Study on Passive Pulse Cooling Method of Secondary Side in PWR Nuclear Power Plant

Abstract

Currently, the supplementary strategy of PWR nuclear power unit to deal with the Station Black-Out (SBO) and Total Loss of Feed-water (TLFW) accidents mainly depends on mobile facilities and manual operation. Under the SBO together with TLFW (SBO+TLFW) beyond design basis accident, the self-sustaining time after the loss of active accident mitigation measures (safety injection / auxiliary feed-water / containment spray) of the nuclear power plant is limited, and the operation time left to the emergency team is relatively less. Especially in the case of external disasters such as super typhoon, the reachability of temporary facilities and personnel is challenged. By analyzing the available resources of the secondary side of the unit after SBO together with TLFW accident, this paper puts forward the passive pulse cooling method of the secondary side: the steam generators are divided into power SG(s) and cooling SG(s), the high-pressure steam of the power SG(s) is used as the passive power source, inject the high-temperature deaerated water stored in the deaerator into the released cooling SG(s), and the core is cooled by pulse water injection and intermittent exhaust. Through qualitative analysis of cooling mechanism, operation strategy and operation mode are given to put into services, and the simulation machine and CATHARE model are used for verification test and simulation calculation respectively. The results show that the two calculation trends are basically the same, which can delay core melting time more than 7 hours after SBO+TLFW accident. According to the probabilistic safety analysis (PSA) of a plant, the core damage frequency (CDF) is reduced by about 7%. The research results in this paper will be helpful to optimize TLFW response strategies and avoid putting into “Feed and bleed mode” too early and contribute to provide mitigation measures for delaying core melting under SBO+TLFW accident, and to gain time for putting external mitigation measures into service.