Technology readiness assessment of partitioning and transmutation in Japan and issues toward closed fuel cycle

•The paper treats technology readiness of partitioning and transmutation in Japan.•Fast reactors with minor actinide bearing oxide or metal fuels are assessed.•Accelerator driven system with minor actinide bearing nitride fuels is assessed.•Homogeneous or heterogeneous single strata and double strata were assessed.•The paper treats issues in the development toward closed fuel cycle.

This paper treats a technology readiness assessment of partitioning and transmutation in Japan and issues toward closed fuel cycles. The generic technology readiness level in this study is based on the definition in the Global Nuclear Energy Partnership: TRL 3 shows the status that critical function are proved and elemental technologies are identified; TRL 4 represents the level that the related technologies are validated at bench-scale in laboratory environment; and TRL 5 indicates the completion of the development related to the subsystem and elemental technologies. The reviewed technological area includes the partitioning and transmutation technologies for minor actinide cycle: fast breeder reactor, and accelerator driven system for minor actinide transmutation; partitioning processes; and minor actinide bearing fuels. The assessments reveal that the TRLs stay around the final step of concept development (TRL 3) and the first half step of elemental technology development (TRL 4) because each system requires more development of its elemental technologies. The fast breeder reactor is assessed to be at TRL 4 because critical experiments with americium and neptunium would be additionally required, and the technology for the accelerator driven system reaches TRL 3 due to several researches. Consequently, a common key issue is how nuclear calculation methodology will be validated for the MA-bearing-fuelled core; however, critical experiments with several kilogrammes of americium or more are difficult in the existing experimental facilities. On the other hand, engineering scale tests of the MA partitioning processes using actual spent fuel, and engineering scale of fabrication and irradiation tests with the separated materials are required to achieve the second half step of elemental technology development (TRL 5); however, they could be a massive investment. Therefore, laboratory-scale tests using actual material are proposed. The tests simulate a nuclear fuel cycle: partitioning actual spent fuels; and fabricating MA bearing fuels from the extracted materials; and then irradiating them. It should be that the tests advance technological readiness from TRL 4 to TRL 4+, which is a reasonable and feasible pathway.