Risk reduction design alternatives for low-power and shutdown operation of a 1500-MW advanced power reactor with a passive auxiliary feedwater system

摘要

The Korean nuclear power regulatory body issued the standard design approval for a 1500-MW advanced power reactor in 2014. The reactor was designed based on a four-train independent safety concept with a passive auxiliary feedwater system. Its full power risk, or core damage frequency (CDF), was determined to be significantly lower than that of the Advanced Power Reactor 1400 (APR1400) used in Units 3 and 4 of the Shin-Kori Nuclear Power Plant. However, because the ratio of the CDF contribution to the internal full power to that of the low-power and shutdown (LPSD) is 17:83, the risk during LPSD operation requires further assessment and reduction. In this study, we investigated design alternatives for reducing LPSD operation risks and analyzed the associated sensitivities. We propose various design alternatives, and their combinations, which are analyzed based on the reduction effect they have on the CDF for plant operating states and on initiating events during LPSD operation. The proposed alternatives, and their combinations in particular, exhibited significant reductions in LPSD CDF, indicating high potential applicability.