ML19260B193

Interim Deficiency Rept Re Certain Seismic Amplified Response Spectrum Curves Used as Input Data to Pipe Stress Analyses.Corrective Action in Progress Using Proper Input Data.Two Pipes Required Mods

ML19260B193
Person / Time
Site:	North Anna
Issue date:	12/07/1979
From:	Brown S VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
References
REF-PT21-79-172-000 934A, NUDOCS 7912070395
Download: ML19260B193 (2)

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VIRGINI A ELECTRIC AND POWER COMP ANY, RICHMOND, VIRGINI A 23261

9. J mes P. n'n.111y, nirecter Serial 'fo aMA Office of Insnection & Enforca ent PSF?l/CGC:Mc:vvig U. S. Nucleir Regulatorv Comnission Region II Oceket v. '0 "a

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O'Rei'ly:

Pursuant to the orovisions of 10CFR50.5S(e) and 10CFR21 you were notified en Novaahae 5, '??? Ind by letter / Serial No. n34) dated fievem5er 0, 1979 roncerning seismic rescense spectru'a cu ves in sc :e pipe stress ana'yses.

In cur November 0 lettar, ne s*1ted t%at tM s orc 51am coplics to 44 USK's en Unit 13 Of 14:251e to Unit ' is viell.

' t %,'Aich are 1D3

'Ac hav? S nce taken ena II) i a

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'r c-u W 3 aw wo rte MV for t'ni' ' tSeref are. vie - W 1 ave "4 YSM's far Uni' 1,17 of which apolv to Unit ?, olus one I'.i MSX unique to Unit ?.

A Jascriotion of tS? oroblem follcws:

a'o have discover?d *nennsistencies in the way in which certain of the seis:nic xrplified response soectruct ( ARS) curvos ware usM as innut ista 'o oice stress anCyses for North Anna Units ' and 7 An investigation has shown three

'v5?s of inconsistencies in the ARS data ;,ere present. The first inconsistency was that certain curves Sad two er more values of acce'eration for the same oeriod (i.e. multiple periods). The second was that the peak-soreading of some curves was not exactly +15 percent of t*e peak's ceriod as described in FSAR Section 3.7.3.

The third discrepancy was that a f w cf the ARS curves were outdated.

It has been deter 11nad, by a complete reviaw of the ARS input to pipe stress clicu'ations, that there are no inconsistencies other than those described above.

'hese discrepancies affect only the dynamic ana'vsis of pioine systems; the static analysis involving seismic building movements is rot affected.

For florth Anna 2, only the second and third types of inconsistencies exist - no multiple periods exist. The use of seismic input with these inconsistencies could ootentially result in norconservative pice stresses, pipe support loids, and equipment loads in safety-related

\\q systems located in the auxiliary building, the service

- '> 0 1512 060 7 912 070 M[

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water pumo house, and the main steam valve house. Systems affecteri are service water, quench spray, safety injection, comoonent cooling water, and containment hogger. Only portions of these systems are affected. No portions of these systems within the containment or the reactor coolant system pressure boundary are affected.

C trective 3ction is in e-caress for t51s oroblem. The piot strass analyses for all 13 M5K's have been rerun using the proce* ARS incut; tbasa ean31vses identified two everstressed pioes each requiring the addition of one support to brino the oice stress wit 51n the allowable. Also identifien by tha i

d D ce strass rear @.*! s is the ne?d for one sucoc-* te -astrict the se' m*:

disolacement of tSc rubber Scansion foints for the servica watcr to the c ~nenent cooling water " eat ex bange.

Still in procrass is the analys's of the ef#ect on existing 010e suoperts, eaufpment, and aauiement succorts of new

'0*ds de*ivad from the 0 pe stress rern31vses. ' Modifications will be We is 4

required.

We consi?er this to be an interim repert; any info *mation not available at this tima will be submitted in a finel reocrt. Should you requia* further information, clease contact t5is office.

Very truly yours,

/

Sam C. ?" en, Ir.

Senior Vice P esident - ?ower Statien Engineering and Construction cc: Mr. Victer Stallo, Directnr Office of Insoection ', Enforc? ment

'ir. Harold R. Denten, Di ector Office of Nuclear Reactor Regulation 0ObObOh0NQ 1512 061