The Impact of americium target in-core loading on reactivity characteristics and ULOF response of sodium-cooled MOX FBR

Yamaji, Akifumi; Kawashima, Katsuyuki; Oki, Shigeo ; Mizuno, Tomoyasu; Okubo, Tsutomu

The homogeneous MA loading core with 3wt% MAs is used as a reference design to evaluate the impact of the americium target in-core loading (20wt% MAs) on reactivity characteristics and ULOF response of sodium-cooled MOX-FBR. The Am target loading method of this study can flatten core radial reactivity worth distributions and effectively reduce reactivity insertion into the core during ULOF. As the result, the core power increase speed during ULOF is reduced. The maximum fuel temperature of the target region does not become particularly high compared with that of the inner core and it is much lower than the melting point. It is promising from the viewpoints of the reactivity characteristics and ULOF response.