Dynamic Approach to Dependency Analysis in Human Reliability Analysis: Application in a Steam Generator Tube Rupture Scenario

Dependence analysis refers to a method for adjusting the failure probability for a human action by considering the impact of the preceding human action in human reliability analysis (HRA). Most of the existing dependence analysis methods have been developed based on the approach suggested in the Technique for Human Error-Rate Prediction (THERP) HRA method. However, the THERP-based approaches may have limitations. For instance, it inevitably presents challenges regarding both the subjectivity of expert evaluation as well as experience using dependence for resource-intensive and time-consuming complex analyses. In addition, the THERP-based quantification approaches rarely explain the adjustment of human error probabilities (HEPs), since the quantification processes do not concretely account for the context at the moment when the action is present. For these reasons, the authors’ previous studies have conceptually suggested a dynamic approach to evaluating dependencies by extending the existing performance shaping factor (PSF) concept used for quantifying HEPs in HRA. The conventional PSF modeling methods are limited to separate modeling for each HFE. However, this study suggests PSFs can affect a set of human actions or a multiple HFE rather than a single HFE. With this assumption, the authors simplified the dependency analysis process to efficiently evaluate dependencies and increase the quantification speed with more explicable backgrounds. In this paper, the authors mainly focus on dependency quantification over time. This study utilizes the eight PSFs suggested in the Standardized Plant Analysis Risk-HRA (SPAR-H) method. The mathematical models and logical algorithms are investigated through literature. Integrating the effects of PSFs to generate HEPs with dependency effects is also investigated. Then, the applicability of the dynamic method is investigated based on a design-based accident scenario, steam generator tube rupture. Lastly, insights from this approach are discussed in the paper.