Core degradation behavior under ULOF transient on CFV-type core equipped SFR

Onoda, Yuichi ; Kubota, Ryuzaburo*; Yamano, Hidemasa   

Calculations of core degradation behavior under Unprotected Loss of Flow (ULOF) accident of ASTRID CFV-type core equipped Sodium-cooled Fast Reactor (SFR) had been conducted using severe accident analysis code SIMMER-III. The main objective of this study is to understand event sequences accompanied by re-criticality due to core material motion. Fuel melting and significant core degradation leading to fuel discharge into the upper and lower direction of the core occurred in the reference case calculation. Two types of sensitivity calculations have been done. One aims to investigate the effect of Fuel-Coolant Interaction (FCI) in the failed control rod guide tube. The other one aims to investigate the effect of pressure generation due to FCI inside a special device which discharges molten core material into the lower plenum. This study is a part of France-Japan collaboration on R&Ds of SFRs conducted from 2020 to 2024.