Investigation on Innovative Water Reactor for Flexible Fuel Cycle(FLWR)

Okubo, Tsutomu; Uchikawa, Sadao; Kugo, Teruhiko ; Akie, Hiroshi  ; Iwamura, Takamichi

A concept of Innovative Water Reactor for Flexible Fuel Cycle(FLWR) has been investigated in JAEA in order to ensure sustainable energy supply in the future based on the well-developed LWR technologies. The concept aims at effective and flexible utilization of uranium and plutonium resources through plutonium multiple recycling by two steps. In the first step, FLWR core realizes a high conversion type core concept, which is basically intended to keep the smooth technical continuity from current LWR and coming LWR-MOX technologies without significant gaps in technical point of view. The core in the second step represents the RMWR core concept, which realizes a high conversion ratio over 1.0 being useful for the long-term sustainable energy supply through plutonium multiple recycling based on the LWR technologies. The key point is that the core concepts in both steps utilize the compatible and the same size fuel assemblies, and hence during the reactor operation period, the former concept can proceed to the latter in the same reactor system, corresponding flexibly to the expected change in the future circumstances of natural uranium resource, or establishment of economical reprocessing technology for the MOX spent fuel. Detailed investigation have been performed on the core design, in conjunction with the other related studies such as on the thermal hydraulics in the tight-lattice core including the experimental activities, and the results obtained so far have shown that the proposed concept is feasible and promising. For commercial realization of the FLWRs in 2030s, a 400MWe class small reactor is proposed to be constructed in 2010s as a leading demonstration plant.