United States Nuclear Regulatory Commission - Protecting People and the Environment

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. 

Page Last Reviewed/Updated Tuesday, November 12, 2013