ABSTRACT
It has been widely recognised that operators working in a highly automated largescale human-machine system such as a nuclear power plant (NPP) may experience cognitively demanding situations during emergency in which workload tends to be high and pre-planned operating procedures may not be fully applicable. Unfortunately, this sometimes causes operators to exhibit erroneous behaviour, as has been shown in some disastrous incidents (e.g. Three Mile Island; Chernobyl). To identify effective measures against this inherent human factors deficiency of highly automated large-scale human-machine systems, it is crucial to understand the reasons that cause the misconduct of the operator. However, the reasons are often diverse, and it is sometimes, if not always, difficult to judge whether operators themselves were really responsible, or work environments-either design or organisational-were deficient. Any human performance or behaviour-either normal or erroneous-must however be seen as a manifestation of interactions among human mechanisms, internal factors (e.g. trait, experiences, knowledge, physical and mental state), and external factors (e.g. design, organisation). It is therefore important to understand the nature of human performance or behaviour, not in isolation, but in conjunction with the internal and external factors. This chapter presents some findings concerning the performance characteristics and performance-shaping factors (PSF) of NPP operators. These findings were obtained from a series of experimental studies using a full-scale training simulator.
