Accident Consequences and Evaluation
Event trees are diagnuns that evaluate the consequences of a specific hazard. The safety Ineasures and the procedures designed to deal with the event are presented here in Chapter 17. The consequences of each specific event that led to the accident are also presented. An event tree is drawn (sequence of events that led up to the accident). The accident is described. This allows the path of the accident to be traced. It sho\vs possible outcolnes that could have arisen had a single event in the sequence been changed. Thus, an event tree provides a diagraIlllnatic representation of event sequences that begin with the so-called initiating event and tenninate in one or Inore undesirable consequences. In contrast to a fault tree, which works backward froln an undesirable consequence to possible causes, an event tree works fonvard froin the initiating event to possible undesirable consequences. As described earlier in Chapter 15, the initiating event Inay be equipillent failure, human error, power failure, or SOUle event that has tile potential for adversely affecting an ongoing process.