Simulation-based Recovery Action Analysis Using the EMRALD Dynamic Risk Assessment Tool

A recovery action is defined as an action that prevents deviant conditions from producing unwanted effects. Recovery action evaluations are a critical part of human reliability analysis (HRA). However, limitations arise when treating recovery actions by using currently available HRA methods only. Representatively speaking, the existing recovery analysis methods do not explicitly consider the various recovery task types and recovery sequences that occur at actual NPPs. To handle challenges stemming from the existing recovery analysis methods, this study proposes a way to analyze recovery actions by employing the dynamic HRA method known as the Procedure-based Risk Investigation Method – HRA (PRIME-HRA). Through PRIME-HRA, dynamic simulation models can be developed using dynamic risk assessment tools such as Event Modeling Risk Assessment Using Linked Diagrams (EMRALD) [1] and the Human Unimodel for Nuclear Technology to Enhance Reliability (HUNTER) [2]. EMRALD and HUNTER are dynamic probabilistic risk assessment (PRA)/HRA tools developed at Idaho National Laboratory. This paper explores the differences between THERP, CBDT, and K-HRA in regard to recovery action analysis. It relates the challenges that stem from these approaches, and how we successfully developed PRIME-HRA. Finally, the proposed approach to analyzing recovery human actions within a dynamic context is touched upon, along with an example.