Appendix B

Interim Report



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ALTERNATIVES FOR HIGH-LEVEL WASTE SALT PROCESSING AT THE SAVANNAH RIVER SITE Appendix B Interim Report

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ALTERNATIVES FOR HIGH-LEVEL WASTE SALT PROCESSING AT THE SAVANNAH RIVER SITE THE NATIONAL ACADEMIES Advisers to the Nation of Science, Engineering, and Medicine National Academy of Sciences National Academy of Engineering Institute of Medicine National Research Council Board on Radioactive Waste Management National Research Council October 14, 1999 Ernest J. Moniz Under Secretary U.S. Department of Energy Washington, D.C.20585 Dear Dr. Moniz: The National Research Council empaneled a committee 1 at your request 2to provide an independent technical review of alternatives for processing the high-level radioactive waste salt solutions at the Savannah River Site3. You requested that the National Research Council provide you with an interim report that identifies significant issues or problems with the processing alternatives before the Department of Energy (DOE) issues a draft environmental impact statement (EIS), which is planned for release in October 1999. The committee's interim report is provided in this letter. This report has been reviewed in accordance with the procedures of the National Research Council4 and reflects a consensus of the committee. The information used to develop this interim report was obtained from several sources. The committee reviewed published documents that describe the salt processing program at Savannah River and the screening process used to select alternative processing options5. The committee also held an information-gathering meeting on September 13-14, 1999 in Augusta, Georgia to receive briefings from DOE staff, Westinghouse Savannah River Company (WSRC) staff, and National Laboratory scientists6 on the alternative processing options and current and planned research and development (R&D) activities. The committee does not yet have enough information to fully address its statement of task7. However, based on the information gathered to date, the committee has reached several conclusions that it believes will be helpful to DOE in finalizing the draft EIS. These conclusions are described in the following paragraphs and are organized around the four bullets of the 1   Committee on Cesium Processing Alternatives for High-Level Waste at the Savannah River Site. The roster for this committee is given in Attachment A. 2   A copy of your letter of request to the National Research Council is given in Attachment B. 3   An overview of the high-level waste program and the alternative processing options is provided in Attachment C. 4   The list of report reviewers is provided in Attachment D. 5   A list of documents received by the committee is provided in Attachment E. 6   See Attachment F for a list of the presentations and personnel involved in the committee 's first information-gathering meeting. 7   The committee's statement of task is given in Attachment G.

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ALTERNATIVES FOR HIGH-LEVEL WASTE SALT PROCESSING AT THE SAVANNAH RIVER SITE committee's statement of task. The committee also offers several recommendations in the concluding paragraphs of this report. Task 1: Was the process used to screen the alternatives technically sound and did its application result in the selection of appropriate preferred alternatives? The screening process (see Attachment C) to identify cesium removal alternatives was undertaken by the Salt Disposition Systems Engineering Team under the sponsorship of WSRC. This team was comprised of 10 members with expertise in science and engineering, operations, waste processing, and safety and regulations. The team interacted with experts throughout the DOE complex and undertook a historical review and literature survey to identify about 140 possible processes that could potentially be used to process the high-level waste salt solutions at Savannah River. These processes were grouped into an “initial list” of 18 alternative processing options, which were subsequently screened using a multi-attribute analysis to obtain a “short list ” of four alternative processing options: small tank tetraphenylborate (TPB) precipitation, caustic side solvent extraction, direct disposal in grout, and crystalline silicotitanate (CST) ion exchange. This screening process has been reviewed by numerous groups, including two expert teams assembled by DOE, and has received generally favorable marks. The committee has not yet had an opportunity to perform a detailed examination of this screening process. Therefore, a full response to this part of the task statement must be deferred to the committee 's final report. However, the committee does have one comment at this time relative to this question: Given the ambitious schedule that the Department has defined for selecting and implementing a process for treating the cesium-bearing salt solutions at Savannah River —a draft EIS is to be issued in October 1999, a Record of Decision (ROD) is to be made in spring 2000, and the selected option is planned to be implemented no later than 20088—a negative answer by the committee to this statement-of-task question could delay Savannah River's plans to process this waste and could markedly increase the total cost of the processing operations9. This question could have been asked earlier to permit more meaningful input into the screening process. The storage of high-level liquid wastes in underground tanks, some of which are several decades old, represents a potential hazard to workers and the environment at the site and a continuing burden on U.S. taxpayers. The committee shares the Department's (and WSRC's) sense of urgency to address this hazard by removing and treating the waste as soon as safe and practical. Consequently, in addressing this part of its statement of task, the committee will be asking the question “Did the screening process lead to the identification of technically sound options for processing the waste?” The committee's initial impression is that the screening process did result in the identification of several potentially viable alternative processing options. The committee will perform a more detailed review of the overall screening process during the remainder of this study. 8   It is not clear to the committee how this process will be implemented. The committee learned that DOE will likely issue a request for proposals (RFP) from industry to implement one of these options. However, DOE Savannah River staff were unable to provide the committee with any details on this RFP. 9   According to WSRC staff, the operating costs of the high-level waste system at Savannah River are about $400 million per year.

