Document: NRC Regulatory Guide
Document ID: 111e064c-2d28-4647-872a-806b29019408
Document Type: regulatory_guide
Title: Design Limit and Loading Combinations for Seismic Category I Fluid System Components
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML1229/ML12298A124.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.48
CFR Part: 
CFR Title: 

Content:
appropriate, to accommodate 4. Environmental and Siting 9. Antitrust Review comments and to reflect new information or experience. 5. Materials and Plant Protection 10. General limits and supplemental requirements are provided for active pumps and valves because the rules for constructi6n of Section II1 apply to the assurance of pressure-retaining integrity but do not assure that pumps and valves designated to perform a system safety function will operate when required. This conclusion is supported by B-1223.4(b) of Appendix B to Section III, "Owner's Design Specification;' which states, "Although Code requirements for the acceptability of a component are not intended to assure the functional adequacy of the component, the higher stress limits permitted for Emergency and Faulted Condition evaluation may result in deformations which preclude operability during or after the event. The. Owner may wish to provide more restrictive limits for components which require close dimensional control and which must operate during and after the event. Such requirements are beyond the scope of this Section (i.e., Section I11)." Footnote 1 to NB-35 10 of Section III also expresses this limitation by stating that, "These requirements for the acceptability of a valve design are not intended to assure the functional adequacy of the valve." In addition, design limits augmenting Section III of the ASME Code are selected for Code Class 2 and 3 components and certain Code Class 1 components in the absence of design limits for other than the normal plant condition (e.g., the emergency and faulted plant conditions). It is emphasized that the design limits delineated in this guide are intended to apply to all fluid system components (vessels, piping, pumps, and valves) that are relied upon to cope with the effects of specified plant conditions. Loading combinations are defined as those loadings or combinations thereof-that are associated with each plant condition or specified seismic event.