ML20128E364

Confirms Results of 921127 Telcon Which Requested Regional Temporary Waiver of Compliance from 1746 CST 921127,until 1746 CST 921128,from TS LCO for Inoperability of NN14 (Safety-Related AC Instrumentation Power Inverter)

ML20128E364
Person / Time
Site:	Callaway
Issue date:	11/27/1992
From:	Campbell W UNION ELECTRIC CO.
To:	Davis A NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML20128E353	List: ML20128E347 ML20128E364
References
ULNRC-2727, NUDOCS 9212080065
Download: ML20128E364 (6)

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Ux Euc}hw ic P3 November 27, 1992 Mr. A. bort Davis Regional Acainistrator Region III U. S. Nuclear Regulatory Corunission 799 Roosevelt Road Cle:, RH yn, Illinois 60137 U1.NRC 2727 De a r dr. Davi a :

LOCKET NUMBER 30-483 cal.LAVAY FlANT UNIT 1 REQUEST FOR Rf.0 ZONAL TEMPORARY EAIVER OF COMPLIM g Thia latter is to confirm the resulte of a taluconference between Union Electric and the NRC Region III Staff o.n November 27, 1992, in which Union Electric requeste.d a Ragional Temporary Vaiver of Compliance from 1746 CST

• ?nvemb e r 27, 1992, until 174G CST Noveimber 28, 1992, from the Technical Specification Limiting Conditions of Operation (140) ft.r the inoperability of NN14 (Safety Related AC Instrumentation Power Inverter). This would allow completion of repairs to the inverter. Currently, the Callaway Plant is lu Mods 1, 100 percent power.

The basis for this requent le provided below:

BACKGROUND:

On Novu=ber 26, loss of Instrument bus NN04. Licensed reactor operators selected all1992, at 1 controlling channela away from t'na failed bus, Engineering personnel began troubleshooting for the root cauce of the invertar failure.

REQV}BEMENTS FOR VHICH THE VATVER IS REQUESTED Technical Specification (T/S) 3.8.3.1 requires 120-Volt A.C. Vital Bus

1. NN04 to be energized from its associated inverter connected to D C wNK04

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With NN14 inoperable, the plant entered action b, which requires the plant -

l tot (1) re energite the.A,C.Lvital bus within two hours or be in at least HOT STAND 8Y within the next six hours and in COLD SHUTDOWN within the following -30 hours; and (2)_ re onergize the A.C. vital' bus from-its anNociated inverter connected to itt associated D.C. bus.within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> or.

be in at losst FOT STANDBY within the-next six hours and in COLD SHUTDOVN within the following 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />.

Action b (1) was met when the operators, per procedure OTN NN 00001,120V Vital AC Instrument Power Class IE (NN), transferred 'the NN04 protective channels to XNF06. Troubleshooting was begun to determine' root cause of the inverter failure, because additienal time is necessary to retest and restore the inverter, an additional 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> is being requested for T/S 3.8.3.1 action b (2). The most probab., cause of failure of the NN14 '

inverter has been determined to be a faulty _ ferroresonant transformer.

and/or wave shaping espacitors which have been replaced.

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CIRCUMST6HGES/JEID FOR PROMPT ACTIONMfY SITUATION COULD NQT F. AVE BEJ,H AVOTDED Technical specification requirements will necessitate a plant shutdown beginning at 1746 CST on November 27, 1992. Extension of the 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> allowed outage time limit is' needed to permit inverter testing and restoration and avoid a shutdown and cooldown transient that would'be -

'impoacd on the plant by an unnecessary shutdown to Mode 5 conditions 1Since _

the failure of NN14 could not have been reasonably predicted, this at tuation could not have been avoided.

-COMPENSATORY ACTIONS During the time frame this temporary waiver of compliance would be in -

affect, the following compensatory actions have been or will be taken:

Licensed utility reactor-operators _ selected all controlling channels away; from failed bus NN04. At 1800 CST, November 26,: 1992,- instrument bus NN04 was re energized using backup-transformer XNN06, par. plant procedure OTN NN 00001. Utility Nuclear Engineering personnel vill verify the_ proper;

-load,-volta 6e and temperature every two hours during _ the period 'of time bus.

