The July 2006 Forsmark-1 event identified a number of design deficiencies related to electrical power supply to systems and components important to safety in nuclear power plants. The CSNI established a task group to examine defence in depth of electrical systems and grid interaction with nuclear power plants. The DIDELSYS Project, carried out in 2008-2009, made recommendations to strengthen the robustness and defence in depth capabilities of individual NPP onsite electric systems.
This was done by systematically evaluating the full range of voltage/frequency transient hazards and plant specific capabilities to cope with these hazards. A DIDELSYS follow-up activity was then initiated in January 2010 to identify elements in a methodology on how to periodically carry out a systematic hazard review of possible voltage/frequency transients which could occur from the grid and in nuclear power plants. The reviews should have covered the initiators coming from the grid and the generators set and other transients including switching manoeuvres, and their consequences on the electrical distribution systems and powered components inside the plant.
The follow-up activity also aimed to identify elements in assessment of the adequacy of design and operational controls ensuring protection against voltage/frequency transients from external/internal electrical systems.
The objective of this workshop was to discuss the progress made since the publication of the DIDELSYS report and to share member countries experiences in assessing the vulnerabilities in safety-related electrical systems in nuclear power plants. The workshop provided a forum to evaluate the results of the DIDELSYS effort and how DIDELSYS findings and recommendations had been factored into design and operating practices in OECD member countries.
Learning from others was a key to success and progress. Information obtained as a result of this workshop provided an understanding of key interpretations on periodically carrying out a systematic hazard review of possible voltage/frequency transients which could occur from the grid and in nuclear power plants, and on potential vulnerabilities in safety-related electrical systems.