Application of commercial-grade digital equipment in nuclear power plant safety systems

Due to obsolescence, increasing maintenance costs, and the lack of qualified spare parts for the equipment and components of the analog instrumentation and control (I&C) systems in operating domestic nuclear power plants, nuclear utilities are replacing equipment and upgrading certain I&C systems. These activities generally involve changing from analog to digital technology. In many cases commercial products offer practical solutions. Digital I&C systems have the potential to enhance safety, reliability, and availability of the plant systems and improve plant operation. However, the use of digital software-based equipment presents challenges and concerns to the U.S. nuclear industry and the Nuclear Regulatory Commission (NRC). The NRC's approach to the review and acceptance of design qualification for digital systems largely focuses on confirming that the applicant or licensee has employed a high-quality development process that incorporated disciplined specification and implementation of design requirements. Inspection and testing is used to verify correct implementation and to validate the desired functionality of the final product.