Document: NRC Regulatory Guide
Document ID: 7da9830f-b2a1-484a-82ce-5b0a588c4fce
Document Type: regulatory_guide
Title: Protection Against Pipe Whip Inside Containment
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML1229/ML12298A123.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.46
CFR Part: 
CFR Title: 

Content:
ortant to safety that are within the reactor containment. This basis is directly related to the design limits and piping procedures contained in Section 'Hereinafter, referred to as "ASME Code" III of the ASME Code (i.e., Subsections NB-3600, NC-3600, and ND-3600 for design of Code Class 1, 2, and 3 piping, respectively). ASME Code Class 1 Piping The locations for which breaks should be postulated to occur for ASME Code Class 1 piping are based on the regions of piping runs or branch runs with the greatest potential for failure under cyclic loading conditions (i.e., locations of high primary plus secondary and peak stress intensities associated with specified seismic events and operational plant conditions). A piping run interconnects components such as pressure vessels, pumps, and valves that act to restrain pipe movement beyond that required for design thermal displacement. A branch run differs from a piping run only in that it originates at a piping intersection as a branch of the main pipe run. Terminal ends of the piping run or branch run (e.g., connections to component nozzles and to other piping) and other points of constraint or limited flexibility (e.g., short-radius elbows, tees, branch connections, and anchors) are piping locations and piping components that may sustain stress intensities which, because of the application of secondary and peak stress indices provided by the Section III design rules, can be substantially greater than the stress intensities occurring in straight runs of piping and long-radius elbows. On the basis of high stress intensities and related considerations (e.g., reactor vessel nozzle safe ends) which indicate a greater probability of failure relative to straight pipe, piping break locations should be postulated to occur at the terminal ends of the piping run or branch run. Similarly, breaks should be assumed to occur at any intermediate locations between terminal ends of piping runs or branch runs that exhibit stress intensities