Study Of Loss Of Flow Accident For AP1000

AP1000 is introduced by China, which is developed by Westinghouse as the third generation of advanced pressurized water reactor nuclear power system. Compared to the traditional PWR,AP1000 adopts lots of passive safety systems,which simplifies the safety system. Loss of flow accident occurs when pump rotor locked in the primary loop, or caused by station blackout and it leads to the coolant flow rate drastically reduce or even interrupt.Based on AP1000 system structure and operating characteristics, the control volumes and the nodes were reasonably divided. The loss of flow accidents were selected to be analyzed,including partial loss of flow, complete loss of flow and pump rotor locked.The short-term analysis of partial loss of flow and complete loss of flow were carried out.The calculation results showed that the DNBR in the core was always higher than the safety analysis limit value and met the safety criterion demand. By changing the rotational inertia of the pump, calculations showed that a greater value of rotational inertia of the pump maintained larger coolant mass flow rate for the primary loop, which is conducive to core cooling and avoid DNB.The short-term analysis of pump rotor locked with off-site power available and unavailable were carried out. The results showed that the peak cladding temperature was below the safety analysis limit value and the acceptance criteria will be guaranteed. Finally,the results of long-term analysis for pump rotor locked without off-site power showed that passive safety system of AP1000 can effectively export core decay heat and maintain the long-term cooling, also insure the core safety.