Document: NRC Regulatory Guide
Document ID: c55ba6c5-aa2d-4ad6-aba2-2001e16524ab
Document Type: regulatory_guide
Title: Ultrasonic Testing of Reactor Vessel Welds During Preservice and Inservice Examinations (Rev. 1)
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML1221/ML12216A015.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.150
CFR Part: 
CFR Title: 

Content:
the flaws that can be missed because of electronic gating may be larger than the flaws permitted with or without evaluation, this unexamined volume is important and needs to be identified. In certain specific cases, areas were not examined because insulation was in the way and the transducer could not scan the volume of interest. NRC was not informed of this situation until much later. In view of the above and to avoid licensing delays, it is advisable that the volume of areas not examined for any or all of the above reasons be reported. The volumes of material that are not effectively examined depend on the particular part geometry and unique situa- tions associated with each RPV. During identification of the material volumes that have not been examined, considera- tion should be given to the types of flaws that are currently being reported in some of the operating plants. These include stress corrosion cracks in the heat-affected zone, fatigue cracks, and cracks that are close to the surface and sometimes penetrate the surface. These volumes of material should be identified and reported to NRC along with the report of welding and material defects in accordance with the recommendation of regulatory position 2.a(3) of Regulatory Guide 1.16, "Reporting of Operating Informa- tion-Appendix A Technical Specifications." C. REGULATORY POSITION Ultrasonic examination of reactor vessel welds should be performed according to the requirements of Section XI of the ASME B&PV.Code, as referenced in the Safety Analysis Report (SAR) and its amendments, supplemented by the following: 1. INSTRUMENT PERFORMANCE CHECKS The checks described in paragraphs 1.2 through 1.5 should be made for any UT system used for the recording and sizing of reflectors in accordance with regulatory position 6 and for reflectors that exceed the Code-allowable criteria. 1.1 Frequency of Checks As a minimum, these checks should be verified within 1 day before and within I day after examining all the welds