Fast reactor core design studies to cope with TRU fuel composition changes in the LWR-to-FBR transition period

Kawashima, Katsuyuki; Maruyama, Shuhei   ; Oki, Shigeo ; Mizuno, Tomoyasu

750 MWe MOX fuel fast reactor core design efforts have been made to cope with the TRU fuel composition changes expected during LWR-to-FBR transition period, in which a various kind of TRU fuel compositions are available depending on the characteristics of the LWR spent fuels and a way of recycling them. It is shown that among the core neutronics characteristics, the burnup reactivity and the safety parameters such as sodium void reactivity and Doppler coefficient are significantly influenced by the TRU fuel composition changes. As a result, a general characteristic in the FaCT core design to cope with TRU fuel composition changes is grasped and the design envelopes are identified in terms of the burnup reactivity and the safety parameters.