ML063310347

Evaluation of the Response to Generic Letter 2004-01, Requirements for Steam Generator Tube Inspections

ML063310347
Person / Time
Site:	San Onofre
Issue date:	12/07/2006
From:	Terao D NRC/NRR/ADRO/DORL/LPLIV
To:	Rosenblum R Southern California Edison Co
Kalynanam N, NRR/DORL/LP4, 415-1480
References
GL-04-001, TAC MC4849
Download: ML063310347 (5)

Text

December 7, 2006 Mr. Richard M. Rosenblum Chief Nuclear Officer Southern California Edison Company San Onofre Nuclear Generating Station P.O. Box 128 San Clemente, CA 92674-0128

SUBJECT:

SAN ONOFRE NUCLEAR GENERATING STATION, UNIT 2 - EVALUATION OF THE RESPONSE TO GENERIC LETTER 2004-01, REQUIREMENTS FOR STEAM GENERATOR TUBE INSPECTIONS (TAC NO. MC4849)

Dear Mr. Rosenblum:

On August 30, 2004, the U.S. Nuclear Regulatory Commission (NRC) issued Generic Letter (GL) 2004-01, Requirements for Steam Generator Tube Inspections. The purpose of GL 2004-01 was to obtain information that would enable the NRC staff to determine whether licensees steam generator tube inspection programs comply with the existing tube inspection requirements (the plant technical specifications in conjunction with Appendix B to Part 50 of Title 10 of the Code of Federal Regulations).

By letter dated October 26, 2004, as supplemented by letters dated November 23, 2005, and July 14, 2006, Southern California Edison (SCE), the licensee for San Onofre Nuclear Generating Station (SONGS), Unit 2, submitted the response to GL 2004-01.

The NRC staff has reviewed the SCE response to GL 2004-01 for SONGS, Unit 2. As discussed in the enclosed evaluation, the NRC staff concluded that the licensees overall response to the GL is acceptable.

If you have any questions, please call the Project Manager, N. Kalyanam, at (301) 415-1480.

Sincerely,

/RA/

David Terao, Chief Plant Licensing Branch IV Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-361

Enclosure:

Staff Evaluation cc w/encl: See next page

ML063310347 *Minor editorial changes were made to staff provided SE OFFICE NRR/LPL4/PM NRR/LPL4/LA NRR/DCI/CSGB* NRR/LPL4/BC NAME NKalyanam LFeizollahi AHiser DTerao DATE 12/5/06 12/5/06 11/21/06 12/7/06 EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RESPONSE TO NRC GENERIC LETTER 2004-01 SOUTHERN CALIFORNIA EDISON SAN ONOFRE NUCLEAR GENERATING STATION, UNIT 2 DOCKET NO. 50-361 On August 30, 2004, the Nuclear Regulatory Commission (NRC) issued Generic Letter (GL) 2004-01, Requirements for Steam Generator Tube Inspections. The purpose of GL 2004-01 was to obtain information that would enable the NRC staff to determine whether licensees steam generator (SG) tube inspection programs comply with the existing tube inspection requirements (the plant Technical Specifications (TSs) in conjunction with Appendix B to Part 50 of Title 10 of the Code of Federal Regulations (10 CFR)).

Licensees who concluded that their SG tube inspections have not been or are not being performed consistent with the NRCs position on the requirements in the TSs, in conjunction with 10 CFR Part 50, Appendix B, were requested to submit a safety assessment. As part of the safety assessment, licensees were to address whether their safety bases for limiting inspections within the tubesheet constitutes a change to the "method of evaluation" for establishing the structural and leakage integrity of the tube-to-tubesheet joint. The NRC staff requested this information since it was expected that licensees safety bases relied on a mechanical expansion joint rather than the tube-to-tubesheet weld. Since the original tube-to-tubesheet joint was most likely designed by demonstrating that the stresses in the tube, weld, and tubesheet satisfy the allowable stress values in Section III of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code), or other similar standard, the NRC staff questioned whether the safety basis for limiting inspections relied on demonstrating that the expansion joint satisfied some criteria (e.g., minimum tube pullout load criteria, allowable leakage) beyond those specified in Section III of the ASME Code.

By letter dated October 26, 2004 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML043020250), as supplemented by letters dated November 23, 2005 (ADAMS Accession No. ML053320210), and July 14, 2006 (ADAMS Accession No. ML061990069), Southern California Edison, the licensee for San Onofre Nuclear Generating Station (SONGS), Unit 2, submitted a response to GL 2004-01.

In its response, the licensee concluded that the safety basis used to support the tube inspection practices in the tubesheet region does not constitute a change to the method of evaluation.

