larger in volume than those at Savannah River, typically contain less radioactivity. This is largely due to the removal of strontium and cesium into capsules that contain almost the same amount of radioactivity (170 × 106 Ci1) as the entire contents of the tanks. The chemical separation processes at Hanford have resulted in approxi- 1    Throughout this report, the term Curie (Ci) is used as the unit of radioactivity. The SI unit of radioactivity is the becquerel (Bq). 1 Ci = 3.7 × 1010 Bq.

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Nuclear Wastes: Technologies for Separations and Transmutation mately 1 Mg of TRU elements in the HLWs and approximately 2,000 Mg of uranium. The wastes at the Hanford site have been chosen as the reference case for application of transmutation and advanced separations to defense HLWs in this study. TRU wastes, primarily solid, are the other significant quantity of defense wastes requiring geologic disposal. These wastes contain TRU elements in quantities greater than 100 nCi/g of total waste material. Prior to 1970 when TRU wastes were defined as those containing >10 nCi/g of TRU, these wastes were buried in surface landfills at DOE sites. Much of these buried wastes may actually be below the 100 nCi/g level for TRU waste. Since 1970, the TRU wastes were stored retrievably to be subsequently disposed of in the WIPP facility. In 1990, approximately 191,000 m3 of buried TRU containing approximately 800 kg of transuranic elements was located at Hanford, Idaho National Engineering Laboratory, Los Alamos National Laboratory, Oak Ridge National Laboratory and Savannah River Site.2 At that time, 61,000 m3 containing approximately 2,200 kg of TRU elements was retrievably stored at these sites with over one-half of the total at Idaho National Engineering Laboratory. In addition to buried and stored TRU waste, it is estimated that as much as 1,800,000 m3 of potentially contaminated soil is present at these sites. In addition, residues from Rocky Flats and remotely handled TRU waste, while smaller in volume, contain approximately 3,000 kg of TRU elements. Consequently, the transuranic element content of all categories of TRU wastes far exceeds that of the tanks at Hanford. TRU wastes are extremely varied in composition, typically consisting of drums and boxes containing organic materials (papers, clothing, plastics), sludges, and contaminated laboratory or production equipment from nuclear materials processing. This nonhomogeneity and diversity in composition make TRU wastes unlikely candidates for advanced separations or transmutations. In fact, many of the concerns about safe disposal of TRU wastes are due to its chemical form and not its content of radioactivity; consequently, processing to modify the waste form is much more likely to result in effective containment in a repository than S&T of its relatively small content of TRU elements. Consequently, this study does not attempt to evaluate the application of S&T to defense TRU wastes. Today, the proposed repository for defense TRU wastes, WIPP, has been completely constructed and awaits the results of a program to evaluate compliance with the EPA standard and a test program to obtain additional information on waste interactions. The program is expected to last several years. If the repository is found to comply with isolation standards of the EPA, disposal operations could begin in the second half of this decade. Agreement on the process to demonstrate compliance and the conduct of experiments using radioactive waters will need to be established. It is likely that continued interaction between DOE, federal and state oversight agencies, and public interest groups could mean additional delays for the program and ultimate operations. A major step for WIPP was completed in 1992 when land withdrawal legislation was passed by Congress (PL 102-579), allowing DOE, after completing several prerequisite actions with the EPA, the National Academy of Sciences, and the state of New Mexico, to conduct the final stage of demonstrating compliance for the WIPP. (DOE subsequently decided to conduct the necessary tests above ground.) This legislation also requires the EPA to develop a disposal standard for WIPP, independent of the standard to be developed for Yucca Mountain. Current Policies Governing High-Level Waste Management The committee has reviewed two broad topics for their implications for waste management: (1) the S&T of certain specific radionuclides from spent fuel; and (2) the separation of HLW produced in weapons research, development, and production. Although not explicitly prohibited by law or regulation, the development and use of a system for transmutation would represent a radical change in current public policy and fuel-management plans. However, current policy does call for the separation of defense HLW before processing it for disposal. Changes in how and to what extent separation is used will require only a modification of current policy and plans. Commercial Spent Fuel Policy. The United States has a set of formal policies concerning the management and disposal of commercial spent fuel embodied in legislation, executive orders, and regulation. In particular, two major laws govern commercial spent-fuel management: the Nuclear Waste Policy Act of 1982 (PL 97-425) and the Nuclear Waste Policy Amendments Act of 1987 (PL 100-203). The 1982 Act was based on a broad consensus about some issues and on compromises concerning others. The 1987 amendments significantly revised the 1982 Act. Passage of each act required considerable compromise and expenditure of political effort. Congress will not lightly alter the basic agreements that were reached through the difficult negotiation required to balance competing interests. Reprocessing. The first U.S. nuclear power plants were designed and built under the assumption that spent fuel 2    800 kg of TRU contains predominantly 239Pu with a specific radioactivity of 61 curies/kgm.

