ML13107A524

San Onofre, Unit 2, Response to Request for Additional Information (RAI 45) Regarding Confirmatory Action Letter Response

ML13107A524
Person / Time
Site:	San Onofre
Issue date:	04/15/2013
From:	St.Onge R J Edison International Co, Southern California Edison Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
TAC ME9727
Download: ML13107A524 (13)

Text

JSOUTHERN CALIFORNIAEDISONAn EDISON INTERNATIONALa' CompanyProprietary InformationWithhold from Public DisclosureRichard 1. St. OngeDirector, Nuclear Regulatory Affairs andEmergency PlanningApril 15, 201310 CFR 50.4U.S. Nuclear Regulatory CommissionATTN: Document Control DeskWashington, DC 20555-0001

Subject:

Docket No. 50-361Response to Request for Additional Information (RAI 45)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. Email from Mr. James R. Hall (USNRC) to Mr. Ryan Treadway (SCE), datedFebruary 20, 2013, Request for Additional Information (RAIs 38-52) RegardingResponse to Confirmatory Action Letter, San Onofre Nuclear GeneratingStation, 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 email dated February 20, 2013 (Reference 3), the NRC issued Requests for AdditionalInformation (RAIs) regarding the CAL response. Enclosure 2 of this letter provides theresponse to RAI 45.Proprietary InformationWithhold from Public DisclosureDecontrolled Upon Removal of Enclosure 2P.O. Box 128San Clemente, CA 92672A4~L Proprietary InformationWithhold from Public DisclosureDocument Control Desk April 15, 2013Enclosure 2 of this submittal contains proprietary information. SCE requests that thisproprietary enclosure be withheld from public disclosure in accordance with 10 CFR 2.390(a)(4).Enclosure 1 provides a notarized affidavit from MHI, which sets forth the basis on which theinformation in Enclosure 2 may be withheld from public disclosure by the NRC and addresseswith specificity the considerations listed by paragraph (b)(4) of 10 CFR 2.390. Enclosure 3provides the non-proprietary version of Enclosure 2.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.

Enclosures:

1. Notarized Affidavit2. Response to RAI 45 (Proprietary)3. Response to RAI 45 (Non-Proprietary)cc: A. T. Howell III, 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 IVProprietary InformationWithhold from Public DisclosureDecontrolled Upon Removal of Enclosure 2 ENCLOSURE 1Notarized Affidavit MITSUBISHI HEAVY INDUSTRIES, LTD.AFFIDAVITI, Jinichi Miyaguchi, state as follows:1. I am Director, Nuclear Plant Component Designing Department, of Mitsubishi HeavyIndustries, Ltd. ("MHI"), and have been delegated the function of reviewing thereferenced documentation to determine whether it contains MHI's information thatshould be withheld from public disclosure pursuant to 10 C.F.R. § 2.390 (a)(4) as tradesecrets and commercial or financial information that is privileged or confidential.2. In accordance with my responsibilities, I have reviewed the following documentation andhave determined that it contains MHI proprietary information that should be withheldfrom public disclosure. Those pages containing proprietary information have beenbracketed with an open and closed bracket as shown here "[ I" / and should bewithheld from public disclosure pursuant to 10 C.F.R. § 2.390 (a)(4).SCE's document-Responses to the Second Request for Additional Information issued by NRC,regarding response to March 27, 2012 Confirmatory Action Letterfor San Onofre Nuclear Generating Station Unit 2 (TAC NO.ME9727)(RAI No, ; #45)3. The information identified as proprietary in the document have in the past been, and willcontinue to be, held in confidence by MHI and its disclosure outside the company islimited to regulatory bodies, customers and potential customers, and their agents,suppliers, and licensees, and others with a legitimate need for the information, and isalways subject to suitable measures to protect it from unauthorized use or disclosure.4. The basis for holding the referenced information confidential is that they describeunique design, manufacturing, experimental and Investigative information developed byMHI and not used in the exact form by any of MHI's competitors. This information wasdeveloped at significant cost to MHI, since it is the result of an intensive MHI effort.5. The referenced information was furnished to the Nuclear Regulatory Commission("NRC") in confidence and solely for the purpose of information to the NRC staff.