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ALTERNATIVES FOR HIGH-LEVEL WASTE SALT PROCESSING AT THE SAVANNAH RIVER SITE Task 2: Was an appropriately comprehensive set of cesium partitioning alternativesidentified, and are there other alternatives that should be explored? Given the compressed schedule for producing this interim report, the committee has focused most of its attention on the four options that were included in the “short list” of alternatives discussed in Attachment C. The committee has not yet had the opportunity to perform a detailed review of the full list of alternatives for processing the salt solutions that were identified by WSRC through its alternatives screening process. The committee did, however, perform a cursory examination of the list of 18 alternative processing options developed by the Salt Disposition Systems Engineering Team. These options included the approaches that were known to committee members to be useful for processing cesium-bearing alkaline salt solutions. Thus, the committee's initial impression is that no major processing options were overlooked in the screening process. However, the committee will perform a more thorough review of alternative processing options for the final report. Task 3: Are there significant barriers to the implementation of any of the preferred alternatives, taking into account their state of development and their ability to be integrated intothe existing Savannah River Site HLW system? The committee examined the four alternatives that passed the multi-attribute screening process (i.e., small tank TPB precipitation, caustic side solvent extraction, direct disposal in grout, and CST ion exchange) to assess whether there were significant barriers to implementation. The committee concluded that any of these four alternatives could probably be made to work if enough time and funding were devoted to overcoming the remaining scientific, technical, and regulatory hurdles. However, the time, cost, and technical risk of implementation of each option could vary widely because all are at different states of development. A preliminary summary of the scientific, technical, and regulatory hurdles for each option is summarized below. For the small tank TPB precipitation, caustic side solvent extraction, and CST ion exchange processing options, the remaining hurdles are both scientific and technical in nature and include the need for obtaining a better understanding of basic chemical processes. The direct disposal in grout option appears to be technically mature but faces significant regulatory hurdles. Small tank TPB precipitation. The small tank TPB precipitation option was developed by WSRC staff to “engineer around” the benzene production problem discovered during large tank in-tank precipitation (ITP) operations (see Attachment C). The development of this option was based on the belief by WSRC staff that they adequately understood the basic chemistry and process phenomena that led to the earlier difficulties with the ITP process. This new option was designed both to reduce the production of benzene during processing and storage of the waste and to reduce benzene explosion hazards. As currently designed, the process will employ 57,000 liter (15,000 gallon) stainless steel reaction vessels and short processing and storage times that, taken together, allow less TPB to be used in processing and reduces the time available for radiolytic and catalytic decomposition of the TPB to form benzene. Additionally, the reaction vessels are designed to maintain a positive pressure so that the head (open) space can be blanketed with a nitrogen atmosphere to reduce explosion hazards. This design also allows for the capture and treatment, if desired, of benzene evolved during processing operations.

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ALTERNATIVES FOR HIGH-LEVEL WASTE SALT PROCESSING AT THE SAVANNAH RIVER SITE Although a positive pressure would allow the reaction vessels to be blanketed with inert gas, this design could promote the release of benzene and possibly of radionuclides to the environment should a leak occur. The standard practice in biological and radiological facilities is to maintain a negative pressure relative to the atmosphere so that leaks result in inflows rather than outflows. The use of positive pressure reaction vessels for this process may require additional containment and safety procedures to minimize hazards should leaks occur. As noted in Attachment C, the current design for this process includes provisions for secondary containment. Small tank TPB precipitation appears to be the alternative preferred by WSRC for processing the cesium-bearing salt solutions at Savannah River. WSRC has over 16 years of experience with TPB and has developed a rudimentary understanding of the cesium precipitation process through R&D work done during ITP development and operations. This option appears to have the most advanced R&D and engineering development of all of the options except direct disposal in grout. Nevertheless, the committee believes that additional R&D is required to demonstrate that this option could be successfully implemented to treat the cesium-bearing salt solutions at Savannah River. WSRC lacks an adequate understanding of the chemistry underlying the TPB decomposition process and the catalysts and catalytic reactions responsible for benzene generation. In place of such an understanding, WSRC appears to be focusing on an engineering-design solution based on untested assumptions about maximum likely benzene production and catalytic pathways. The WSRC staff who briefed the committee indicated that WSRC has a limited understanding of the mechanisms of catalysis responsible for benzene production and also that WSRC has collected little experimental data on the sources or roles of likely catalysts such as soluble transition metal complexes and dispersed palladium metal particles. The committee believes that WSRC must obtain a better understanding of the chemistry of the TPB decomposition process before this option could be selected and deployed to treat the cesium-bearing salt solutions at Savannah River. The extreme complexity of the chemical system in the alkaline tank waste at Savannah River—which consists of more than 35 elements in a variety of phases and chemical compounds, including solid and liquid complexes—increases the likelihood that significant and unanticipated technical problems will be encountered unless benzene generation and release processes are better understood.10 The committee believes that it would be advantageous from both time-efficiency and cost-efficiency standpoints to undertake this R&D work before this process is selected and deployed. The alternative—namely, to proceed with deployment immediately and engineer around the gaps in chemistry knowledge—carries a high technical risk and could result in a repeat of the ITP failure. CST ion exchange. Crystalline silicotitanate is an inorganic material that has a high selectivity for cesium over other alkali metals and is thus a potentially useful ion-exchange material for cesium removal from alkaline tank waste. Although ion exchange for cesium removal is a well known technique, CST ion exchange has never been used in a large-scale nuclear waste application, and CST has never been manufactured in commercial-scale 10   This conclusion was previously reported in Recommendation 96-1 from the Defense Nuclear Facilities Safety Board.

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ALTERNATIVES FOR HIGH-LEVEL WASTE SALT PROCESSING AT THE SAVANNAH RIVER SITE quantities. Consequently, additional R&D will be required to demonstrate this technology for cesium removal from tank waste at Savannah River. The committee learned during its information-gathering meeting that WSRC has discovered two significant and potentially insurmountable problems with the CST ion exchange process. First, WSRC staff discovered that cesium is desorbed (i.e., released) from CST at elevated temperatures —this phenomenon was observed to occur at temperatures of 50 °C and probably operates (albeit at reduced rates) at lower temperatures, including at the planned 25 °C to 30 °C processing temperatures. This desorption process appears to be irreversible—that is, once cesium is released, it is not reabsorbed once temperatures are lowered. Second, CST appears to react with constituents in the alkaline tank waste to produce new solid phases that may be capable of plugging the ion exchange columns. Because either of these problems could lead to extended and costly shutdowns of tank waste processing operations at the site if this processing option were to be implemented, these problems must be resolved before this process can be deployed. WSRC staff do not yet understand the chemical processes responsible for either of these phenomena, although they speculated to the committee that the tank waste reactions with CST may be due to manufacturing impurities. Additional R&D work is required to address these problems. Caustic side solvent extraction. Solvent extraction is a mature and widely implemented technology for separating uranium and plutonium from acidic solutions (e.g., in the PUREX process), but it has never been used to treat highly alkaline wastes like the cesium-bearing salt solutions at Savannah River. There is a great deal of process experience with solvent extraction across the DOE complex, including at Savannah River. Furthermore, this “all liquid” process is highly compatible with the existing high-level waste system at the site. The process would produce a liquid cesium-bearing solution that could be sent directly to the Defense Waste Processing Plant without additional processing steps. The caustic side solvent extraction process has been developed by scientists at the Oak Ridge National Laboratory and appears to the committee to be a potential “break-through” technology. However, caustic side solvent extraction is at an immature stage of development relative to the other three options and, although there do not appear to be any insurmountable problems with this process, additional R&D will be required to demonstrate that it could be successfully implemented to treat the cesium-bearing salt solutions at Savannah River. In particular, additional R&D needs to be done to obtain performance data under real-life conditions —for example, R&D to determine the radiation stability of the solvent system (including the stability of the cesium chelator, diluent, and modifier; see Attachment C), the ability to scrub and recycle the expensive solvents, and the ability to mitigate contaminant formation during processing. It may be possible to answer these questions relatively quickly in a small-scale pilot study under process conditions. Additionally, the cesium chelator for this system has never been manufactured in commercial quantities, so a significant scale-up of manufacturing capabilities would have to be demonstrated to ensure that reagent-grade material could be produced in quantities required for processing the cesium-bearing salt solutions at Savannah River. Direct disposal in grout. This process is very similar to the so-called “saltstone process” that was to have been used to dispose of the salt solutions from the ITP process. As noted previously, this is a very mature technology and has already been demonstrated at the site for

