Event tree analysis advantages

There are hoth advantages and limitation of event tree analysis ... 

Fault Tree Analysis - working backwards from a failure or potential failure, this logical procedure identifies all the possible causes, and hence, the origins of that failure. The fault tree consists of branches connected by AND and OR nodes - all the branches below an AND node need to coincide for the event above the node to occur, but only one of the branches below an OR node is required to condition the same. In these terms, a cause-effect map of failure is constructed. The advantage of such analysis is that it codifies a common understanding of the intrinsic logic of failure possibility. 

Qualitative reliability analysis are used to identify possible ways in which a system can fail. The calculation can result in all combinations of components and human failures that lead to safety (protection) system failure, which prevents the safety system to shut-down the reactor upon request. For this analysis a top-down logic model, known as a Master Logic Diagram (MLD), similar to a fault-tree, could advantageously be used with a top event of a safety system failure upon request. The results of this analysis can be used to prove the fulfillment of the important single failure design criteria. 

One of the advantages of the fault tree method is its adaptability to mathematical analysis. The probabilities of the basic events at the bottom of the tree must be known or estimated. Analysis then moves up the tree with the aid of Boolean algebra. We are interested in two possible relationships between events leading to a step up the tree. First, either of the two events may suffice. Chlorine escapes when its rate of flow is too high OR the rate of supply of NaOH is too low. Either failure causes a gas release even if the... 

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