Procedure Progression Similarity, an Aspect of Dependence between Human Failure Events
Authors: Yochan Kim, Jaewhan Kim, Jinkyun Park
Abstract: To characterize the probabilistic nature of human errors, many kinds of human reliability analysis (HRA) techniques have been developed and applied. HRA practitioners assess the dependencies between human failure events based on some contextual factors because of the belief that the failure of a previous action can influence the reliability of a subsequent action. Among the factors determining such dependency, there is an issue regarding the similarity between the procedure progressions of different events. In many abnormal or emergency situations, the operators respond to the plant situations using procedures consisting of several sequential steps. Because the operators work by following the procedural sequences, how reliably they transfer to the relevant procedures is significant to the human reliabilities. In terms of dependency, it can be seen that two events have a common factor producing human failures if they are performed with similar procedural sequences. Therefore, the similarity between procedure progressions should be counted in the dependency assessment of any HRA technique. This paper asserts the importance of such procedure progression similarity in dependency analyses and proposes two ways to estimate the joint error probability that comes from the similarity. The first approach decomposes the human error probabilities and identifies the probabilities commonly involved in both events based on the EMBRACE method. The second approach quantifies the similarity using a sequence alignment technique and estimates the dependency level based on similarity scores for traditional HRA methods. With some application studies, we discuss potential improvements of current dependency analysis and future works.
Keywords: Human reliability analysis, Dependency analysis, Human error
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