Introduction

Technological systems function safely most of the time, but they are not fail-safe. The massive escape of toxic gas from the chemical plant in Bhopal, the enormous release of radioactivity from the nuclear power plant in Chernobyl, and the huge spill of crude oil from the oil tanker Exxon Valdez in Prince William Sound demonstrate how calamitous the failures can be. Technological risk assessment provides information about the frequency of system failures, the ways in which they might occur, and the potential severity of the consequences.