Sensitivity analysis of failure correlation between structures, systems, and components on system risk

A seismic event caused an accident at the Fukushima Nuclear Power Plant, which further resulted in simultaneous accidents at several units. Consequently, this incident has aroused great interest in the safety of nuclear power plants worldwide. A reasonable safety evaluation of such an external event should appropriately consider the correlation between SSCs (structures, systems, and components) and the probability of failure. However, a probabilistic safety assessment in current nuclear industries is performed conservatively, assuming that the failure correlation between SSCs is independent or completely dependent. This is an extreme assumption; a reasonable risk can be calculated, or risk-based decision-making can be conducted only when the appropriate failure correlation between SSCs is considered. Thus, this study analyzed the effect of the failure correlation of SSCs on the safety of the system to realize rational safety assessment and decision-making. Consequently, the impact on the system differs according to the size of the failure probability of the SSCs and the AND and OR conditions.(c) 2023 Korean Nuclear Society, Published by Elsevier Korea LLC. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Automated summary

An earthquake at the Fukushima Nuclear Power Plant caused accidents at multiple units, sparking global concerns about nuclear power plant safety. Current probabilistic safety assessments in the nuclear industry assume either independent or completely dependent failure correlations between structures, systems, and components (SSCs), which can lead to unreasonable risk calculations and decision-making. This study aims to analyze the impact of failure correlations among SSCs on system safety to enable rational safety assessments and decision-making.