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:
d in this guide be sized at 20 percent DAC as well as at 50 percent DAC. In certain cases, it is possible for various reasons that a flaw would not reflect enough energy to the search unit to make the indication height 50 percent of the DAC curve height. However, if such a flaw were large, a persistent signal could be obtained over a large area. It is therefore recommended that all continuous signals that are 20 percent of DAC with transducer travel movement of more than 1 inch plus the beam spread (as defined in Article 4, non- mandatory Appendix B, Section V of the ASME Code, 1977 edition) should be considered significant and should be recorded and investigated further. The beam spread effect in some cases can make very small flaws appear to be large when judged at 20 percent DAC; hence, beam spread has to be considered in judging the significance of flaws. 8 It is therefore recommended that only signals with a total transducer travel movement greater than the beam spread should be considered significant. 7. REPORTING OF RESULTS This guide gives recommendations for recording the charac- teristics of the UT examination system. This information can be of significance in later analysis for determining the location, dimensions, orientation, and growth rate of flaws. Records pertaining to UT examinations should be con- sidered quality assurance records. Recommendations on the .collection, storage, and maintenance of these records are given in Regulatory Guide 1.88, "Collection, Storage, and Maintenance of Nuclear Power Plant Quality Assurance Re- cords." Availability of these records at a later date will permit a review of the UT results from the data gathered during previous ultrasonic examinations. When ultrasonic examination is performed, certain vol- umes of material such as the following are not effectively examined: a. Material volume near the front surface because of near- field effects, cladding disturbance, or electronic gating. b. Material volume near the