Safety Analysis for Sub-channel Blockage in the PGSFR

The flow perturbation caused by the blockage could raise the local coolant temperature in the incident and it might eventually lead to the degradation of the fuel rods. Therefore, a partial flow blockage accident must be a safety concern in the SFR design. In this regard, analyses were performed for the flow blockage accident postulated in a conceptual design of a 150MWe Proto-type SFR using the MATRA-LMR/FB and analysis result was compared to the safety acceptance criterion shown in Table 1 developed by KAERI. The maximum coolant temperatures for 6, 24 channels blockage occurred at the end of the fuel slug and both of them satisfied the safety limits. However, for the 54 channels blockage, the maximum coolant temperature was found in the downstream of the blockage and it could not meet the safety limits. It was caused by the recirculation region in the downstream of the blockage. In conclusion, satisfactory margins were obtained for 6, 24 channel blockage cases