Analysis of Impact on Core Level Monitoring System due to Judgement of Main Coolant Pump Status During LOCA

CCMS (Core Cooling Monitoring System) is widely used in current CPR1000 (Improved Chinese PWR) nuclear power plant to calculate core level and subcooling margin in the reactor vessel. In order to validate the effectiveness of core level calculation under condition of LOCA (Loss of Coolant Accident), and quantitatively analyze water level calculation difference of two judgment methods of main coolant pump status in control system, the measuring principles of CCMS are analyzed. The level and error of CCMS calculation under these two conditions is calculated using RELAP5 (Reactor Excursion and Leak Analysis Program) to simulated thermal hydraulic part of CPR1000 unit and virtual DCS (Distributed Control System) to emulate control system. The result shows that CCMS system will introduce large error of water level between calculation value and real level in reactor during LOCA, and operator may be misled by the incorrect information to an improper operation procedure.