6. The referenced information is not available in public sources and could not be gatheredreadily from other publicly available information. Other than through the provisions inparagraph 3 above, MHI knows of no way the information could be lawfully acquired byorganizations or individuals outside of MHI.7. Public disclosure of the referenced information would assist competitors of MHI in theirdesign and manufacture of nuclear plant components without incurring the costs or risksassociated with the design and the manufacture of the subject component. Therefore,disclosure of the information contained in the referenced document would have thefollowing negative impacts on the competitive position of MHI in the U.S. and worldnuclear markets:A. Loss of competitive advantage due to the costs associated with development oftechnologies relating to the component design, manufacture and examination.Providing public access to such information permits competitors to duplicate ormimic the methodology without incurring the associated costs.B. Loss of competitive advantage of MHI's ability to supply replacement or new heavycomponents such as steam generators.

I declare under penalty of perjury that the foregoing affidavit and the matters stated thereinare true and correct to the best of my knowledge, information and belief.Executed on this / dayof r -,p ,2013.Jinichi Miyaguchi,Director- Nuclear Plant Component Designing DepartmentMitsubishi Heavy Industries, LTDSworn to and subscribedBefore me this / dayof A 2r20137Rm"a~ka4ý14-t_A P 1ý1 , '1 2. 10 i JNotary Public73My Commission does Not expire 3* 15* 17... ..... ..* /0V*12* 104'1 -*~ 14x 138IX 14litb21221..............:1-a A lA Registered Number 7 3Date APR. 12.2013NOTARIAL CERTIFICATEThis is to certify that JINICHI MIYAGUCHI , Director-Nuclear PlantComponent Designing Department MITSUBISHI HEAVY INDUSTRIES, LTDhas affixed his signature in my very presence to the attacheddocument.Kobc~, 4K,'MASAHIKO KUBOTANotary44 Akashimachi, Chuo-Ku,Kobe, JapanKobe District Legal Affairs Bureau ENCLOSURE 3SOUTHERN CALIFORNIA EDISONRESPONSE TO REQUEST FOR ADDITIONAL INFORMATIONREGARDING RESPONSE TO CONFIRMATORY ACTION LETTERDOCKET NO. 50-361TAC NO. ME 9727Response to RAI 45(NON-PROPRIETARY)

