Advanced LWR Concept of FLWR for TRU Recycling

An advanced LWR concept of FLWR has been investigated at JAEA in order to ensure sustainable energy supply in the future based on the well-experienced ?? LWR technologies. FLWR is essentially a BWR-type reactor, and its core design is characterized by use of the hexagonal-shaped fuel assemblies with the triangular tight-lattice fuel rod configuration of the highly enriched MOX fuel, resulting in the hard spectrum. The concept aims at effective and flexible utilization of uranium and plutonium resources through plutonium multiple recycling in two steps. In the first step, FLWR realizes a high conversion type core concept, which is basically intended to keep the smooth technical continuity from the current LWR and MOX-LWR technologies without significant gaps in technical point of view. The core in the second step increases its tightness and represents the Reduced-Moderation Water Reactor core concept, which realizes a high conversion ratio over 1.0 for the long-term sustainable energy supply through plutonium multiple recycling. 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, flexibly corresponding tomore » the expected change in the future circumstances such as the reprocessing technologies for the MOX spent fuel. In order to establish a robust nuclear energy supply system for the future, an appropriate combination of both the LWR and the FBR technologies, i.e. FLWR and Na- FBR, is considered to be preferable and realistic. This type of preferable combination is proposed in this paper. Detailed investigations for the FLWR concept 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. (authors)« less