ML13022A405

San Onofre, Unit 2, Response to Request for Additional Information (RAI 28), Regarding Confirmatory Action Letter Response (TAC No. Me 9727)

ML13022A405
Person / Time
Site:	San Onofre
Issue date:	01/21/2013
From:	St.Onge R J Southern California Edison Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
TAC ME9727
Download: ML13022A405 (4)

Text

K SOUTHERN CALIFORNIA Richard J. St. OngeaEDISON Director, Nuclear Regulatory Affairs and-Emergency PlanningAn EDISON INTERNATIONAL Company10 CFR 50.4January 21, 2013U.S. Nuclear Regulatory CommissionATTN: Document Control DeskWashington, DC 20555-0001

Subject:

Docket No. 50-361Response to Request for Additional Information (RAI 28)Regarding Confirmatory Action Letter Response(TAC No. ME 9727)San Onofre Nuclear Generating Station, Unit 2

References:

1. Letter from Mr. Elmo E. Collins (USNRC) to Mr. Peter T. Dietrich (SCE), datedMarch 27, 2012, Confirmatory Action Letter 4-12-001, San Onofre NuclearGenerating Station, Units 2 and 3, Commitments to Address Steam GeneratorTube Degradation2. Letter from Mr. Peter T. Dietrich (SCE) to Mr. Elmo E. Collins (USNRC), datedOctober 3, 2012, Confirmatory Action Letter -Actions to Address SteamGenerator Tube Degradation, San Onofre Nuclear Generating Station, Unit 23. Letter from Mr. James R. Hall (USNRC) to Mr..Peter T. Dietrich (SCE), datedDecember 26, 2012, Request for Additional Information Regarding Responseto Confirmatory Action Letter, San Onofre Nuclear Generating Station, Unit 2

Dear Sir or Madam,

On March 27, 2012, the Nuclear Regulatory Commission (NRC) issued a Confirmatory ActionLetter (CAL) (Reference 1) to Southern California Edison (SCE) describing actions that the NRCand SCE agreed would be completed to address issues identified in the steam generator tubesof San Onofre Nuclear Generating Station (SONGS) Units 2 and 3. In a letter to the NRC datedOctober 3, 2012 (Reference 2), SCE reported completion of the Unit 2 CAL actions andincluded a Return to Service Report (RTSR) that provided details of their completion.By letter dated December 26, 2012 (Reference 3), the NRC issued Requests for AdditionalInformation (RAIs) regarding the CAL response. Enclosure 1 of this letter provides theresponse to RAI 28.There are no new regulatory commitments contained in this letter. If you have any questions orrequire additional information, please call me at (949) 368-6240.Sincerely,P.O. Box 128San Clemente, CA 92672 ,-\L(-.

Document Control Desk January 21, 2013

Enclosures:

1. Response to RAI 28cc: E. E. Collins, Regional Administrator, NRC Region IVJ.. R. Hall, NRC Project Manager, SONGS Units 2 and 3G. G. Warnick, NRC Senior Resident Inspector, SONGS Units 2 and 3R. E. Lantz, Branch Chief, Division of Reactor Projects, NRC Region IV ENCLOSURE 1SOUTHERN CALIFORNIA EDISONRESPONSE TO REQUEST FOR ADDITIONAL INFORMATIONREGARDING RESPONSE TO CONFIRMATORY ACTION LETTERDOCKET NO. 50-361TAC NO. ME 9727Response to RAI 28Page 1 RAI 28Reference 5, Section 2.6.1 -What is the estimated growth rate of the tube to tube wear in steamgenerator 3E0-88, tube R106C78? Describe how it was determined.RESPONSENote: Reference 5 in RAI 28 is the Westinghouse operational assessment.Tube-to-tube wear (TTW) rates were not calculated for tubes in Unit 3 since that was notrequired as part of the operational assessment for Unit 2. Benchmarking of Unit 3 determinedthat all tubes with TTW were found to either be unstable in the in-plane direction, or were incontact with tubes that were unstable.The Westinghouse evaluation determined that the wear associated with tube-to-tube contact inUnit 2 was not a result of in-plane instability. The analysis determined that the tube-to-tubecontact was a result of a proximity condition, meaning that the tubes were closer together thanwhat would be indicated in the design. Therefore, no significant TTW growth is predicted in Unit2. Appendix A of Reference 5 contains a summary of the TTW that occurred in the free span ofUnit 2. This appendix addressed the Unit 2 tubes with TTW and did not evaluate TTW in Unit 3.In summary, no TTW calculations were performed for SG 3E-088, tube R1 06C78, as the tubewear in Unit 3 was produced from a different mechanism than the TTW that occurred in Unit 2.As a result, this was not a necessary calculation to support the Unit 2 operational assessment.Page 2