30.1 Introduction

Probabilistic risk assessment (PRA) is an analytical methodology for computing the likelihood of health, environmental, and economic consequences of complex technologies caused by equipment failure or operator error. It can also be used to compute the risks resulting from normal, intended operation of these technologies. PRAs are performed for various end uses. These include: understanding the safety characteristics of a particular engineering design, developing emergency plans for potential accidents, improving the regulatory process, and communicating the risks to interested parties. These are a few broadly stated examples of applications of the methodology.

The requirements of the end uses should determine the scope and depth of the particular assessment. A PRA often requires the collaboration of experts from several disciplines. For example, it could require the designers and operators of a facility to provide a characterization of the normal and potential off-normal modes of behavior of the facility; it could require analysts who develop and codify scenarios for the off-normal events; it could require statisticians to gather data and develop databases related to the likelihood of the occurrence of events; it could require physical scientists to compute the physical consequences of off-normal events; it could require experts in the transport of effluents from the facility to the environment; it could require experts in the understanding of health, environmental, or economic impacts of effluents. Experts in all phases of human behavior related to the normal and offnormal behavior of a facility and its environment could be required.

PRA...