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ALTERNATIVES FOR HIGH-LEVEL WASTE SALT PROCESSING AT THE SAVANNAH RIVER SITE less radioactive salt solutions. Some additional R&D work may be needed to develop grout that will retain cesium to satisfy regulatory requirements. In general, cesium sorption on cementitious material like Portland cement is lower than virtually all other radionuclides. Given the large inventory of cesium that would be disposed of in grout under this option, the demonstration of compliance under applicable regulations (see the next paragraph) may require the development of grout formulations with a higher cesium sorption coefficient. Additionally, engineering design would be required to develop a facility that could be remotely operated and maintained to protect workers from high radiation fields. However, the required R&D and engineering work appear to be relatively straightforward, and the committee knows of no insurmountable problems with this option. The major hurdles with the direct grouting option are regulatory in nature11. The process would be intended to produce Class C low-level waste that would be disposed of at Savannah River in a land-disposal facility (see Attachment C). To be eligible for such onsite disposal, the cesium-bearing salt solutions would have to be declared to be “incidental waste” under DOE Order 435.1 12. To be declared as incidental waste, DOE would have to demonstrate that the wastes “Have been processed, or will be processed, to remove key radionuclides to the maximum extent that is technically and economically practical” and that the waste “Will be managed to meet the safety requirements comparable to the performance objectives set out in 10 CFR Part 61, Subpart C ....” The latter criterion would require DOE to undertake a detailed performance assessment analysis to demonstrate that disposal of the grout onsite would meet the U.S. Nuclear Regulatory Commission's (USNRC's) radionuclide release criteria for land disposal facilities as well as intruder barrier requirements for Class C waste13. However, DOE would not be required to seek formal USNRC approval for this assessment. Additionally, DOE would likely be required to seek permits from South Carolina and/or the U.S. Environmental Protection Agency to operate this facility because it contains other regulated wastes14. It is not clear to the committee whether resolution of these regulatory issues would be possible under the current schedule constraints. “Front-end” actinide and strontium removal. As noted in Attachment C, the four cesium removal options discussed above are designed to process waste streams that have been treated to remove actinides and strontium. Savannah River plans to remove these radionuclides at the “front end” of processing operations by treating the waste with monosodium titanate (MST), which sorbs actinides and strontium. To the committee 's knowledge, this process has not been used elsewhere to process tank waste and therefore would be a first-of-its-kind implementation, subject to the usual problems inherent with such applications. In fact, there do appear to be some remaining technical questions that will need to be resolved before this process could be implemented successfully at Savannah River, and the committee learned at its information-gathering meeting that WSRC appears to be pursuing these questions vigorously. In particular, MST reaction kinetics are not well understood—work 11   Public acceptance may also be a significant barrier with this option, because it will entail the shallow-land disposal of isotopes that will be highly radioactive for hundreds to thousands of years. 12   DOE O 435.1, Radioactive Waste Management, Approved July 9, 1999. 13   Additionally, it is unclear whether the regulations 10 CFR Part 61 can even be reasonably applied to this waste—the amount of cesium to be disposed of in the saltstone would be about a thousand times larger than what was considered in the EIS analyses for Part 61. 14   The Saltstone Facility at Savannah River, for example, operates under an permit for a landfill disposal site, even though it contains Class A levels of radioactive waste.

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ALTERNATIVES FOR HIGH-LEVEL WASTE SALT PROCESSING AT THE SAVANNAH RIVER SITE by WSRC staff suggests that actinide and strontium reactions with the MST may proceed more slowly than anticipated, thus requiring higher MST concentrations to achieve the required throughputs. However, titanium (a component of the MST) is incompatible with borosilicate glass, so there are limits on the amount of MST that could be used in processing operations. There are some indications that these limits could be approached or exceeded to meet actinide removal requirements for the planned disposal of the residual salt solutions in the saltstone facility. Recent work by WSRC suggests that waste dilution and waste blending (i.e., combining waste from different tanks) may be required to meet the performance requirements for this process. This additional processing will add time, cost, and technical risk to waste processing operations. To the committee's knowledge, WSRC is not considering any alternative processes for removal of actinides and strontium from the tank waste. Thus, this process must work as intended for the high-level waste processing program to succeed. Additional R&D work, especially on reaction kinetics, will be required to demonstrate that this process can meet both performance and regulatory requirements. If this work identifies any insurmountable problems, then WSRC will have to find alternative processes for removing these radionuclides. The committee's initial impression is that this process can be made to work, but WSRC must get on with the pilot-scale testing to demonstrate that this process will achieve the needed throughput. Task 4: Are the planned R&D activities, including pilot-scale testing, adequate to support implementation of a single preferred alternative? A consideration of planned R&D activities will be a major component of the committee's future work, and at this point in the study the committee only has enough information to make two general observations about ongoing and planned R&D activities. The committee's first observation is that R&D resource allocations for the four alternative processing options have been markedly inequitable. In FY99, R&D funding for the four alternative processing options totaled about $11 million —about $4.4 million for small tank TPB, $6.0 million for CST ion exchange, $0.3 million for caustic side solvent extraction, and $0.3 million for direct disposal in grout. Funding for the R&D work on solvent extraction was provided not by WSRC, but through DOE's Office of Science and Technology. Part of this funding inequity can be traced to the late 1998 decision by WSRC to pursue only one primary (small tank TPB) and one backup (CST ion exchange) option for processing the cesium-bearing salt solutions. However, this funding disparity appears to be primarily responsible for the different levels of technical maturities of the four processing options, independent of their likelihoods of success. The committee got the sense from its discussions with WSRC and DOE staff at the information-gathering meeting that WSRC did not appear to be serious about pursuing R&D on any option but small tank TPB precipitation. Second, WSRC does not appear to have a well thought out R&D plan for the small tank TPB precipitation and CST ion exchange options15. There are no written R&D plans for either of these options. Moreover, in response to committee questions, the WSRC and DOE participants at the committee's information-gathering meeting were unable to describe an R&D scope for these options that would resolve the outstanding issues. Rather, the committee was presented with lists of research needs, but these needs were not prioritized. The committee was puzzled 15   The committee learned at its information-gathering meeting that WSRC has discontinued all R&D work on the caustic side solvent extraction or direct grouting options.

