FINDINGS AND RECOMMENDATIONS
The committee learned from ANL that substantial progress has been made in the development and testing of waste forms, although it is also clear that this work is in its early stages. The committee expects that the development program will be more sharply focused at the conclusion of this preliminary phase.
The continuing delay of the large-scale demonstration processing of EBR-II spent fuel at ANL-W is the result of questions raised by external groups about the adequacy of existing NEPA documentation. As a result, DOE completed in late January 1996 a revised environmental assessment14 that was undergoing public comment at the time of the committee's March 14-15 meeting. The quantity of fuel to be treated under the revised environmental assessment appears to be sufficient for demonstration of the process under radiochemical operating conditions. The committee continues to believe that the demonstration with irradiated fuels is the most important element in DOE's evaluation of applicability of the electrometallurgical technology to other DOE nuclear fuels and other materials.15In addition, all actions necessary for commencing operations with irradiated fuels appear to have been completed.
Consequently, the committee recommends that DOE assign high priority to authorization of hot operations at ANL-W.
The phase transformations observed by ANL during hot isostatic pressing of the loaded zeolite raise important issues of salt and nuclide partitioning and their effect on the overall performance of the GBZ waste form. The changes in intracrystalline void volume caused by these phase changes could result in movement of nuclides from the zeolite cages into the glass matrix. ANL will need to develop a better understanding of the details affecting and controlling the phase transformations and performance characteristics.
The committee recommends that ANL's ongoing studies be extended to include efforts aimed at defining 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 limited test results presented by ANL showed similar low leach rates for hot isostatically pressed product rich in either zeolite A or sodalite, but extrapolations from such leach tests may not “be applicable to predicting performance of waste packages in geologic repositories.”16 In particular, the ion exchange properties of the zeolite (or sodalite) waste matrix may result in a fundamentally different release behavior of radionuclides upon contact by groundwater compared to glass and ceramic waste forms.17 While leach tests under American Society of Testing and Materials (ASTM) protocols and
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14 |
DOE Office of Nuclear Energy, Science and Technology, Draft Environmental Assessment: Electrometallurgical Treatment Research and Demonstration Project in the Fuel Conditioning Facility at Argonne National Laboratory -West, DOE/EA-1148, January 29, 1996. |
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15 |
An Assessment of Continued R&D into an Electrometallurgical Approach for Treating DOE Spent Nuclear Fuel, National Research Council, National Academy Press, Washington, D.C., July, 1995, pp. 34-36. |
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16 |
A Study of the Isolation System for Geologic Disposal of Radioactive Wastes, National Research Council, National Academy Press, Washington, D.C., 1983, p. 6. |
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17 |
See, for example, A Study of the Isolation System for Geologic Disposal of Radioactive Wastes, National Research Council, National Academy Press, Washington, D.C., 1983, p. 56. |
others utilized by the waste community can show release behavior of the proposed ANL waste—as compared with other waste forms under these conditions—extrapolation may not correctly predict the performance in waste packages in geologic repositories. New, revised test and analysis protocols may be required before the release behavior of these new waste forms can be modeled with confidence.
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 geologic repository.
The support of personnel at ANL-East (ANL-E) will be required for operations with radioactive spent fuel at ANL-W, and an ongoing, effective, and integrated waste form development and testing program will require collaboration between both sites. The effort would benefit from regular, formal review meetings between ANL-E and ANL-W personnel. Increased communication between the two ANL sites and with other programs within the DOE complex would ensure adequate transfer of information about the problems being encountered and relevant research achievements.
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.
In its 1995 report, the committee recommended that “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. ”18 Accordingly,
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.
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18 |
An Assessment of Continued R&D into an Electrometallurgical Approach for Treating DOE Spent Nuclear Fuel,National Research Council, National Academy Press, Washington, D.C., July, 1995, p. S-11. |
