Computer-based Systems Important to Safety (COMPSIS) Project
Joint project

Control room, PAKS NPP.


Software-based systems are used and retrofitted in operating nuclear power plants worldwide. The failure modes of both hardware and software in these systems are to some extent different from the analogue instrumentation and control (I&C) systems. When initiating the project, there was no established international database where the failure modes of computerised systems were collected. The general aim of the Computer-based Systems Important to Safety (COMPSIS) Project was to exchange information on computer-based system reliability in a structured way. The high-level objective was to contribute to the improvement of safety management and to the quality of software risk analysis for software-based equipment. Software and hardware faults in safety-critical systems are typically rare events. Consequently, most countries had not experienced enough faults to allow for meaningful syntheses. Combined information from several countries, however, was expected to yield sufficient data to help draw conclusions. The main objectives of the COMPSIS Project were to:

  • define a format and collect software and hardware fault experience in computer-based safety-critical nuclear power plant (NPP) systems (hereafter called COMPSIS events) in a structured, quality-assured and consistent database
  • collect and analyse COMPSIS events over a long period to better understand such events, their causes and their prevention
  • generate insights into the root causes of and contributors to COMPSIS events, which could then be used to derive approaches or mechanisms for their prevention or for mitigating their consequences
  • establish a mechanism for an efficient feedback of experience gained in connection with COMPSIS events, including the development of defences against their occurrence, such as diagnostics, tests and inspections
  • record event attributes and dominant contributors so that a basis for national risk analysis of computerised systems could be established.

Work during the first phase of the project (2005-2007) concentrated on the development of COMPSIS data collection guidelines, quality assurance and a data exchange interface. Data collected during first and second phases were about 80 licensee event report (LER) events covering the period from the early 1990s to 2010.

Further to the December 2011 Committee on the Safety of Nuclear Installations (CSNI) request about the future of the COMPSIS Project, the Secretariat informed the CSNI in June 2012 that the International Common-cause Failure Data Exchange (ICDE) Project was willing to integrate computer failures as a new component to allow for the preservation of COMPSIS data and the qualitative analysis of these failures at no additional cost. The related database is now addressed in the on-going ICDE project.


Finland, Chinese Taipei, Germany, Hungary, Korea, Sweden, Switzerland and United States.

Project period

January 2005 -December 2011


EUR 100k/year