8.2.1 Introduction to the risk analysis process

Since HRA is usually applied in the context of technical safety and risk assessment, sometimes referred to as Formal Safety Analysis (FSA), we will first provide a brief overview of this process. The overall purpose of technical safety analysis and risk assessment is the identification and management of risks so that they are reduced to an acceptable level. The stages of the process can be summed up as follows:

• Identification of the hazards. These are aspects of a system likely to cause harm to people (e.g. high temperatures, pressures, toxic substances, voltages, high velocities) or financial loss.

• Evaluation of scenarios or credible incidents. These are events or sequences of events that could release the hazards.

• Evaluation of consequences. This is concerned with the different ways in which the hazard could exert its effects or influences on people, company assets or the environment once released.

• Evaluation of the probability or frequency with which the hazard is likely to be released (e.g. once every 10,000 operations of the system, once every 10 years).

• Evaluation of the risk. The product of the severity of the consequences and the frequency of its occurrence is the risk (alternatively the product of the severity of consequences, the frequency of exposure and the probability of the incident leading to the release of the consequences).

• Assessment of whether the risk is acceptable, using risk criteria, or bands of acceptability.

• Modification of the system if...