An open phase condition (OPC) occurs when one or two of the three phases of a power circuit are disconnected. As a recognised phenomenon that can impact the safety-related electrical systems in nuclear power plants, OPC was discussed by the global reactor safety community extensively at the Robustness in Electrical Systems (ROBELSYS) workshop held in 2014 under the auspices of the NEA Committee on the Safety of Nuclear Installations (CSNI). Subsequently, the International Atomic Energy Agency (IAEA) issued its Safety Report Series No. 91: Impact of Open Phase Conditions on Electrical Power Systems of Nuclear Power Plants in 2016 in order to provide technical guidance on OPC in nuclear power plant electrical systems.
Building on this work, the NEA Working Group on Electrical Power Systems (WGELEC) and the IAEA organised a joint workshop on the “Current Implementation Status of Measures to Manage Open Phase Conditions in Electrical Power Systems of Nuclear Power Plants” on 27-29 October 2020. The event attracted over 60 participants from nuclear regulatory authorities, research and technical support organisations, nuclear power plant operators, manufacturers and other organisations.
The online workshop provided a forum for the exchange of information on the robustness of safety-related electrical systems in nuclear power plants around the world. The participants discussed the mitigation measures that have been implemented in nuclear power plants within the past several years to address vulnerability to OPC in the plant electrical systems. They agreed that due to the ongoing improvements being made in this area, the exchange of information among NEA and IAEA member countries should continue. A report on the workshop’s findings will be issued in the coming months.