Читать книгу Risk Assessment - Marvin Rausand - Страница 46

An identified event that represents the beginning of an accident scenario. (Adapted from IAEA 2002 .)

This definition states that the initiating event represents the beginning of an accident scenario, but it is not clearly specified where and when the beginning is. In Example 2.1 , we said that “gas leak from flange A” was the beginning of the accident scenario, that is the initiating event, but we do not say anything about why the leak occurred. If this was because of an impact against the flange, we could have said that “impact against flange A” was the initiating event. In practice, it is up to the risk analyst to decide what she wants to define as the beginning. This depends on what the focus of the analysis is, the limitations of the analysis, limitations in our knowledge about the system or the accident scenarios, and so on. Among the causes of initiating events are hazards.