Development of core deformation reactivity evaluation method, 1; Application to the EBR-II SHRT-45R test

Doda, Norihiro  ; Kato, Shinya  ; Yoshimura, Kazuo; Uwaba, Tomoyuki ; Yokoyama, Kenji   ; Tanaka, Masaaki  

JAEA has developed an evaluation method coupling neutronics, core thermal-hydraulics, and core structural mechanics to evaluate more realistically core deformation reactivity due to reactor power variation during anticipated operational occurrence or accidents in sodium-cooled fast reactors. The analysis results of the EBR-II SHRT-45R test simulating a loss of flow event using the evaluation method showed that the core deformation reactivity was negative from the start. When the core temperature rose, fuel assemblies bowed outward in the core due to the difference in thermal expansion between the facing wrapper walls of the assembly, causing negative reactivity in the fuel region and the surrounding reflector region due to the displacement of fuel and structural materials. As a result, the availability of the core deformation reactivity evaluation method was confirmed.