Approaches to Identification of Functional Requirements and Development of Specifications for Digital I&C Systems Upgrades

Abstract

Increasing challenges due to obsolete systems and components, as well as recent market conditions have driven the nuclear power plants (NPPs) owners to increase their focus on operation and maintenance cost reduction. Upgrading outdated Instrumentation and Control (I&C) systems to digital is considered an effective approach for reducing the O&M cost and increasing plants reliability. As most operating plants in the U.S. have already extended their license to 60 years (and several are preparing for the extension to 80 years), upgrade of the outdated 1960s and 70s technology becomes unavoidable. As existing analog systems age, maintenance personnel are tasked to repair rather than replace broken equipment. Although repair is often cheaper than replacement, multiple repairs on a singular component or module increases the risk of human error or the possibility that the item is damaged and cannot be repaired. Digital technologies, although constantly improving and evolving, often provide the flexibility of backward compatibility that eases the burden of obsolescence on the licensee. A significant lesson learned from the digital upgrades in U.S. NPPs, both safety and non-safety, it is critically importance of having a well-defined and detailed Functional Requirements Specification (FRS). Most Original Equipment Manufacturers (OEMs) will concur that one of the most important factors in reducing project cost is assuring that all requirements are well defined and complete prior to starting the project. A detailed and high quality Functional Requirements Specification is critical in documenting these requirements. This paper provides some guidelines on development of functional and procurement specifications.