Risk Assessment: Theory, Methods, and Applications

CHAPTER 11

DEVELOPMENT OF ACCIDENT SCENARIOS

11.1 INTRODUCTION

This chapter deals with the third question in the triplet definition of risk: How can the possible consequences of a hazardous event be determined? An accident scenario was defined in Chapter 2 as a sequence of events from a hazardous (or initiating) event to an end event with undesired consequences. This may also be regarded as a pathway from a hazardous event to an asset. Development of accident scenarios means to identify and describe the possible pathways from a hazardous event to one or more assets. Identification of relevant hazards and hazardous (or initiating) events was discussed in Chapter 9.

A hazardous event may in practice lead to a wide range of consequences to assets (see Chapter 2). Which assets should be considered depends on the objectives of the analysis. The analysis may focus on a single asset or several assets at the same time. Some authors prefer to use the term target instead of asset. The development of accident scenarios is also called accident sequence analysis.

11.1.1 Objectives of the Development of Accident Scenarios

The objectives of developing accident scenarios are to:

1. Determine the possible accident scenarios (event sequences) that can possibly take place after a specified hazardous event has occurred.
2. Identify existing and possible reactive barriers that can stop or mitigate the various accident scenarios.
3. Identify external events or conditions that can influence each accident scenario. ...