Scheme showing the technical scope of NEA ICDE project activities, NEA
Common-cause failure (CCF) events can significantly affect the availability of safety systems of nuclear power plants. In recognition of this, CCF data is systematically collected and analysed in several countries. Due to the low probability of occurrence of such events it is not possible to derive a comprehensive evaluation of all relevant CCF-phenomena only from the operating experience from one individual country. Therefore, it is necessary to make use of the international operating experience from other countries using similar technology. The usage of international NPP operating experience with CCF requires a common understanding of what CCFs are and how to collect data about them. To develop a common understanding, an international common-cause failure working group was founded in 1994. This working group has elaborated the project International Common-Cause Failure Data Exchange (ICDE) which the NEA has formally operated since 1998.
The ICDE project collects qualitative and quantitative information about CCFs in NPP, analyses the collected data and distributes the gained insights about CCFs and methods to prevent CCFs, as reports to the concerned professional audience. The objectives of the ICDE project are to:
The ICDE project operates with a clear separation between data collection and analysis. The analysis results mostly in qualitative CCF information. This information may be used for the assessment of 1) the effectiveness of defences against CCF events and 2) the importance of CCF events in the probabilistic safety assessment (PSA) framework. The qualitative insights on CCF events generated by the analysis are being made public as CSNI reports.
The data collection and qualitative analysis result in a quality assured database with consistency verification performed with the project. ICDE activity defines the format for collection of CCF events in order to achieve a consistent database. This task includes the development and revision of a set of coding guidelines describing the classification, methods, and documentation requirement necessary for the ICDE database(s).
The general coding 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.
ICDE data collection also includes potential CCF events, or ICDE Events, which include impairment of two or more components (with respect to performing a specific function), which exists over a relevant time interval and is the direct results of a shared cause.
The ICDE Project shares the engineering insights of its analyses in public reports published by the NEA Committee on Safety of Nuclear Installations (CSNI).
The ICDE project has meanwhile published 11 reports on collection and analysis of CCF events of specific component types (centrifugal pumps, emergency diesel generators, motor operated valves, safety and relief valves, check valves, batteries, level measurements, switching devices and circuit breakers, control rod drive assemblies, and heat exchangers) and six topical reports on a number of different topics (external factors, diesels all affected, plant modifications, improving testing, multi-unit events, and inter-system dependencies) while one topical report on collection and analysis of common-cause pre-initiator human failure events is under preparation.
In addition, two topical reports (safety culture, ICDE quantification procedure and data interpretation in component-specific quantitative applications) will be published soon.
Further to the December 2011 CSNI request about the future of the Computer-based Systems Important to Safety (COMPSIS) project, the ICDE project has integrated computer failures as a new component that allows for the preservation of the COMPSIS data and for qualitative analysis of these failures.
The ICDE project is based on the willingness of the participants to share their operating experience; to encourage that, participating organisations get access to the database in accordance with their own contributions to the data collection. The project has successfully completed the previous eight phases from 1994 to 2022 and is preparing for the Phase 9 which will start in January 2023 and will end in December 2026.
Currently, data analysis and exchange cover the following components:
Canada, Czechia, Finland, France, Germany, Japan, the Netherlands, Sweden, Switzerland and the United States.
Phase 1-7: August 1994 to December 2018
Phase 8: January 2019 to December 2022
Phase 9: January 2023 to December 2026
Phase 8: EUR 150 K/year