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ALTERNATIVES FOR HIGH-LEVEL WASTE SALT PROCESSING AT THE SAVANNAH RIVER SITE by the lack of program planning and pursuit of important uncertainties. Even for the WSRC-favored small tank TPB processing option, R&D planning and establishment of priorities apparently have not been done. Conclusions and Recommendations. As noted previously, DOE plans to release a draft EIS in October 1999 that will be used as a basis for a spring 2000 ROD that selects a single processing option. WSRC is now in the process of preparing the draft EIS, and the committee was told by WSRC staff that the draft EIS would likely recommend the selection of small tank TPB precipitation as the preferred processing option. Based on the committee 's initial review of the processing options, it is not clear that the small tank TPB precipitation option favored by WSRC will necessarily be the committee's preferred choice after the committee's detailed review is completed. Although the committee recognizes the need for selecting and implementing an option as soon as possible—both because of the high ($400 million per year) operating costs for the high-level waste system at Savannah River and because of the potential hazard posed by the aging waste tanks—the committee concludes from the preceding discussion that there are significant technical or regulatory risks in selecting any of the four options, including the small tank TPB precipitation option that is apparently preferred by WSRC. Therefore, the committee recommends that WSRC pursue vigorously one primary and several backupoptions forprocessing the cesium-bearing salt solutions at Savannah River until the remainingtechnical and regulatory issuesare resolved. This may require that DOE delaythe issuanceof the planned EIS and ROD, or that DOE adopt a phased-decision approach inthe EIS and RODthat would allow several processing options to be pursued in parallel until aclearly superior option is identified. DOE and WSRC should enlist the help of specialists in industry, National Laboratories, universities, and other federal agencies toresolve these scientific, technical, and regulatory issues. To meet the ambitious time schedule for selecting and implementing any processing option, the committee concludes that DOE and WSRC will have to develop and implement a sharply focused R&D program to resolve the open issues. To this end, the committee offers the following recommendations: Actinide and Strontium Removal. WSRC should continue its efforts to address the remaining technical questions concerning reaction kinetics of the MST process for removal of actinides and strontium from the tank wastes and get on to pilot-scale testing as soon as possible. Small Tank TPB Precipitation. WSRC should develop and implement a vigorous, well-planned, and adequately funded R&D program to address the remaining scientific hurdles with the small tank TPB precipitation. R&D should, at a minimum, address TPBdecomposition process(es) and the envelope of catalysts and catalytic reactions responsible for benzene generation. CST Ion Exchange. A vigorous, well planned, and adequately funded R&D effort should be undertaken to address the remaining scientific hurdles with the CST ion exchange option. This R&D should address, at a minimum, the cesium desorption process and reactions between CST and the alkaline waste. This effort also should bepursued independently of WSRC, which does not have the needed R&D expertise on site.

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ALTERNATIVES FOR HIGH-LEVEL WASTE SALT PROCESSING AT THE SAVANNAH RIVER SITE Direct Disposal in Grout. WSRC and DOE should undertake a vigorous program to determine the regulatory acceptability of the direct grout option through discussions with relevant staff at DOE, the U.S. Nuclear Regulatory Commission, the U.S. Environmental Protection Agency, and South Carolina Department of Health and Environmental Control. These discussions should focus on the likely feasibility of demonstrating compliance with regulations and the strategy needed to achieve regulatory approvals. Caustic Side Solvent Extraction. A vigorous, well planned, and adequately funded R&D effort should be undertaken to address the remaining scientific and technical hurdles with the caustic side solvent extraction option. This R&D should address, at a minimum, the stability of the solvent system in radiation fields, the ability to scrub and recycle the solvents, the ability to mitigate contaminant formation during processing, and the ability to produce the chelating agent in quantities necessary for this application. If started immediately, it may be possible to complete this work by next spring, in time for the final EIS. This effort should be pursued independently of WSRC, which does not have the needed R&D expertise on site for this particular solvent extraction system. The committee's next information-gathering meeting will be held in Augusta, Georgia on November 21-22, 1999, and a major part of that meeting will be devoted to further discussions of the R&D needed to resolve the issues identified in this report. The committee plans to ask Department and WSRC staff to report on their future R&D plans to resolve the open issues. The committee will provide a critique of these plans in its final report, which it hopes to issue by April 2000. Sincerely yours, Milt Levenson, Chair Greg Choppin, Vice Chair

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ALTERNATIVES FOR HIGH-LEVEL WASTE SALT PROCESSING AT THE SAVANNAH RIVER SITE ATTACHMENT A COMMITTEE ON CESIUM PROCESSING ALTERNATIVES FOR HIGH-LEVEL WASTE AT THE SAVANNAH RIVER SITE MILTON LEVENSON,Chair,Bechtel International (retired), Menlo Park, California GREGORY CHOPPIN,Vice-Chair,Florida State University, Tallahassee JOHN BERCAW, California Institute of Technology, Pasadena DARYLE BUSCH, University of Kansas, Lawrence TERESA FRYBERGER, Brookhaven National Laboratory, Upton, New York GEORGE KELLER, Union Carbide Corporation (retired), South Charleston, West Virginia MATTHEW KOZAK, Monitor Scientific, LLC, Denver, Colorado ALFRED SATTELBERGER, Los Alamos National Laboratory, Los Alamos, New Mexico BARRY SCHEETZ, The Pennsylvania State University, University Park MARTIN STEINDLER, Argonne National Laboratory (retired), Downers Grove, Illinois NRC Staff KEVIN CROWLEY,Study Director DOUGLAS RABER, Director, Board on Chemical Sciences and Technology ROBERT ANDREWS, Senior Staff Officer, Board on Radioactive Waste Management JOHN WILEY, Senior Staff Officer, Board on Radioactive Waste Management LATRICIA BAILEY, Project Assistant MATTHEW BAXTER-PARROTT, Project Assistant

