Development of A Novel Electrolytic Process for Metallic Fuel Reprocessing

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Presently, the metallic fuel cycle is regarded as one of the most innovative technologies for fast breeder reactor (FBR). The feasibility of the FBR depends on the development of a reprocessing technology. And, molten salt electrolytic process is a key process in this reprocessing technology. The present authors have already proposed a new type of electrolytic process which incorporates the use of gas electrodes and solid electrolytes, and studied its possibility from both fundamental and engineering aspects. Results are summarized as follows :1)When various elements are electrochemically extracted from a molten salt to a liquid metal cathode, solid intermetallic compounds are formed at the interface between the salt and liquid metal. This was considered being an obstacle to the molten salt electrolytic process. Ni-Y intermetallic compound was selected as a model system and its formation reaction was carefully investigated. As a result, the Ni-Y intermetallic compound formation mechanism was revealed and the diffusion coefficients of yttrium in various intermetallic compounds were determined.2)Diffusion coefficients of actinide and lanthanide ions in molten salts were measured by a capillary method. The dependence of the diffusion coefficients on temperature and ionic charge were discussed.3)Molten salt electrochemical processes, such as metallizing of ceramics with zirconium and surface nitriding of titanium, were developed for high corrosion resistive materials to be used for molten salt electrolysis. Furthermore, a novel method to from high corrosion resistive nanometer order oxide layr on metal surfaces e.g., Ni was also developed.