Investigation on innovative water reactor for flexible fuel cycle (FLWR). (2) Recycle characteristics

A concept of Innovative Water Reactor for Flexible Fuel Cycle (FLWR) has been investigated in Japan Atomic Energy Research Institute (JAERI) in order to ensure sustainable energy supply in the future based on the well-developed Light Water Reactor (LWR) technologies. The concept aims at effective and flexible utilization of uranium and plutonium resources through plutonium multiple recycling by two stages. In the first stage, 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 stage represents the Reduced-Moderation Water Reactor (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 stages 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 resources or establishment of economical reprocessing technology of MOX spent fuel. The FLWR is basically a BWR-type reactor, and its core design is characterized by the short flat core, which consists of hexagonal-shaped fuel assemblies in the triangular lattice fuel rod configuration with highly enriched MOX fuel and Y-shaped control rods. Detailed investigations have been performed on the core design, in conjunction with the other related studies, and the results obtained so far have shown the proposed concept is feasible and promising. In the present paper, the recycling characteristics of the FLWR core are presented, for both the first and the second stages of the FLWR concept. (author)