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:
ceptable level (e.g., a system damaged by pipe whip may be capable of performing its safety function but not capable of completely fulfilling its design function such as delivering design rated flow). Although a limited number of postulated piping break locations are determined herein for any specific Code Class 1, 2, or 3 piping run or branch run, installation of all restraints necessary to provide the required pipe whip protection measures for structures, systems, and components important to safety will also provide protection against a substantially greater number of postulated piping break locations (i.e., protection is provided for a major portion of the pipe run or branch run). Piping locations where breaks are not postulated nor protection provided are restricted to those locations whose probability of failure is sufficiently low as to be acceptable without the need for restraints. C. REGULATORY POSITION 1. ASME Section III Code Class 1 piping2 breaks should be postulated to occur at the following locations in each piping run3 or branch run: a. The terminal ends; b. Any intermediate locations between ternminal ends where the primary plus secondary stress intensities 2Piping is a pressure-retaining component consisting of straight or curved pipe and pipe fittings (e.g., elbows, tees, and- reducers). 3 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 brarnch of the main pipe run. (circumferential or longitudinal) derived on an elastically calculated basis under the loadings associated with specified seismic events 4 and operational plant conditions' exceed 2 Sm6 for ferritic steel and.2.4 Sm for austenitic steel; c. Any intermediate locations between terminal ends where the cumulative usage factor U7 derived from the piping fatigue analysis under