Quantifying Safety Significance: An In-Depth Analysis of Importance Measures in Level 1 PSA for the VVR 10-MW Water-Water Research Reactor

The effectiveness of contemporary strategies for conducting fault tree/event tree (FTET) analyses within the realm of probabilistic risk assessment has recently come under rigorous examination. In light of such investigation, facility managers have gained a more profound understanding of the risk and safety implications inherent in the structural and componential integrity of systems (structures, systems, and components). This comprehensive research endeavor harnesses the power of risk models, employing both FTET and binary decision diagrams, to scrutinize and optimize the operational performance of a 10-MW reference Russian research reactor [Water-Water Research Reactor (VVR)] within the framework of probabilistic safety assessment. Moreover, this investigation delves into the intricate web of interrelationships existing among an array of analytical methodologies. These encompass the Fussell-Vesely (FV) importance measure, criticality analysis, Birnbaum analysis, risk achievement worth (RAW), and the differential importance measure, all with a focus on specific foundational events and vital components. Additionally, this note delves into the analysis of multiple significant measures frequently employed for VVR. Notably, the study establishes that merely two importance measures (IMs) prove sufficient for the core damage equation. Furthermore, this note investigates various important measures often employed for VVR. It is shown that two IMs are enough for the core damage equation. In conclusion, RAW, FV importance, or a blend of the two are adequate enough to be frequently employed for the VVR.