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:
his position. 3. NEAR-SURFACE EXAMINATION AND SURFACE RESOLUTION This position recommends that an estimation of the capability to effectively detect defects at the metal front and back surfaces of the actual component should be made and reported. This will not require any additional calibration or examination time but will simply require an estimate of this capability by the examiner, which will be reported to NRC. No additional radiation exposure is expected because of this position. 4. BEAM PROFILE This position recommends that the beam profile (for each search unit used) should be determined if any signif- icant flaws are detected during the RPV examination. Assuming that no more than three search units are likely to be used during an RPV examination, this step is likely to require no more than 2 hours of examination time. No additional radiation exposure is expected because of this position. 5. SCANNING WELD-METAL INTERFACE This position recommends that the beam angles used to scan welds should be based on weld/parent-metal interface 1.150-21 geometry and at least one of these angles should be such that the beam is almost perpendicular (±l 5 degrees to the perpen- dicular) to the weld/parent-metal interface, unless it can be demonstrated that large (Code-unacceptable) planar flaws unfavorably oriented can be detected by the UT technique. On the basis of information available, it appears that it is difficult 1 ,2,3 to detect large planar flaws (e.g., service-induced fatigue or stress corrosion cracks) oriented at right angles to the surface, using the ASME Code UT procedure. However, the option is being provided to demonstrate that such flaws can be located by conventional methods or by using new advances in UT techniques. In these cases, the technique will be acceptable as a volumetric examination method. Otherwise, the use of high-intensity radiography or tandem-probe UT technique, among other techniques, should be considered. The above type of flaw is the