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:
s of statistically significant field data. Performance stability of automated electronic equipment is dependent on system performance parameters (essential variables), and the ASME Code has no quality standards to control these performance parameters. Until the performance stability of UT systems can be ensured by the introduction of quality standards, it is not reasonable to increase the period between calibration checks. Therefore, recommendations have been made to check instrument performance parameters more frequently than is specified in the ASME Code. Requirements of Appendix I, Article I, 1-4230, Section XI of the ASME Code, 1974 edition, state: "System calibration shall be clecked by verifying the distance-amplitude correction curve (1-4420 or 1-4520) and the sweep range calibration (1-4410 or 1-4510) at the start and finish of each examination, with any change in examination personnel, and at least every 4 hours during an examination." In the 1977 edition, these requirements were changed. According to Article 4 (T-432.1.2), Section V of the ASME Code, 1977 edition, the following applies: "A calibration check on at least one of the basic reflectors in the basic calibration block or a check using a simulator shall be made at the finish of each examination, every 4 hours during the examination and when examination personnel are changed." This requirement has several minor deficiencies, including the following: a. One-Point Check A calibration check is now required on only one of the basic reflectors. As a result, the accuracy of only one point on the DAC curve, and not the accuracy of three points as previously required, is checked. This alteration would permit the instrument drift for other metal path distances to go unnoticed, which is not desirable. b. Secondary 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