The committee’s first report was issued shortly after the committee began its work. Following briefings from a number of individuals in the nuclear energy field concerning different aspects of the electrometallurgical process, the committee made the following two statements:
The committee concluded that electrometallurgical techniques represent a sufficiently promising technology for treating a variety of DOE spent fuels to warrant continued R&D in federal FY96.
During the next 12 months the DOE should closely follow the progress of the proposed R&D program to determine whether it should be continued beyond FY96.
As the demonstration project progressed, the committee recommended three criteria for judging the success of the demonstration project (a minimum definition of “successful application”):
Demonstration of batch operation of an electrorefiner and a cathode processor with a capacity of approximately 200 kg/day of radioactive EBR-II spent fuel without failure for about 30 days.
Quantification (for both composition and mass) of recycle, waste, and product streams that demonstrate projected material balance with no significant deviations.
Demonstration of an overall dependable and predictable process, considering uptime, repair and maintenance, and operability of linked process steps.
Demonstration that releases of radioactivity remain at or below those levels anticipated and specified in equipment design and operating plans. Exposure of operating personnel to radiation must be minimal and must in all cases remain below limits set by the U.S. Nuclear Regulatory Commission.
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Electrometallurgical Techniques for DOE Spent Fuel Treatment: Final Report APPENDIX D Recommendations and Selected Findings and Conclusions from Previous Reports of the Committee on Electrometallurgical Techniques for DOE Spent Fuel Treatment PHASE ONE A Preliminary Assessment of the Promise of Continued R&D into an Electrometallurgical Approach for Treating DOE Spent Fuel (Report 1, 1995) The committee’s first report was issued shortly after the committee began its work. Following briefings from a number of individuals in the nuclear energy field concerning different aspects of the electrometallurgical process, the committee made the following two statements: The committee concluded that electrometallurgical techniques represent a sufficiently promising technology for treating a variety of DOE spent fuels to warrant continued R&D in federal FY96. During the next 12 months the DOE should closely follow the progress of the proposed R&D program to determine whether it should be continued beyond FY96. An Assessment of Continued R&D into an Electrometallurgical Approach for Treating DOE Spent Nuclear Fuel (Report 2, 1995) As the demonstration project progressed, the committee recommended three criteria for judging the success of the demonstration project (a minimum definition of “successful application”): Demonstration of batch operation of an electrorefiner and a cathode processor with a capacity of approximately 200 kg/day of radioactive EBR-II spent fuel without failure for about 30 days. Quantification (for both composition and mass) of recycle, waste, and product streams that demonstrate projected material balance with no significant deviations. Demonstration of an overall dependable and predictable process, considering uptime, repair and maintenance, and operability of linked process steps. Demonstration that releases of radioactivity remain at or below those levels anticipated and specified in equipment design and operating plans. Exposure of operating personnel to radiation must be minimal and must in all cases remain below limits set by the U.S. Nuclear Regulatory Commission.
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Electrometallurgical Techniques for DOE Spent Fuel Treatment: Final Report The committee then proposed that the demonstration project should proceed. Its recommendation included options for the treatment of other spent fuel in the DOE inventory: ANL should proceed with its development plan in support of the EBR-II demonstration. Further development of the lithium reduction process should be carried out only if the DOE decides that it is likely that the electrometallurgical approach will be pursued as a possible treatment for the oxidized N-reactor fuel at Hanford. If the EBR-II demonstration is not accomplished successfully, the ANL program on electrometallurgical processing should be terminated. On the other hand, if the EBR-II demonstration is successful, the DOE should revisit the ANL program at that time in the context of a larger, “global” waste management plan to make a determination for possible continuance. PHASE TWO An Evaluation of the Electrometallurgical Approach for Treatment of Excess Weapons Plutonium (Report 3, 1996) As a result of its statement of task for phase two (Appendix A), the committee’s composition was changed to emphasize expertise in weapons plutonium. The committee’s third report addressed the issue of the use of electrometallurgical technology for treatment of excess