Experimental Study on Nuclear Power Plant Operators’ Performance during a Major Earthquake with Aftershocks

Abstract

Abstract Experiments were conducted to clarify the effects of seismic motion and aftershocks on the performance and physiological and psychological states of nuclear power plant operators. Nine reactor operators (average experience: 5.2 years) responded to various events associated with a great earthquake using a virtual reality simulator that simulated the main control room and plant behavior and a chair-type earthquake simulator. The experimental conditions were the presence and absence of vibrations. For each condition, the differences in the following indices were analyzed: The errors and utterances made during plant response were performance indices; cardiac sympathetic index, cardiac vagal index, and skin conductance level were physiological indices; and responses to a questionnaire on stress were psychological indices. Results revealed that operators experienced transient physiological stress at the time of the main shock, and felt the seismic motion’s effects on plant operations, such as “delay in initial response” and “disruption of priorities,” which did not seem threatening. They did not perceive any impact on performance. For aftershocks, it was found that the motion of the aftershocks themselves had almost no effect on the operators, but that the presence of aftershocks increased omission errors for events occurring immediately before the aftershocks, and that “work interruption” and “changes in plant conditions” due to aftershocks had affected them. Adding a seismic vibration experience using a simulated environment to regular training will contribute to the collection of performance data for operators and improve operators’ preparedness for earthquakes.