Research on flow resistance characteristics of reactor coolant pump under large break LOCA at inlet

Abstract

In the event of a large break loss-of-coolant accident (LBLOCA) at the inlet of the nuclear Reactor Coolant Pump (RCP), the RCP is likely to enter an extreme working condition of the reverse pump mode. In this mode, the pump actually acts as a stopper to the coolant out of the circulation system. When the flow rate remains constant, the head reflects the flow resistance capacity. In previous studies, we have found that the head of the RCP increases and then decreases with increasing cavitation under the reverse pump mode. Objective to research into this situation, numerical simulation of the RCP under the reverse pump mode has been used to analyze the flow resistance characteristics inside the impeller. Results show that the high-velocity flow generated by the cavitation region is the crucial factor causing the variation in pump head in comparison with the vapor volume fractions of the impeller blade surface. To investigate the effect of high-velocity flow on the pump head under different cavitation conditions and to even better reveal the flow resistance characteristics, entropy production analysis and vorticity analysis are carried out for the internal flow field of the impeller.