Combined use of MOX and UO fuel rods in fuel assembly designs for plutonium conservation in FLWR

Uchikawa, Sadao; Nakano, Yoshihiro ; Okubo, Tsutomu

The FLWR is an innovative BWR-type reactor with hard neutron spectrum based on the well-experienced LWR technologies. It aims at effective and flexible utilization of uranium and plutonium resources by adopting a two-stage concept of core designs corresponding to the advancement of the fuel cycle technologies and related infrastructures. A new concept of the fuel assembly design named FLWR/MIX has been proposed for the first stage of FLWR to conserve plutonium effectively with a fissile-plutonium conversion ratio of around 1.0, keeping negative void reactivity characteristics. The enriched UO fuel rods are arranged in the peripheral region of the assembly, surrounding the MOX fuel rods in the central region. Performance evaluation shows that the FLWR/MIX concept is feasible and promising under the framework of the UO and MOX fuel technologies and related infrastructures which have been established for the current LWR-MOX utilization.