Abstract
A systematic probabilistic safety assessment for a boiling water nuclear reactor core is performed using fault trees and event trees analysis models. Based on a survey of the BWR’s safety systems against potential hazards, eight independent failure modes (initiating events) triggered scenarios are modelled and evaluated in the assembled fault-event trees, obtaining the two key outcome probabilities of interest, i.e., complete core meltdown (CCMD) frequency and minor core damage (MCD) frequency. The analysis results indicate that the complete loss of heat sink accounts for the initiating accident most vulnerable to CCMD (with a frequency of 1.8 × 10 − 5 per year), while the large break in the reactor pressure vessel is the least susceptible one (with a frequency of 2.9 × 10 − 12 per year). The quantitative risk assessment and independent review conducted in this case study contributed a reference reliability model for defense-in-depth core optimizations with reduced costs, informing risk-based policy decision making, licensing, and public understanding in nuclear safety systems.
Highlights
IntroductionImproving the safety margin and cost-efficiency of reactors in the existing fleet, such as pressurized water reactors (PWR) and boiling water reactors (BWR), exhibits the highest priority
The merits of nuclear energy have been re-discovered over recent years to address the future global energy needs [1] in an environmentally conscious and resource-sustainable way [2]
The modelling and analysis in this study provide a physical insight into the complex nuclear system, based on which risks and mitigation priorities are proposed, targeting cost effectiveness
Summary
Improving the safety margin and cost-efficiency of reactors in the existing fleet, such as pressurized water reactors (PWR) and boiling water reactors (BWR), exhibits the highest priority To this end, probabilistic safety assessment (PSA) [10,11] based on fault tree [12,13] and event tree [14] analyses present these characteristics and can be designed to tailor for the overall risk assessment of PWRs and BWRs. Historically developed for nuclear [15] and petrochemical [16]. It is of importance to give to the nuclear regulatory body and the academic community an independent verification of the core meltdown and the minor core damage frequency calculations (a case study for the BWR in this work), as an independent study; if available, multi-benchmarking creates trust in safety reports. The potential beneficiaries are nuclear power plant operators, risk assessors, regulators, government energy policymakers, electricity suppliers and the wider academic community
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