Plant control diagnostic failure-just a matter of time?

The role of time as a critical determinant of human performance, particularly the diagnostic performance that is essential in potential accident sequences in complex systems such as nuclear power plants, is reviewed. Two main questions are asked. What is the actual role of time in cognitive activity? and how dominant should time be as a performance shaping factor in the prediction of human reliability? The first question is addressed by considering major relevant psychological models for process control-type activities. The second is explored by analyzing how each of fifteen models of human reliability quantification utilize time in their predictions. These various roles of time, some dominant, some negligible, are then considered in the light of realistic accident scenarios.<>