Integrated Human Reliability Analysis Methodology for External Control Room Emergency Response Scenarios: Application to Modeling FLEX Human Actions in Nuclear Power Plants

Abstract Existing human reliability analysis (HRA) methods, commonly applied for modeling main control room (MCR) operator performance at nuclear power plants (NPPs), are not designed to address the influence of spatiotemporal evolution of environmental conditions on human performance in external control room (Ex-CR) scenarios due to the following challenges: (i) limited empirical human performance data in Ex-CR scenarios, (ii) difficulty in obtaining a complete set of performance shaping factors (PSFs) applicable and important for Ex-CR scenarios, (iii) limited ability to adequately address spatiotemporal and bidirectional interactions between human performance, system response, and hazard progression, and (iv) difficulty in handling the large uncertainty associated with plant conditions during the time window of Ex-CR scenarios. This paper develops a novel HRA methodology, namely, the integrated human reliability analysis (I-HRA) methodology, to overcome these challenges. Compared to existing HRA methods, I-HRA possesses a unique combination of four key features: (i) it integrates simulation-based human performance modeling and existing nonsimulation-based HRA methods under a unified agent-based modeling platform; (ii) it is equipped with a coupling of physics and human performance simulation models to explicitly capture the underlying, bidirectional, and spatiotemporal interactions among these elements; (iii) it enables explicit simulation-based treatment of dependencies; and (iv) it allows for adequate consideration of aleatory and epistemic uncertainties. The I-HRA methodology is demonstrated using a case study that involves deploying diverse and flexible mitigation strategies (FLEX) equipment in responding to an external flood at an NPP.