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:
cludes the effect of pressure acting on the flaw faces. For an axial or circumferential flaw with depth 'a' equal to (0.25t + 0.1 in.), the "steady-state" (time independent) sess intensity factor from radial thermal gradients is obtained by using Equation 8: KIt = ((CR)10oo)t" F3 (8) F3 = 0.69 + 3.127(a/t) - 7.435(a/62 + 3.532(a/t)3 This equation for Kit is valid for 0.2 :g a/t 0.50, and 0 s CR g 100F&r. This equation does not include the contribution to K, from the cladding thickness, t ... If the steady-state values of thermally induced K,, are used, the material J-R curve should correspond to the temperature at the beginning of the transient, when a uniformly high temperature is present across the vessel wall thickness, leading to the lowest J-R curve. The above Kjt expression can be replaced with an improved accuracy solution if an appropriate justification is provided. Calculate the effective flaw depth for small-scale yielding, a,, using Equation 9: a, = a + (T) [ ( t•_.. 7[ U (9) Step 2 For an axial flaw, calculate the stress intensity factor from internal pressure for small-scale yielding, C, by substituting a. in place of 'a' in Equation 6, including the equation for F,. For a circumferential flaw, calculate K; by substituting a. in place of 'a' in Equation 7, including the equation for F2. For an axial or circumferential flaw, calculate the sress intensity factor from the radial thermal gradients for small-scale yielding Ký, by substituting a, in place of 'a' in Equation 8, including the equation for F3. The J-integral from the applied loads for small-scale yielding is given by Equation 10: J,,,,~a = 1000(K,,a.4 IE' (10) Alternatively, in place of the steady-state Equation 8, a thermal transient stress analysis may be performed for the limiting cooldown rate, including the contributions of cladding to thermal stress and the thermal stress intensity factor. For this alternative analysis method (also described in Reference, 4), the main features for