Abstract
In order to ensure the sustainable energy supply in the future based on the matured light water reactor (LWR) technologies, a concept of innovative water reactor for flexible fuel cycle (FLWR) has been investigated in JAEA. The concept utilizes the tight-lattice core loaded with the plutonium mixed oxide (MOX) fuel, and consists of two steps in the chronological sequence. The first step realizes a high conversion type one (HC-FLWR), which is basically intended to keep the smooth technical continuity from the current LWR / MOX-LWR technologies. The second represents the reduced-moderation water reactor (RMWR) concept, which realizes a high conversion ratio over 1.0 and is preferable for the long-term sustainable energy supply through plutonium multiple recycling. In the present paper, investigation results on the FLWR conceptual design are presented mainly from the neutronics point of view. The design of the HC-FLWR core has been recently improved, and detailed core properties have been evaluated by neutronics and thermal-hydraulics coupled calculations. The core can achieve the average burn-up around 55GWd/t as well as the negative void reactivity coefficients. The size of its fuel assembly is the same as in RMWR, and hence, it can be replaced with the highly tight one for RMWR.
