ML060950510

Summary of the Staff'S Review of the Steam Generator Tube Inservice Inspection Reports for the End-of-Cycle 13 Refueling Outage in 2004

ML060950510
Person / Time
Site:	Sequoyah
Issue date:	05/01/2006
From:	Pickett D Plant Licensing Branch III-2
To:	Singer K Tennessee Valley Authority
Pickett D, NRR/DLPM, 415-1364
References
TAC MC8712
Download: ML060950510 (6)

Text

May 1, 2006 Mr. Karl W. Singer Chief Nuclear Officer and Executive Vice President Tennessee Valley Authority 6A Lookout Place 1101 Market Street Chattanooga, Tennessee 37402-2801

SUBJECT:

SEQUOYAH NUCLEAR PLANT, UNIT 1

SUMMARY

OF THE STAFFS REVIEW OF THE STEAM GENERATOR TUBE INSERVICE INSPECTION REPORTS FOR THE END-OF-CYCLE 13 REFUELING OUTAGE IN 2004 (TAC NO. MC8712)

Dear Mr. Singer:

By letter dated November 22, 2004, (Agencywide Documents Access and Management System Accession Number, ML043280625), Tennessee Valley Authority (TVA, the licensee) submitted the steam generator (SG) tube plugging report in accordance with Technical Specification (TS)

Section 4.4.5.5.a. By letter dated February 15, 2005, (ML050550413), TVA submitted the 90-day inservice inspection summary report in accordance with the American Society of Mechanical Engineers Boiler and Pressure Vessel Code,Section XI, Article IWA-6230. By letter dated October 20, 2005, (ML053050386), TVA submitted the 12-month SG inspection report in accordance with TS Section 4.4.5.5.b. By letter dated February 22, 2006 (ML060540483), TVA provided additional information concerning their SG tube inservice inspections. The Cycle 13 SG tube inservice inspections were the first SG tube inspections since SG replacement.

The Nuclear Regulatory Commission staff has completed its review of these reports and concludes that the licensee provided the information required by Sequoyah Nuclear Plant, Unit 1 TSs, and that no additional followup is required at this time. The staffs review of the reports is enclosed.

Sincerely,

/RA/

Douglas V. Pickett, Senior Project Manager Plant Licensing Branch II-2 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-327

Enclosure:

Staffs Review cc w/encl: See next page

ML060950510 NRR-106 OFFICE LPL2-2 LPL2-2/PM LPL2-2/RA DCI/CSGB LPL2-2/BC NAME SCrane DPickett RSola EMurphy (by memo) MMarshall DATE 4/28/ 06 4/28/ 06 4/28/ 06 3 / 10 / 06 5/1/ 06 Mr. Karl W. Singer SEQUOYAH NUCLEAR PLANT Tennessee Valley Authority cc:

Mr. Ashok S. Bhatnagar, Senior Vice President Mr. Glenn W. Morris, Manager Nuclear Operations Corporate Nuclear Licensing Tennessee Valley Authority and Industry Affairs 6A Lookout Place Tennessee Valley Authority 1101 Market Street 4X Blue Ridge Chattanooga, TN 37402-2801 1101 Market Street Chattanooga, TN 37402-2801 Mr. Larry S. Bryant, Vice President Nuclear Engineering & Technical Services Mr. Paul L. Pace, Manager Tennessee Valley Authority Licensing and Industry Affairs 6A Lookout Place ATTN: Mr. James D. Smith 1101 Market Street Sequoyah Nuclear Plant Chattanooga, TN 37402-2801 Tennessee Valley Authority P.O. Box 2000 Mr. Robert J. Beecken, Vice President Soddy Daisy, TN 37384-2000 Nuclear Support Tennessee Valley Authority Mr. David A. Kulisek, Plant Manager 6A Lookout Place Sequoyah Nuclear Plant 1101 Market Street Tennessee Valley Authority Chattanooga, TN 37402-2801 P.O. Box 2000 Soddy Daisy, TN 37384-2000 Mr. Randy Douet Site Vice President Senior Resident Inspector Sequoyah Nuclear Plant Sequoyah Nuclear Plant Tennessee Valley Authority U.S. Nuclear Regulatory Commission P.O. Box 2000 2600 Igou Ferry Road Soddy Daisy, TN 37384-2000 Soddy Daisy, TN 37379 General Counsel Mr. Lawrence E. Nanney, Director Tennessee Valley Authority Division of Radiological Health ET 11A Dept. of Environment & Conservation 400 West Summit Hill Drive Third Floor, L and C Annex Knoxville, TN 37902 401 Church Street Nashville, TN 37243-1532 Mr. John C. Fornicola, Manager Nuclear Assurance and Licensing County Mayor Tennessee Valley Authority Hamilton County Courthouse 6A Lookout Place Chattanooga, TN 37402-2801 1101 Market Street Chattanooga, TN 37402-2801 Ms. Ann P. Harris 341 Swing Loop Road Rockwood, Tennessee 37854

