ML13092A116

Response to Request for Additional Information (RAI 62) Regarding Confirmatory Action Letter

ML13092A116
Person / Time
Site:	San Onofre
Issue date:	03/29/2013
From:	St.Onge R Southern California Edison Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
TAC ME9727
Download: ML13092A116 (9)

Text

Richard J. St. Onge JSOUTHERN EDISON CALIFORNIA An EDISON INTERNATIONAL Company Proprietary Information Director. Nuclear Regulatory Affairs and Emergency Planning Withhold from Public Disclosure March 29, 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 62)

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. Letter from Mr. James R. Hall (USNRC) to Mr. Peter T. Dietrich (SCE), dated March 18, 2013, Second Request for Additional Information 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 letter dated March 18, 2013 (Reference 3), the NRC issued Requests for Additional Information (RAts) regarding the CAL response. Enclosure 2 of this letter provides the response to RAI 62.

Proprietary Information Withhold from Public Disclosure P.O. Box 128 Decontrolled Upon Removal From Enclosure 2 San Clemente, CA 92672

Document Control Desk March 29, 2013 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). provides a notarized affidavit from AREVA NP Inc., 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.

Proprietary information in Enclosure 2 was extracted from AREVA document 51-9197672-003, SONGS Probability of FEI Operational Assessment RAI Responses, which is addressed in the affidavit. 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.

Sincerely,

Enclosures:

1. Notarized Affidavit

2. Response to RAI 62 (Proprietary)

3. Response to RAI 62 (Non-Proprietary) cc: E. E. Collins, 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 From Enclosure 2

ENCLOSURE 1 Notarized Affidavit

AFFIDAVIT STATE OF NORTH CAROLINA

) ss.

COUNTY OF MECKLENBURG )

1. My name is Dennis C. Williford. I am Manager, Product Licensing, for AREVA NP Inc. (AREVA NP) and as such I am authorized to execute this Affidavit.

2. I am familiar with the criteria applied by AREVA NP to determine whether certain AREVA NP information is proprietary. I am familiar with the policies established by AREVA NP to ensure the proper application of these criteria.

3. I am familiar with the AREVA NP information contained in the document titled "51-9197672-003, 'SONGS Unit 2 Probability of FEI Operational Assessment RAI Responses',"

and referred to herein as "Document." Information contained in this Document has been classified by AREVA NP as proprietary in accordance with the policies established by AREVA NP for the control and protection of proprietary and confidential information.

4. This Document contains information of a proprietary and confidential nature and is of the type customarily held in confidence by AREVA NP and not made available to the public. Based on my experience, I am aware that other companies regard information of the kind contained in this Document as proprietary and confidential.

5. This Document has been made available to the U.S. Nuclear Regulatory Commission in confidence with the request that the information contained in this Document be withheld from public disclosure. The request for withholding of proprietary information is made in accordance with 10 CFR 2.390. The information for which withholding from disclosure is

requested qualifies under 10 CFR 2.390(a)(4) "Trade secrets and commercial or financial information":

6. The following criteria are customarily applied by AREVA NP to determine whether information should be classified as proprietary:

(a) The information reveals details of AREVA NP's research and development plans and programs or their results.

(b) Use of the information by a competitor would permit the competitor to significantly reduce its expenditures, in time or resources, to design, produce, or market a similar product or service.

(c) The information includes test data or analytical techniques concerning a process, methodology, or component, the application of which results in a competitive advantage for AREVA NP.

(d) The information reveals certain distinguishing aspects of a process, methodology, or component, the exclusive use of which provides a competitive advantage for AREVA NP in product optimization or marketability.

(e) The information is vital to a competitive advantage held by AREVA NP, would be helpful to competitors to AREVA NP, and would likely cause substantial harm to the competitive position of AREVA NP.

The information in the Document is considered proprietary for the reasons set forth in paragraphs 6(c) and 6(d) above.

7. In accordance with AREVA NP's policies governing the protection and control of information, proprietary information contained in this Document has been made available, on a limited basis, to others outside AREVA NP only as required and under suitable agreement providing for nondisclosure and limited use of the information.

8. AREVA NP policy requires that proprietary information be kept in a secured file or area and distributed on a need-to-know basis.

9. The foregoing statements are true and correct to the best of my knowledge, information, and belief.

SUBSCRIBED before me this ____

day of / 2013.

Thomas A. Casias NOTARY PUBLIC, STATE OF NORTH CAROLINA, COUNTY OF MECKLENBURG MY COMMISSION EXPIRES: 14 December 2014

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 62 (NON-PROPRIETARY)

RAI 62

In Reference 10, Figure 8-3, the staff understands that the stability ratio (SR) in the context of Figure 8-3 is a 95% upper bound estimate, both for the last operating period for both Units 2 and 3 and for the next operating period for Unit 2. Why wasn't a best estimate SR used for benchmarking the probability of SR>1 at the conclusion of the last operating period for both Units 2 and 3? (Benchmarking refers to selecting a contact force criterion for effective AVB support such as to produce probabilities of SR>1 at the end of the last operating period consistent with what was actually observed.) How would a best estimate SR have affected the curves presented for the last operating period? Discuss whether the use of a 95% upper bound estimate for benchmarking purposes essentially negates the conservatism of using 95% upper bound SR estimates for future operation of Unit 2?

RESPONSE

Note: RAI Reference 10 is "SONGS U2C17 Steam Generator Operational Assessment for Tube-to-Tube Wear," prepared by Areva NP Inc. Document No. 51- 9187230-000, Revision 0, October 2012.

The goal of mechanistically based probabilistic models is to accurately simulate service performance in a probabilistic manner. To achieve this goal, mechanistically based probabilistic models are benchmarked to the observed behavior. Benchmarking is successful when model results show agreement, not conservatism, compared to observed behavior.

Conservatism of estimates for future operation is typically established by demonstrating that an unwanted future event has an acceptably low probability of occurrence. Applying a factor of safety to the unwanted event provides additional conservatism. For example, in tube integrity probabilistic models, the industry established requirement is that the probability of a tube burst at 3 times the normal operating differential pressure, 3AP, considering all degraded tubes in the bundle, must be maintained below 0.05.

For the probabilistic evaluation of tube-to-tube wear, the unwanted event is the first onset of in-plane fluid elastic instability (FEI) in Unit 2 at 70% power. Benchmarking of the probabilistic FEI model is achieved by showing agreement with the observed FEI behaviors of both Unit 3 and Unit 2 in the previous cycle with a stability ratio (SR) threshold of 1.0.

Why wasn't a best estimate SR used for benchmarking the probability of SR>1 at the conclusion of the last operating period for both Units 2 and 3? How would a best estimate SR have affected the curves presented for the last operating period?

Benchmarking to upper 9 5 th percentile SRs produces support criteria that are physically realistic based on laboratory testing and field performance.

Enclosure 3 Page 2 of 3

Discuss whether the use of a 95% upper bound estimate for benchmarking purposes essentially negates the conservatism of using 95% upper bound SR estimates for future operation of Unit 2?

Using upper 95th percentile SRs for benchmarking does not negate the conservatism of SR estimates for future operation of Unit 2 because benchmarking matches the observed FEI behavior in the previous cycle.

Enclosure 3 Page 3 of 3