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 components is evaluated with the help of fracture mechanics. Flaw sizes need to be known for fracture mechanics evalua- tions. Uncertain determination of flaw sizes leads to uncer- tainties in the determination of the safety of the components. Uncertainties in component safety lead to delays in licensing. There is a need to specify and standardize the performance required of most UT system components to achieve better consistency in UT results so that delays in the licensing process may be reduced. This guide will provide supplementary procedures with the objective of improving conventional UT procedures, as defined in the ASME Code. This guide is based partly on the information available in literature concerning both U.S. and European procedures and partly on the judgment of the NRC staff and their consultants. On the basis of support work being performed at the Oak Ridge National Laboratory, the staff plans to issue a revision to this guide that should further improve flaw characterization. The use of new techniques such as holography or synthetic aperture imaging of flaws by UT that have not been imple- mented into practice and could considerably increase the cost of inservice examination is not being proposed here. 1.3 Value/Impact of Proposed Action 1.3.1 NRC Reporting UT examination results as indicated in this guide would help the NRC staff and their consultants to better assess the results of the data. At present, the NRC staff must spend a great deal of time on controversy over deter- mining the safety of components from inconsistent UT results. Lack of faith in flaw size determination from uncertain UT results points toward the adoption of some 1.150-17 conservative safety measures that are undesirable, for the most part, to the industry managers. Licensing delays occur because decisions have to be made on the basis of uncertain information. Flaw size determination from consistent UT results would help remove or reduce the uncertainties and debates