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Executive Summary ·eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee The United States Department of Energy (DOE) has approximately 400 million liters (100 million gallons) of liquid high-level waste (HLW) stored in underground tanks and approximately 4,000 cubic meters of solid HLW stored in bins. The current DOE estimate of the cost of con- verting these liquid and solid wastes into stable forms for shipment to a geological repository exceeds $50 billion to be spent over several decades (DOE, 2000~. This committees was appointed by the National Research Council (NRC) to advise the Environmental Management Science Program (EMSP)2 on a long-term research agenda addressing the above problems related to HLW3 stored in tanks and bins at DOE sites.4 The complete statement of task is reproduced in Sidebar P.1 of the Preface. The committee outlined HLW problem areas that either cannot be addressed effectively with current technologies, or that are anticipated for the future. From these problem areas, the committee identified research objectives, leaving to EMSP investigators the role of determin- ing the pathway to achieving these objectives through basic research. Moreover, it is not the purpose of this report to circumscribe the invest) gators' creativity by giving a detailed list of research projects. Committee on Long-Term Research Needs for Radioactive High-Level Waste at Department of Energy Sites. 2The EMSP currently provides the DOE's Office of Environmental Management with a basic research program to reduce costs, time, and risks associated with cleaning up the nation's nuclear complex. 3HLW is the highly radioactive waste from the chemical reprocessing of spent fuel and target materials to recover plutonium and uranium for the production of nuclear weapons. The committee did not address issues related to spent nuclear fuel, transuranic waste, in particular plutonium, or other secondary waste streams from the processing and handling of HLW (see Chapter 1). 4The HLW sites are the Hanford Site, Washington, the Savannah River Site, South Carolina, the Idaho Engineering and Environmental Laboratory, and the West Val ley Demonstration Project, New York. E x e c u t i v e S u m m a r y

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Throughout the report, examples of research topics are provided to illustrate how the committee would address the identified HLW prob- lems. These examples are not to be considered as recommendations or research priorities. Long-Term Research Needs for HEW Management The recommended long-term research agenda is organized accord- ing to DOE's current approach to HLW management as follows: Characterization Retrieval and pretreatment · I mmobi I ization · Tank closure The motivation for selecting the long-term basic research activities in this report is to provide contingency approaches for DOE's HLW management programs and to improve process effectiveness. The com- mittee recommends research topics that would provide contingency approaches as the basis for program support in case of interferences or disruptions to current HLW management plans. Results from these research activities wou Id help reduce technological risk. The committee also recommends research topics that wou Id improve process effective- ness. The long-term basic research activities are summarized below in terms of research objectives. More details can be found in the chapters indicated in parenthesis. Characterization (Chapter 31: Innovative methods to achieve real- time and, when practical, in situ characterization data for HLW and process streams that could be useful for all phases of the waste man- agement program. The objective of research activities in the area of characterization is to provide the scientific basis for the following: · developing remote sensing instruments, and · developing on-line or in situ instruments. Pretreatment (Chapter 4~: High-efficiency, high-throughput separa- tion methods that could reduce HLW program costs over the next sev- H ~ G H - L E V E E W A S T E

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eral decades. The objective of research activities ment is to provide the scientific basis for the following: in the area of pretreat- · improving sol ids-l iquid separation methods, · improving underlying science and technology for sludge leach- ing operations, and · increasing the efficiency of liquid decontamination methods. Immobilization (Chapter 51: Robust, high-loading immobilization methods and materials that could provide enhancements or alterna- tives to the current immobilization strategy. The objective of research activities in the area of immobilization is to provide the scientific basis for the fol lowi ng: · identifying alternative immobilization media to overcome limita- tions of borosilicate glasses, · i nvestigati ng the effect of i ncreased crystal content on the du ra- bility of the borosilicate glass matrix, improving phenomenological models to predict long-term leach- ability of various glass waste forms, · evaluating advantages of using unreacted glass-forming chemi- cals compared to premelted glass frit, · understanding foaming in loule-heated melters, . mitigating the effects of precipitation of noble metals and crys- tal I i ne phases i n You [e-heated melters, improving Joule-heated melters to achieve higher processing temperatures, and · developing alternatives to Joule-heated melting. Tank closure and other long-term issues (Chapter 61: Innovative methods to achieve tank closure, non-invasive monitoring of the near- field areas, as well as improved containment barriers. The objective of research activities on this topic is to provide the scientific basis for the fol lowi ng: · developing highly innovative and effective retrieval methods for removal of residual HLW materials from tanks, · developing highly innovative and effective retrieval methods for removal of HLW materials from connecting pipelines, · improving the characterization of residual waste in tanks, developing noninvasive near-field monitoring techniques, and Improving near-field containment methods through the use of barriers. . . E x e c u t i v e S u m m a r y