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ALTERNATIVES FOR HIGH-LEVEL WASTE SALT PROCESSING AT THE SAVANNAH RIVER SITE waste through evaporators to remove excess water. After processing, the waste was pumped back into the tanks, where it cooled and crystallized. Radionuclide Immobilization. The Defense Waste Processing Facility (DWPF) was constructed to immobilize radioactive waste in borosilicate glass for eventual shipment to and disposal in a geological repository. The glass-making process is referred to as vitrification. This glass is produced by combining the processed high-level waste (the processing operations are discussed below) with specially formulated glass frit and melting the mixture at about 1150 °C. The molten glass is then poured into cylindrical stainless steel canisters, allowed to cool, and sealed. The DWPF canisters are about 60 centimeters (2 feet) in diameter and about 300 centimeters (10 feet) in length and contain about 1,800 kilograms (4,000 pounds) of glass. About 700 canisters have been produced to date, and Savannah River estimates that a total of about 6,000 canisters will be produced by 2026, when the tank waste processing program is planned to be completed. These canisters will be stored at the site until a repository is opened and ready to receive them. Extended Sludge Processing is used to prepare the sludge portion of the tank waste for processing into glass. The sludge is removed from the tanks by hydraulic slurrying, and it is then washed to remove aluminum and soluble salts, both of which can interfere with the glass-making process. The washed sludge is transferred to the DWPF for further processing before being incorporated into glass. Salt Processing will be used to remove radionuclides from the HLW salt for eventual processing into glass. The salt will be redissolved and transferred out of the tanks. It will then be mixed with a sorbent to remove any remaining actinides (mainly uranium and plutonium) and strontium. The currently planned sorbent is monosodium titanate (MST). The solution will then be subjected to another (and as-yet undetermined) process to remove cesium. This processing step is the focus of the present study. The separated actinides, strontium, and cesium will be washed to remove soluble salts and sent to the DWPF for immobilization. Salt Disposal. A variety of secondary waste streams are formed during the processing operations described above. Some of these waste streams are recycled back to the tanks, other wastes are recycled within the various processing operations, and yet other wastes are treated and released to the environment. Most notably, the residual salt solutions (i.e., the solutions remaining after actinide and cesium removal) will be disposed of onsite in a waste form known as saltstone. The residual solutions are classified as “incidental waste” from the processing of high-level waste. Saltstone is created by mixing the residual salt solutions with fly ash, slag, and Portland cement to create a grout slurry. This slurry is then poured into concrete vaults, where it cures and is eventually covered with soil. The saltstone also contains some radionuclides, for example technetium-99 and tin-126. The Saltstone Production Facility is permitted by the South Carolina Department of Health and Environmental Control as waste water treatment facility. The saltstone vaults are designed as a controlled release landfill disposal site. The operating permit limits the average concentrations of radioactive contaminants to the limits specified by the U.S. Nuclear Regulatory Commission for Class A Waste17. In the direct disposal in grout processing option, which is discussed below, cesium also would be immobilized in the grout. At present, Savannah River is processing sludge from the tanks to make glass at the DWPF, and it has a wastewater permit from South Carolina to produce saltstone. The current 17   As provided in 10 CFR Part 61.

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ALTERNATIVES FOR HIGH-LEVEL WASTE SALT PROCESSING AT THE SAVANNAH RIVER SITE high-level waste processing schedule calls for the salt solutions to be processed to recover the actinides, strontium, and cesium beginning about 2008. The 2008 schedule has been proposed to maintain operations at the DWPF and to ensure that there is sufficient space in the tank farms to continue operations at the site18. To meet this schedule, however, Savannah River must develop, test, and implement a process for removing actinides, strontium, and cesium from the salt in the tanks. A brief review of Savannah River's efforts to develop this process is provided in the next section. SALT PROCESSING OPTIONS The objective of the salt processing step is to reduce the volume of salt waste to be immobilized in glass and, consequently, to reduce the time and cost of the immobilization operations. There are approximately 120 million liters (31 million gallons) of HLW salt in the F and H Tank Farms, but Savannah River estimates that this salt could be processed to yield about 11 million liters (3 million gallons) of actinide- and cesium-bearing solutions or precipitates for vitrification, roughly a ten-fold reduction in volume. At present, Savannah River plans to remove actinides, strontium, and cesium from the salt solutions in two processing steps. As noted previously, actinides and strontium will be removed by mixing the salt solutions with MST. The resulting reaction leads to the sorption of actinides and strontium. The product of this reaction could be removed from the salt solutions by filtration for subsequent processing and immobilization. This process has been demonstrated in conjunction with the in tank precipitation program, which is discussed below, but additional R&D is under way to resolve some remaining problems. The removal of cesium from the salt solutions is potentially feasible through a number of processes, for example, precipitation reactions, ion exchange, or solvent extraction. In the 1980's, Savannah River developed a process for removing cesium from salt solutions through a precipitation reaction involving sodium tetraphenylborate (TPB): The Savannah River Site refers to this process as in-tank precipitation (ITP). The TPB was to be added directly to a large waste tank to produce a cesium-bearing precipitate, which could then be processed like tank sludge. Savannah River undertook an ITP pilot project in 1983 to demonstrate proof of principle. The process removed cesium from the salt solution, but it also resulted in the generation of benzene from radiolytic reactions and possibly from catalytic reactions with trace metals in the waste, in particular, palladium and copper. In September 1995, Savannah River initiated ITP processing operations in a tank that contained about 1.7 million liters (450,000 gallons) of salt solutions. The operations were halted after about three months because of higher-than-expected rates of benzene generation. Savannah River staff then initiated a research program to understand the mechanisms of benzene generation and release, and staff also considered possible design changes so that the benzene, which is highly flammable, could be handled safely during processing operations. In 1996, the Defense Nuclear Facility Safety Board (DFNSB) issued Recommendation 96-1, which urged DOE to halt all further testing and to begin an investigative effort to understand the mechanisms of benzene formation and release (DNFSB, 1996): 18   At present, the F and H Tank Farms have about 2.6 million liters (700,000 gallons) of empty space.

