Participants of the kick off meeting (Photo credit: NEA)
The safe operation of nuclear power plants relies on a large volume of experimental data. The CSNI Code Validation Matrix (CCVM) of the NEA is a repository of nuclear data and identified phenomena used to run tests, experiments and other procedures to ensure safety assessments and related operational validation for computational safety codes.
A kick-off meeting to update and extend the CCVM’s activities was organised online on 19 March 2025 by the NEA with Italy’s ENEA (National Agency for New Technologies, Energy and Sustainable Economic Development), Japan’s Atomic Energy Agency and France’s ASNR (Authority for Nuclear Safety and Radiation Protection). The meeting brought together 70 experts from 14 countries and one international organisation. Representatives from industry, regulatory authorities, research institutes and academia discussed the task group, the structuring of the CCVM update and the prioritisation of key topics.
The initiative aims to incorporate recent experimental data for both current and advanced water reactors: pressurised water reactors, boiling water reactors, water-water energetic reactors, pressurised heavy water reactors as well as water-cooled small modular reactors. These advanced reactor designs integrate innovations such as passive safety systems, new operational behaviors, and extended boundary conditions while maintaining key features of existing reactors. The updated CCVM will focus on reactor coolant systems and containment thermal-hydraulics research, identifying gaps in the current CCVM related to key safety phenomena and highlighting research priorities for future experimental programmes and code validation efforts.
The experts are helping to shape a robust and reliable CCVM, ensuring it remains a cornerstone of safety assessments. This represents the first step toward a broader update of the CCVM that will also address non-water-cooled reactor designs in future phases.
Example of CCVM for integral test facilities
