ML13296A018

Response to Preliminary White Finding Relating to Steam Generator Tube Leak

ML13296A018
Person / Time
Site:	San Onofre
Issue date:	10/21/2013
From:	Peter Dietrich Southern California Edison Co
To:	Reynolds S NRC Region 4
References
EA-13-083
Download: ML13296A018 (4)

Text

Peter T. Dietrich I* EDISON SOUTHERN CALIFORNIA Senior Vice President & Chief Nuclear Officer An EDISON INTERNATIONA L Company October 21, 2013 10 CFR 50.4 Mr. Steven A. Reynolds Acting Regional Administrator, Region IV U.S. Nuclear Regulatory Commission 1600 E. Lamar Blvd.

Arlington, Texas, 76011-4511

Subject:

Docket Nos. 50-361 and 50-362 Response to Preliminary White Finding Relating to Steam Generator Tube Leak San Onofre Nuclear Generating Station, Unit 3

References:

1. Letter from Mr. Steven A. Reynolds, (US NRC) to Mr. Peter T. Dietrich (SCE), dated September 20, 2013, NRC Confirmatory Action Letter Response Inspection 05000361/2012009 and 0500362/2012009

2. Letter from Mr. Peter T. Dietrich (SCE) to Mr. Steven A. Reynolds, (US NRC), dated September 30, 2013, Response to San Onofre Nuclear Generating Station - NRC Confirmatory Action Letter Inspection 05000361/2012009 and 0500362/2012009

3. Letter from Mr. Elmo E. Collins (NRC) to Mr. Peter T. Dietrich (SCE),

dated July 18, 2012, San Onofre Nuclear Generating Station -- NRC Augmented Inspection Team Report 05000361/2012007 and 05000362/2012007

4. Letter from Mr. Michael Cheok, (US NRC) to M. Ikuo Otake (Mitsubishi Heavy Industries, Ltd.), dated September 20, 2013, Nuclear Regulatory Commission Inspection Report No. 99901030/3013-201, Notice of Nonconformance

Dear Mr. Reynolds,

In Reference 1, the NRC describes a preliminary finding and associated apparent violation relating to the steam generator tube leak that occurred on January 31, 2012, in one of the steam generators in Unit 3 of the San Onofre Nuclear Generation Station (SONGS).

Reference 1 offered SCE the opportunity to submit its position on the preliminary finding.

In Reference 2, SCE informed the NRC that SCE intended to submit its position to the NRC in writing. This Response provides SCE's perspective on the preliminary finding and associated apparent violation. As noted in Reference 3, upon detection of the leak, P.O. Box 128 San Clemente, CA 92672 (949) 368-6255 PAX 86255 Fax: (949) 368-6183 Pete. Diet ric h@sce.com I

Mr. Steven A. Reynolds Acting Regional Administrator October 21, 2013 SONGS plant operators responded in a manner that protected the public health and safety.

The leak did not cause any adverse safety impact to plant workers, the public, or the environment.

In connection with the tube leak, the NRC has identified a preliminary "white" finding of low to moderate safety significance. The preliminary finding is based upon failure to comply with SONGS Technical Specification requirements for maintenance of steam generator tube integrity and leakage control, and upon an apparent violation of the requirements of 10 CFR Part 50, Appendix B, Criterion III regarding design control. SCE agrees that the finding of low to moderate safety significance is appropriate and that the determination is therefore appropriately characterized as a "white" finding.

SCE is providing additional information with respect to the apparent violation of the design control requirements contained in 10 CFR Part 50, Appendix B, Criterion Il. SCE is providing this perspective in order to ensure fuller understanding of the relevant facts and circumstances.

As noted in the NRC Notice of Nonconformance issued to MHI on September 20, 2012 (Reference 4), SCE had contracted with MHI to perform the quality assurance activities required for compliance with Part 50, Appendix B, including the Criterion III requirements for verifying and checking the design of the SONGS replacement steam generators (RSGs). Criterion I of 10 CFR Part 50, Appendix B, states that a nuclear power plant licensee "may delegate to others, such as contractors, agents, or consultants, the work of establishing and executing the quality assurance program, or any part thereof, but shall retain responsibility for the quality assurance program." SCE's design specification for the RSGs specifically required MHI to perform these functions. Pursuant to Section 3.15 of the Design Specification for the RSGs (S023-617-01), MHI was required to perform all RSG work "in accordance with the [MHI's] QA program...which complies with 10 CFR 50, Appendix B." In particular, Section 3.21.2 of the Design Specification required that MHI's "calculations/analyses shall be prepared, reviewed, and approved in accordance with

[MHI's] QA program," and Section 1.11.8 required MHI to 'independently verify and assure that the Work complies with all of the requirements of the Purchase Order," which included compliance with Appendix N of ASME Section III.

