Event tree, investigation tools

Other examples of inductive tools that have limited application in incident investigation include failure mode and effects analysis (FMEA), hazard and operability study (HAZOP), and event tree analysis (ETA). These are detailed in the CCPS book, Guidelines for Hazard Evaluation Procedures... 

The committee s analysis was conducted on several levels. First, members investigated the causal factors for each of the seven events listed in Tables 2-1 and 2-2. They then developed a notional causal tree for each of the two events in Table 2-2 that were analyzed in depth. For illustrative purposes, a causal tree developed by the committee for the December 3-5,2000, incident at JACADS appears at Appendix F. The tree is a standard tool in reliability analysis and is particularly useful in human reliability analysis where operator actions contribute either positively or negatively to an incident. Lastly, the committee provides a series of general and specific observations about the events. 

Fault tree analysis was created in the military industry during the Minuteman missile program. It is a graphical tool used to identify the faults in a system and which events lead to that catastrophic event they have proven so useful that other industries are starting to use them. The chemical industry is starting to use fault trees, especially in accident investigation. 

The main objective of this paper is to investigate the safety implications of the proposed system on a NPP. Probabilistic Safety Assessment (PSA) is used as tool for risk assessment. A PSA model of generation two NPP is used as a case study. The reference PSA model is modified in order to consider the proposed system. The change in core damage frequency is used as risk measure. The proposed system is modelled using the fault tree approach with a top event defined as a possible failure to deliver water to the nuclear power plant. 

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