A framework to estimate task opportunities from the operational experience of domestic nuclear power plants

Since one of the most important issues in operating socio-technical systems is to enhance their safety through reducing the likelihood of human errors, it is prerequisite to secure reliable human performance data clarifying when and why human operators make an error. In this regard, many researchers tried to calculate an HEP (Human Error Probability) from operational experience data based on its traditional definition (i.e., HEP = number of errors observed/number of task opportunities for error). Accordingly, most of existing HEPs mainly based on the number of task opportunities being estimated from routine or periodic tasks that are usually performed in a full power condition with fixed time intervals. In contrast, calculating an HEP for a task being conducted in an off-normal condition is relatively seldom because it does not happen with a fixed time interval. For this reason, in this study, a novel framework is proposed, which can be used to estimate the number of task opportunities in terms of off-normal tasks from the operational experience of domestic NPPs. Although the proposed framework still has a couple of limitations, it could be a good starting point not only to enrich the ability of HEP calculation from the operational experience data but also to provide a reference information for HEPs obtained from other sources of information (e.g., full-scope simulators).