A fuzzy based model for safety assessment of AP-1000 and VVER-1200 nuclear reactors for cold leg break loss of coolant accident with turbine trip

Abstract

Carbon neutral electricity generation from nuclear energy is essential for continuous and reliable electricity production as well as for climate change mitigation. However, performance improvement of safety systems of nuclear power plants (NPPs) is one of the major aspects of making nuclear energy more acceptable to the public. Many researchers studied the fault diagnostics of NPPs. But various combinations of malfunctions may produce diverse consequences in a system. Therefore, in this study, a Global Safety Index (GSI) indicator has been developed for the AP-1000 and VVER-1200, two-generation III+ nuclear reactors, using the performance of safety systems. Sensing time, response time, recovery time, and core damage frequency (CDF) were taken as inputs for the Fuzzy Inference System (FIS). The first three inputs were taken from the PCTran simulator by simulating a 100% of 100 cm2 cold leg break Loss of Coolant Accident (LOCA) concurrent with turbine trip for both reactors. It was found that VVER-1200 has a quicker sensing and response time than the AP-1000 for safety instrumentation systems. Furthermore, GSI values were compared for both the VVER-1200 and the AP-1000 reactors. The GSI value of VVER-1200 was found to be higher than that of the AP-1000. The performance of active and passive safety systems for both reactors was found satisfactory in mitigating any consequences of the postulated combination of malfunctions.