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EMSP Research Portfolio: Technological Risk and Desired Attributes The committee provides programmatic recommendations on the management of technological risk and discusses desired attributes for the EMSP research portfolio. An analysis of this portfolio, with respect to HLW research activities, is provided as an interim report, reproduced i n Append ix A. The mai n fi nd i ngs and recom mendations from Append ix A are included in the body of this report. , , Managing Technological Risk The research program proposed by the committee could help the EMSP in reducing technological risk.5 Technological risk can be reduced by improving process effectiveness and by providing contin- gency approaches to baseline technologies before disruptions or inter- ferences to current HLW processing programs occur. Improving Process ,. .. . . . . . . .. . a 1 electiveness can lean to more robust approaches that require fewer steps to achieve the desired result; therefore, a simple and robust process presents less technological risk compared to a multi-step process. This is because there is a finite probability of encountering a problem causing process failure in any one of the individual steps. For instance, separation techniques removing more than one targeted species in a single step pose fewer technological risks than a series of steps to achieve the same result. To provide contingency approaches, it is necessary to allocate funding for exploratory research relevant to HLW cleanup. The committee recognizes that exploratory research efforts do not bear fruit immediately and that results often are not deployed in the field. However, the success of a basic research program should not be measured only by the proportion of projects that become field-appl icable. Desired Attributes of the EMSP Research Portfolio In selecting the projects for future HLW proposal cycles, attention to the following programmatic recommendations is also warranted: 1. Maintain long-term vision. Research projects should be focused not only on DOE's short-term issues but also on significant long- 5A technological risk in HLW management is the risk that existing technologies will fail to accomplish goals and performance requirements set by environmental remediation policies or regulations. H ~ G H - L E V E E VV A 5 T E ~ A ~

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term problems to advance the state of knowledge well beyond the next decade. This approach maintains the EMSP long-term mission and mitigates the technological risk that would interrupt the Office of Environmental Management (EM) HLW program. 2. Maintain relevance. The EMSP should support basic research on processes and phenomena that support the EM program mission. These projects can then feed into other EM programs and spark the applied research and development that will be needed for implementation at the sites. Synergies between the EMSP and other research programs are natural and should be exploited to their fullest extent. Collaborations with foreign countries with relevant HLW research activities should be encouraged. At a minimum, the EMSP should be aware of scientific results and research trends for HLW management in countries with similar problems. 3. Provide for contingencies. The EMSP should promote underlying science and technology that will support contingency approach- es to address unanticipated difficulties encountered in baseline processes. Some fraction of EMSP projects should support exploratory and innovative research involving non-conventional technologies, possibly leveraged from other disciplines. The pro- jects should represent a balanced range of research styles, from large-scale teams to single investigators. 4. Develop working relationships. EMSP i Investigators shou Id i nter- act with problem holders at the sites to learn about the nature of the problems to be solved. In return, problem holders might gain a better understanding of the scientific gaps underlying HLW problems. EMSP researchers could visit DOE sites regularly to learn more about specific issues. Conversely, EMSP could identi- fy "liaisons" among the problem holders at the sites to communi- cate with its investigators. The liaisons will not only have the greatest knowledge about the sites but will also be able to assist i n i ntegrati ng the resu Its of EMSP research i nto the long-term EM effort. 5. Prioritize objectives. The EMSP should prioritize the two research objectives of providing contingency approaches and improving process effectiveness, as follows. The EMSP should strive for a balanced portfolio addressing both already identified problems and future potential problems. The portfolio should have a pri- mary focus on identified problems that must be solved either for efficient HLW processing operations or to provide for contingen- cies. Characterization, separation, immobilization methods and processes are problem areas where EMSP research could improve operations and provide immediate support in case of E x e c u t i v e S u m m a r y

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interferences or disruptions to current HLW processing programs. At the same time, there should also be a consideration of poten- tial problems that could arise or become exacerbated in the future. Examples of recommended research to address future potential problems are the following: new or better separation techniques to remove bulk non-hazardous material from the HLW stream, methods to achieve higher waste loading in immo- bilized waste forms, and improvements in tank closure and near- field monitoring issues. The committee recognizes that the EMSP cannot address all of the recommended research areas equally in the next few years, nor can its portfolio acquire all the recommended program attributes immediately. The committee is also aware of DOE's commitments and of the difficul- ties in implementing changes, both from a technology and regulatory point of view. However, current plans to treat and dispose of HLW are fraught with technical uncertainties, and many of the planned treatment activities are first-of-a-kind efforts presenting enormous technical chal- lenges. Given the long-term duration of this planned clean-up effort, it is expected that new technologies will emerge and that greater scientif- ic understanding wil I be achieved in the next decades. Therefore, the EMSP is the ideal setting to develop truly innovative approaches for the management of HLW that could lead to scientific breakthroughs in the future. If a scientific breakthrough can help reduce risks, cleanup time, and costs, then regulations can be revised accordingly and obstacles to implementing changes at the sites can be removed. In this respect, the EMSP is a "small but vital element" to the long-term success of the EM . . . cleanup mission. H ~ G H - L E V E E W A S T E