ML20151H154

Safety Evaluation Accepting Util 880301 Response to NRC Bulletin 88-002, Rapidly Propagating Fatigue Cracks in Steam Generator Tubes

ML20151H154
Person / Time
Site:	Sequoyah
Issue date:	07/22/1988
From:	NRC OFFICE OF SPECIAL PROJECTS
To:
Shared Package
ML20151H152	List: ML20151H150 ML20151H154
References
IEB-88-002, IEB-88-2, NUDOCS 8808010162
Download: ML20151H154 (3)

Text

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SAFETY EVALUATION BY THE OFFICE OF SPECIAL PROJECTS TVA'S RESPONSE TO NRC BULLETIN NC. 88-02 "PAPIOLY PROPAGATING FATIGUE. CRACKS IN STEAM GENERATOR TUBES" TENNESSEE VALLEY AUTHORITY SEQUOYAH NUCLEAR POWER PLANT, UNIT 2 00CKET NO. 50-328

!. INTRODUCTION The purpose of HRC Bulletin No. 88-02 dated February 5,1988, was to request that owners of Westinghouse designed nuclear powee teacters with 4 steam generators having carbon steel support platts take tpecified actions to minimize the potential for a steam generator tube rupture event caused by a rapidly propagating fatigue crack. Si;ch an event occurred at North Anna Unit 1 on July 15, 1987.

EVALUATION II. ,

TVA's prelininary report to NRC Bulletin No. 88-02 for Sequoyah Unit 2  ;

was enclosed in their letter dated March 1.1988, subject as above.

! The report addressed the actions required by the Bulletin as follows: i a

A) The results of the most recent steam generator eddy current examination f' i

showed no evidene.e of tube denting induced by corrosion of the upper tube support plate. The inspection met the time and extent requirerents l of the Bulletin. A previous examination dic' identify magnetite frem i i sludge deposits in a small number of upper tube support plate / tube intersections. TVA's position is that SQN unit 2 has no corrosion i

induced denting at the upper tube support plate.

B) For plants with no denting found at the tube to upper tube support i plate intersections, the Bulletin required that the results of '

future steam generator tube inspections be reviewed for evidence of 4

denting at the upper tube support plate, and if denting is found in I

the future, the actions specified in paragraph C.1 and C.2 of the Bulletin are to be taken. TVA did cemit to reviewing the next steam generator tubo inspecticns for denting, but conservatively decided to take the actions specified in paragraphs C.1 and C.2.

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C1) The Bulletin requires for those plants where denting is found..an enhanced primary-to-secondary leak rate monitoring system be implemented. TVA, even though no denting has occurred, has decided to implement an enhanced primary-to-secondary leak rate monitoring program for Sequoyah P. The program will be implemented by March 25, 1988, or before exceeding the 50% pcwer level, which ever comes first, and will be in accordance with th'e recomendations in

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Paragraph C.1 of the Bulletin.  !

C2) The Bulletin required that a procram be ivaplemented to minimize the prcbability of a rapidly propagating fatigue failure such as occurred l at North Anna Unit 1. TVA, even though no denting has occurred, has established a program to gather the data necessary to perfom an analysis of the stability ratios and locations of the anti-vibration bars with technical support from Westinghouse. TVA comitted to complete the analyses and the long tem corrective action three months af ter startup frem the Sequoyah Unit 2 cycle 3 refueling outage. .

l  !!!. CONCLUSIONS TVA has ret the requirements for reporting at this time. Powever, the licensee has not comitted to inspect for denting of the uppennost tube j support plate during tube inspections after the next refueling outage. I j

i It is the intent of the Bulletin that such inspections continue for the '

4 remairing life of the plant and that if denting is found, the provisions of Paragraph C in the Bulletin should apply. In lieu of such a comitment, the licensee states that it is implementing Paragraph C.1 and C.2 of the Bulletin as if denting were actually found to be present. The staff finds this approach to be acceptable provided the details of the licensee's program are submitted as specified in the Bulletin. Furthermore, actions taken to fulfill Paragraph C,.2 of the Bulletin are subject to NRC review j and approval, again according to a schedule censistent with Paragraph C.2 of the Bulletin.

Principal Centributor: D. Smith I i

j cated: July 22, 1988 I

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. . Mr. S. A. White Tennessee Valley Authority Sequoyah Nuclear Plant

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General Counsel Regional Administrator, Region Il Tennessee Valley Authority U.S. Nuclear Regulatory Comission 400 West Sumit Hill Drive 101 Marietta Street, N.k.  ;

E11 B33 . Atlanta, Georgia 30323 ,

) Knnville, Tennessee 37902 3

Resident inspector /Seouoyah NP Mr. R. L. Gridley c/o U.S. Nuclear Pegulatory Comission  ;

i Tennessee Valley Authority 2600 Igou Ferry Road t 4

EN 1578 Lookout Place Soddy Daisy. Tennessee 37379  !

! chattanooga, Tennessee 37402-2801 i Mr. H. L. Abercrombie Mr. Michael H. Mobley, Director  :

Tennessee Valley Authority Division of Radiolohical Health Sequoyah Nuclear Plant T.E.R.R.A. Building, 6th Floor P.O. Box 2000 150 9th Avenue North Soddy Daisy. Tennessee 37379 Nashville, Tennessee 37219-5404 l j Mr. M. R. Harding Dr. Henry Myers Science Advisor  ;

] Tennessee Valley Authority Comittee on Interior

! Sequoyah Nuclear Plant and Insular Affairs '

4 P.O. Box 2000 U.S. House of Representatives Soddy Daisy, Tennessee 37379 Washington, D.C. 20515 Mr. D. L. Williams  ;

Tennessee Valley Authority l 1 400 West Sumit Hill Drive I W10 885 (

j Knoxville Tennessee 37902  !

I County Judge  !

j Hamilton County Courthouse r

Chattanooga, Tennessee 37402 1 1 l i

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