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 CALIFORNIA EDISONAn EDISON INTERNATIONALa' Company Proprietary Information Withhold from Public Disclosure Richard 1. St. Onge Director, Nuclear Regulatory Affairs and Emergency Planning April 15, 2013 10 CFR 50.4 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001

Subject:

Docket No. 50-361 Response 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), dated March 27, 2012, Confirmatory Action Letter 4-12-001, San Onofre Nuclear Generating Station, Units 2 and 3, Commitments to Address Steam Generator Tube Degradation

2. Letter from Mr. Peter T. Dietrich (SCE) to Mr. Elmo E. Collins (USNRC), dated October 3, 2012, Confirmatory Action Letter -Actions to Address Steam Generator Tube Degradation, San Onofre Nuclear Generating Station, Unit 2 3. Email from Mr. James R. Hall (USNRC) to Mr. Ryan Treadway (SCE), dated February 20, 2013, Request for Additional Information (RAIs 38-52) Regarding Response to 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 Action Letter (CAL) (Reference

1) to Southern California Edison (SCE) describing actions that the NRC and SCE agreed would be completed to address issues identified in the steam generator tubes of San Onofre Nuclear Generating Station (SONGS) Units 2 and 3. In a letter to the NRC dated October 3, 2012 (Reference 2), SCE reported completion of the Unit 2 CAL actions and included 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 Additional Information (RAIs) regarding the CAL response.

Enclosure 2 of this letter provides the response to RAI 45.Proprietary Information Withhold from Public Disclosure Decontrolled Upon Removal of Enclosure 2 P.O. Box 128 San Clemente, CA 92672 A4~L Proprietary Information Withhold from Public Disclosure Document Control Desk-2-April 15, 2013 Enclosure 2 of this submittal contains proprietary information.

SCE requests that this proprietary 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 the information in Enclosure 2 may be withheld from public disclosure by the NRC and addresses with specificity the considerations listed by paragraph (b)(4) of 10 CFR 2.390. Enclosure 3 provides the non-proprietary version of Enclosure 2.There are no new regulatory commitments contained in this letter. If you have any questions or require additional information, please call me at (949) 368-6240.

Enclosures:

1. Notarized Affidavit 2. Response to RAI 45 (Proprietary)

3. Response to RAI 45 (Non-Proprietary) cc: A. T. Howell III, Regional Administrator, NRC Region IV J. R. Hall, NRC Project Manager, SONGS Units 2 and 3 G. G. Warnick, NRC Senior Resident Inspector, SONGS Units 2 and 3 R. E. Lantz, Branch Chief, Division of Reactor Projects, NRC Region IV Proprietary Information Withhold from Public Disclosure Decontrolled Upon Removal of Enclosure 2

ENCLOSURE 1 Notarized Affidavit MITSUBISHI HEAVY INDUSTRIES, LTD.AFFIDAVIT I, Jinichi Miyaguchi, state as follows: 1. I am Director, Nuclear Plant Component Designing Department, of Mitsubishi Heavy Industries, Ltd. ("MHI"), and have been delegated the function of reviewing the referenced documentation to determine whether it contains MHI's information that should be withheld from public disclosure pursuant to 10 C.F.R. § 2.390 (a)(4) as trade secrets and commercial or financial information that is privileged or confidential.

2. In accordance with my responsibilities, I have reviewed the following documentation and have determined that it contains MHI proprietary information that should be withheld from public disclosure.

Those pages containing proprietary information have been bracketed with an open and closed bracket as shown here "[ I" / and should be withheld 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 Letter for 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 will continue to be, held in confidence by MHI and its disclosure outside the company is limited to regulatory bodies, customers and potential customers, and their agents, suppliers, and licensees, and others with a legitimate need for the information, and is always subject to suitable measures to protect it from unauthorized use or disclosure.

4. The basis for holding the referenced information confidential is that they describe unique design, manufacturing, experimental and Investigative information developed by MHI and not used in the exact form by any of MHI's competitors.

This information was developed 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 gathered readily from other publicly available information.

Other than through the provisions in paragraph 3 above, MHI knows of no way the information could be lawfully acquired by organizations or individuals outside of MHI.7. Public disclosure of the referenced information would assist competitors of MHI in their design and manufacture of nuclear plant components without incurring the costs or risks associated with the design and the manufacture of the subject component.

Therefore, disclosure of the information contained in the referenced document would have the following negative impacts on the competitive position of MHI in the U.S. and world nuclear markets: A. Loss of competitive advantage due to the costs associated with development of technologies relating to the component design, manufacture and examination.

Providing public access to such information permits competitors to duplicate or mimic the methodology without incurring the associated costs.B. Loss of competitive advantage of MHI's ability to supply replacement or new heavy components such as steam generators.

I declare under penalty of perjury that the foregoing affidavit and the matters stated therein are 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 Department Mitsubishi Heavy Industries, LTD Sworn to and subscribed Before me this / day of A 2r2013 7 Rm"a~ka4ý14-t_A P 1ý1 , '1 2. 10 i J Notary Public 73 My Commission does Not expire 3* 15* 17... ..... ..* /0 V*12* 104'1 -*~ 14 x 138 IX 14 litb 21 221..............

