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Enhancing Workload Estimates for Validation Activities Associated With DBA and BDBA Scenarios

Abstract of the technical paper/presentation presented at:
10th International Topical Meeting on Nuclear Plant Instrumentation, Control and Human Machine Interface Technologies
June 11–15, 2017

Prepared by:
Aaron Derouin and Alice Salway
Canadian Nuclear Safety Commission


Since the Fukushima Daiichi accident, nuclear regulators around the world have required that power reactor licensees develop more extensive emergency mitigating responses and severe accident management provisions beyond the defense-in-depth measures for design-basis accidents (DBAs) and beyond-design-basis accidents previously in place. Workload assessments represent common validation techniques that are used to demonstrate that workers are able to perform tasks without unacceptable performance degradation. High workload is known to induce stress and fatigue and may severely diminish a worker’s capacity to perceive, recognize and respond appropriately during emergency or unanticipated events, which may result in undesirable consequences. In estimating workload during emergency and severe accident scenarios, power reactor licensees tend to rely on subjective measures of workload, such as NASA-TLX. Due to reported mismatches in the literature between subjective and physiologically derived estimates of workload, it is prudent to see what more can be done to improve the current state of practice in the context of emergency and severe accident conditions.

This presentation puts forth the idea that to improve confidence in workload estimates, the nuclear industry should integrate physiologically based measures into current practices by making use of "on-body" or "wearable" physiological sensors. In this paper, an overview of three different types of empirical workload approaches is provided. The advantages of wearable physiological sensors are considered in the context of extreme environments and occupations, with tangible examples including heat stress and pupillometry. Suggestions for a consensus forum on workload are provided, and a research plan directed at improving the current practice of workload estimation is offered for consideration.

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