Effect of PHT Pump Seal Leakage on Unmitigated SBO Transient in CANDU-6

Abstract

Under a station blackout (SBO) condition with no mitigation actions for the recovery of safety functions, steam generators would be depleted due to the failure to feed water and the continuous steam discharge through main steam safety valves. Following the failure of the heat sink to the primary system, the core would overheat, leading to fuel damage. The coolant could also leak out due to the seal failure of the primary heat transport (PHT) pumps, resulting in reducing the inventory and pressure of the PHT system and increasing the fuel sheath temperature up to the limit criterion. In this study, the effect of PHT pump seal leakage under an unmitigated SBO condition in CANDU-6 plants was investigated using the MARS-KS code. This study provides new results on the application of the code to the SBO transient by examining the characteristics of the system responses.