1-a A lA Registered Number 7 3 Date APR. 12.2013 NOTARIAL CERTIFICATE This is to certify that JINICHI MIYAGUCHI , Director-Nuclear Plant Component Designing Department MITSUBISHI HEAVY INDUSTRIES, LTD has affixed his signature in my very presence to the attached document.Kobc~, 4K,'MASAHIKO KUBOTA Notary 44 Akashimachi, Chuo-Ku, Kobe, Japan Kobe District Legal Affairs Bureau ENCLOSURE 3 SOUTHERN CALIFORNIA EDISON RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION REGARDING RESPONSE TO CONFIRMATORY ACTION LETTER DOCKET NO. 50-361 TAC NO. ME 9727 Response to RAI 45 (NON-PROPRIETARY)

RAI 45 In Reference 5, p. 4-12 (38 of 66), Section 4.7, "Effect of Power Reduction," the probability of initiation (POI) is based on a calculation of dynamic pressure.

Please provide the location in the U-bend selected to compute the parameter and provide justification for selection for this application.

It is not clear that dynamic pressure is a key parameter for correlation of the TTW damage patterns experienced at SONGS.RESPONSE Note: RAI Reference 5 is "Operational Assessment for SONGS Unit 2 SG for Upper Bundle Tube-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(pv 2) was used to calculate the reduction factor in the probability of initiation (POI) equation in the Operational Assessment (OA) report (RAI Reference 5, Section 4.7). The value of dynamic pressure was obtained from an ATHOS thermal hydraulic analysis of the SONGS Unit 2 Steam Generators.

A dynamic pressure contour of the Unit 2 steam generator secondary side was calculated during the analysis for the 70% and 100% power level cases. The maximum dynamic pressure for the two operating power levels was used for the calculation of the reduction factor. The maximum dynamic pressure for each power level (i.e., 2,430 N/m 2 and 4,140 N/m 2) was located in the tube-free lane approaching the U-bend near the middle 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) damage patterns experienced at SONGS. The dynamic pressure ratio was the parameter selected to identify the reduction in probability of fluid elastic instability (FEI) due to reducing the power level to 70%.The use of the dynamic pressure ratio as a parameter in the TTW initiation model was verified in the 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 wear region as shown in Figure 1 (L5-04GA567, Figure 7.2-1). The MHI SR evaluation assessed the potential 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 to loss of contact force). The MHI model contained several other key variables besides dynamic pressure 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). The MHI assessment results show a systematic monotonic reduction in the normalized SR from 100% to 50% power levels for the range of support effectiveness.

At 70% power, the normalized SR for the various cases when supports are modeled as inactive falls between 0.528 and 0.652 with an average value of 0.608. The ratio of dynamic pressure (solid black square symbol in Figure 2) falls within the range for normalized stability ratio (SR) and represents a reasonable estimate of the effect of power reduction on T-W initiation.

This comparison is a technical justification for using the linear decreasing model for FEI as well as a reduction factor of 0.586 in the POI equation to account for the benefit of reduced power operation in the high wear region.Enclosure 3 Page 2 of 5 The basis for selecting dynamic pressure to define the reduction factor for 70% power operation and 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 dynamic pressure in its formulation.

The general form of Connors' equation from "Flow-Induced Vibration of Power and Process Plant Components:

A Practical Workbook," by M. K. Au-Yang, 2001, is: Vc = O3fn .274 mt. 1/2 P where 13 is the fluid-elastic instability constant (Connors' constant) determined from experimental tests and is dependent on tube array geometryýn is the modal damping ratio of the tube f% is the modal frequency of the tube mt is the total mass per length of tube vc is the critical velocity through the gaps between tubes p is the fluid density The FEI constant, which is important in determining the stability condition for a tube, is related to the dynamic pressure 1/2 (pVc 2) from Connors' equation 1 [(1/2) PV2 11/2 13fn LE ý;n Mt The SR is defined as the ratio of pitch (gap) velocity to the critical velocity, v^/Vc. For SR less than 1.0, tubes are stable.The decrease in dynamic pressure due to reduced power operation is a measure of the net beneficial effect on TTW initiation and the corresponding tube burst probabilities.

As shown in Figure 2, the reduction factor of 0.586 based on maximum dynamic pressure used in the OA was justified in its' application to the Unit 2 OA for the 70% power case.Enclosure 3 Page 3 of 5 Row Column 80 70 80 80 100 70 100 80 120 70 120 80 95 85 125 85 138 84* Plugged tubes o Representative tube for OA-A-O

• 140 135.e' 130:125-120 o : ** *115 40 -A- -0 0110* *0 0.**. ** ::, 105 o * * *

• o* * * "95*7 90 85 O o ' 70 60 65 70 75 80 85 COL Fig.7.2-1 Evaluated Tubes Figure 1 -Unit 2 Tubes Evaluated by MHI Enclosure 3 Page 4 of 5 J Figure 2 -Verification of Reduction Factor in Initiation Model for 70% Power Operation (From RAI Reference 5, Figure 4-14)Enclosure 3 Page 5 of 5