Document: NUREG-0800
Document ID: 89a50aec-b387-4999-9c8e-3b8e4f289a55
Document Type: srp
Title: Revision 3 - March 2007
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0708/ML070800027.pdf
Revision Date: 2023-06
Chapter: 3
Section ID: 3
CFR Part: 
CFR Title: 

Content:
upplemental protection of those structures and systems shall be provided to cope with the environmental effects (including the effects of jet impingement) of a single postulated open crack at the most adverse location(s) with regard to those essential structures and systems, the length of the crack being chosen not to exceed the critical crack size. The critical crack size is taken to be 1/2 the pipe diameter in length and 1/2 the wall thickness in width. The criteria used to determine the design basis piping break locations in the piping systems should be equivalent to the following: a. ASME Section III Code Class I piping2 breaks should be postulated to occur at the following locations in each piping run3 or branch run: 1. The terminal ends; 2. Any intermediate locations between terminal ends where the primary plus secondary stress intensities S (circumferential or longitudinal) derived on an elastically calculated basis under the loadings associated with one-half safe shutdown earthquake and operational plant conditions4 exceeds 2.0 Sm 5 for ferritic steel, and 2.4 Sm for austenitic steel; 3. Any intermediate locations between terminal ends where the cumulative usage factor (U)6 derived from the piping fatigue analysis and based on all normal, upset, and testing plant conditions exceeds 0.1; and 4. At intermediate locations in addition to those determined by (1) and (2) above, selected on a reasonable basis as necessary to provide protection. As a minimum, there should be two intermediate locations for each piping run or branch run. b. ASME Section III Code Class 2 and 3 piping breaks should be postulated to occur at the following locations in each piping run or branch run: 1. The terminal ends; 2. Any intermediate locations between terminal ends where either the circumferential or longitudinal stresses derived on an elastically calculated basis under the loadings associated with seismic events and operational plant conditions exceed 0.8 (Sh+ SA)7 or the