ML051810404

Evaluation of Steam Generator Tube Inspection Report for Cycle 13 Outage

ML051810404
Person / Time
Site:	San Onofre
Issue date:	07/11/2005
From:	Bo Pham NRC/NRR/DLPM/LPD4
To:	Ray H Southern California Edison Co
Pham B, NRR/DLPM, 415-8450
References
GL-04-001, TAC MC4970
Download: ML051810404 (6)

Text

July 11, 2005 Mr. Harold B. Ray Executive Vice President Southern California Edison Company San Onofre Nuclear Generating Station P.O. Box 128 San Clemente, CA 92674-0128

SUBJECT:

SAN ONOFRE NUCLEAR GENERATING STATION (SONGS) UNIT 3 -

EVALUATION OF STEAM GENERATOR TUBE INSPECTION REPORT FOR CYCLE 13 OUTAGE (TAC NO. MC4970)

Dear Mr. Ray:

By letter dated October 25, 2004, as supplemented by letter dated April 21, 2005, Southern California Edison submitted to the Nuclear Regulatory Commission (NRC) its special report on inservice inspection of steam generator (SG) tubes for Cycle 13 at SONGS Unit 3.

Enclosed is the NRC staffs evaluation of the SG tube inspection report. The NRC staff did not identify any issues warranting additional plant-specific follow-up at this time.

Please contact me at (301) 415-8450 if you have any questions on this issue.

Sincerely,

/RA/

Bo M. Pham, Project Manager, Section 2 Project Directorate IV Division of Licensing Project Management Office of Nuclear Reactor Regulation Docket No. 50-362

Enclosure:

Staff Evaluation cc w/encl: See next page

ML051810404 NRR-106 OFFICE PDIV-2/PM PDIV-1/LA EMCB

• PDIV-2/SC NAME BPham DBaxley LLund DSCollins for RGramm DATE 7/11/05 7/11/05 6/27/05 7/11/05

STAFF EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION SPECIAL REPORT: INSERVICE INSPECTION OF STEAM GENERATOR TUBES, CYCLE 13 SOUTHERN CALIFORNIA EDISON COMPANY SAN ONOFRE NUCLEAR GENERATING STATION (SONGS) UNIT 3 DOCKET NO. 50-362 By letter dated October 25, 2004 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML043020275), as supplemented by letter dated April 21, 2005 (ADAMS Accession No. ML051150262), Southern California Edison (SCE or the licensee) submitted its special report on inservice inspection (ISI) of steam generator (SG) tubes for Cycle 13 at SONGS Unit 3. The NRC staff's evaluation of the inspection results is provided below.

SONGS Unit 3 has two Combustion Engineering Model 3410 SGs. There are 9350 mill annealed Alloy 600 tubes in each of the SGs. The tubes have an outside diameter (OD) of 0.75 inch, a wall thickness of 0.048 inch, and are supported at various locations by eggcrate tube supports, diagonal bars, and/or vertical straps.

During our review of the 2003 SONGS Unit 3 ISI report (ADAMS Accession No. ML032120701),

the NRC staff noted that the licensee has provided several qualitative arguments regarding the adequacy of the length of tube inspected in the tubesheet region to prevent tube pullout. This issue is not discussed in the licensees current ISI report, and will be addressed separately in the NRC staff's review of the licensee's response to Generic Letter (GL) 2004-01, "Requirements for Steam Generator Tube Inspections."

During the 2004 inspection, the licensee performed tube inspections in both SGs. The scope and results of the inspection are discussed in the material provided by the licensee. The NRC staff's review of the material provided by the licensee identified several noteworthy issues, which are discussed below along with the NRC staff's observations.

Approximately 29 percent of the tubes in the cold leg (CL) top-of-tubesheet (TTS) region were scheduled to be inspected with a +Point' probe in both SGs to detect axial or circumferential OD initiated stress corrosion cracking (ODSCC), axial or circumferential primary water stress corrosion cracking (PWSCC), and volumetric OD indications slightly above the TTS. The length of tube inspected was from one inch above the CL TTS to the lower [axial distance] of the following:

(i) the difference between the CL TTS and 1 inch, (CL TTS - 1 inch), or

(ii) the difference between the CL TTS and sum of the absolute bottom of the expansion transition (BET) measurement and the nondestructive examination (NDE) axial position uncertainty:

(CL TTS - (BET+NDE axial position uncertainty)).

