Cooling capability of remaining core fuel after core degradation in SFRs

Imaizumi, Yuya ; Sogabe, Joji*; Onoda, Yuichi ; Yamano, Hidemasa   

Cooling capability of core remaining fuel after core degradation in ULOF accident in a SFR was evaluated. Two analysis cases with and without coolant re-entry from lower side of transfer tubes were defined in this study, because the cooling capability depends on it. For the no coolant re-entry case where stratified layers of fuel and steel are formed and cooled down in a long time, new analysis code with one-dimensional heat and mass transfer model, called PAHRCR, was developed and applied. As a result of the analyses, the melting of lower core structure stopped in the 60 % fuel inventory case, but it was melted and almost lost in the 70 % fuel inventory case. This result showed the coolable inventory of the core fuel. For the analysis of the coolant re-entry case with assumption of molten fuel discharge, the SIMMER-III code was used. As a result, the remaining core fuel was cooled down in relatively short time, and all fuel particles were finally immersed in the coolant.