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ALTERNATIVES FOR HIGH-LEVEL WASTE SALT PROCESSING AT THE SAVANNAH RIVER SITE The additional investigative effort should include further work to (a) uncover thereason for the apparent decomposition of precipitated TPB in the anomalousexperiment, (b) identify the important catalysts that will be encountered in thecourse of ITP, and develop quantitative understanding of the action of thesecatalysts, (c) establish, convincingly, the chemical and physical mechanisms that determine how and to what extent benzene is retained in the waste slurry, why it is released during mixing pump operation, and any additional mechanisms thatmight lead to rapid release of benzene, and (d) affirm the adequacy of existingsafety measures or devise such additions as may be needed. Investigations by Savannah River in 1997 uncovered the possible role of metal catalysts in the benzene formation process. However, Savannah River concluded that both safety and production requirements could not be met, which led to the suspension of operations altogether in early 1998. At the time of suspension, Savannah River had spent $489 million to develop and implement the ITP process. In March 1998, the Savannah River contractor, Westinghouse Savannah River Company (WSRC), formed a systems engineering team to identify alternatives to the ITP process for separating cesium. This team was comprised of 10 members with expertise in science and engineering, operations, waste processing, and safety and regulations. The team interacted with experts throughout the DOE complex and undertook a historical review and literature survey to identify about 140 processes that could potentially be used to separate cesium from the salt solutions. These processes were grouped into an “initial list” of 18 alternative processing options, which were subsequently screened using a multi-attribute analysis to obtain a “short list” of four alternative processing options: (1) small tank tetraphenylborate (TPB) precipitation, (2) crystalline silicotitanate (CST) ion exchange, (3) caustic side solvent extraction, and (4) direct disposal in grout. Small tank TPB precipitation is carried out in specially designed processing vessels to control benzene generation. TPB is the same precipitating agent used in the ITP process. The process allows for closer temperature control and faster cycling times to reduce the generation of benzene and improved agitation of the liquid to facilitate benzene removal. The process is also designed with secondary containment and positive pressure control so that the processing vessels could be blanketed with nitrogen to reduce explosion hazards and facilitate benzene removal. The process generates a precipitate slurry that will be transferred to the DWPF. CST ion exchange is based on conventional ion exchange concepts but utilizes a non-elutable inorganic solid that has a high selectivity for cesium over other alkali metals. The waste would be processed by pumping it through columns packed with this material. As the salt solutions pass through the CST, cesium is trapped. Once loaded with cesium, the CST would then be sent directly to the DWPF for further treatment and vitrification. Although ion exchange for cesium removal has been used in the nuclear industry, CST ion exchange has never been used in a large-scale waste application, and CST has never been manufactured in commercial-scale quantities. Caustic side solvent extraction also is based on conventional solvent extraction concepts, such as those used in the widely known PUREX process to separate U and Pu from dissolved irradiated targets. The process involves the mixing and subsequent separation of two immiscible feed streams: an aqueous solution containing the radionuclide to be extracted and

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ALTERNATIVES FOR HIGH-LEVEL WASTE SALT PROCESSING AT THE SAVANNAH RIVER SITE an organic solvent containing a chelating agent (also known as the extractant) for that radionuclide. Other chemicals may be added to improve the extraction efficiency or to inhibit the formation of undesirable reaction products. The two feed streams are pumped through a series of centrifugal contactors, where they are mixed and subsequently separated on the basis of density. During the mixing process, the radionuclide is chelated by the extractant, which results in its transfer from the aqueous feed stream to the organic feed stream. The radionuclide is then recovered through a series of stripping steps, and the organic solvent is recycled back into the front end of the extraction process. For caustic side solvent extraction of cesium, the organic solvent consists of a diluent (Isopar®-L, a mixture of branched alkanes), modifier (Cs-3, a fluorinated alcohol that prevents the formation of additional chemical phases), and extractant (BOB Calix19 , a calixarene crown ether). When the salt solution is mixed with the organic solvent, cesium ions are complexed by the extractant (“L” in the following reaction) to form a cesium nitrate ion pair: This ion pair is subsequently extracted into the organic solvent and then is recovered by separation of the aqueous stream from the solvent stream followed by a series of acid washing steps. The Isopar ®-L and BOB Calix are recycled, and the cesium nitrate liquid can be sent directly to the DWPF without further processing. Although solvent extraction is a mature technology for separating radionuclides from acid solutions (acid side solvent extraction), solvent extraction of cesium from highly alkaline solutions has never been demonstrated on an industrial scale, and the chelator (BOB Calix) has never been produced in commercial quantities. It is currently being manufactured in small quantities and is priced at about $500 per gram. The price could presumably be reduced significantly once production was scaled up. Direct disposal in grout is very similar to the saltstone process that was to have been used to immobilize the residual salt solutions from ITP operations. After removal of the actinides and strontium with MST, the cesium-bearing salt solutions would be mixed with fly ash, slag, and Portland Cement and poured into concrete vaults on the site. About 520,000 cubic meters (18 million cubic feet) of grout would be produced. This waste would meet the limits of Class C low-level waste20. Savannah River performed a flowsheet analysis, risk analysis, and lifecycle cost analysis of the four alternatives in late 1998. Based on this analysis, WSRC recommended small tank TPB as the preferred alternative and CST ion exchange as the backup alternative. However, DOE's analysis of the information concluded that additional research was needed before a preferred alternative could be selected. Additional R&D needs were identified for each of these alternatives, and work to address these needs was underway as the committee began this study. 19   Formally, Calix[4]arene-bis(t-octylbenzo-crown-6). 20   The total cesium-137 activity of the grout would be about 120 million curies.