RAI 45In Reference 5, p. 4-12 (38 of 66), Section 4.7, "Effect of Power Reduction," the probability ofinitiation (POI) is based on a calculation of dynamic pressure. Please provide the location in theU-bend selected to compute the parameter and provide justification for selection for thisapplication. It is not clear that dynamic pressure is a key parameter for correlation of the TTWdamage patterns experienced at SONGS.RESPONSENote: RAI Reference 5 is "Operational Assessment for SONGS Unit 2 SG for Upper BundleTube-to-Tube Wear Degradation at End of Cycle 16", prepared by Intertek APTECH for Areva,Report No. AES 12068150-2Q-1, Revision 0, September 2012.The dynamic pressure 1/2(pv2) was used to calculate the reduction factor in the probability ofinitiation (POI) equation in the Operational Assessment (OA) report (RAI Reference 5, Section4.7). The value of dynamic pressure was obtained from an ATHOS thermal hydraulic analysisof the SONGS Unit 2 Steam Generators. A dynamic pressure contour of the Unit 2 steamgenerator secondary side was calculated during the analysis for the 70% and 100% power levelcases. The maximum dynamic pressure for the two operating power levels was used for thecalculation of the reduction factor. The maximum dynamic pressure for each power level (i.e.,2,430 N/m2 and 4,140 N/m2) was located in the tube-free lane approaching the U-bend near themiddle of the steam generator.The tube wear damage occurred in a region of high fluid velocities and insufficient tube support.Dynamic pressure alone does not directly correlate to the tube-to-tube wear (TTW) damagepatterns experienced at SONGS. The dynamic pressure ratio was the parameter selected toidentify the reduction in probability of fluid elastic instability (FEI) due to reducing the power levelto 70%.The use of the dynamic pressure ratio as a parameter in the TTW initiation model was verified inthe OA by comparing this reduction factor with the reduction of in-plane stability ratios (SRs)computed by MHI (Report L5-04GA567, Rev. 6). MHI evaluated nine tubes within the high wearregion as shown in Figure 1 (L5-04GA567, Figure 7.2-1). The MHI SR evaluation assessed thepotential for FEI for different power levels (50% to 100%) and for various support configurations(i.e., number of consecutive anti-vibration bar (AVB) supports that are no longer effective due toloss of contact force). The MHI model contained several other key variables besides dynamicpressure in the analysis to include tube and support geometry, flow direction, damping(structural, two-phase, and squeeze-film), void fraction, and vibration mode.Verification of the reduction factor is shown in Figure 2 (RAI Reference 5, Figure 4-14). TheMHI assessment results show a systematic monotonic reduction in the normalized SR from100% to 50% power levels for the range of support effectiveness. At 70% power, thenormalized SR for the various cases when supports are modeled as inactive falls between0.528 and 0.652 with an average value of 0.608. The ratio of dynamic pressure (solid blacksquare symbol in Figure 2) falls within the range for normalized stability ratio (SR) andrepresents a reasonable estimate of the effect of power reduction on T-W initiation. Thiscomparison is a technical justification for using the linear decreasing model for FEI as well as areduction factor of 0.586 in the POI equation to account for the benefit of reduced poweroperation in the high wear region.Enclosure 3Page 2 of 5 The basis for selecting dynamic pressure to define the reduction factor for 70% power operationand its application in the OA is the accepted semi-empirical approach of Connors' equation.Connors' equation defines the critical velocity for FEI, and uses dimensionally, the dynamicpressure in its formulation.The general form of Connors' equation from "Flow-Induced Vibration of Power and ProcessPlant Components: A Practical Workbook," by M. K. Au-Yang, 2001, is:Vc = O3fn .274 mt. 1/2Pwhere13 is the fluid-elastic instability constant (Connors' constant) determined fromexperimental tests and is dependent on tube array geometryýn is the modal damping ratio of the tubef% is the modal frequency of the tubemt is the total mass per length of tubevc is the critical velocity through the gaps between tubesp is the fluid densityThe FEI constant, which is important in determining the stability condition for a tube, is related tothe dynamic pressure 1/2 (pVc2) from Connors' equation1 [(1/2) PV2 11/213fn LE ý;n MtThe SR is defined as the ratio of pitch (gap) velocity to the critical velocity, v^/Vc. For SR lessthan 1.0, tubes are stable.The decrease in dynamic pressure due to reduced power operation is a measure of the netbeneficial effect on TTW initiation and the corresponding tube burst probabilities. As shown inFigure 2, the reduction factor of 0.586 based on maximum dynamic pressure used in the OAwas justified in its' application to the Unit 2 OA for the 70% power case.Enclosure 3Page 3 of 5 Row Column80 7080 80100 70100 80120 70120 8095 85125 85138 84* Plugged tubeso Representative tube for OA-A-O

• 140135.e' 130:125-120o : ** *11540 -A- -00110* *0 0.**. ** ::, 105o * * *

• o* * * "95*7 9085O o -75-' 7060 65 70 75 80 85COLFig.7.2-1 Evaluated TubesFigure 1 -Unit 2 Tubes Evaluated by MHIEnclosure 3Page 4 of 5 JFigure 2 -Verification of Reduction Factor in Initiation Model for 70% Power Operation(From RAI Reference 5, Figure 4-14)Enclosure 3Page 5 of 5