The scope of the CL TTS was expanded to include 100 percent of the tubes in both SGs based on the detection of one circumferentially-oriented OD indication at the TTS of one SG. The length of tube inspected in the expanded inspection was the same as that in the original sample. There were no inside diameter (ID) indications in either the planned or expanded inspection scope. There were no other OD indications detected in the expanded inspection.

The axial length of the inspection was not increased further into the tube sheet since the indication at the TTS was initiated from the OD. In addition, SONGS systematically measured BET locations, and removed from service those tubes for which eddy current does not show evidence of the tube expansion.

The NRC staff notes that Table 3, "List of Nondestructive Examination (NDE) Techniques Utilized for Each Degradation Mechanism for the U3C13 Refueling Outage," of the inspection report, lists the applicable probe types for detection and characterization of indications found during cycle 13. The other potential degradation mechanisms considered during the inspection are provided in the licensee's letter dated April 21, 2005.

SG E-089 is listed in Table 4, Number of Tubes Repaired and Active Degradation Mechanisms Found During the U3C13 Refueling Outage," of the October 25, 2004, report, as having one tube with miscellaneous volumetric indications (not an active degradation mechanism). This single OD volumetric indication was detected in Row 78, Column 60, measuring 0.39 inches in length, 26-percent in depth, and 0.51 V with the +Point' probe. A historical review of the eddy current probe data for this location concluded that this is not an active degradation mechanism.

One postulated cause for the indication is tube wear against an adjacent tube; however, an inspection of all the adjacent tubes noted that there is no associated degradation in this area.

Principal Contributor: C. Lauron Date: July 11, 2005

San Onofre Nuclear Generating Station Units 2 and 3 cc:

Mr. Daniel P. Breig, Plant Manager Mr. Ed Bailey, Chief Nuclear Generation Radiologic Health Branch Southern California Edison Company State Department of Health Services San Onofre Nuclear Generating Station Post Office Box 997414 (MS7610)

P. O. Box 128 Sacramento, CA 95899-7414 San Clemente, CA 92674-0128 Resident Inspector/San Onofre NPS Mr. Douglas K. Porter c/o U.S. Nuclear Regulatory Commission Southern California Edison Company Post Office Box 4329 2244 Walnut Grove Avenue San Clemente, CA 92674 Rosemead, CA 91770 Mayor Mr. David Spath, Chief City of San Clemente Division of Drinking Water and 100 Avenida Presidio Environmental Management San Clemente, CA 92672 P. O. Box 942732 Sacramento, CA 94234-7320 Mr. Dwight E. Nunn, Vice President Southern California Edison Company Chairman, Board of Supervisors San Onofre Nuclear Generating Station County of San Diego P.O. Box 128 1600 Pacific Highway, Room 335 San Clemente, CA 92674-0128 San Diego, CA 92101 Mr. James D. Boyd, Commissioner Eileen M. Teichert, Esq. California Energy Commission Supervising Deputy City Attorney 1516 Ninth Street (MS 31)

City of Riverside Sacramento, CA 95814 3900 Main Street Riverside, CA 92522 Mr. Ray Waldo, Vice President Southern California Edison Company Mr. Gary L. Nolff San Onofre Nuclear Generating Station Power Projects/Contracts Manager P.O. Box 128 Riverside Public Utilities San Clemente, CA 92764-0128 2911 Adams Street Riverside, CA 92504 Mr. Brian Katz Vice President, Nuclear Oversight and Regional Administrator, Region IV Regulatory Affairs.

U.S. Nuclear Regulatory Commission San Onofre Nuclear Generating Station 611 Ryan Plaza Drive, Suite 400 P.O. Box 128 Arlington, TX 76011-8064 San Clemente, CA 92764-0128 Mr. Michael Olson San Diego Gas & Electric Company P.O. Box 1831 San Diego, CA 92112-4150 April 2005

San Onofre Nuclear Generating Station Units 2 and 3 cc:

Mr. Steve Hsu Department of Health Services Radiologic Health Branch MS 7610, P.O. Box 997414 Sacramento, CA 95899 Adolfo Bailon Field Representative United States Senator Barbara Boxer 312 N. Spring St. Suite 1748 Los Angeles, CA. 90012