Nuclear power plant (NPP) operators perform a variety of tasks that differ in mental workload. These include detection tasks that may be vulnerable to vigilance decrement. The present study used a simulation of NPP operation to investigate possible loss of vigilance during detection. Metrics used to assess operator functioning included subjective measures of workload and stress, physiological indices of workload, and objective performance. Detection, checking and response implementation tasks were compared, in the context of a simulated Emergency Operating Procedure (EOP). Study findings suggested three conclusions. First, detection imposed higher subjective workload and distress than other tasks, but physiological data suggested more complex differences between tasks. Second, vigilance decrements in detection performance were observed within 5-min task \u27steps\u27. However, analyses of physiological metrics suggested that multiple temporal processes may operate. Third, there were consistent individual differences in task-induced workload responses. Implications of the findings for evaluating NPP interface designs and monitoring operators are discussed
