Ensuring Electromagnetic Compatibility in Nuclear Power Plant beyond Equipment Qualification Tests

Abstract

Electromagnetic compatibility (EMC) is defined as the capability of equipment or system to function satisfactorily in its electromagnetic environment without introducing intolerable electromagnetic disturbances to anything in that same environment [1]. EMC regulatory requirements for instrumentation and control (I&C) equipment were not developed or in effect until the last few years. Therefore, there is a considerable number of plant equipment that has not been qualified for EMC. The current EMC regulatory requirements address new and modified equipment only, and do not call for testing of existing equipment. There is a gap, which has to be overcome, in order to understand the current level of EMC within the plant. Equipment qualification normally implies formal tests in EMC chambers, which is not practical for the equipment already installed. This paper is a short overview of the preparation phase of a project that includes various EMC-related activities currently being performed in Krško nuclear power plant (NPP). The activities are categorized into two main groups: equipment immunity (susceptibility) tests, used as an assessment of the immunity of the existing equipment such as process cabinets, transmitters and similar, and zone mapping measurements, which are performed to record the electromagnetic environment of the selected plant areas. There is no clear, detailed and unambiguous guidance on how to perform any of these tests. It takes a lot of engineering judgement to optimize them for a specific plant. Some of the most important questions addressed in this paper are 1) the selection of the plant areas for zone mapping measurements and susceptible equipment to be tested for immunity, 2) choice of electromagnetic disturbances, which shall be simulated during those tests, and 3) practical performance, i.e. harmonization of immunity tests with operation of other plant systems. It is necessary to decide which operation mode poses the “worst-case”, i.e. how and when the immunity tests and zone mapping measurement should be performed. The paper also addresses troubleshooting of poor EMC design and installation practices, which can significantly reduce the number of EMC-related problems in a plant.