OECD/NEA ICDE Project

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, the preparation for the international common-cause data exchange (ICDE) project was initiated in August of 1994. Since April 1998, the NEA has formally operated the project. The objectives of the ICDE project are to:

a) collect and analyse CCF events over the long term so as to better understand such events, their causes, and their prevention;

b) generate qualitative insights into the root causes of CCF events which can then be used to derive approaches or mechanisms for their prevention or for mitigating their consequences;

c) establish a mechanism for the efficient feedback of experience gained in connection with CCF phenomena, including the development of defences against their occurrence, such as indicators for risk based inspections;

d) generate quantitative insights and record event attributes to facilitate quantification of CCF frequencies in member countries; and

e) use the ICDE data to estimate CCF parameters.

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 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. The ICDE prepares reports containing conclusions on the analysis performed whenever major steps of the project have been completed. 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:

• centrifugal pumps;
  
• diesel generators;
  
• motor-operated valves;
  
• safety and relief valves;
  
• check valves;
  
• batteries;
  
• reactor protection system components (level measurement, control rod drives, etc);
  
• circuit breakers;
  
• heat exchangers.