Common-cause failure (CCF) events can significantly affect the availability of nuclear power plant safety systems. In recognition of this, CCF data is systematically collected and analysed in several countries. A serious obstacle to the use of national qualitative and quantitative data collections by other countries is that the criteria and interpretations applied in the collection and analysis of events and data differ. A further impediment is that descriptions of reported events and their root causes, which are important to the assessment of the events, are usually written in the native language of the countries where the events were observed.
To overcome these obstacles, preparation for the International Common-cause Failure Data Exchange (ICDE) Project was initiated in August 1994. Since April 1998, the NEA has formally operated the project. The objectives of the ICDE Project are to:
The ICDE project operates with a clear separation between data collection and analysis. The data collection and analysis firstly results in qualitative CCF information that can be used for the assessment of the effectiveness of defences against CCF events and the importance of CCF events in the probabilistic safety assessment framework. The qualitative insights on CCF events generated by the analysis are being made available to CSNI countries through published reports.
Data collection guidelines have been developed during the ICDE project and are continually revised. They describe the methods and documentation standards necessary for the development of the ICDE databases and reports. The format for data collection is described in the general coding guidelines and in the component-specific guidelines. Component-specific guidelines are developed for all analysed component types as the ICDE project evolves. So far the ICDE Project is the only international effort where large amounts of data from different countries are collected and analysed to draw conclusions about CCF.
The ICDE Project aims to include all possible events of interest, comprising complete, partial, and incipient CCF events, called “ICDE events”. The ICDE events are defined as “Impairment of two or more components with respect to performing a specific function that exists over a relevant time interval and is the direct result of a shared cause.”
The ICDE Project has furthermore established a principle that it shares the engineering insights of its analyses through the NEA Committee on Safety of Nuclear Installations (CSNI) by writing public reports of the analysis results of each component.
Reports have been produced for pumps, diesel generators, motor-operated valves, safety and relief valves, check valves and batteries. Data exchange for switchgear and breakers and reactor level measurement was completed.
In 2011 the ICDE finalised the revised report "Collection and Analysis of Common-cause Failures of Centrifugal Pumps". This report documents a study performed on a set of ICDE events related to centrifugal pumps and had been collected in the ICDE database. Organisations from Canada, Finland, France, Germany, Japan, Spain, Sweden, the United Kingdom and the United States contributed to the exchange. Three-hundred-fifty-three ICDE events, exhibiting at least some degree of dependency, and spanning a period from 1975 through 2009, were examined in this study. The database contains general statistical information about event attributes like impairment of the components in the observed populations, root cause, coupling factor, detection methods and corrective actions taken. The events contained in the ICDE database were analysed with respect to failure modes, degree of impairment, failure symptoms, failure causes, and technical fault aspects.
Further to the December 2011 CSNI request about the future of the Computer-based Systems Important to Safety (COMPSIS) Project, the NEA informed CSNI in June 2012 that the ICDE Project is willing to integrate computer failures as a new component that will allow for the preservation of the COMPSIS data and for qualitative analysis of these failures without additional cost.
The intention is to make the project results known to a larger audience. Data analysis and exchange covers for the time being the following components:
Canada, Czech Republic, Finland, France, Germany, Japan, Korea, Netherlands, Sweden, Switzerland and United States.
January 2019 to December 2022
EUR 150 K/year