Document: NUREG-0800
Document ID: fb538e14-08a0-4d3f-a974-8170cbfe0b5b
Document Type: srp
Title: ASME CODE CLASS 1, 2, AND 3 COMPONENTS,
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0523/ML052340603.pdf
Revision Date: 2023-06
Chapter: 3
Section ID: 3.9.3
CFR Part: 
CFR Title: 

Content:
d 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 operability is also demonstrated. This appendix is necessary to improve consistency and understanding of the basic approach in the selection of load combinations applicable to safety- related systems and to establish acceptable relationships between plant postulated events, plant and system operating conditions, component and 3.9.3-12 Rev. 1 - April 1984 component support design, and service stress limits, functional capability, and operability. B. DISCUSSION Current reviews of both standardized plants and custom plants have indicated the need for additional guidance to reach acceptable design conclusions in the following areas: (1) Relationship between certain plant postulated events, plant and system operating conditions, resulting loads and combinations thereof, and appropriate design and service stress limits for ASME Class 1, 2 and 3 components and component supports and Class CS core support structures. (2) Relationship of component operability assurance, functional capability, and allowable design and service stress limits for ASME Class 1, 2, and 3 components and component supports. The Code provides five categories of limits applicable to design and service -loadings (design, level A, level B, level C, and level D). The Code rules provide for structural integrity of the pressure retaining boundary of a component and its supports, but specifically exclude the subject of component operability and do not directly address functional capability. The types of loadings to be taken into account in designing a component are specified in the Code, but rules specifying how the loadings, which result from postulated events and plant and system operating conditions, are to be