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ALTERNATIVES FOR HIGH-LEVEL WASTE SALT PROCESSING AT THE SAVANNAH RIVER SITE ATTACHMENT D LIST OF REPORT REVIEWERS This letter report has been reviewed in draft form by individuals chosen for their diverse perspectives and technical expertise, in accordance with procedures approved by the NRC's Report Review Committee. The purpose of this independent review is to provide candid and critical comments that will assist the institution in making the published report as sound as possible and to ensure that the report meets institutional standards for objectivity, evidence, and responsiveness to the study charge. The review comments and draft manuscript remain confidential to protect the integrity of the deliberative process. We wish to thank the following individuals for their participation in the review of this report: Andrew Campbell, U.S. Nuclear Regulatory Commission Rodney Ewing, University of Michigan Mary Good, Venture Capital Investors, LLC Michael Kavanaugh, Malcolm-Pirnie, Inc. Tobin Marks, Northwestern University Royce Murray, University of North Carolina Kenneth Raymond, University of California, Berkeley Robin Rogers, University of Alabama Vincent Van Brunt, University of South Carolina While the individuals listed above have provided constructive comments and suggestions, it must be emphasized that responsibility for the final content of this report rests entirely with the authoring committee and the institution.

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ALTERNATIVES FOR HIGH-LEVEL WASTE SALT PROCESSING AT THE SAVANNAH RIVER SITE ATTACHMENT E DOCUMENTS RECEIVED BY THE COMMITTEE Case, Joel. 1998. Memorandum to James Owendoff Regarding the Savannah River High Level Waste Salt Disposition Independent Project Evaluation Team Review And Assessment (OPE-HLW-99-005). December 26. Defense Nuclear Facilities Safety Board. 1996. Recommendation 96-1 to the Secretary of Energy pursuant to 42 U.S.C. 2286(a) (5) Atomic Energy Act of 1954, as amended. August 14. Department of Energy. 1998. Savannah River Review Team Final Report on the High Level Waste Salt Disposition Alternatives Evaluation. December. General Accounting Office. 1999. Nuclear Waste: Process to Remove Radioactive Waste from Savannah River Tanks Fails to Work. GAO/RCED-99-69. April. Independent Evaluation Team. 1998. Independent Assessment of the Savannah River Site High-Level Waste Salt Disposition Alternatives Evaluation. DOE/ID-10672. December. McCullough, J.W. 1999. Department of Energy, Savannah River Management Plan for Phase IV of the High Level Waste Salt Disposition Alternatives Evaluation. April. McCullough, J.W., and P.C. Suggs. 1998. Department of Energy, Savannah River Review Team Report on the HLW Salt Disposition Alternatives. July 28. Papouchado, L., E. Kosiancic, J. Carlson, and P. Suggs. 1998. Trip Report—Site Visited: Hanford Site visited May 7 and 8. May 22. Papouchado, L., E. Kosiancic, J. Carlson, and P. Suggs. 1998. Trip Report—Sites Visited: Willowcreek (INEEL), ICPP (INEEL). May 11. Perella, V. 1998. Memorandum to Steve Piccolo Regarding the Results of the HLW Salt Disposition Systems Engineering Team, Phase II: Criteria Selection and Weighting For HLW Salt Disposition “Initial List” Down Selection. June 9. Piccolo, Steve. 1998. Candidate Selections for the HLW Salt Disposition Systems Engineering Team. Revision 0. March 25. Piccolo, Steve. 1998. Candidate Selections for the HLW Salt Disposition Systems Engineering Team. Revision 1. September 15. Piccolo, S., K. Reuter, P. Hudson, J. Barnes, and B. Spader. 1998. Trip Report—Site Visited: Sellafield. June 2. Poirier, M.R. 1998. Memorandum to Steve Piccolo Regarding the Evaluation of Potential Cesium Removal Technologies. SRT-WPT-98-008. June 5.

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ALTERNATIVES FOR HIGH-LEVEL WASTE SALT PROCESSING AT THE SAVANNAH RIVER SITE Poirier, M.R., R. D. Hunt, and C. Carlson. 1998. Identification of Cesium Removal Technologies. WSRC-TR-98-00181. May 29. Rudy, Greg. 1998. Memorandum to James Owendoff Regarding Program Plan for the Evaluation of High Level Waste Salt Disposition Alternatives. March 16. Rueter, K., P. Hudson, E. Murphy, and P. Suggs. 1998. Trip Report —Site Visited: Oak Ridge National Laboratory on May 21, 1998. May 31. Rueter, K., E. Murphy, and P. Suggs. 1998. Trip Report—Site Visited: West Valley Site on May 19. June 1. Savannah River Site, High Level Waste Salt Disposition Team. 1998. Identification of Alternatives Briefing Package. March 12. Savannah River Site, High Level Waste Salt Disposition Team. 1998. Position Paper on the Evaluation Leading to the “Initial List” of Alternatives. April 17. Savannah River Site, High Level Waste Salt Disposition Team. 1999. HLW Salt Disposition Alternatives Identification Preconceptual Phase II Summary Report. Revision 2. WSRC-RP-98-00165. June 24. Savannah River Site, High Level Waste Salt Disposition Systems Engineering Team. 1998. Position Paper on Identifying Alternatives to the In-Tank Precipitation Process. March 24. Savannah River Site, High Level Waste Salt Disposition Systems Engineering Team. 1998. Preconceptual, Phase I Initial Design Input. April 2. Savannah River Site, High Level Waste Salt Disposition Systems Engineering Team. 1998. Systems Engineering Management Plan for Development of Alternatives to Process and Dispose of High Level Waste Salt. WSRC-RP-98-00163. Revision 0. April 17. Savannah River Site, High Level Waste Salt Disposition Systems Engineering Team. 1998. HLW Salt Disposition Alternatives Identification Preconceptual Phase I, Summary Report. WSRC-RP-98-00162. April 17. Savannah River Site, High Level Waste Salt Disposition Systems Engineering Team. 1998. Position Paper on Identifying and Documenting Dissenting Opinions in the Evaluation and Selection of Alternatives to the In-Tank Precipitation Process. HLW-SDT-980005. May 15. Savannah River Site, High Level Waste Salt Disposition Systems Engineering Team. 1998. Position Paper on the Approach to Flowsheet Analysis. Revision 0. HLW-SDT-980009. May 29. Savannah River Site, High Level Waste Salt Disposition Systems Engineering Team. 1998. Position Paper on the Approach to Information Handling, Analysis and Reporting. Revision 0. HLW-SDT-980010. June 4.

