INDESCO: Integrated Decision Support System to Aid the Cognitive Activities of Operators

The possibility of human failure or human error has a significant impact on the safety or reliability of large-scale systems. Most analysis results of accidents, including Chernobyl and TMI-2 accidents indicate that human error is one of the main causes of accidents. Forty-eight percent of incidents in an analysis of 180 significant NPP events occurring in the United States were attributed to failures in human factors [1]. Human factors are analyzed to prevent human errors and are considered in performing a more reliable safety assessment of a system. HRA and human factors are described in Chapter 7 and Chapter 8. An approach to assessing the safety of a system, including human operators, is introduced in Chapter 11, which suggests an integrated safety model that includes both digital control systems and human operators. The adequacy of procedures, stress (available time), training/experience of human operators, and sensor failure probabilities are found to be relatively important compared to other factors in a sensitivity analysis described in Section 11.3.5. The safety of a system is more affected by these four factors. Efficient improvement in the safety of a system is achieved by improving them in the system. Such factors related to humans have been becoming more important than other factors related to hardware and software because only highly reliable hardware and software components can be used in safety-critical systems, such as NPPs.