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:
ral arising from the applied loads for small-scale yielding is given by Equation 15: JWpphtd = 1000 (K: 7P+ K)2 IE / (15) In an actual transient the cooldown rate initially may vary sigoificantly with time. Therefore, transient-specific peak thermal stress-induced KCH and K,4& computations may be necessary. If so, in place of Equation 13, a thermal transient 1.161-7 stress analysis may be performed for the specific transient, including the contrinbutions of cladding to thermal stress and the stress intensity factor. For this alternative analysis method the main features for computing K. and I., which are applied on examples in Appendix A, are given in Appendix B.u The limiting condition should be determined for the transient time at which the materiars resistance (I-R curve) will be greater than or equal to the J,, for evaluating Equations I and 2. The main steps are: a. Determine the temperature gradient across the vessel wall thickness, in 10 to 20 time steps over the full duration of the transiet, and compute the corresponding thermal stress history, taking into account the cladding thickness, tI. b. For each time step, compute Ka and KkL values as a function of the crack depth in the range 0.05 : a/t' < 0.5. c. For Equation 1, calculate the pressure-induced Ky. and the J.P.., using Equations 14 and 15, at a crack-tip depth of ((0.( t + tý, + 0.1 in.) < 1 in.) for each time step. d. Use Step a to find crack-tip temperature history at each time step. See Figure A-i in Appendix A for an example. e. For a given imterial condition, dtermine the J-R values at the crack extension of 0.1 inch by using the crack-tip temperature history from Step d. See Figure A-2 in Appendix A for an example. f. Compare the material's J-R values as a function of time in Step e with the J3 values in Step c. See Figure A-2 in Appendix A for anexample. The time at which the J-R value is just equal to the J, determines the critical condition for evaluating Equation 1. g. At the