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ALTERNATIVES FOR HIGH-LEVEL WASTE SALT PROCESSING AT THE SAVANNAH RIVER SITE Savannah River Site, High Level Waste Salt Disposition Systems Engineering Team. 1998. Position Paper on Determination of Risk and Risk Handling Strategies for the Initial List Alternatives. Revision 1. HLW-SDT-980004. June 4. Savannah River Site, High Level Waste Salt Disposition Systems Engineering Team. 1998. Position Paper on Dispositioning of Pro-Formas Received During Phase II. Revision 0. HLW-SDT-980014. June 8. Savannah River Site, High Level Waste Salt Disposition Systems Engineering Team. 1998. Position Paper on Preliminary Life Cycle Cost Analysis to Select the Short List of Alternatives. Revision 0. HLW-SDT-980013. June 8. Savannah River Site, High Level Waste Salt Disposition Systems Engineering Team. 1998. Preconceptual, Phase I Initial Design Input. June 24 Revision. Savannah River Site, High Level Waste Salt Disposition Systems Engineering Team. 1998. Results Report on Preliminary Life Cycle Cost Estimates for Initial List Alternatives. Revision 0. HLW-SDT-980018. June 25. Savannah River Site, High Level Waste Salt Disposition Systems Engineering Team. 1998. Position Paper on the Sensitivity Analyses of Alternative Methods for Disposition of High Level Salt Waste. Revision 0. WSRC-TR-98-00236. June 26. Savannah River Site, High Level Waste Salt Disposition Systems Engineering Team. 1998. Systems Engineering Management Plan for Development of Alternatives to Process and Dispose of High Level Waste Salt. Revision 1. WSRC-RP-98-00163. August 21. Savannah River Site, High Level Waste Salt Disposition Systems Engineering Team. 1998. Position Paper on the Use of Weighted Evaluation Criteria to Select the Short List of Alternatives. Revision 2. HLW-SDT-980006. September 17. Savannah River Site, High Level Waste Salt Disposition Systems Engineering Team. 1998. Results Report on Preliminary Risk Assessment with Adjusted Risk Values. Revision 1. HLW-SDT-980015. October 14. Savannah River Site, High Level Waste Salt Disposition Systems Engineering Team. 1998. Results Report on Utility Function Evaluation. Revision 1. HLW-SDT-980019. October 14. Savannah River Site, High Level Waste Salt Disposition Systems Engineering Team. 1998. Final Report (3 Volumes), Recommendation Preconceptual Design and Initial Cost Estimate. WSRC-RP-98-00170. October 29. Savannah River Site, High Level Waste Salt Disposition Systems Engineering Team. 1999. Applied Technology Integration Scope of Work Matrix for Decision Making (Small Tank TPB Precipitation, CST Non-Elutable Ion Exchange and Direct Disposal of Grout) HLW-SDT-99-0009. April 14. Scott, A.B. 1990. Letter to Roy Schepens Regarding the HLW Salt Disposition Systems Engineering Team Charter and Attached Charter. March 13.

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ALTERNATIVES FOR HIGH-LEVEL WASTE SALT PROCESSING AT THE SAVANNAH RIVER SITE Westinghouse Savannah River Company. 1998. High Level Waste Salt Disposition Interface Requirements. WSRC-RP-98-00164. May 20. Westinghouse Savannah River Company. 1998. Bases, Assumptions, and Results of the Flowsheet Calculations for the Initial Eighteen Salt Disposition Alternatives. Revision 1. WSRC-RP-98-00166. September 15. Westinghouse Savannah River Company. 1999. Briefing Packages for the National Research Council Committee on Cesium Processing Alternatives for High-Level Waste at the Savannah River Site. Presentations given September 13 and 14. Unpublished. Westinghouse Savannah River Company. Undated. Draft High Level Waste Salt Disposition Interface Requirements. Revision C.

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ALTERNATIVES FOR HIGH-LEVEL WASTE SALT PROCESSING AT THE SAVANNAH RIVER SITE ATTACHMENT F PRESENTATIONS GIVEN DURING FIRST COMMITTEE MEETING Background on Cesium Separations at Savannah River. Steve Piccolo, Westinghouse Savannah River Company (WSRC) Roy Schepens, U.S. Department of Energy Background on the In-Tank Precipitation (ITP) Process. Joe Carter, WSRC Walt Tamosaitis, Savannah River Technology Center (SRTC) Mark Barnes, SRTC Roy Jacobs, WSRC Mike Montini, WSMS Small Tank TPB Option. Sam Fink, SRTC Reid Peterson, SRTC Mark Barnes, SRTC Hank Elder, WSRC Jack Collins, Oak Ridge National Laboratory (ORNL) David Hobbs, SRTC CST Non-Elutable Ion Exchange Option. Doug Walker, SRTC Roy Jacobs, WSRC John Harbour, SRTC Dan Lambert, SRTC Bill Wilmarth, SRTC Caustic Side Solvent Extraction Option. Ken Rueter, WSRC Ralph Leonard, Argonne National Laboratory Bruce Moyer, ORNL Reid Peterson, SRTC John Fowler, WSRC Direct Disposal in Grout Option. Ed Stevens, SRTC Christine Langton, SRTC Jim Cook, SRTC Elmer Wilhite, SRTC

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ALTERNATIVES FOR HIGH-LEVEL WASTE SALT PROCESSING AT THE SAVANNAH RIVER SITE ATTACHMENT G STATEMENT OF TASK The committee will review the Department of Energy's work to identify alternatives for separating cesium from high-level waste at the Savannah River site. This review will address the following points: Was an appropriately comprehensive set of cesium partitioning alternatives identified, and are there other alternatives that should be explored? Was the process used to screen the alternatives technically sound and did its application result in the selection of appropriate preferred alternatives? Are there significant barriers to the implementation of any of the preferred alternatives, taking into account their state of development and their ability to be integrated into the existing SRS HLW system? Are the planned R&D activities, including pilot-scale testing, adequate to support implementation of a single preferred alternative?