Investigating the Effect of Task Complexity on the Occurrence of Human Errors observed in a Nuclear Power Plant Full-Scope Simulator

•The appropriateness of the TACOM measure is confirmed by comparing human error data.•Human error data were collected from a full-scope simulator of a domestic Korean NPP.•Variations in the number of UAs and the TACOM scores are statistically correlated•The TACOM measure is confirmed to be meaningful in explaining the performance of human operators with respect to the number of UA occurrences.•The TACOM measure is appropriate to quantify the complexity of proceduralized tasks. The task complexity (TACOM) measure was previously developed to quantify the complexity of the proceduralized tasks performed by nuclear power plant main control room operators, and its suitability has been verified by comparing TACOM scores with two different types of human performance data, response times and subjective workload scores. The full appropriateness of the measure has yet to be sufficiently validated though, because of a current lack of comparisons between TACOM scores and associated human errors. In this regard, the purpose of this study was to further confirm the appropriateness of the TACOM measure by comparing human error data collected from a full-scope simulator of a domestic Korean nuclear power plant with the associated TACOM scores. Results show that the number of human errors increases proportionally with an increase in TACOM score. This result strongly implies that the TACOM measure is suited for use as a tool to estimate the complexity of proceduralized tasks, which would act as a key indicator to identify the vulnerable points most likely to lead to operator performance degradation.