ABSTRACT
This chapter discusses methods for quantifying the extent to which complex engineering systems can be designed and operated safely. It introduces methods of probabilistic risk assessment (PRA), sometimes called probabilistic safety assessment (PSA), and briefly discusses its potential, some limitations, and various areas of application. The chapter describes and illustrates key concepts of risk analysis and PRA, and explains how it can be used to inform and improve risk management decisions. It introduces core techniques of PRA modeling: hazard identification; fault trees and event trees; and frequency-severity diagrams ('F-N curves'). The chapter considers how the inputs to these and other risk models can be obtained, using both subjective estimates and alternatives such as accident precursor analysis; and discusses techniques for characterizing and bounding uncertainty in risk results, given uncertainties about the inputs and about the validity of the risk models used to calculate outputs from the inputs.
