Evaluating Operators’ Real-Time Mental Workload with Eye Movement Analysis in Nuclear Power Plants’ Operations

Nuclear power plant (NPP) operators need to have sufficient real-time cognitive ability to ensure their adherence to operational procedures and solve unexpected problems. The heavy cognitive load will degrade such ability and lead to operation errors. Previous studies show that the NPP workflows' (a network of activities) properties, such as workflow structure types, activity types, and recurring activities, can significantly impact the operators' cognitive load. However, which workflow properties could lead to a higher cognitive load are unclear. This study examines what workflow properties pose cognitive challenges to operators and quantitatively evaluates these properties' impact on the operators' cognitive load. The authors designed a simulation experiment on a nuclear reactor operation simulator called "Rancor" and recruited four students as pseudo-operators to perform reactor startup tasks. In the experiment, we collected the students' eye movement data using a mobile eye tracker. Participants' pupil diameter changes and eye movement types can indicate cognitive load and information searching strategies. The correlation analysis results indicate that workflow structure (i.e., sequential and parallel structures) and activity types correlate with participants' pupil diameter changes. Such correlation indicates that parallel structure and recurring activities demand relatively high cognitive efforts. Moreover, eye movement analysis reveals that recurring activities require more fixed attention from operators. Overall, a quantitative evaluation of the relationship between workflow properties and the cognitive process advances understanding about NPP operators' cognitive load and information searching strategies while executing different types of workflows.