Best estimate plus uncertainty analysis of the China advanced large-scale PWR during LBLOCA scenarios

Abstract China advanced large-scale Pressurized Water Reactor (PWR) implements series of passive safety systems to provide core cooling and decay heat removal in case of some unexpected accidents. The development of reactor best estimate system analysis codes has realized the transition from conservative safety analysis to Best Estimate plus Uncertainty (BEPU) analysis for the purpose of achieving more realistic results and digging larger safety margins. The BEPU analysis during Large Break Loss of Coolant Accident (LBLOCA) has been widely used for the licensing application of Nuclear Power Plants (NPPs). In this paper, the BEPU analysis of China advanced large-scale PWR was performed under the conditions of LBLOCA scenarios employing RELAP5 code. The models of reactor coolant system with all the passive safety systems were established and the influence of uncertainties of important parameters on the Peak Cladding Temperature (PCT) was evaluated. The results show the obtained PTC (1314 K) through the BEPU analysis is far below the 10CFR50.46 PCT acceptance criteria (1477 K) in case of LBLOCA and is also lower than the conservative calculation value (1348 K), indicating a larger safety margin. This work provides a meaningful evaluation method for China advanced large-scale PWR safety assessment.

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