[2M18-22] New Type Reactor Development 1

[2M21] A Sodium-cooled Fast Reactor Core Concept with Enhanced Inherent Safety

Feasibilty study of the void reactivity and burnup reactivity reduction countermeasure

*Koji Fujimura¹, Takeshi Nitawaki², Toshikazu Takeda³ (1. Hitachi, Ltd., 2. Hitachi-GE Nuclear Energy, Ltd., 3. University of Fukui)

Keywords:SFR, Sodium void reactivity, Burnup reactivity, Sodium plenum, Axially heterogeneous core (AHC), Minor actinide (MA), Unticipated loss of flow accident , Unticipated transient over power

Considering the core concept of a sodium cooled MOX fuel fast reactor that can avoid core damage at the time of ULOF and UTOP event due to its intrinsic nuclear characteristics. In order to realize the above mentioned, we set the design goal to simultaneously satisfy the negative void reactivity and burnup reactivity less than 1 $. As a measure to reduce the void reactivity that can prevent deterioration of core performance, installation of an axial heterogeneous core (AHC) with a sodium plenum and a gas expansion module (GEM) was examined. In addition, as a counter measure to reduce burnup reactivity, a measure was taken to utilize the nuclear features of MA as a burnable absorber and good fertile material by adding minor actinide (MA) from light water reactor to the inner blanket of AHC .