Meeting EMC Requirements for Digital Systems
Article first appeared in Nuclear Plant Journal, March 2010
The integration of digital systems in Nuclear Power Plants has been the subject of much scrutiny for (at least) the last 20 years. In 1997 the NRC commissioned the National Research Council to review the implementation of digital systems in the nuclear environment. It concluded that: “Digital I&C systems offer powerful capabilities that can, however, affect nuclear power plant safety; therefore, digital systems should be treated carefully, particularly in safety-critical applications.”
The popularity of plant life extension has led many nuclear plants to consider upgrades of old and obsolete systems and the commissioning of electronic control systems. To meet the requirements specified by the code of federal regulations, new equipment installed as upgrades in existing plants are to be designed to accommodate the effects of environmental conditions and that design control measures such as testing are to be used to check the adequacy of the design. Electromagnetic Compatibility (EMC) is an important environmental and design factor that must be taken into account. NRC Regulatory Guide (RG) 1.180 details the test levels and requirements that are designed to minimize interference and susceptibility of safety-related instrumentation and control equipment in the plant environment. Meeting these requirements represents a major commitment on the part of equipment manufacturers and can be a challenge to complete. Good planning is essential to execute a well-ordered introduction of equipment into the Electromagnetic Environment (EME) of Nuclear Power Plants.
The refueling cycle outage at a nuclear power plant is an opportunity to upgrade obsolete equipment, install upgrades, and commission new systems. As the operating life of plants is extended and as new technology comes available, interference-free operation is a necessity, especially for safety-critical systems. An understanding of the Electromagnetic Environment in nuclear plants is mature, has been well-characterized over the years and numerous standards and test methods developed to test equipment to various stimuli.
Compliance must be demonstrated to a rather comprehensive set of test standards that must be met before equipment can be commissioned. To deal with these requirements, it is necessary to integrate an EMC plan into equipment procurement and development. We call this an EMC Implementation Plan (EIP); the purpose of this plan is to streamline the integration of new equipment into the plant systems and operations.
This article outlines the following elements of an EIP for equipment manufacturers and operators as they develop equipment for upgrades and plant life extension. The principal elements include; Site Survey, EM Evaluation, Equipment Design, and Test Planning & Execution. The objective is to give manufacturers and project teams insight into the proper execution of an EIP.