Effect of user interface layout on the operators' mental workload in emergency operating procedures in nuclear power plants

The improved control interface designs in nuclear power plants (NPPs) have been constantly developed in order to satisfy actual requirements. In this article, the effect of user interface layout on mental workload (MWL) of operators in emergency operating procedures in NPPs is analyzed. The control circuit interface of the Chemical and Volume Control system (RCV) was redesigned based on some human factor criterions and it was compared to the original interface during the procedure of system boots. The multi-index evaluation method based on performance measures (i.e., time to complete and error rate), subjective rating (i.e., NASA Task Load Index (NASA-TLX)) and physiological measure (i.e., eye movement) was used to evaluate MWL of operators. Twenty-two engineering students tested both interfaces in randomized order. The results showed that interface design has a significant effect on operators' MWL. Specifically, the redesigned interface was rated significantly lower in overall workload, time to complete, and fixation indices, but higher blink rate. The results suggested that human factor criterions have a significant effect on operators' MWL so they should be considered during designing of interface, and using of NASA-TLX tool and eye movement technique is useful for assessing of human-computer interface (HCI) designs in NPPs.