Material balance evaluation of pyroprocessing for minor actinide transmutation nitride fuel

Abstract

ABSTRACT Fuel cycle technology for the transmutation of long-lived minor actinides (MAs) using an accelerator-driven system has been developed under the double-strata fuel cycle concept. A mononitride solid solution of MAs and plutonium diluted with zirconium nitride is a prime fuel candidate for transmutation of MAs. Pyroprocessing is suitable for recycling the residual MAs in spent nitride fuel with high radiation doses and decay heat. The spent nitride fuel is anodically dissolved, and the actinides are recovered simultaneously into a liquid cadmium cathode via molten salt electrorefining, which is the core step of the process. The process should be designed to achieve the target recovery yield of MAs and the acceptable impurity level of rare earth fission products in the recovered material. In this study, we evaluated the material balance during the pyroprocessing of spent nitride fuel to gain important insight on the design process. We examined the effects of changing the stage numbers in the countercurrent extraction and the zeolite treatment on material flow and quantity of waste. The results show that multistage extraction is necessary to meet the targets and the stage number of the zeolite treatment is recommended to be more than three from the aspect of the amounts of glass-bonded sodalite wastes.