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:
'1'2 3 5iid industry tests4 have indicated that UT. procedures .that have been used for examination of reactor vessel welds may not -be. adequate to consistently detect and reliably characterize flaws during inservice examination of reactors."This lack of reproducibility of location and characterization of flaws has resulted in the need for additional examinations and evaluations with associated delays in the licensing process. 1. INSTRUMENT SYSTEM PERFORMANCE CHECKS Instrument system performance checks to determine the characteristics of the UT system should be performed at intervals short enough to permit each UT examination to be correlated with particular system performance parameters to help compare results. These determinations will help make it possible to judge whether differences in observations made at different times are due to changes in the instrument system characteristics or are due to real changes in the flaw size and characteristics. Determinations for "Frequency-Amplitude Curve" and "Pulse Shape" recommended in regulatory posi- tions 1.4 and 1.5 may be made by the licensee's examination agent by using any of the common industry methods for measuring these parameters as long as these methods are adequately documented in the examination record. These measurements may be performed in the laboratory before and after each examination, provided the identical equip- ment combination (i.e., instrumentation, cable, and search unit) is used during the examination. These determinations are to aid third-party evaluations when different equipment is used to record indications on subsequent examinations and are not intended to qualify systems for use. The intent of regulatory position 1.5 is to establish the instrument pulse shape in a way that actual values of pulse length and voltages can be observed on an oscilloscope. The calibrated time base does not necessarily have to follow the time base of the distance-amplitude correction (DAQ curve bit may be chosen