Human factor in probability assessment of nuclear power plant operating safety

A method of human factor reliability assessment is described and an example of an application is given. The analysis consists of 12 steps, viz.: familiarization with the power plant; obtaining information on the man-machine interaction from failure trees; consultations with personnel; analysis of tasks; construction of an event tree for the analysis of the human factor effect; assignment of probabilities to human errors; assessment of the relative effect of circumstances; assessment of relations between human errors; determination of probabilities of successful and unsuccessful interventions; determination of the effect of error correction; analysis of uncertainty; supplying results in the failure trees for the analysis of system reliability. An example is shown of an application where the failure tree showed that one of the reasons of non-intervention of the reactor accident protection system was an incorrect calibration of all the three measuring channels for the technological parameter which attained the accident limit. (J.B.). 2 figs., 3 refs