American National Standard Safety And Pressure Integrity Classification Criteria For Light Water Reactors

This standard specifies criteria for the safety classification of items [structures, systems, components, and parts (including consumables)] in a light water reactor nuclear power plant as either safety-related (Q), supplemented grade (S), or non-safety-related (N). Criteria are also provided to establish a procurement subclassification within Class Q, called commercial grade (C). In addition, pressure integrity classification criteria are provided for the assignment of Classes 1, 2, 3, 4, or 5 to the pressure retaining portions of items. Withdrawn as an ANSI standard, 2003.

This standard provides design criteria for systems that perform the safety-related functions necessary to shut down a reactor and maintain it in a safe shutdown condition for selected design-basis events, i.e., any design-basis events that do not require operation of engineered safety features. For design-basis events that require operation of engineered safety features, this standard can be selectively applied because of plant features specifically designed for these conditions. For systems that serve multiple functions, the design criteria associated with the most limiting function shall be applied. The following safety-related functions are required for safe shutdown and are addressed in this standard (1) reactor core reactivity control, (2) reactor core heat removal, (3) reactor coolant pressure boundary integrity provided by (a) temperature control, (b) pressure control, and (c) inventory control.

ANS 58.9-1981 (R2020) provides criteria for the designer which interpret the requirements of Title 10, Code of Federal Regulations, Part 50, "Licensing of Production and Utilization Facilities," Appendix A, "General Design Criteria for Nuclear Power Plants," with respect to design against single failures in safety-related Light Water Reactor (LWR) fluid systems. Means of treating both active and passive failures are addressed for safety-related fluid systems following various initiating events. Current acceptable practice is used as a basis for these criteria.

This standard contains criteria for determining the variables to be monitored by the control room operator of a light water reactor as required for safety during the course of an accident including long-term stable shutdown. Also included are criteria for determining the requirements for the equipment used to monitor those variables. The scope of the standard is limited to onsite environment and process monitoring.

This standard presents the requirements of the Nuclear Safety Related Cooling Water Systems (NSRCWS) for Light Water Reactors (LWRs). It establishes nuclear safety requirements in the areas of design, materials, fabrication, placement and testing of systems. This standard is applicable to open and closed NSRCW systems. 58.9-1981 (R2020) provides criteria for the designer which interpret the requirements of Title 10, Code of Federal Regulations, Part 50, "Licensing of Production and Utilization Facilities," Appendix A, "General Design Criteria for Nuclear Power Plants," with respect to design against single failures in safety-related Light Water Reactor (LWR) fluid systems. Means of treating both active and passive failures are addressed for safety-related fluid systems following various initiating events. Current acceptable practice is used as a basis for these criteria.