SUMMARY

OF THE STAFFS REVIEW STEAM GENERATOR TUBE INSPECTION REPORTS FOR THE END-OF CYCLE 13 REFUELING OUTAGE IN 2004 SEQUOYAH NUCLEAR PLANT, UNIT 1 TAC NO. MC8712 DOCKET NO. 50-327 By letter dated November 22, 2004 (Agencywide Documents Access and Management System (ADAMS) Accession Number ML043280625), Tennessee Valley Authority (TVA, the licensee) submitted the steam generator (SG) tube plugging report in accordance with Technical Specification (TS) Section 4.4.5.5.a. By letter dated February 15, 2005, (ADAMS Accession Number ML050550413), TVA submitted the 90-day inservice inspection summary report in accordance with the American Society of Mechanical Engineers Boiler and Pressure Vessel Code,Section XI, Article IWA-6230. By letter dated October 20, 2005, (ADAMS Accession Number ML053050386), TVA submitted the 12-month SG inspection report in accordance with TS Section 4.4.5.5.b. By letter dated February 22, 2006 (ADAMS Accession Number ML060540483), TVA provided additional information concerning their SG tube inservice inspections. The Cycle 13 SG tube inservice inspections were the first SG tube inspections since SG replacement.

Sequoyah Nuclear Plant (SQN), Unit 1 has four steam generators designated Model 57AG that were fabricated by Doosan. All four SGs were inspected during the November 2004 refueling outage. The SG consists of 4983 tubes which have an outside diameter of 3/4-inch and a wall thickness of 0.043-inch. The tubes were hydraulically expanded into the tubesheet and are supported by several type 409 stainless steel, lattice grid tube supports. The U-bend portion of the tubes is supported by diagonal and vertical straps.

The licensee provided the scope, extent, methods, and results of SQN, Unit 1 SG tube inspections in the documents referenced above. In addition, the licensee described corrective actions (i.e., tube plugging) taken in response to the inspection findings.

Of particular note from the inspections is that the licensee detected eleven wear indications in the area of the 2nd and 4th vertical straps. The largest indication had penetrated through 17 percent of the wall thickness. Although the tubes could have been left in service, all were preventively plugged. The licensee performed an evaluation that determined the likely cause and examined the probability of future wear indications. The most likely cause of the wear was identified as local variations in the clearance between the tubes and the vertical straps. The 2nd Enclosure

and 4th vertical straps do not have lock bars for controlling the spacing between the straps; therefore, local variations in the clearance can occur (e.g., when the vertical strips were welded to an arch plate, the strips might have had local deviations in spacing from each other or might have deviated from a vertical orientation due to weld distortion). The licensees evaluation also indicated that the wear rate for an indication would decrease as the tube-to-support contact area increases (i.e., volumetrically linear wear progression).

Based on a review of the information provided, the Nuclear Regulatory Commission (NRC) staff concludes that the licensee provided the information required by their TSs. In addition, the NRC staff concludes that there are no technical issues that warrant followup 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.

Principal Contributor: K. Karwoski Date: May 1, 2006