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:
tivities affecting quality. Consistent with applicable regulatory requirements, the applicant is required to establish such requirements concerning record retention as duration, location, and assigned responsibility. This guide describes procedures acceptable to the NRC staff for implementing the above requirements with regard to the preservice and inservice examinations of reactor vessel welds in light-water-cooled nuclear power plants by ultrasonic testing (UT). The scope of this guide is limited to reactor vessel welds and does not apply to other structures and components such as piping. B. DISCUSSION Reactor vessels must periodically be volumetrically examined according to Section XI of the ASME Code, which is incorporated by reference, with NRC staff modifica- tions, in § 50.55a of 10 CFR Part 50. The rules of Section XI require a program of examinations, testing, and inspections to evidence adequate safety. To ensure the continued structural integrity of reactor vessels, it is essential that flaws be reliably detected and evaluated. It is desirable that results from prior UT examinations be compared to results from subsequent examinations so that flaw growth rates may be estimated. Lack of reliability of UT examination results is partly due to the reporting of ambiguous results, such as reporting the length of flaws to be shorter during subsequent examinations. This lack of reproducibility arises because the Code requirements are not specific about many essential variables in t 'e UT procedures. Recommenda- tions of this guide providc guidance that would help to obtain reproducibility of results. Reporting of UT indications as recommended in this guid" will help to provide a means for assessing the ambiguity of t1- ý reported data. USNRC REGULATORY GUIDES Regulatory Guides are issued to describe and make available to the public methods acceptable to the NRC staff of implementing specific parts of the Commission's regulations, to delineate tech- niques used