For treating the wide variety of spent fuels known to be in the DOE inventory, the ANL proposal1 included head-end treatments for fuel disassembly and, when required, steps such as oxide reduction. The ANL proposal also included processes for the treatment of electrorefining effluent streams and, when appropriate, for the recycle and reuse of reagents to minimize the generation of secondary waste streams. The end products of the electrometallurgical treatment are two product streams and two waste streams. The product streams would be a nearly pure uranium metal stream and a transuranic metal stream composed of about 30% uranium by weight, the remaining actinides (primarily plutonium), and some rare-earth fission products. The first of the two waste streams would consist of the fission products not reduced to the elemental form (e.g., Sr, Cs, I, and Se) plus trace amounts of the actinides incorporated in a glass-bonded zeolite (GBZ) waste form. The second waste stream would contain the fission products least easily oxidized (the noble metal fission products Nb, Tc, Zr, Mo, the Pt group, and possibly Sn) and the undissolved cladding material remaining at the anode. This second waste stream would be placed in a metal waste form as a mixture of Zr-rich and Fe-rich phases of a Fe-Zr alloy. The original process flow sheet for use of the electrometallurgical technique to treat DOE spent nuclear fuels placed the product metal forms (uranium and the TRU) in interim storage. ANL is initiating a program to evaluate the two forms.

More recently, ANL has modified its flow sheet (Fig. 2) by eliminating the cadmium cathode, which would leave the transuranic elements in the molten salt. This modification would eliminate one of the product streams and the corresponding need for its interim storage. In the new scheme, the transuranic elements would remain with the fission products and be disposed of in the GBZ waste form.

In its earlier reports, the committee observed that “the electrometallurgical technique is not a new technology,”2 and that “the chemical feasibility of the technique is well established except with respect to the proposed zeolite-based steps for waste treatment ” and the possible deleterious effects of high levels of radiation. 3 The committee noted that a major limitation of the electrometallurgical process was its present inability to produce waste forms with behavior that is well understood. Even without considering the uncertainty regarding the waste forms, the committee concluded that a “substantial development and demonstration program is still necessary to show whether the electrometallurgical technique can be a viable option ” for the treatment of DOE spent fuels.4 This observation is consistent with DOE's commitment to process EBR-II spent fuels, for which development and demonstration of the electrometallurgical treatment technology are expected to continue during the several years required for processing (i.e., until 2001, the scheduled completion date for processing EBR-II driver and blanket fuel). In its July 1995 report, the committee further concluded that if the EBR-II processing demonstration were successful, the electrometallurgical technique developed by ANL should be considered as a candidate technology in the context of a larger, “global” waste management plan for the DOE, specifically for the possible treatment of other DOE fuels.

As part of its present task, the committee was asked to undertake an evaluation of the scientific and technological issues surrounding the potential application of the electrometallurgical treatment technology to the disposition of excess weapons plutonium. Of the estimated 1,100 metric tons (MT) of plutonium in

1  

For a description of the ANL proposal, see Appendix A of the committee's first report, A Preliminary Assessment of the Promise of Continued R&D into an Electrometallurgical Approach to Treating DOE Spent Fuel, National Research Council, Washington, D.C., February 1995.

2  

See the report cited in footnote 1, p. 2.

3  

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.

4  

See the report cited in footnote 3.



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