ML120740373

Review of Steam Generator Tube Inspection Report for the 16th Refueling Outage in Fall 2010

ML120740373
Person / Time
Site:	Diablo Canyon
Issue date:	03/15/2012
From:	Joseph Sebrosky Plant Licensing Branch IV
To:	Conway J Pacific Gas & Electric Co
Sebrosky J, NRR/DORL/LPL4, 415-1132
References
TAC ME6345
Download: ML120740373 (3)

Text

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 March 15, 2012 Mr. John T. Conway Senior Vice President - Energy Supply and Chief Nuclear Officer Pacific Gas and Electric Company Diablo Canyon Power Plant 77 Beale Street, Mail Code B32 San Francisco, CA 94105

SUBJECT:

DIABLO CANYON POWER PLANT, UNIT NO.1 - REVIEW OF STEAM GENERATOR TUBE INSPECTION REPORT FOR THE 16TH REFUELING OUTAGE IN FALL 2010 (TAC NO. ME6345)

Dear Mr. Conway:

By letter dated April 21,2011 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML111160101), Pacific Gas and Electric Company (the licensee) submitted information summarizing the results of the steam generator tube inspections for the 16th refueling outage in fall 2010 at Diablo Canyon Power Plant, Unit No.1.

The U.S. Nuclear Regulatory Commission (NRC) staff has completed its review of this report and concludes that the licensee provided the information required by its technical specifications.

The NRC staff's review of the reports is enclosed.

If you have any questions, please contact me at 301-415-1132 or via e-mail at joseph. sebrosky@nrc.gov.

or Project Manager Docket No. 50-275

Enclosure:

As stated cc w/encl: Distribution via Listserv

OFFICE OF NUCLEAR REACTOR REGULATION REVIEW OF STEAM GENERATOR TUBE INSPECTION REPORT FOR THE 16TH REFUELING OUTAGE IN FALL 2010 PACIFIC GAS AND ELECTRIC COMPANY DIABLO CANYON POWER PLANT, UNIT NO.1 DOCKET NO. 50-275 By letter dated April 21,2011 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML111160101), Pacific Gas and Electric Company (the licensee) submitted information summarizing the results of the steam generator (SG) tube inspections for the 16th refueling outage in fall 2010 at Diablo Canyon Power Plant, Unit NO.1.

Diablo Canyon Power Plant, Unit No.1 has four recirculating Westinghouse Model Delta 54 replacement SGs. This is the first inservice inspection conducted on the Unit 1 SGs since they were replaced in the 15th refueling outage. Each SG has 4444 tubes; each tube has a nominal outside diameter of 0.75 inches and nominal tube wall thickness of 0.043 inches. The tubes are hydraulically expanded the full depth within the tubesheet. The eight tube support plates (TSPs) are stainless steel (Type 405) and are 1.125 inches thick. All TSPs have trefoil-shaped holes, produced by broaching. The end of each tube is tack expanded using a urethane plug expansion process. Tubes in rows 1 through 16 were full-length stress relieved following bending. Row 1 has the smallest U-bend radius of 3.25 inches.

The licensee provided the scope, extent, methods, and results of the SG tube inspections in the document referenced above. In addition, the licensee described corrective actions (Le., tube plugging) taken in response to the inspection findings.

During the inspections, one tube was identified with wear at an anti-vibration bar and four tubes were identified as being in close proximity. The eddy current signal characteristics for these four tubes had not changed (worsened) since the pre-service inspection.

Based on a review of the information provided, the NRC staff concludes that the licensee provided the information required by its technical specifications. In addition, the staff concludes that there are no technical issues that warrant follow-up action at this time since the inspections appear to be consistent with the objective of detecting potential tube degradation and the inspection results appear to be consistent with industry operating experience at similarly designed and operated units.

Enclosure

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