Research on multi-recycle HTGR system

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Safety of radioactive waste disposal is ensured by evaluating public dose, and even with existing Light Water Reactor (LWR)’s waste disposal, its safety is confirmed. On the other hand, with Partitioning and Transmutation (P&T) technologies, we confirmed the waste reduction. Moreover, with Minor Actinoid (MA) transmutation, potential toxicity, which attract attentions from the viewpoint of public acceptance, can be reduced, and ultimate waste reduction can be achieved. In addition, the potential toxicity reduction, which can shorten a cooling time to decay the potential toxicity to natural uranium level to 300 years, is also the research and development (R&D) target of Fast Reactor (FR) and Accelerator Driven System (ADS). The potential toxicity is defined as ingestion dose when the all toxicity was taken into human body. Until now, it is said that the MA transmutation by multi-recycling can be achieved only with the fast neutron reactor system including ADS. In the previous study, we confirmed feasibility of the MA transmutation with multi-recycling by using HTGR which is a thermal neutron reactor, and the first in the world. As shown in the figure below, with group partitioning technologies and the multi-recycling MA transmutation, the cooling time to reduce potential toxicity, which is originally hundred thousand years without transmutation, can be reduced to 300 years, and repository footprint can be reduced to 1/300 compared with a representative reprocessing scenario as same as FR and ADS. In addition, Fission Products (FPs) and Np, one of MAs will be disposed of because these nuclides are not problematic from the viewpoint of potential toxicity.

Proposed multi-recycling HTGR system

Proposed multi-recycling HTGR system

Reference
Y. Fukaya, M. Goto, H. Ohashi, et al.,"Uranium-based TRU multi-recycling with thermal neutron HTGR to reduce environmental burden and threat of nuclear proliferation," J. Nucl. Sci. Technol., 55(11), p.1275-1290, (2018).