IR 05000361/2012007

IR 05000361-12-007, 05000362-12-007, 03/15/2012 through 06/18/2012, San Onofre Nuclear Generating Station; Augmented Inspection Team

ML12188A748
Person / Time
Site:	San Onofre
Issue date:	07/18/2012
From:	Collins E E Region 4 Administrator
To:	Peter Dietrich Southern California Edison Co
References
IR-12-007
Download: ML12188A748 (95)

Text

July 18, 2012

Mr. Peter Dietrich Senior Vice President and Chief Nuclear Officer Southern California Edison Company San Onofre Nuclear Generating Station P.O. Box 128 San Clemente, CA 92674-0128

SUBJECT: SAN ONOFRE NUCLEAR GENERATING STATION - NRC AUGMENTED INSPECTION TEAM REPORT 05000361/2012007 and 05000362/2012007

Dear Mr. Dietrich:

The U. S. Nuclear Regulatory Commission (NRC) completed an inspection at your San Onofre Nuclear Generating Station (SONGS). The enclosed report documents the inspection results, which were discussed with you and other members of your staff during a public exit meeting on June 18, 2012.

The Augmented Inspection Team (AIT) was established to review the causes, safety implications, and your staff's actions following an event that occurred on January 31, 2012, involving a reactor coolant leak identified in a Unit 3 steam generator and a subsequent identification that multiple steam generator tubes in Unit 3 had experience substantial and unusual wear, eight of which failed pressure testing. The SONGS Unit 3 steam generators were new and had been in operation for less than one operating cycle. At the time of the event, SONGS Unit 2 was shutdown in a refueling outage with steam generators that had been in service for one operating cycle. This augmented inspection was chartered to review the circumstances surrounding the tube degradation; review the licensee's actions following discovery of the conditions; evaluate the licensee's determination of the causes of the unusual steam generator tube wear; review the steam generator modeling; and, assess the differences between Unit 2 and Unit 3 steam generators. The charter is available in ADAMS at ML12075A258. It is not the responsibility of an AIT to determine compliance with the NRC rules and regulations or to recommend enforcement actions, this will be done through subsequent NRC inspection or review. The team concluded that plant operators responded to the January 31, 2012, steam generator tube leak in accordance with procedures and in a manner that protected public health and safety. Plant safety systems worked as expected during the event. The NRC team identified ten items requiring additional review for regulatory action. These items are documented as "unresolved" items in the enclosed report. The NRC will conduct subsequent inspections or reviews to determine what, if any, regulatory actions result from the "unresolved" items.

SONGS Unit 3 steam generators had experienced excessive vibration of tubes in the U-bend region of the steam generators to the extent that the tubes rubbed against each other (tube-to-tube interactions) causing excessive wear and loss of structural integrity. Your staff determined that the vibration was caused by the steam conditions in the U-bend region of the steam generators by a phenomenon called "fluid elastic instability." The NRC inspection team concluded that the steam generators' design and configuration did not provide the necessary margin to prevent this phenomenon. Although the steam generator tube degradation from this phenomenon observed in Unit 2 steam generators was not as severe, the NRC team concluded that both units' steam generators were of similar design with similar thermal hydraulic conditions and configurations. Therefore, SONGS Unit 2 steam generators are also susceptible to this phenomenon. Accordingly, as documented in NRC Confirmatory Action Letter dated March 27, 2012, (ML12087A323), you are required to submit in writing to NRC for review and acceptance, your actions and plans to prevent recurrence of loss of tube integrity before the resumption of power operations in both SONGS Units 2 and 3. In accordance with 10 CFR 2.390 of the NRC's "Rules of Practice," a copy of this letter, its enclosure, and your response (if any) will be available electronically for public inspection in the NRC Public Document Room or from the Publicly Available Records (PARS) component of the NRC's document system (ADAMS). ADAMS is accessible from the NRC Web site at http://www.nrc.gov/reading-rm/adams.html (the Public Electronic Reading Room).

Sincerely,/RA/ Elmo E. Collins Regional Administrator Docket No.: 50-361, 50-362 License No: NPF-10, NPF-15

Enclosure:

1. Inspection Report 05000361/2012007 and 05000362/2012007 Attachment(s): 1. Supplemental Information 2. Sequence of Events