Protecting People and the EnvironmentUNITED STATES NUCLEAR REGULATORY COMMISSION
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.
