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:
gher toughness materials. However, test results reported in NUREG/CR-5265, "Size Effects on J-R Curves for A-302B Plate" (Ref. 15), clearly show J-R curves with very little, if any, increase in slope. References 15,16, and 17 provide some insight into the nature of the low toughness issue for the plate materials. While there are several variables that influence the fratr toughness, sulphur content seeins to be areasonable indicator of the plate tougnss, with a "higher" sulphur content indicating "lower' fracture toughness ( 17). A sulphur content ofO.018 wt-% is a good demarcation for high- and low-toughness values. Because of the low-toughness plate issue, and because of the relat*ivy sparse data base that could be used to estimate the firature toughness for these materials, a fracture toughness model is only provided for high-toughness plate materials. If the sulphur content of the plate is less than 0.018 wt-%, the plate models described in Reference 10 may be used. How ever, if the sulphur content is greater than or equal to 0.018 wt-%, justification sbxzld be provided for use of the models in Reference 10. Factors that might justify use of these high toughness models could include information about the year of manufacture of the plate and any special thermo-mechanical processing that would serve to improve the fracture toughness of the plate. If adequate justification cannot be provided, a low-toughness plate model should be developed and used. The CVN value should be for the proper orientation of the plate material (see Figure 2). For example, for axial flaws the CVN value for the L-T (strong) orientation in the vessel wall should be used. Similarly, for circunferential flaws the CVN value for the T-L (weak) orientation should be used. In many cases, the CVN values for both orientations may not be known. ff the CVN value for the T-L (weak) orientation is not available, the L-T (strong) orientation CVN value may be multiplied by a factor of 0.65 (Ref. 18) to