A reliability analysis method based on signed directed graph

The Signed Directed Graph (SDG) is a qualitative fault diagnosis method grounded in graph theory, effectively illustrating the relationships between variables in complex systems and elucidating the propagation paths of potential hazards and faults. Renowned for its simplicity in modeling and comprehensive coverage, SDG has been extensively utilized in safety evaluation and fault diagnosis across various fields. Despite its widespread application, the limitations of SDG, particularly its lack of quantitative analysis and the unwieldy size of its models, have become increasingly apparent. To address these challenges, this paper introduces a reliability analysis method that leverages SDG. Initially, a hierarchical approach predicated on accessibi lity is employed to streamline the system's SDG model. Subsequently, quantitative dimensions, including system failure probability and component importance, are integrated into the hierarchical SDG model. The method's feasibility and validity are demonstrated through a case study involving the Safety Injection System (SIS) of a pressurized water reactor nuclear power plant, where a hierarchical SDG model of the SIS is developed and used to conduct a quantitative reliability analysis.