ML070370630
| ML070370630 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 02/20/2007 |
| From: | Kalyanam N NRC/NRR/ADRO/DORL/LPLIV |
| To: | Rosenblum R Southern California Edison Co |
| Kalyanam N, NRR/DORL/LP4, 415-1480 | |
| References | |
| TAC MD0191 | |
| Download: ML070370630 (6) | |
Text
February 20, 2007 Mr. Richard M. Rosenblum Senior Vice President and 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 - CORRECTION LETTER FOR THE ISSUANCE OF RELIEF REQUEST RE: RELIEF REQUEST ISI-3-18, FROM THE REQUIREMENTS OF THE AMERICAN SOCIETY OF MECHANICAL ENGINEERS BOILER AND PRESSURE VESSEL CODE (TAC NO. MD0191)
Dear Mr. Rosenblum:
By letter dated February 22, 2006, as supplemented by letters dated March 17 and May 10, 2006, Southern California Edison (SCE, the licensee) submitted a request for the use of alternatives to certain American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code),Section XI, requirements at San Onofre Nuclear Generating Station, Unit 2 (SONGS 2). Specifically, Relief Request (RR) ISI-3-18 requests approval to use alternatives to the requirements of the ASME Code, Section Xl, 1995 Edition through 1996 Addenda, IWA-4000, for repair/replacement activities related to the performance of structural weld-overlay repairs at SONGS 2 for the third 10-year inservice inspection (ISI) interval.
The U.S. Nuclear Regulatory Commission staff, by letter dated December 14, 2006, authorized RR ISI-3-18 for the remaining third 10-year ISI interval for SONGS 2, which ends on August 17, 2013.
R. Rosenblum It was subsequently brought to our attention that the Safety Evaluation (SE) that accompanied the December 14, 2006, letter did not contain the authorization for pressurizer safety valve nozzle weld 02-005-029, which had been requested in the application dated February 22, 2006.
This was an oversight and we are enclosing revised pages 14 and 17 of the SE where pressurizer safety valve nozzle weld 02-005-029 is included. The changes are identified by a vertical bar on the right. We regret the oversight.
If you have any questions, please call me at (301) 415-1480.
Sincerely,
/RA/
N. Kalyanam, Project Manager Plant Licensing Branch IV Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-361
Enclosure:
Safety Evaluation Pages 14 and 17 cc w/encl: See next page
ML070370630 OFFICE NRR/LPL4/PM NRR/LPL4/LA NRR/LPL4/BC NAME NKalyanam LFeizollahi DTerao DATE 2/20/07 2/20/07 2/20/07
March 2006 San Onofre Nuclear Generating Station Units 2 and 3 cc:
Mr. Daniel P. Breig Southern California Edison Company San Onofre Nuclear Generating Station P.O. Box 128 San Clemente, CA 92674-0128 Mr. Douglas K. Porter, Esquire Southern California Edison Company 2244 Walnut Grove Avenue Rosemead, CA 91770 Mr. David Spath, Chief Division of Drinking Water and Environmental Management P.O. Box 942732 Sacramento, CA 94234-7320 Chairman, Board of Supervisors County of San Diego 1600 Pacific Highway, Room 335 San Diego, CA 92101 Mark L. Parsons Deputy City Attorney City of Riverside 3900 Main Street Riverside, CA 92522 Mr. Gary L. Nolff Assistant Director - Resources City of Riverside 3900 Main Street Riverside, CA 92522 Regional Administrator, Region IV U.S. Nuclear Regulatory Commission 611 Ryan Plaza Drive, Suite 400 Arlington, TX 76011-8064 Mr. Michael R. Olson San Diego Gas & Electric Company 8315 Century Park Ct. CP21G San Diego, CA 92123-1548 Director, Radiologic Health Branch State Department of Health Services P.O. Box 997414, MS 7610 Sacramento, CA 95899-7414 Resident Inspector/San Onofre NPS c/o U.S. Nuclear Regulatory Commission Post Office Box 4329 San Clemente, CA 92674 Mayor City of San Clemente 100 Avenida Presidio San Clemente, CA 92672 Mr. James T. Reilly Southern California Edison Company San Onofre Nuclear Generating Station P.O. Box 128 San Clemente, CA 92674-0128 Mr. James D. Boyd, Commissioner California Energy Commission 1516 Ninth Street (MS 31)
Sacramento, CA 95814 Mr. Ray Waldo, Vice President Southern California Edison Company San Onofre Nuclear Generating Station P.O. Box 128 San Clemente, CA 92764-0128 Mr. Brian Katz Southern California Edison Company San Onofre Nuclear Generating Station P.O. Box 128 San Clemente, CA 92764-0128 Mr. Steve Hsu Department of Health Services Radiologic Health Branch MS 7610, P.O. Box 997414 Sacramento, CA 95899 Mr. A. Edward Scherer Southern California Edison Company San Onofre Nuclear Generating Station P.O. Box 128 San Clemente, CA 92674-0128 value of paragraph 3.2(b), any flaws extending beyond 0.10-inch into the overlay material would be identified as such from the characterized dimensions. Flaws less than 0.10 inch may not be sized because of the tolerance for depth sizing. The staff determined that reporting of an extension in the overlay material is non-productive because of the flaw-sizing tolerance.
