Document: NRC Regulatory Guide
Document ID: 2704425a-c58a-45c4-93ab-8761721c3e7a
Document Type: regulatory_guide
Title: Evaluation of Reactor Pressure Vessels with Charpy Upper-Shelf Energy Less Than 50 Ft-Lb
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML0037/ML003740038.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.161
CFR Part: 
CFR Title: 

Content:
time at which the metal at the tip of the flaw being analyzed reaches a tm rau equivalent to the adjusted RT. plus 500F. In this regulatory guide, an adusted RTmr plus 50WF (which typically represents the low-temperatu overpressure protection systen's enabling temperature) is taken as the lower tempera ture limit for upper-shelfbehavior. This regulatory guide states that licensees should consider a spectrum of transients, including ATWS (antici pated transient without scram). Although ATWS is not a design basis transient, for compliance with Appendix G to 10 CFR Part 50 it was considered in Reference 4 for evaluation of low upper-shelf energy materials. Based on the generic analyses in Refermne 4 and additional staff calculations, ATWS in currently operating light-water-reactor (LWR) vessels in the United States is not found to be a dominant transient with respect to the low Charpy upper-shelf energy issue, and no further action is necessary with respect to ATWS. However, for designs other than the currently operat ing LWR vessels in the United States, ATWS could become a dominating transient, and as such needs to be considered as a Service Level C transient for further evaluation. A plant specific justification should be provided for consideration of such designs at another service load level. For such designs, lioensees should consider the assumptions used in the generic analyses of Reference 4 to be sure that they are bounding for theirplant-specific applications. If these generic analyses are not bounding, plant-specific analyses should be performed. 4.1 Plant-Specific Transients To provide reasonable assurance that the limiting service loading conditions have been identified on a plant specific basis, the Service Level C and D design transients and events that are necessary to demonstrate compliance with Standard Review Plan 3.9.3 (Ref. 11) should be used. When Ihis transient list isnot available or is incomplete, the most complete list oftransicnts for these