Contracting with the equipment vendor to perform required nuclear quality assurance activities, as authorized by 10 CFR Part 50, Appendix B, Criterion I, is the normal and standard practice for utilities engaged in purchasing nuclear plant components. Like other purchasers of replacement steam generators, at the time the SONGS RSGs were designed and built, SCE itself did not have personnel with sufficient experience and expertise to develop the SONGS RSG design. This was particularly true with respect to design verification of the computer codes and models and their output used for design of the RSGs, some of which (such as the FIT-Ill code used by MHI to estimate thermal hydraulic conditions in the steam generators) are proprietary to MHI.

By contrast, MHI, as the holder of an "N-Stamp" from the American Society of Mechanical Engineers (ASME), had the expertise and was authorized to design safety-related nuclear components. In addition, MHI's Quality Assurance Program had been properly certified as

Mr. Steven A. Reynolds Acting Regional Administrator October 21, 2013 acceptable for ensuring the quality of those components and had been subject to NRC inspection.

For these reasons, SCE appropriately relied upon MHI's expertise to perform the design and quality assurance functions properly as required by its contract and to comply with NRC regulations.

However, as described in the inspection report and Notice of Nonconformance issued to MHI by the NRC (Reference 4), investigations resulting from the SONGS RSG tube failures found flaws embedded in MHI's computer modeling for steam generators that pre-dated the SONGS RSG project. These flaws involved MHI's failure to convert flow velocity data produced by the FIT-Ill computer code to the appropriate gap velocities for use as input to the FIVATS computer code used in calculating the potential for tube vibration. The NRC also notes that these flaws originated in the 1990s due to misunderstandings within MHI's design organizations. SCE was unaware of these embedded flaws at the time the SONGS RSGs were designed and installed. Reference 4 also notes that these same flaws were embedded in the MHI computer modeling of RSGs for four other nuclear power plants prior to the design of the SONGS RSGs. None of these other MHI customers was apparently aware of these flaws, nor had they been discovered during design review activities prior to the installation and operation of those steam generators. As noted in Reference 4, MHI failed to detect these flaws, despite the fact that it was specifically required to verify and check its design and calculations by NRC regulations, by the ASME Code, and under its contract with SCE.

SCE acknowledges the responsibility imposed upon it by 10 CFR Part 50, Appendix B, Criterion I, and takes that responsibility very seriously. However, as Criterion I makes clear, the licensee may delegate to a vendor the "work of establishing and executing the quality assurance program." The differing roles of the vendor and licensee are also recognized in NCA -3260 Section III of the ASME Boiler & Pressure Vessel Code, incorporated into NRC requirements under 10 CFR Section 50.55a, which states that while the purchaser is responsible for reviewing design reports, "The responsibility for the method of analysis and the accuracy of the Design Report remains with the Certificate Holder and the Designer." (MHI was both the Certificate Holder and Designer for the SONGS RSGs).

As a purchaser and not the Certificate Holder or Designer, SCE itself did not have the expertise to perform - and never intended to perform - the specific verification activities that it had contracted MHI to execute.

Nonetheless, SCE recognizes that, while SCE "may delegate" to MHI "the work of establishing and executing the quality assurance program, or any part thereof," SCE "shall retain responsibility for the quality assurance program." Therefore, SCE does not contest its responsibility under NRC regulations for a violation of Criterion II1.

In that regard, SCE understands that the NRC's issuance of the finding and violation relates only to compliance with NRC's regulations, and does not involve any determination with respect to prudency, culpability, or financial responsibility, including financial responsibility for MHI's actions and omissions or for the failure of the RSGs. SCE reserves the right to contest factual conclusions contained in Reference 1 in other venues and for other purposes.

Mr. Steven A. Reynolds Acting Regional Administrator October 21, 2013 Should you have any questions regarding this letter, please do not hesitate to contact me or Richard St. Onge, Manager of Regulatory and Emergency Preparedness at (949) 368-6240.

Sincerely, cc: NRC Document Control Desk J. R. Hall, NRC Project Manager, SONGS Units 2 and 3 B. J. Benney, NRC Project Manager, San Onofre 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