ML18283B390

Transmitting Final Report of Reportable Deficiency, Possibility of Marginally Adequate Support Structure on Main Steam & Relief Valve Discharge Piping - in Control No. HO-1127F2

ML18283B390
Person / Time
Site:	Browns Ferry
Issue date:	05/17/1976
From:	Gilleland J Tennessee Valley Authority
To:	Moseley N NRC/RGN-II
References
HO-1127F2
Download: ML18283B390 (5)

Text

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TE ESSEE VALLEY AUTHORITY ~

O 8 P CHATT'ANOOGA, TENNESSEE 37401

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Mr. Norman C. Hp cloy, Director Office of I Paction and Enforcement U.S. Nucl Regulatory Cotmission Region - Quite 818 230 cachtree Street> Ntf.

anta, Georgia 30303

Dear Mr,

1foseloy!

BIUNNS FERRY NUCLEAR PLANT UNIT 3 RHPOP~LE DHFICXENCY POSSIBILITY OF MARGIIQLLYADEQUATE SUPPORT STRUCTURE ON MAXN STP&f AND RELXHF VALVE DISCHARGE PIPING IE CONTROL NOe HOll27F2 Xnitial report of the subject reportable deficiency ~ras made to G. R. Klingler, NRC-IE, Region XX, on Decenber 23, 1975, and +as follnrcd by our January 20, 3.976, letter, J, E, Gilleland to Donald F. 7~th A second intex'im report was submitted to

,NRC by oux AprQ. 29> 1976, letter, J. E. Gilleland to Norman C.

kfoseley.. Enclosed. is our final rcport concerning this deficiency (Hnclosure 1) and a copy of the Teledyne analysis (Enclosure 2) re1ating to this deficiency.

Very truly yours'.

E. Gilleland Assistant Manager of Power Enclosures CCI4 Dr. E. Volgenau> Dixector Office of Inspection and Enforcement U.S. Nuclear Regulatory Commission Hashington, DC 20555 8 ~5+@

An Equal Opportunity Employer

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ENCLOSURE 1 BRQ'INS FERRX NUCLEAR PLANT UNIT 3 ADEQUATE SUPPORT STRUCTURE

,ON MAIN STEAM AIR RELIEF VALVE DXSCEIARGE PIPING DDR.223 - FINAL REPORT On December 23, 1975, an initial report was made to NRC-OXE Region IX Inspector, G. R. Klingler by T. V. Abbatiello, T. M. Barkalo~r, M. A. Linn, and. 8. H. Mindel. The report was made in compliance with 10CFR50.55(e}.

This is the fina1 report for this occurrence.

Descri tion of Occurrence An analysis of the Browns Ferry main steam lines and. relief valve which was done in conjunction with the proposed substitution of two discharge'iping, Crosby relief valves for two Target Rock relief valves on unit 3, revealed that the existing piping support of these lines was not adequate to prevent stresses from exceed.ing those reported in the FSAR.

Cause of Deficienc The Browns. Ferry plant was origina11y designed. using the criteria set forth in the 1967 issue of ANSX B31.3... Since this code did not address the transient relief= va1ve d"scharge loading condition and a mathematica1 model of these forces was not available, engineering judgment and. con-servatism were used. in'esigning for this condition. Experience in fossil plant design had. shown that while'lines of this type do vibrate, e.g.,

start up systems with high pressure critical systems blcrring darn to the condenser, they stabilize within a short period. of time and. stresses are within the endurance stress limit of the piping. Present day modeling and. computer solution of the transient loading phenomenon, when considered.

in conjunction with the other load.ing conditions and. exi.sting piping support, show stresses in the piping to be above the stated. FSAR values.

Safet Im lications The analysis of the main steam lines and relief valve discha"ge piping she< the maximum stress to occur in the 26"x6" sweepolet connecting the lines. Upon considering pressure, deadweight and. other sustained. mechanical loads, seismic, and. relief valve operation, stresses are above the stated FSAR values and. near the yield stress of the material at design temperature.

Assuming all these loads occurring simultaneously and. of suffici.ent magna>>

tule to cause a failure at the sweepolet, a smaU. diameter pipe loss accident could. occur. The emergency core cooling system is sized of'oolant to readily mitigate such an accident. However, the possibility that such a failure could. have occurred. is very remote since the highest ca1culated.

stress was stiU. below that necessary to cause such a failure.

Dcscri Cion of Corrective Action 9.'cledyne Materials Research has conducted. a new stress analysis for each main steam and. relief'alve discharge line in all units at Browns Ferry.

The criteria of Al'1SX 331.1, 1973 edition, includ.ing all aMenda up to summer 3.97/,have been used, for this analysis. Additional mechanical shock arrestors and. restraints have been added. to the lines for satis-faction of the criteria.

Means Taken to Prevent a Recurrence A13. TVA nuclear plants will be analyzed. considering all loading conditions as required. by the applicable codes and. SAR commitments.

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