This conclusion appears to be based, in part, on an assumption that the GL was implying that the selection of nondestructive evaluation techniques define the limits of the reactor coolant pressure boundary. The GL's discussion of the original design basis, however, was related to the safety analysis performed by certain licensees to support a conclusion that flaws located a

certain distance below the top of the tubesheet do not have any safety implications. This safety basis relies on a mechanical interference fit between the tube and the tubesheet for establishing the tube-to-tubesheet joint (i.e., forming the reactor coolant pressure boundary).

However, for many plants (if not all), the original design of the SG gave no credit for this interference fit since the weld between the tube and the tubesheet ensured the integrity of the tube-to-tubesheet joint. In fact, the design rules (ASME Code,Section III) do not address the use of an interference fit for maintaining pressure boundary integrity.

Although the licensees response to the method of evaluation item did not focus on the NRC staff's area of concern, we conclude that its overall response to the GL is acceptable, as discussed further below.

With respect to inspecting the portion of the tube within the tubesheet, the licensee indicated that its tube inspection practices at SONGS, Unit 2, are not consistent with the NRC staff position, and that this has been entered into its corrective action program. The licensee further indicated its plan to submit a license amendment to clarify its SG tube inspection practices in the tubesheet region. This license amendment request was submitted on November 3, 2005, and was approved by the NRC staff on November 9, 2006 (ADAMS Accession No. ML062970441). The method for evaluating the tube-to-tubesheet joint (i.e., for ensuring tube integrity) was reviewed as part of the license amendment request.

With respect to inspecting the portion of the parent tube adjacent (behind) the nickel-band region of Combustion Engineering Alloy 690 tungsten inert-gas welded sleeves, the licensee could not demonstrate that the technique being used to inspect this region was capable of finding the forms of degradation that could occur there. As a result, the licensee performed additional testing and analyses to demonstrate that structural and leakage integrity of the tube (at this location) are maintained with the existing inspections being performed behind the nickel band (assuming credible forms of degradation of the parent tubing behind (adjacent to) the nickel band). In addition, the licensee proposed, in a letter dated July 14, 2006, to amend its TSs to reflect its inspection practices (and the bases for these inspection practices) in this region of the tube. This amendment is currently being reviewed by the NRC staff.

With respect to the other regions of the SG tubes, the licensee concluded that its inspection practices were consistent with the NRC staffs position outlined in GL 2004-01.

In summary, given that the licensee has modified (or is in the process of modifying) its TSs consistent with the NRC staffs position outlined in GL 2004-01, the staff concludes the licensees overall response to the GL is acceptable.

Principal Reviewers: K Karwoski P. Klein Date: December 7, 2006

San Onofre Nuclear Generating Station Units 2 and 3 cc:

Mr. Daniel P. Breig Resident Inspector/San Onofre NPS Southern California Edison Company c/o U.S. Nuclear Regulatory Commission San Onofre Nuclear Generating Station Post Office Box 4329 P. O. Box 128 San Clemente, CA 92674 San Clemente, CA 92674-0128 Mayor Mr. Douglas K. Porter, Esquire City of San Clemente Southern California Edison Company 100 Avenida Presidio 2244 Walnut Grove Avenue San Clemente, CA 92672 Rosemead, CA 91770 Mr. James T. Reilly Mr. David Spath, Chief Southern California Edison Company Division of Drinking Water and San Onofre Nuclear Generating Station Environmental Management P.O. Box 128 P. O. Box 942732 San Clemente, CA 92674-0128 Sacramento, CA 94234-7320 Mr. James D. Boyd, Commissioner Chairman, Board of Supervisors California Energy Commission County of San Diego 1516 Ninth Street (MS 31) 1600 Pacific Highway, Room 335 Sacramento, CA 95814 San Diego, CA 92101 Mr. Ray Waldo, Vice President Eileen M. Teichert, Esq. Southern California Edison Company Supervising Deputy City Attorney San Onofre Nuclear Generating Station City of Riverside P.O. Box 128 3900 Main Street San Clemente, CA 92764-0128 Riverside, CA 92522 Mr. Brian Katz Mr. Gary L. Nolff Southern California Edison Company Power Projects/Contracts Manager San Onofre Nuclear Generating Station Riverside Public Utilities P.O. Box 128 2911 Adams Street San Clemente, CA 92764-0128 Riverside, CA 92504 Mr. Steve Hsu Regional Administrator, Region IV Department of Health Services U.S. Nuclear Regulatory Commission Radiologic Health Branch 611 Ryan Plaza Drive, Suite 400 MS 7610, P.O. Box 997414 Arlington, TX 76011-8064 Sacramento, CA 95899 Mr. Michael Olson Mr. A. Edward Scherer San Diego Gas & Electric Company Southern California Edison Company P.O. Box 1831 San Onofre Nuclear Generating Station San Diego, CA 92112-4150 P.O. Box 128 San Clemente, CA 92674-0128 Mr. Ed Bailey, Chief Radiologic Health Branch State Department of Health Services Post Office Box 997414 (MS7610)

Sacramento, CA 95899-7414 November 2005