weapons plutonium: Modified Spent Fuel Processing Flow Sheet Recommendations: Pretreatment requirements for the nonmetal plutonium feed streams should be determined and, if possible, R&D should be started to validate the treatment and subsequent compatibility with the electrometallurgical process. The effects of major impurities such as additional salts (NaCl/KCl and CaCl2) and other impurities such as Si, Mg, and C on the performance of the electrometallurgical treatment operations should be evaluated. Greater priority should be given to the development of a strategy and a relevant test protocol to demonstrate acceptability of waste forms. This activity is of the highest importance relative to all other aspects in the development of the electrometallurgical technique for WPu disposition. A decision on the use of the electrometallurgical technique for weapons plutonium disposition cannot be made until the demonstration of this technology shows whether or not this process is viable for treating DOE spent fuels. If a weapons plutonium disposition technology is to be selected for use with weapons pits before the electrometallurgical technology demonstration program is concluded, this committee recommends that the electrometallurgical technique not be included as a candidate technology. The potential of the electrometallurgical technique as an adjunct for long-term disposition of non-pit excess plutonium remains a possibility, but the technology is still at too early a stage of development to be evaluated relative to disposition alternatives such as glass or MOX. Electrometallurgical Techniques for DOE Spent Fuel Treatment: A Status Report on Argonne National Laboratory’s R&D Activity (Report 4, 1996) The committee’s fourth report addressed the first task for phase two. The report provided an ongoing evaluation of the scientific and technological aspects of the R&D program for spent fuel treatment. The findings and recommendations relate to the demonstration project: The committee recommends that DOE assign high priority to authorization of hot operations at ANL-W. The committee recommends that ANL’s ongoing studies be extended to include efforts aimed at defining
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Electrometallurgical Techniques for DOE Spent Fuel Treatment: Final Report the phase changes in the salt-loaded zeolite during hot isostatic pressing and determining the fate of the salt, which would no longer be as well isolated from the environment. The committee recommends that attention be given to establishing the performance of both the zeolite and metal waste forms under conditions relevant to their disposal in a geological repository. The committee recommends that the several aspects of ANL’s substantial effort in waste form development be integrated into a formal, comprehensive program plan. The committee also recommends that ANL establish a program of regular, formal meetings between ANL personnel and staff of the DOE’s Yucca Mountain project as a useful (and perhaps essential) step in guiding ANL’s future testing program. The committee recommends that upon satisfactory completion of the demonstration with EBR-II fuel, the electrometallurgical technique should be evaluated in the broader context of alternative technologies for processing spent nuclear fuel. Electrometallurgical Techniques for DOE Spent Fuel Treatment: Fall 1996 Status Report on Argonne National Laboratory’s R&D Activity (Report 5, 1997) The committee’s fifth report continued to fulfill the first task for phase two by providing an ongoing evaluation of ANL’s R&D activity. The recommendations in this report cover most aspects of ANL’s demonstration project. Spent Fuel Recommendations A well-defined set of performance criteria needs to be developed. The criteria would provide ANL with a clear set of objectives. The achievement of those objectives would better position ANL to request approval to proceed to additional applications of its electrometallurgical technology program. A more focused, better-coordinated testing and implementation plan is needed between ANL-E and ANL-W to ensure that performance criteria and demonstration schedules are met. Waste Form Recommendations ANL should develop and implement immediately an overall strategic plan that defines the following: The planned state of waste form development at the end of the demonstration phase and the objectives that will remain to be addressed and The methods for ensuring optimal, synergistic use of all ANL resources for ceramic waste form development and evaluation. Electrometallurgical Techniques for DOE Spent Fuel Treatment: Status Report on Argonne National Laboratory’s R&D Activity Through Spring 1997 (Report 6, 1997) Like report 5, report 6 continued to address the first task for phase two. This report reiterated previous committee recommendations: The committee reaffirms its overall recommendation of the July 1995 report [Report 2]. The committee encourages ANL to proceed aggressively to resolve the R&D issues and move rapidly into a demonstration phase that identifies process definitions and conditions.
