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Information Notice No.80-15 – Axial (Longitudinal) Oriented Cracking in Piping
SSINS No.: 6870 Accession No. 8002280660 UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D.C. 20555 April 21, 1980 Information Notice No. 80-15 AXIAL (LONGITUDINAL) ORIENTED CRACKING IN PIPING On March 8, 1980, the Commonwealth Edison Company reported to the NRC that slight leakage was observed from the "A" loop core spray injection piping during a reactor coolant system leakage test at their Quad-Cities Unit 2 Nuclear Power Station. The source of leakage was subsequently identified to be located adjacent to a shop weld joining a 90
elbow and a wedge section of elbow material used to extend the elbow to 105 . Subsequent ultrasonic inspections revealed additional cracking in several other elbows in "A" and "B" core spray loops. The cracks are located adjacent to welds and oriented transverse to the weld in the axial (longitudinal) piping direction. The affected elbows have been removed and currently failure analyses are in progress. Preliminary results from liquid penetrant examinations of the elbow interior surface in the counter bore/weld root area revealed axial oriented cracks on both sides of the weld in the counter bores adjacent to the weld roots. From the limited metallography performed to date, the cracking mode appears to be intergranular stress corrosion cracking. The cracking, however, only appears to be slightly branched. A determination as to whether or not the cracking extends into and across the welds cannot be made at this time. It is significant to point out that these service sensitive lines, as defined by NUREG 313, had been examined on an augmented basis per NUREG 313 requirements. Two of the affected welds were inspected ultrasonically at the current outage prior to the leakage being observed at the pressure test with no indication of cracking reported. Further ultrasonic examinations, using standard ASME Section XI methods, performed after discovery of the leak clearly revealed the cracking (approximately 100% over the reference level). Licensees are requested to inform NDE inspection personnel of the above stated information and to emphasize the need for care when performing circumferential UT scans of the weld and adjacent areas in piping components. Particular importance should be stressed when the examinations are performed on BWR service sensitive 304 stainless steel piping and on PWR 304 stainless steel piping in stagnant systems. This Information Notice is provided as an early notification of a possibly significant matter that is still under review by the NRC staff. It is expected that recipients will review the information for possible applicability to their facility. No specific action or response is requested at this time. If you have any questions regarding this matter, please contact the Director of the appropriate NRC Regional Office.
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