Probabilistic Safety Assessment of Tehran research reactor based on a synergy between plant topology and hierarchical evolutions

• Plant topology and hierarchical evolutions are used for PSA study.
• SPAR – H method is used for human reliability analysis.
• Dynamic piping and instrumentation diagram is used as framework.
• Multiple core damage states are considered.

Probabilistic Safety Assessment (PSA) is a powerful means in assessing risk and reliability of nuclear plants to complement the achievement of safe operation. A software has been developed in this study to perform failure and reliability analysis (in a PSA context), which are extremely important elements for improving plant operation and safety. This software introduces many advantages such as causal relationships, integrating the analysis tool with plant topology, using plant topology as the basis for explaining the relationships, dynamic navigation through plant model and highlighting fault propagation paths. In the software, plant topology plays the major role. It defines the relationships among plant components, systems and structures and provides the system configurations and causal relationships needed to perform reliability and risk analyses. These advantages are achieved via using some hierarchical evolutions with integrating plant topology (i.e., causal, Part-whole, and Topological hierarchies) and dynamic piping and instrumentation diagrams (DP&IDs). As a case study to verify the software efficiency, PSA of Tehran Research Reactor (TRR) at full power is performed with both the proposed software and System Analysis Programs for Hands-On Integrated Reliability Evaluation (SAPHIRE) (which is used as benchmark software in U.S. Nuclear Regulatory Commission), and good agreement was found.