Development of a robust multi-phase heat transfer model and optimization of multi-layer core catcher for future Indian sodium cooled fast reactors

Abstract

In the evolutionary design of Sodium Cooled Fast Reactors (SFR), core catcher has to handle debris generated from damage of whole core. This requirement combined with large core size demand that newer core catcher has to accommodate large volume of debris and consequently a thick debris bed having the risk of re-melting. To cater to this, a one-dimensional multi-phase heat transfer model for re-melting/re-solidification of core debris on a multi-layer core catcher is developed. Versatility of the model for various conditions is established. Then the model is applied to core catcher of future Indian SFR of 600 MWe capacity. Based on parametric studies, it is found that a 40 mm thick delay bed made of Thoria restricts the heat shield plate temperature within permissible limit. The corresponding minimum radius of debris spread is 3.25 m. This avoids core debris re-melting, provided melt-arrival time exceeds 1000 s.