Comparison of MATRA-S and COBRA-SFS for Low Flow Subchannel Analysis

In this study, we compared the MATRA-S with COBRA-SFS for the PNL test because the COBRASFS is believed to be superior to MATRA-S for the low flow conditions. COBRA-SFS code was developed for subchannel analysis of spent fuel storage system based on COBRA-3C, COBRA-4I, and COBRA-WC. As the code was designed to predict temperature and flow distributions in spent fuel storage system, it can analyze thermal hydraulic fields of natural convection as well as radiation and conduction heat transfer. In the way of improving XSHCME of MATRA-S to be applicable to low flow problems, we compared MATRA-S XSCHEM and COBRA-SFS RECIRC for steady state and flow transient. Both methods use similar algorithms to solve pressure, axial flow and cross flow. MATRA-S XSCHEM predicted flow velocity profile well even negative flow in recirculation flow