Document: NRC Regulatory Guide
Document ID: a4944d20-ef6e-480b-a45d-14425bedd2e5
Document Type: regulatory_guide
Title: ASME Code Cases Not Approved for Use (Rev. 8)
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML2219/ML22196A065.pdf
Revision Date: 2023-05
Chapter: 
Section ID: RG-1.193
CFR Part: 
CFR Title: 

Content:
standards of Table IWB-3410-1 must be removed. Although it is recognized that operating experience has shown that large through-wall flaws and leakages have developed in previously repaired welds as a result of weld residual stresses, the NRC has the following concerns in regard to the proposed alternative in Code Case N-813: (1) The requirements of Section XI, Paragraph IWB-3112, were developed to ensure that defective welds were not placed in service. A preservice flaw detected in a weld that exceeds the acceptance standards of Table IWB-3410-1 demonstrates poor workmanship or inadequate welding practice and procedures. The unacceptable preservice flaw needs to be removed, and the weld needs to be repaired before it is placed in service. (2) Under Code Case N-813, large flaws would be allowed to remain in service because Section XI, Paragraphs IWB-3132.3, through IWB-3643, allows a flaw up to 75% through-wall to remain in service. Larger flaws could grow to an unacceptable size between inspections, thus reducing structural margin and potentially challenging the structural integrity of safety-related Class 1 and Class 2 piping. Paragraph C-3112(a)(3) of Code Case N-813 provides the same alternatives for Class 2 piping as that of Paragraph B-3122(a)(3). The staff has the same concerns for Class 2 piping as it does for Class 1 piping. 0/21E N-826 Ultrasonic Examination of Full Penetration Vessel Weld Joints in Fig. IWB- 2500-1 Through Fig. IWB-2500-6 Reduction of the inspection volume from ½ t to ½ inch conflicts with 10 CFR 50.61a, “Alternate Fracture Toughness Requirements for Protection against Pressurized Thermal Shock Events.” Licensees implementing 10 CFR 50.61a must first examine the volume described in Section XI, Figures IWB-2500-1 and IWB-2500-2, using Appendix VIII-qualified 7/16/12 DG-1408, Page 20 CODE CASE NUMBER TABLE 2 UNACCEPTABLE SECTION XI CODE CASES SUMMARY DATE OR SUPPLEMENT/ EDITION procedures, equipment, and personnel to obtain the