Software safety analysis of function block diagrams using fault trees

Younju Oh, Junbeom Yoo, Sungdeok Cha, Han Seong Son

Research output: Contribution to journalArticlepeer-review

38 Citations (Scopus)


As programmable logic controllers (PLCs) are often used to implement safety-critical embedded software, safety demonstration of PLC code is needed. In this paper, we propose a fault tree analysis technique on Function Block Diagrams (FBDs) which is one of the most widely used PLC programming languages. FBD is currently being used to develop Reactor Protection System (RPS) for a nuclear power plant in South Korea. Our approach to fault tree analysis, which combines fault-oriented and cause/effect-oriented viewpoints, is easy to understand and offers systematic guidelines to ensure safety of PLC code. Domain experts found the approach to be useful through a case study on RPS, and this paper compares completeness and comprehensiveness of the semi-automatically generated fault trees using the proposed approach against the one manually prepared by nuclear safety engineers.

Original languageEnglish
Pages (from-to)215-228
Number of pages14
JournalReliability Engineering and System Safety
Issue number3
Publication statusPublished - 2005 Jun
Externally publishedYes


  • Fault tree analysis
  • Function block diagram
  • Programmable logic controller
  • Safety analysis

ASJC Scopus subject areas

  • Safety, Risk, Reliability and Quality
  • Industrial and Manufacturing Engineering


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