A Core hot spot evaluation by statistical method for pool-type sodium-cooled fast reactors, 3; Applicability assessment of the evaluation method under natural circulation conditions

Mochinaga, Shota  ; Doda, Norihiro  ; Iwasaki, Takashi*; Igawa, Kenichi*; Tanaka, Masaaki 

A core hot spot (CHS) evaluation method (e.g., maximum cladding temperature in a fuel pin) is being developed for the safety evaluation of a pool-type demonstration sodium-cooled fast reactor. During decay heat removal by natural circulation (NC), buoyancy drives the coolant flow, making the influences of uncertainty factors complicated relationship with thermal-hydraulic behavior. Therefore, a statistical approach to the CHS evaluation is effective in the NC transient. In this study, the fuel pin model including effects of coolant flow distribution and buoyancy within the assembly was newly constructed and the applicability of the statistical CHS method for several NC events was confirmed.