Probability Safety Analysis for Nuclear Power Plant Long-Term Temporary Shutdown State

Abstract

In recent years, due to the influence of power grid demand and other factors, some nuclear power plants have long-term temporary SHUTDOWN. At present, there is no mature quantitative analysis method to measure which Plant operational state is safer under long-term temporary shutdown. Taking a second-generation nuclear power plant as an example, this paper first briefly introduces the PSA analysis method; Secondly, the difference is analyzed qualitatively, which between standard long-term temporary shutdown condition and refueling shutdown condition. Thirdly, from the quantitative point of view, the model processing methods and analysis assumptions are introduced, the risk views are given, and the quantitative calculation and sensitivity analysis are carried out; Finally, the analysis conclusion is obtained. Stay in the standard long-term temporary shutdown state for 15/30/45/60 days, after supplementing the calculation of the thermal shutdown condition,the risk per unit time of long-term temporary staying Maintenance Cold Shutdown mode is lower. The risk sequence is: Cooldown with the residual Heat Removal mode > Hot shutdown condition > Maintenance Cold Shutdown mode with closed primary loop. From the perspective of the risk of core damage, it is suggested that the Maintenance cold shut mode in which the primary loop is kept closed is recommended for long-term temporary shutdown of the power plant.