Therefore, the staff concludes that PDIs elimination of highlighting a crack extending beyond 0.10 inch into the overlay material is acceptable.
Based on the above evaluation, the staff has determined that the licensees proposed alternative to use the PDI qualification program for the UT examination of overlay repaired piping welds is acceptable, because it will provide an acceptable level of quality and safety.
3.5.3.2 Inspection of Cast Stainless Steel The UT examinations required by N-504-2 were not achievable for the CSST material used in the fabrication of the components. The UT examination volume consists of the weld-overlay and the upper 25 percent of the base metal beneath the overlay. The UT examination must be performed with qualified Section XI, Appendix VIII, Supplement 11, personnel and procedures.
Supplement 11 qualification requires blind performance demonstrations on representative mock-ups containing representative construction flaws. The licensee performed the required examination of the weld-overlay, ferritic nozzle base material, and weld base material in accordance with Code Case N-504-2, but could not take credit for the CSST safe-end base material because the procedures and personnel have not yet been demonstrated on CSST. In lieu of the Code-required examination of the CSST base material, the licensee performed a best-effort UT examination using the existing qualified Supplement 11 personnel and procedures.
At the time of the repair, the licensee did not have access to representative mock-ups containing representative construction flaws of overlaid CSST piping for blind performance demonstrations. Thus, the licensee could not qualify personnel and procedures. The licensee is working with the industry to obtain the necessary mock-ups, qualified personnel, and procedures. The licensee has committed to subjecting the UT procedures that were used for the best-effort examination of the subject welds to a Supplement 11 performance demonstration containing CSST mock-ups by the end of the next two refueling cycles (about 2010). Because this issue is not resolved at this time, the staff limits the approval of performing a best-effort examination to pressurizer safety valve nozzle welds 02-005-027, 02-005-028, and 02-005-029 only.
The staff finds that this after-the-fact demonstration is an appropriate approach because (1) the weld-overlay is a full structural overlay that does not take any credit for the original weld, (2) the material used in the weld-overlay is Alloy 52M, which is resistant to PWSCC due to its composition, especially its chromium content, (3) the flaws detected in nozzles 27 and 28 are in the lower one-third of the base material near the inside diameter and well within the favorable compressive stress field induced by the weld-overlay that limits their growth, and (4) the flaws detected in these nozzles were confirmed by eddy current examination to be not surface-connecting.
17 The staff finds that the thickness of the weld overlay satisfies Code Cases N-504-2 and N-638-1 and, therefore, is acceptable.
The staff asked the licensee to discuss the inspection schedule for the four weld-overlay repairs during the third 10-year ISI inspection interval and any conflict between the inspections required by Examination Category B-F, and Articles Q-4000 and Q-4300 in Appendix Q to the ASME Code,Section XI. In the March 17, 2006, letter, the licensee responded that as specified in Subarticle Q-4300 Inservice Inspection, it will perform weld-overlay examinations of the volumes specified in Figure Q-4300-1. These welds will be added to the inspection plan and UT examined during the first or second refueling outage following application. Weld-overlay examination volumes that show no indication of crack growth or new cracking will be placed in the population to be examined on a sampling basis. Twenty-five percent of this population will be examined once every 10 years. If the weld-overlay examinations do not meet the acceptance standard as specified in Q-4300(b) and (c), then the inservice examination of the weld overlay will comply with the requirements of the Q-4300(e), Q-4300(f), and Q-4310.
The licensee stated further that the existing welds are classified as RI-ISI, Code Category B-F.
RI-ISI is a living program and requires the program to be updated based on changes in the plant. After the weld-overlay, the licensee will perform qualified UT examinations per the PDI program as specified in Article Q-4200, Preservice Examination, and Q-4300, ISI. The design of the weld configuration has changed after the structural weld-overlay installation. Code Case N-504-2 and Section XI, Appendix Q, examination rules govern the future inservice examination. Therefore, there is no conflict.
The staff finds that the inspection schedule of the four weld-overlay repairs follows the appropriate ASME Code requirement and, therefore, is acceptable.
4.0 CONCLUSION
The staff has determined that (1) the licensees proposed alternative to use the PDI program for weld-overlay qualifications as described in the submittal, in lieu of Supplement 11 to Appendix VIII of Section XI of the ASME Code, and (2) modifications to Code Cases N-504-2 and N-638-1, will provide an acceptable level of quality and safety. Therefore, pursuant to 10 CFR 50.55a(a)(3)(i), the proposed RR ISI-3-18 is authorized for the remaining third 10-year ISI interval at SONGS 2.
The licensee has not qualified nondestructive examination (NDE) personnel and procedures to the requirements of Supplement 11 for the examination of CSST base material. However, the licensee is working toward completing that goal by approximately 2010. Because this issue is not resolved at this time, the staff limits approval of performing a best-effort examination to pressurizer safety valve nozzle welds 02-005-027, 02-005-028, and 02-005-029 only.
All other requirements of the ASME Code, Sections III and XI, for which relief has not been specifically requested and approved remain applicable, including third-party review by the Authorized Nuclear Inservice Inspector.