An influence diagram extension of the unified partial method for common cause failures

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Modelling Common Cause Failures (CCFs) is an essential part of risk analyses, especially for systems such as nuclear power plants, which are required to have high reliability. The Unified Partial Method (UPM) is the main approach of the UK for modelling CCFs. This paper presents an Influence Diagram model for CCFs which extends UPM and represents uncertainty on system performance. This allows more detailed modelling of CCFs in terms of root causes and coupling factors, creates a context for using information in the industry database, and captures the non-linearity in the way system defences influence reliability. A structured expert elicitation process is used to construct the Influence Diagram model and to identify the non-linear structure of the domain, using an example of Emergency Diesel Generators (EDGs) from nuclear power plants. Insights and experiences from the elicitation process are described.
Original languageEnglish
Pages (from-to)111-128
Number of pages17
JournalQuality Technology and Quantitative Management
Issue number1
Publication statusPublished - 2007


  • common cause failures
  • coupling factors
  • epistemic uncertainty
  • expert judgment
  • influence
  • diagram
  • root causes
  • Unified Partial Method

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