Risk-Informed Safety Classification for New Plant Designs

Risk-informed safety classification can be used to identify power plant components that are important to plant safety. Alternative treatment requirements can then be allowed for select components based on their risk-informed safety classification. This concept has been embraced in Section XI of the ASME Boiler and Pressure Vessel Code through the approval of Code Cases N-660 and N-662. Draft Code Case N-720 provides an approach to applying risk-informed safety classification to new plant designs in Section III of the ASME Boiler and Pressure Vessel Code. For new plant designs some unique challenges exist compared to those encountered in the application of the concept to an operating plant. This paper will discuss the risk-informed safety classification approach in Code Case N-720 and the key differences in its application to new plant designs. The alternative treatment requirements proposed in the Code Case and their benefits will also be discussed.