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Nuclear Wastes: Technologies for Separations and Transmutation would be reprocessed, that the recovered plutonium and some other actinides would be used in fuel for light-water reactors, and that the resulting HLW would be solidified and then disposed. President Carter, however, delayed reprocessing because of concern about nuclear weapons proliferation. President Reagan removed the prohibition, declaring that reprocessing was the responsibility of private industry to develop without government assistance. Utilities now store spent fuel at power plants and expect to dispose of its as unreprocessed waste. Interim storage. The NWPAA authorized the siting, construction, and operation of a monitored retrievable storage facility (MRS) for the interim storage of commercial spent fuel, subject to certain conditions linking MRS development to repository development: DOE cannot select a site for an MRS before the Secretary of Energy has recommended approval of a site for the development of a repository; the license for MRS must contain conditions that allow construction and operation of the MRS to continue only when repository construction and operation is proceeding. Total capacity of the MRS is limited to 15,000 tons. The NWPAA also established the Office of the Nuclear Waste Negotiator to negotiate agreements with states or Indian tribes willing to host a repository or an MRS. Such an agreement could contain different conditions than those imposed on a DOE-sited facility. The term of the Office of the Nuclear Waste Negotiator has now expired, and the Office was not reauthorized by Congress. Ownership of spent fuel. The federal government will eventually own and be responsible for the disposal of commercial spent fuel. The NWPA directed utilities to levy fees on electricity generated by nuclear power and to pay those fees into the federal Nuclear Waste Fund to be used to develop and operate a repository. In return, the NWPA directed the federal government to accept ownership of spent fuel ''beginning not later than January 31, 1998" and to start accepting the waste as a repository is available. Repository. Both acts establish building a repository for the disposal of HLW as a top government priority for HLW management. Some people support this policy because they believe that those who benefitted from the processes that generated the waste (that is, those who used the electricity) must dispose of the resulting waste. Others support the policy because they believe that the survival of nuclear power depends on demonstrating the ability to dispose of spent fuel. The NWPA of 1982 limits the amount of waste placed initially in a first repository. This limitation was imposed as a matter of policy, rather than on the basis of technical considerations. Only the equivalent of 70,000 metric tons of heavy metal in spent fuel and/or in solidified HLW can be emplaced in a first repository before a second repository is operating. Under current plans, 7,000 metric tons of heavy metal equivalent of solidified HLW from the weapons program is to be disposed of in the civilian repository, leaving the balance for commercial spent fuel. The NWPA delays congressional consideration of the need for a second repository until after the year 2007. According to Section 122 of the NWPAA, spent fuel placed in a repository must be retrievable during an appropriate period of operation of the facility for "any reason pertaining to the public health and safety, or the environment, or for the purpose of permitting the recovery of the economically valuable contents" of the spent fuel. NRC regulations require that provisions must be made to enable the spent fuel to be retrieved on a reasonable schedule, starting any time up to 50 years after waste emplacement begins. Transmutation proposals. All proposals for transmuting commercial spent fuel require reprocessing as a first step. Some assume that reprocessing would occur initially to recover radionuclides for producing electricity and that additional transmutation for waste management and disposal purposes would occur as an auxiliary process. These proposals require that elaborate new reactor or accelerator systems be developed and operated, most for many decades. Such operations would result in new and varied waste streams. As discussed in Chapter 5, these proposals have far-reaching implications for current policies about the ownership of spent fuel and the fuel resources in it; responsibility and time duration for spent-fuel storage; the forms of the waste to be eventually disposed of and the implications for repository capacity and design; and the development, regulation, and financing of new technology for transmutation systems and their operation over decades. At present, there are no affirmative policies that support the extensive research, development, and capital investment required to develop a transmutation system. Defense High-Level Waste For many years the country's nuclear weapons facilities were largely closed to public review and outside regulation. However, increased public concern about environmental issues, passage of state and federal laws extending environmental regulation and oversight to government activities, and court rulings eventually led the federal government to acknowledge significant legal obligations to comply with environmental regulations and standards. The legal basis for policies for managing and disposing of HLW in tanks at Hanford is contained in the Hanford Federal Facility Agreement and several current and planned environmental impact statements. The Washington State