NN04 is energized from bus XNN06. Licensed plant operators have been

- briefed and are aware of actions that;would be. required to be taken,in the event of the failure of XNN06 and subaequent-loss of NN04. No unnecessary _-

work or surveillsnce activities associated with the NN04 bus or the XNN06z voltage regulating transformer will be performed while this' temporary waivce is in effect, f

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Page 3 ULNP.0 2727 SAFETY' SIC 41FICANCE AND POTENTIAL. CONSFOUP.'4CES OF PSOPCSFD REQUEST This is a one time request for approval of an allowed outa68 CIE8 of 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> with one Instrument AC powac in*erter inoperable -This request would extend the axisting Technical Specification allowed outa5e ties by 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> to permit completion of the u.aintenance and necessary tests to the NN14 inverter.

The attachment to this letter presents the configuration of the power supplies to the RN04 but and identifies major loads rupplied. The XNN06 transformer is a safety.related transformer which is supplied from vital power supply source NG02. This back up power source is conoidered highly reliable.

A failure of XNN06 vould not prevent the various EnSineered Safety Feature systems and reactor protection systems from performing their intended safety functions. The impact on plant protection from KNN06, voltage regulatin6 transformer, has been evaluated and XNN06 failure vould not result in the initiation of a plant transient or a challenge to any safety systems.

Maintenance and testing antivities which would place coincident reactor protection output channals in a trip condition vill be deferred until NN14 is aligned to the NN04 bus.

DURATION JUSTfFICATION The proposed temporary vaiver of compliance is for a one time approval of plant operation for up to 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> with one Instrument AC power inverter inoperable. The additional tima vill provide sufficient time to repair and retest the inverter and restore the NN04 loads (see attached drawing) to normal power. Should NN14 fall for any other reason, the licensee will meet the Technical Specification shutdown action statement requirements of T/S 3.P 3.1 if the duration of this temporary vaiver of compliance is exceeded.

RAlli FOR_N0_$_IONTFICANT HAZARDS CONSIDER.ATION Union Electric has concluded that the requested temporary watver of compliance does not involve a significant hazard in that it would not increase the probebility of an accident previously evaluated, nor create the possibility of a new or different kind of accident, nor involve a si nificant reduction in any margin of safety.

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P.9/7 Page 4 UIEEC 2727 Loads normally powered by NN04 have been switched to back.up power (XNN06) per T/s 3.8.3.1 action b (1). In addition, the operators selected all controlling channels away from NN04 to NN01 (refer to FSAR Figure 8 b 6),

Assuming single f ailure criteria, a failure of LNN06 would not prevent the

.various Engineered Safety Features systems from performing their intended safety functions.

WJLEOR.FO..I'ALTW1811:.ENvIRgNMENTA1. coNsrovEscrs ne proposed temporary waiver of compliance to continue p'over operstion for an additional 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> with one Instrument AC power inverter inoperable to perforra corrective maintenance has no enviroreental impact.

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roe callaway Plant On Site Review Conmittee has appfoved this request for a temporary waiver of compliance and concurs with the above determinations.

This proposed request for-a temporary waiver of compliance involves no undue safety risk nor irreveraible environmental consequences.

k'han Technical Specification statement 3.8.3.1 action b (2) is exited, we will inform the Site Resident Inspector.

Very truly yours, f/

>+/M k', R. Campbell Manager, Callaway Plant L'RC/MKD/lrj cc's distribution attached

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.a cc distribution for ULNRC 2727 Hr. L, Raynard k'harton (2 copies)

U. S. Nuclear Regulatory Commission OWFN-Mail Stop 13E21 Veshington. D. C.

20555 Manager, Electric Department Missouri Public Service Commission P. O, Box 360 Jefferson City, MO 65102 Records Center Institute of Nuclear Power Operations Suite 1500 1100 Circle 75 Parkway Atlanta. CA 30339 Mr. Art Mah Wolf Creek Nuclear Operating Corporation P. O. Box 411 Burlington, KS 66839 Mr. I. N. Jackiv Chief, Project Section 3C U. S. Nuclear Regulatory Commission Region 111 799 Roosevelt Road Glen Ellyn, IL 60137 U. S. Nuclear Re6ulatory Commission Document Control Desk Washington, D. C.

20555 NRC Senior Resident Inspector I

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