On the use of data and judgment in probabilistic risk and safety analysis

Abstract This paper reviews the line of thought of a nuclear plant probabilistic risk analysis (PRA) identifying the points where data and judgment enter. At the “bottom” of the process, data and judgment are combined, using one and two stage Bayesian methods, to express what is known about the element of variables. Higher in the process, we see the use of judgment in identifying scenarios and developing plant models and specifying initiating event categories. Finally, we discuss the judgments involved in deciding to do a PRA and in applying the results.