An Integrated Risk Assessment Process of Safety-Related Digital I&C Systems in Nuclear Power Plants

Hongbin Zhang, Han Bao, Tate Shorthill, Edward Quinn

Research output: Contribution to journalArticlepeer-review

2 Scopus citations

Abstract

Upgrading the existing analog instrumentation and control (I&C) systems to state-of-the-art digital I&C (DI&C) systems will greatly benefit existing light water reactors. However, the issue of software common cause failure (CCF) remains an obstacle in terms of qualification for digital technologies. Existing analyses of CCFs in I&C systems mainly focus on hardware failures. With the application and upgrading of new DI&C systems, design flaws could cause software CCFs to become a potential threat to plant safety, considering that most redundancy designs use similar digital platforms or software in their operating and application systems. With complex multilayer redundancy designs to meet the single failure criterion, these I&C safety systems are of particular concern in U.S. Nuclear Regulatory Commission licensing procedures. In Fiscal Year 2019, the Risk-Informed Systems Analysis (RISA) Pathway of the U.S. Department of Energy’s Light Water Reactor Sustainability Program initiated a project to develop a risk assessment strategy for delivering a strong technical basis to support effective, licensable, and secure DI&C technologies for digital upgrades and designs. An integrated risk assessment for the DI&C process was proposed for this strategy to identify potential key digital-induced failures, implement reliability analyses of related digital safety I&C systems, and evaluate the unanalyzed sequences introduced by these failures (particularly software CCFs) at the plant level. This paper summarizes these RISA efforts in the risk analysis of safety-related DI&C systems at Idaho National Laboratory.

Original languageEnglish
Pages (from-to)377-389
Number of pages13
JournalNuclear Technology
Volume209
Issue number3
Early online dateJul 11 2022
DOIs
StatePublished - Jul 11 2022

Keywords

  • Digital instrumentation and control
  • common cause failure
  • hazard analysis
  • reliability analysis
  • risk assessment

INL Publication Number

  • INL/JOU-21-65396
  • 105400

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