ML080640210

Review of the 2006 Refueling Outage Steam Generator Tube Inservice Inspection Report

ML080640210
Person / Time
Site:	Vogtle
Issue date:	04/01/2008
From:	Siva Lingam NRC/NRR/ADRO/DORL/LPLII-1
To:	Tynan T Southern Nuclear Operating Co
Lingam, Siva NRR/DORL 415-1564
References
TAC MD5394
Download: ML080640210 (5)

Text

April 1, 2008 Mr. Tom E. Tynan Vice President - Vogtle Vogtle Electric Generating Plant 7821 River Road Waynesboro, GA 30830

SUBJECT:

VOGTLE ELECTRIC GENERATING PLANT, UNIT 1, REVIEW OF THE 2006 REFUELING OUTAGE STEAM GENERATOR TUBE INSERVICE INSPECTION REPORT (TAC NO. MD5394)

Dear Mr. Tynan:

By letter dated April 18, 2007 (Agencywide Documents Access and Management System (ADAMS) Accession Number ML072480031), Southern Nuclear Operating Company, Inc (the licensee) submitted information summarizing the results of the 2006 steam generator (SG) tube inspections at Vogtle Electric Generating Plant, Unit 1 (Vogtle 1). These inspections were performed during the thirteenth refueling outage (1R13). The licensee provided additional information in a letter dated January 31, 2008 (ADAMS Accession Number ML080320298). In addition, the Nuclear Regulatory Commission (NRC) staff summarized a conference call about the 2006 SG tube inspections at Vogtle 1 in a letter dated December 19, 2006 (ADAMS Accession Number ML063390165).

The NRC staff has completed its review of these reports and concludes that the licensee provided the information required by their technical specifications and that no additional follow-up is required at this time. The NRC staffs review of the report is enclosed.

Sincerely,

/RA/

Siva P. Lingam, Project Manager Plant Licensing Branch II-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-424

Enclosure:

Inspection Summary Report cc w/encl: See next page

ML080640210 *transmitted by memo dated OFFICE NRR/LPL2-1/PM NRR/LPL2-1/LA NRR/DCI/CSGB/BC NRR/LPL2-1/BC NAME SLingam MO=Brien AHiser MWong DATE 3/4/08 3/10/08 2/28/08* 4/1/08 REVIEW OF THE 2006 REFUELING OUTAGE STEAM GENERATOR TUBE INSPECTION REPORT SOUTHERN NUCLEAR OPERATING COMPANY, INC.

VOGTLE ELECTRIC GENERATING PLANT, UNIT 1 DOCKET NO. 50-424 By letter dated April 18, 2007 (Agencywide Documents Access and Management System (ADAMS) Accession Number ML072480031), Southern Nuclear Operating Company, Inc.

(the licensee) submitted information summarizing the results of the 2006 steam generator (SG) tube inspections at Vogtle Electric Generating Plant, Unit 1 (Vogtle 1). These inspections were performed during the thirteenth refuelling outage (1R13). The licensee provided additional information in a letter dated January 31, 2008 (ADAMS Accession Number ML080320298). In addition, the Nuclear Regulatory Commission (NRC) staff summarized a conference call about the 2006 SG tube inspections at Vogtle 1 in a letter dated December 19, 2006 (ADAMS Accession Number ML063390165).

Vogtle 1 has four Westinghouse Model F SGs, each of which contains 5,626 U-bend thermally treated Alloy 600 tubes. Each tube has a nominal outside diameter of 0.688 inches and a nominal wall thickness of 0.040 inches. During SG fabrication, the tubes were hydraulically expanded, at both ends, over the full depth of the tubesheet. Type 405 stainless steel support plates, which have broached quatrefoil holes, support the vertical section of the tubes, and anti-vibration bars support the U-bend section of the tubes.

At the time of this inspection, the SGs had accumulated approximately 205 Effective Full Power Months (EFPM) of operation. At the time of the inspection, the SG had experienced approximately 71 EFPM of operation in the 90 EFPM sequential period.

The licensee provided the scope, extent, methods, and results of their SG tube inspections in the documents referenced above.

After review of the information provided by the licensee, the NRC staff has the following comments/observations:

A full-bundle chemical cleaning was performed on the Vogtle 1 SGs, to reduce the potential for the onset of tube corrosion and to eliminate the potential that severe secondary fouling would cause significant power reductions in the future. The chemical cleaning, along with the follow-up mechanical cleaning techniques, removed 6819 pounds of deposits. Based on the sludge removed and secondary visual inspection results, the chemical cleaning was considered successful by the licensee. In-bundle inspections were performed in SG1 above the seventh tube support plate, in a couple of cold leg and hot leg columns. The columns selected were found to Enclosure

be free of foreign objects and sludge. The quatrefoil lobes and lands were clean and open. No anomalous conditions were observed during these inspections.

Ultrasonic Energy Cleaning (UEC) was performed in all four Vogtle 1 SGs in both the 1R11 and 1R12 outages, and in SG1 in the 1R10 outage. The UEC was performed to remove scale deposits and scale collars from the top of the tubesheet. During the 1R13 outage, bobbin inspections identified several tubes with differential freespan signals. Upon further examination with a rotating probe, the bobbin indications were characterized as areas of shallow (less than or equal to 10-percent through-wall thickness) flaws. A previous bobbin inspection of these tubes during the fall 2003 outage (1R11) after the UEC was performed resulted in no shallow wall loss being detected. The licensee speculates that the full-bundle chemical cleaning may have improved the detectability of the indications.

In SG4, the outside-diameter stress-corrosion crack at row 5 column 68 initiated slightly above the bottom of the expansion transition and continued downward into the tubesheet, with almost all of the 0.46-inch long indication being below the bottom of the expansion transition.

Based on a review of the information provided, the NRC staff concludes that the licensee provided the information required by their technical specifications. In addition, the NRC 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.

Vogtle Electric Generating Plant, Units 1 & 2 cc:

Mr. Tom E. Tynan Arthur H. Domby, Esquire Vice President - Vogtle Troutman Sanders Vogtle Electric Generating Plant Nations Bank Plaza 7821 River Road 600 Peachtree Street, NE Waynesboro, GA 30830 Suite 5200 Atlanta, GA 30308-2216 Mr. N. J. Stringfellow Manager, Licensing Resident Inspector Southern Nuclear Operating Company, Inc. Vogtle Plant P.O. Box 1295 8805 River Road Birmingham, AL 35201-1295 Waynesboro, GA 30830 Mr. Jeffrey T. Gasser Office of the County Commissioner Executive Vice President Burke County Commission Southern Nuclear Operating Company, Inc. Waynesboro, GA 30830 P.O. Box 1295 Birmingham, AL 35201-1295 Mr. Bob Masse Resident Manager Mr. Steven M. Jackson Oglethorpe Power Corporation Senior Engineer - Power Supply Vogtle Electric Generating Plant Municipal Electric Authority of Georgia 7821 River Road 1470 Riveredge Parkway, NW Waynesboro, GA 30830 Atlanta, GA 30328-4684 Mr. Reece McAlister Executive Secretary Georgia Public Service Commission 244 Washington St., SW Atlanta, GA 30334 Mr. Harold Reheis, Director Department of Natural Resources 205 Butler Street, SE, Suite 1252 Atlanta, GA 30334 Attorney General Law Department 132 Judicial Building Atlanta, GA 30334 Mr. Laurence Bergen Oglethorpe Power Corporation 2100 East Exchange Place P.O. Box 1349 Tucker, GA 30085-1349