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Electrometallurgical Techniques for DOE Spent Fuel Treatment: Final Report The committee went on to present new recommendations related to the demonstration project. The committee looks forward to receiving the demonstration project implementation plan after it is approved by DOE. Before the demonstration is completed, DOE should establish criteria for success in the demonstration phase to allow evaluation of the electrometallurgical technology for further use in treating DOE spent fuel. A new EA will be required before additional EBR-II spent fuel can be treated. DOE should begin plans for such an EA now so that its preparation does not become the source of a major operational delay, if the current demonstration project is successful. The committee continues to believe that successful demonstration of the electrometallurgical process for treating EBR-II fuel is essential to support development of applications of this technique to treatment of other DOE spent fuels. ANL’s research efforts have involved the investigation of the electrometallurgical technology for treatment of non EBR-II fuels such as the N-reactor fuel. However, the DOE Office of Environmental Management (EM) may proceed with plans for the N-reactor fuel that do not include the use of electrometallurgical technology. Since the current approach of DOE-EM is to develop project plans for implementation within the next 10 years, the offices of Nuclear Energy (NE) (which funds the present program) and Environmental Management (EM) should maintain close contact to ensure proper coordination of their activities. DOE should establish acceptance criteria for waste forms scheduled for storage in a geological repository. The committee suggests that ANL utilize external technical experts in specific scientific areas of the program. These technical experts should be recognized for their in-depth knowledge in particular technical areas. PHASE THREE Electrometallurgical Techniques for DOE Spent Fuel Treatment: Spring 1998 Status Report on Argonne National Laboratory’s R&D Activity (Report 7, 1998) The committee’s seventh report concentrated on the second and third tasks for the third phase. The committee examined electrometallurgical technology in light of other possible treatment technologies for spent nuclear fuel, and it evaluated the success criteria developed by ANL and DOE for the demonstration project: Confirmation that the waste forms produced by EMT are acceptable within the DOE’s Office of Radioactive Waste (DOE-RW) Office of Civilian Radioactive Waste Management (OCRWM) program for final geological disposal must be a key component in a full qualification of the EMT process. If DOE concludes that the EMT process is unsuitable for processing the remainder of EBR-II fuel, then the PUREX process could be evaluated for its applicability to treatment of EBR-II fuel. However, a significant issue for treating EBR-II fuel at SRS by PUREX relates to public concerns about the transportation of the fuel from the current storage site at ANL-W to SRS. In recognition of the progress that ANL has made in the demonstration and in accord with the committee’s previous recommendations, the committee recommends to DOE that ANL’s demonstration project be carried to completion. The committee finds that the criteria established by U.S. DOE are reasonable for judging the success of the EBR-II spent fuel treatment demonstration.
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Electrometallurgical Techniques for DOE Spent Fuel Treatment: Final Report Electrometallurgical Techniques for DOE Spent Fuel Treatment: Status Report on Argonne National Laboratory’s R&D Activity as of Fall 1998 (Report 9, 1999) The committee’s eighth report fulfilled its task to provide an ongoing evaluation of ANL’s demonstration project: ANL should broaden its perspective regarding the Mark-V ACM by seeking information about the following: The physical, morphological, and mechanical characteristics (e.g., plasticity) of the uranium/salt mixture produced during HTER operating conditions; The electrochemical behavior of uranium in molten LiCl-KCl under HTER operating conditions; and Useful strategies from the metal electrowinning industry that can be applied to the uranium electrometallurgical process. ANL should evaluate the potential impact of the higher salt content of the Mark-V HTER product on the performance of the cathode processor. ANL should evaluate the effects of cathode surface roughness on the adhesion of the uranium deposit; other materials or metallic coatings that might reduce adhesion of uranium on the ACM cathode should be considered. Surface analysis by XPS or AES should be performed for selected samples drawn from the characterization tests. The committee notes that ANL-E has one of the leading experts in this area. It is recommended that only a few of these samples be fully characterized. ANL needs to refocus near-term testing by reducing product consistency testing under relatively mild conditions and instead emphasizing product performance testing under more stringent conditions that may reveal significant corrosion effects and address success criterion 2, goal 2. ANL should evaluate how the MWF performance model will be used and whether ongoing MWF testing will provide information needed for developing the performance model. Assuming that an increased amount of glass in the waste form is acceptable, then in addition to HUP, conventional cold pressing and sintering should also be considered as a viable processing option. The committee believes that characterization of the ceramic waste form should be accelerated in order to determine the mechanism of transformation of salt-loaded zeolite 4A to sodalite. Electrometallurgical Techniques for DOE Spent Fuel Treatment: An Assessment of Waste Form Development and Characterization (Report 9, 1999) In conversations between personnel of DOE and the NRC, it was agreed that the committee would produce a report that would examine the issue of waste form testing and development as it related to ANL’s demonstration project. Specifically, the committee assessed whether the testing plan in place for the ceramic and metal waste forms was the proper one to qualify these waste forms for placement in a geologic repository. Although final criteria for repository placement have not yet been finalized, the committee based its assessment on the question of whether it believed that the testing program was valid. Relevant findings and conclusions from this report are included with the recommendations: Finding: From interactions with the DOE’s Office of Civilian Radioactive Waste Management (RW), ANL has developed a strategy appropriately based on RW’s waste acceptance criteria for the characterization of its MWF and CWF for eventual acceptance by RW for geologic storage and/or disposal based on RW.
