Evaluation of Manual Ultrasonic Examinations Applied to Detect Flaws in Primary System Dissimilar Metal Welds at North Anna Power Station

Anderson, Michael T. ; Diaz, Aaron A. ; Doctor, Steven R.

Pacific Northwest National Laboratory (U.S.)

关键词: Flaws;    Flaws;    Ultrasonic Examination;    North Anna Power Station;    Nuclear Reactor;   

DOI  :  10.2172/1049027
RP-ID  :  PNNL-21546
RP-ID  :  AC05-76RL01830
RP-ID  :  1049027

美国|英语

来源: UNT Digital Library

【 摘 要 】

During a recent inservice inspection (ISI) of a dissimilar metal weld (DMW) in an inlet (hot leg) steam generator nozzle at North Anna Power Station Unit 1, several axially oriented flaws went undetected by the licensee's manual ultrasonic testing (UT) technique. The flaws were subsequently detected as a result of outside diameter (OD) surface machining in preparation for a full structural weld overlay. The machining operation uncovered the existence of two through-wall flaws, based on the observance of primary water leaking from the DMW. Further ultrasonic tests were then performed, and a total of five axially oriented flaws, classified as primary water stress corrosion cracking (PWSCC), were detected in varied locations around the weld circumference.