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Nuclear Wastes: Technologies for Separations and Transmutation Department of Ecology, the U. S. Environmental Protection Agency, and the U.S. Department of Energy signed the Hanford Federal Facility Agreement and Consent Order in 1989 (referred to as the "Tri-Party Agreement"). The agreement is based on provisions of Executive Order 12580, Washington State Hazardous Waste Management Act, and several federal laws: the Comprehensive Environmental Response, Compensation, and Liability Act, as amended by the Superfund Amendments and Reauthorization Act of 1986; the Resource Conservation and Recovery Act, as amended by the Hazardous and Solid Waste Amendments of 1984; and the Atomic Energy Act of 1954, as amended. The agreement may be amended by unanimous agreement of the signatories. An action plan delineates actions to be taken, provides a schedule, and specifies procedures for modifying or amending the action plan. Under the 1989 Tri-Party Agreement, as amended until January 1994, tank waste is to be separated. The high activity fractions are to be solidified as glass and stored until disposal in a repository. The low activity fraction was originally destined to be immobilized in grout and stored on site; in 1993, the parties agreed to change the waste form to glass. In 1992, preliminary site preparation began for a waste vitrification plant at Hanford, but work was halted under an agreement to consider a revised technical strategy for Hanford. In 1993, the three parties agreed to suspend, until the year 2002, the start of construction of the high activity fraction vitrification plant, and agreed to begin construction of the low activity fraction vitrification plant in 1997. ORGANIZATION OF THE REPORT The report is organized in three parts: an Executive Summary, a main report of six chapters, and 16 appendices. The Executive Summary is a stand-alone document that gives the findings, the recommendations, and the conclusions of the STATS Committee. The Executive Summary also, in most cases, explains the basis on which the conclusions, recommendations, and findings were reached. The complete technical justification is not given in the Executive Summary. The detailed technical analysis appears either in the main report or in one of the 16 appendices. The first chapter of the report gives the scope and objectives of the study and a brief history of U.S. efforts in the area of high level radioactive wastes from the late 1950s to the present. It also describes the organization of the report. Chapter 2 discusses the nature of the radioactivity in spent power reactor fuel. It reviews the radionuclides of most concern and looks at the potential public exposure from current and some proposed fuel cycles. This chapter also gives a description of the three Separations and Transmutation (S&T) scenarios. Chapter 3 looks in detail at the separations technology that is available and could be potentially available for the separations required in the S&T approach. Chapter 4 looks in detail at the three candidates' concepts for carrying out the transmutation step in this approach. In particular, calculations are presented that show how long it requires to accomplish a specified level of burnup of the radionuclides of concern. Chapter 5 looks at the problems of dealing with defense high level waste, which are usually liquids containing fission products with relatively little heavy metal. The particular case of the waste stored in tanks at the Hanford reservation are reviewed for applications of S&T to that particular problem. Finally, Chapter 6 looks at a number of technical and societal issues that are involved in the adoption of any of the S&T systems proposed. The appendices give more detailed technical information on the subjects identified in their titles. Because acronyms, abbreviations, and technical jargon are widely used in this technology, the reader may find appendices N and O useful. REFERENCES U.S. Department of Energy (DOE). 1991. Integrated Data Base for 1991: U.S. Spent Fuel and Radioactive Waste Inventories, Projections and Characteristics. DOE/RW0006, Rev. 7. Washington, D.C.: U.S. Department of Energy. U.S. Department of Energy (DOE). 1991/1992. National Energy Strategy. Powerful Ideas for America. DOE/S-0083. Washington, D.C.: U.S. Department of Energy.

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