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Electrometallurgical Techniques for DOE Spent Fuel Treatment: Final Report Conclusion: Continued interaction between ANL and RW will become even more important in the post-demonstration phase. Conclusion: There remains uncertainty regarding which DOE organization will be charged with the ultimate responsibility for performance-confirmation testing of waste forms suitable to support a repository licensing decision. As this uncertainty in responsibility could lead to costly duplication of effort and lack of consensus among DOE organizations regarding data supporting future decisions, DOE should take the lead in achieving a documented resolution to this issue. Finding: An SS-5 Zr MWF shows severe rusting and pitting in the vapor hydration test. Conclusion: Data for the SS 15-Zr MWF standard need to be obtained. Recommendation: Surface analysis by X-ray photoelectron spectroscopy (XPS) or Auger electron spectroscopy (AES) should be performed for selected samples to determine the chemical composition of passivation filings and/ or corrosion products. Because a large number of samples to be tested differ only very slightly in minor alloying elements, it is recommended that only a few of these samples be subjected to full characterization. These samples should be selected using a statistical analysis approach. Finding: Some of the corrosion products, which may sequester radionuclides, might remain on the sample surface and might not be detected by solution analysis. Finding: Results from corrosion testing of the MWF in rather benign environments suggest that the corrosion behavior of the MWF is similar to that of stainless steel. Finding: At the present time, ANL has not indicated how it plans to conduct crevice corrosion studies. Finding: ANL has carried out a large number of corrosion tests in solutions which are not expected to lead to significant corrosion damage. Recommendation: Instead of continuing to conduct a large number of such tests using mild conditions, it would be better to subject a few carefully selected samples to additional evaluation by surface analysis to determine the chemical composition of the corrosion products. It may be better to concentrate on a few key samples, expose them at higher temperatures, and then obtain electrochemical and surface analysis data. Finding: ANL’s tests over the several months duration of the test indicate that the CWF dissolves at a rate equal to or less than reference defense high level waste borosilicate glass. Conclusion: If there is no change in long-term release mechanism under simulated repository conditions, the release performance of CWF (dissolution rate) will be at least comparable to borosilicate glass. Finding: During the conduct of the alpha-decay tests, plutonium oxide was observed as nanocrystals in the grain boundaries. Conclusion: Plutonium may not be in the sodalite phase. Its presence in potentially colloid-sized products may have implications on the long-term release behavior of plutonium and any other radionuclides that also segregate into such colloid-size phases.
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Electrometallurgical Techniques for DOE Spent Fuel Treatment: Final Report Recommendation: The EMT Program should continue to evaluate and demonstrate that test protocols and conceptual models developed for monolithic single-phase borosilicate glass can adequately represent the behavior of the nonhomogeneous multiphase EMT CWF. Finding: The Material Characterization Center Test (MMC-1) and Product Consistency Test (PCT) designed to model the release behavior of inert, major components of the CWF may be irrelevant with respect to evaluating the release of plutonium and other actinides partitioned into separate oxide phases. Conclusion: The committee believes that ANL is taking appropriate steps to coordinate its waste-qualification program with the DOE RW repository program. It remains undemonstrated, however, that direct adaptation of test procedures and models developed for measuring the rate of general corrosion of the matrix of homogeneous, vitrified HLW forms are sufficient for evaluating the performance of the heterogeneous, crystalline CWF under long-term repository conditions. Conclusion: These continuing concerns are not expected to jeopardize the timely completion of the EBR-II demonstration project in 1999, but attention should be devoted to their resolution prior to extending the EMT process past the demonstration. Conclusion: Alternative, conservatively bounding strategies for assuring safe disposal of such relatively small quantities of novel HLW may result in significant cost avoidance while still protecting public safety.
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