Document: NRC Regulatory Guide
Document ID: cf1737d6-2a8a-4765-aaf5-f5f2a617ef91
Document Type: regulatory_guide
Title: Design of Main Steam Isolation Valve Leakage Control Systems for Boiling Water Reactor Nuclear Power Plants
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML0037/ML003740263.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.96
CFR Part: 
CFR Title: 

Content:
X A SUPPLEMENTAL DESIGN FEATURES FOR QUALITY GROUP A PORTION OF LEAKAGE CONTROL SYSTEM PIPING This appendix provides supplemental design features for any portion of piping for a leakage control system (LCS) that connects to steam system piping between inner and outer containment isolation valves of the main steam system for either single- or dual-barrier contain ment structures. Such piping, up to and including the first isolation valve in the LCS piping, should be constructed to meet the requirements of the ASME Code in Subarticle NE-1 120 of Section III, supple mented by the following: 1. The following design stress and fatigue limits should not be exceeded: a. The maximum stress range should not exceed 2.Sm.I b. The maximum stress range between any two load sets (including the zero load set) should be calculated by Equation (10) in Paragraph NB-3653, ASME Code, Section II, for upset plant conditions and an operating basis earthquake transient. If the calculated maximum stress range of Equation (10) exceeds 2.4Sm but is not greater than 3Sm, the cumulative usage factor should be less than 0.1. If the calculated maximum stress range of Equation (10) exceeds 3Sm, the stress ranges calculated by both Equation (12) and Equation (13) in Paragraph NB-3653 should not exceed 2A4Sm and the cumulative usage factor should be less than 0.1. 2. Welded attachments to this portion of piping for pipe supports or other purposes should be avoided. 3. The number of circumferential and longitudinal welds in the piping should be minimized. 4. The portion of piping extending to the first shutoff valve should be as short as practical. 5. The design of piping restraints should not require welding directly to the outer surface of the piping. 6. The design of this portion of the leakage control system should permit the conduct of inservice examina tions required by the rules of Section XI of the ASME Boiler and Pressure Vessel Code, and the extent of examinations during each inspection