ML20042F169

Responds to NRC Bulletin 88-009, Thimble Tube Thinning in Westinghouse Electric Corporation Reactors. Wear Acceptance Criteria Established & Appropriate Corrective Actions Noted. Criteria & Corresponding Disposition Listed

ML20042F169
Person / Time
Site:	Sequoyah
Issue date:	05/03/1990
From:	Michael Ray TENNESSEE VALLEY AUTHORITY
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
IEB-88-009, IEB-88-9, NUDOCS 9005070316
Download: ML20042F169 (3)

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4 TENNESSEE VALLEY AUTHORITY CHATTANOOGA, TENNE 6$EE 37401 SN 1578 Lookout Place l

MAY 031990 U.S. Nuclear Regulatory Commission ATIN:

Document Control Desk Washington, D.C.

20555 Gentlemen:

In the Matter of

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Docket Nos. 50-327 Tennessee Valley Authority

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50-328 SEQUOYAH NUCLEAR PLANT (SQN) - NRC BULLETIN 88-09, THIMBLE TUBE lHINNING IN WESTINGHOUSE ELECTRIC CORPORATION REACTORS As required by the subject bulletin, TVA has developed a thimble tube inspection program for SQN Unit 1.

Wear ecceptance criteria have been established and appropriate corrective actions identified.

The criteria and corresponding disposition are as follows.

1.

Equal to or greater than 60 percent through-wall less requlres thimble tube plugging.

2.

Equal to or greater than 30 percent through-wall loss and less than l

60 percent through-wall loss require repositioning the thlmble tube by a minimum of two inches.

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3.

Less than 30 percent through-wall loss requires no corrective action for the next fuel cycle.

The inspection frequency has been established as each refueling outage until a wear database is estabitshed, and the inspections will be accomplished by eddy-current testing.

Eddy-current testing and analysis were completed for Unit 1 on April 4, 1990.

None of the tubes ex lined have equal to or greater than 60 percent through-wall loss.

Nine tubes hase equal to or greater than 30 percent and less than 60 percent through-wall loss. As a preventative measure however, all Unit I thimble tubes were previously repositioned at the end of Cycle 3 operation.

The wear identified in seven of the nine tubes is indicative of wall loss before being repositioned.

Therefore, only two of the nine tubes with equal to or greater than 30 percent and less than 60 percent through-wall loss, Tubes 12 and 46, required additional repositioning.

Forty-two tubes have less than 30 percent and greater than 0 percent through-wall loss, and six tubes have no identifiable loss.

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, U.S.* Nuclear Regulatory Commission g

i One tube, Tube 29, was inaccessible for full-length eddy-current testing.

Although the eddy-current probe would not pass through the tube, incore detection instrumentation will. As a precaution, the tube has been repositioned.

This is considered acceptable since examination results for the balance of the thlmble tubes indicate that the maximum loss in Unit 1 15 46 percent. Additionally, SQN has adequate makeup capability for a postulated thimble tube leak and has the capability to isolate leaking thimble tubes at the seal table.

The enclosure provides a list of the three tubes that have been repositioned as a result of the thimble tube inspection program.

No commitments are contained in this submittal.

Please direct questions concerning this issue to Kathy S. Whitaker at (615) 843-7748.

Very truly yours, TENNESSEE VALLEY AUTHORITY

\\/h M. J. Ray, M ger l

Licensing Project Management Sworn nd subscr ed before me this day of Idxi 1990 Notary Public My Commission Expires //-

Enclosure cc (Enclosure):

Ms. S. C. Black, Assistant Director for Projects TVA Projects Division U.S. Nuclear Regulatory Commission One White filnt, North 11555 Rockville Pike Rockville, Maryland 20852 NRC Resident inspector Sequoyah Nuclear Plant 2600 Igou ferry Road Soddy Daisy, Tennessee 37379 Mr. B. A. Hilson, Assistant Director for Inspection Programs TVA Projects Division U.S. Nuclear Regulatory Commission Region 11 101 Marietta Street, NW, Suite 2900 Atlanta, Georgia 30323

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