Robustness of Electrical Systems of NPPs in Light of the Fukushima Daiichi Accident

NEA/CSNI/R(2015)4
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ROBELSYS Workshop Proceedings

The Defence in Depth of Electrical Systems (DIDELSYS) Project (2008-2011) was launched after a switchyard-induced voltage surge event at Forsmark Nuclear Power Plant (NPP) in July 2006 which caused the loss of two out of four safety-related AC buses along with all connected I&C and support systems. The DIDELSYS Project was focused on providing recommendations to address internal plant and grid upset events and the ability to safely recover from these events. Due to the tsunami-induced AC and DC station blackout accident at Fukushima Daiichi a loss of power associated with severe external events which were beyond the scope of the DIDELSYS Project were identified. The Committee for the Safety of Nuclear Installations (CSNI) called a Senior Task Group on Robustness of Electrical Systems of NPPs in Light of the Fukushima Daiichi Accident (ROBELSYS) to evaluate the safety implications of severe external events on safety related electrical systems. The ROBELSYS task group is responsible for the committee's programme work in the area of improving the robustness of safety related electrical systems in nuclear power plants.

The main purpose of the ROBELSYS Project is to improve the robustness of nuclear power plant electrical systems and defence in depth by comparing design practices, plant emergency and operating procedures in member countries. Furthermore, the safety review process of nuclear power plant electrical systems can be improved by learning from best practices in member countries and the cooperation among member countries to improve safety can be promoted.