Document: NUREG-0800
Document ID: 3d8f7691-e488-4083-af2f-eef689c0ec98
Document Type: srp
Title: ASME CODE CLASS 1, 2, AND 3 COMPONENTS AND COMPONENT SUPPORTS,
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0704/ML070430397.pdf
Revision Date: 2023-06
Chapter: 3
Section ID: 3.9.3
CFR Part: 
CFR Title: 

Content:
upports, to deliver rated flow and retain dimensional stability. The combination of loadings, the selection of the applicable design and service stress limits appropriate to each load combination, and the proper consideration of functionality is beyond the scope of the Code. The treatment of functionality, including collapse and deflection limits, is not adequately treated by the Code for all situations. Such factors should therefore be evaluated and appropriate information should be developed for inclusion in the Design Specification or other referenced documents. Applicants require guidance with regard to the selection of acceptable design and service stress limits associated with various loadings and combinations thereof, resulting from plant and system operating conditions and design basis events, natural phenomena, and site-related hazards. The relationship and application of the terms "design conditions," "plant operating conditions," "system operating conditions," and the formerly used term "component operating conditions," now characterized by four levels of service stress limits, require clarification. 3.9.3-18 Revision 2 - March 2007 For example, under the "faulted plant or system condition" (e.g., due to LOCA within the reactor coolant pressure boundary), the emergency core cooling system (ECCS) should be designed to operate and deliver rated flow for an extended period of time to ensure the safe shutdown of the plant. Although the "plant condition" is termed "faulted," components in the functional ECCS must perform the safety function under a specified set of service loadings which includes those resulting from the specified plant postulated events. The selection of Level "D" (related to the "faulted" condition) service stress limits for this system, based solely on the supposition that all components may use this limit for a postulated event resulting in the faulted plant condition cannot be justified, unless system functionality is also demonstrated.