10
Uncertainty Representation and Propagation in Event Tree Analysis
In this chapter, we illustrate the application of the uncertainty representation and propagation methods to event tree analysis in the nuclear industry. The application is in part based on Baraldi and Zio (2008).
10.1 Event Tree Analysis
Event tree analysis (ETA) is an inductive logic method for identifying the various accident sequences which can result from a single initiating event and is based on the discretization of the real accident evolution into a few macroscopic events. The accident sequences are then quantified in terms of their probability of occurrence. In the following, we give only the very basic principles of the technique. The interested reader is invited to look at the specialized literature for further details, for example, Zio (2007) and Henley and Kumamoto (1992), and references therein, from which the material here has been synthesized.
ETA begins with the identification of the initiating event, which is typically a component failure or an external failure. Then, all the safety functions which are intended to mitigate the accident are defined and organized according to their logic of intervention. For example, Figure 10.1 shows a graphical example of an event tree: the initiating event is depicted by the initial horizontal line and the system states are then connected in a stepwise, branching fashion: system success and failure states have been denoted by and respectively. The accident ...
