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:
ary Reference . The change allows a one-point check by a mechanical or electronic simulator instead of a check against the basic calibration block. A mechanical simulator could be a plastic, steel, or aluminum block with a single reference reflector, which may be a hole or a notch. Without specified details, the electronic simulator could be any device that I II I 1.150-2 provides an electrical signal. With the resulting uncertainty, there may be errors in checking against the secondary reference (simulator), the magnitude of which is undefined and unknown. c. Electronic Simulator Subarticle T-432.1.3 of Article 4, Section V of the ASME Code, 1977 edition, allows the use of an electronic simulator and also permits the transducer sensitivity to be checked separately. Both these provisions may introduce errors that will be very difficult to detect. To avoid the introduction of errors and to ensure repeatability of examinations at a later date, it would be advisable to check the calibration of the entire system rather than that of individual components. Checking system calibration without the transducer and the cable is not advisable because these tests do not detect possible leakage or resistance changes at the connectors. This is especially important when the UT examination is performed under conditions of high humidity or under water and the connec- tors may not be waterproof or moistureproof. Checking the transducer sensitivity separately (sometimes weeks in advance) also neglects the effects of possible damage due to transport or use. The transducer characteristics may change because of damage to or degradation of internal bonding agents or inadvertent damage to the transducer element. Further, the use of an electronic block simulator (EBS) as a secondary standard introduces an error band in the calibra- tion process. The error band may depend on, among others, the following factors: (1) Drift due to ambient temperature change. (2) Drift due to high temperature