Document: NRC Regulatory Guide
Document ID: 0ae1e098-eccd-43e7-b12e-43b05aa1fe48
Document Type: regulatory_guide
Title: Safety-Related Concrete Structures for Nuclear Power Plants (Rev. 3)
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML1617/ML16172A240.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.142
CFR Part: 
CFR Title: 

Content:
I 349-13 is based on ACI 318-08, “Building Code Requirements for Structural Concrete and Commentary” (Ref. 13), with modifications in ACI 349-13 to accommodate the requirements specific to nuclear safety-related concrete structures. Discussion of Regulatory Positions The following provides background technical information for a selection of regulatory positions in Section C of this guide to provide clarification for those provisions. Only those regulatory positions with supporting information are listed below. Regulatory Position 1 This position addresses acceptable standards for design of pressure resisting portions of concrete structures within the reactor containment. To ensure that the pressure retaining functions and leak tightness of those structures are not compromised during the loss-of-coolant accident (LOCA), Regulatory Position 1 provides conditions that complement the ultimate strength design (USD) approach in ACI 349-13. Regulatory Position 2 2.1 In complex structural systems, the definitions of structural components such as walls, slabs, and foundations provided in ACI 349-13 may not be completely adequate for nuclear safety-related structures. This position alerts the designer to consider whether structural components are acting as parts of flexural frames. Because structural components generally experience flexural effects, they are designed as a frame when the flexural moment from seismic loads equals or exceeds a large percentage of the flexural capacity. By setting this limiting ratio at two-thirds, the flexure from seismic loads alone would be within the design capacity even with a seismic event equal to 150 percent of the SSE. 2.3 Use of high-strength (HS) reinforcement (Grade 75 and 80) as used in ACI 349-13 is not endorsed. Research and development that integrates implications for the general use of, for example, crack control, material and component ductility, deflection limits, over-strength factors, and strength-reduction factors, is