View source for Event tree

An '''event tree''' is an inductive analytical diagram in which an event is analyzed using Boolean logic to examine a chronological series of subsequent events or consequences. For example, event tree analysis is a major component of nuclear reactor safety engineering.<ref name="wang69">Wang, John '' et al.'' (2000). {{Google books|x4Ft7H_2Ik0C|''What Every Engineer Should Know About Risk Engineering and Management,'' p. 69.|page=69}}</ref>
An event tree displays sequence progression, sequence end states and sequence-specific dependencies across time.<ref>IAEA, [http://www-ns.iaea.org/downloads/ni/training/specific_expert_knowledge/psa-level1/III1_2_A%20Accident%20sequence%20modelling.pdf  "Accident sequence modelling," p. 3.]</ref>

==Analytical tool==
[[Event tree analysis]] is a logical evaluative process which works by tracing forward in time or forwards through a causal chain to model risk.  It does not require the premise of a known hazard.<ref>National Research Council. (2002). {{Google books|pIKrHQDY-mgC|''Environmental Effects of Transgenic Plants: the Scope and Adequacy of Regulation,'' p. 5.|page=5}}</ref> An event tree is an inductive investigatory process.<ref name="wang69"/>

In contrast, the [[Fault tree analysis]] (FTA) evaluates risk by tracing backwards in time or backwards through a cause chain.  The analysis takes as a premise a given hazard.<ref>National Research Council, {{Google books|pIKrHQDY-mgC|p. 4.|page=4}}</ref>  FTA is a deductive investigatory process.<ref>Wang, {{Google books|x4Ft7H_2Ik0C|p. 58.|page=58}}</ref>

==Applications==
An event tree may start from a specific initiator such as loss of critical supply,<ref>Compare Timeline of the Fukushima I nuclear accidents</ref> or component failure.<ref>Compare Northeast Blackout of 2003#Causes.</ref>

Some industries use both fault trees and event trees.  Software has been created for fault tree analysis and event tree analysis and is licensed for use at the world's nuclear power plants for Probabilistic Safety Assessment.

==See also==
* [[Event structure]]
* [[Root cause analysis]]
* [[Ishikawa diagram]]
* Why-Because analysis
* [[Failure mode and effects analysis]] (FMEA)

== Notes ==
{{Reflist}}

==References==
* National Research Council (US), Committee on Environmental Impacts Associated with Commercialization of Transgenic Plants, Board on Agriculture and Natural Resources, Division on Earth and Life Studies. (2002). ''Environmental Effects of Transgenic Plants: the Scope and Adequacy of Regulation.'' Washington, D.C.: National Academy Press. {{ISBN|9780309082631}}; [https://www.worldcat.org/oclc/231950695  OCLC 231950695]
* Wang, John X. and Marvin L. Roush. (2000). ''What Every Engineer Should Know About Risk Engineering and Management.'' London: CRC Press. {{ISBN|9781420026962}}; [https://www.worldcat.org/oclc/503045241  OCLC 5030452]

{{DEFAULTSORT:Event tree}}
[[Category:Reliability engineering]]
[[Category:Risk analysis methodologies]]
[[Category:Safety engineering]]



{{Sourceattribution|Event tree}}