ML20067A187

Forwards 6-month Rept of Eagle 21 Functional Upgrade Commitments for 900617-1216

ML20067A187
Person / Time
Site:	Sequoyah
Issue date:	01/18/1991
From:	Wallace E TENNESSEE VALLEY AUTHORITY
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
NUDOCS 9101240284
Download: ML20067A187 (5)

Text

L TENNESSEE VALLEY AUTHORITY

-CHATTANOOGA l TENNESSEE 37401 l

SE' Lookout P1' ace

JAN 181991 U.S. Nuclear Regulatory Commission I

ATTNt--Document Control Desk

= Washington,.D.C. ;20555 i

Gentlemen In the Matter of

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' Docket No' 50-327-Tennessee Valley Authority

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+1 SEQUOYAH NUCLEAR PLANT (SQN) - UNIT 1 - EAGLE 21-SIX-MONTH' REPORT-

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Reference:

TVA letter to NRC da+.ed May110, 1990, "Sequoyah Nuclear Plant-(SQN) - Eagle 21 Funetional: Upgrade Commitments"-'

In the referenced letter, TVA' committed to submit _ periodic; reports at approximately six-month-intervals' describing design hardware,4 design-software, and maintenance problems with-_ Eagle 21 during Unit 1 Cycle 5 operation.-- The information in the enclosure-is provided_to satisfy.the;first'ofLthree reports to meet this commitment. This report l covers the 1eriod of' June 17, 1990, (Unit L1 at -100 percent power) :to; December:16,190 During a May 21, 1990, telecon with NRC. TVA also_ agreed to provide NRC with a summary of TVA's review of-technical specification (TS) changes to'the original Eagle 21 TS submittal; This = summary will' be' provided under a separate cover letter.

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If you-have any questions concerning:this issue, please contact Keith C. Weller I

at (615) 843-7527.

Very truly yours,.

TENNESSEE VALLEY AUTHORITY l

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Enclosure cc:- See page 2 ADOCK0500g7

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- An Equal Opportuniky Employer ;

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U.S. Nuclear Regulatory Comis sion jg i

cc (Enclosure):

i Ms. S. C. Black, Deputy Director Project Directorate II-4 U.S. Nuclear Regulatory Comission One White Flint, North 11555 Rockville Pl.:e Rockville, Maryland 20852 Mr. J. N. Donohew Project Manager 4

U.S. Nuclear Regulatory Comission One White Flint, North

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11555 Rockville Pike 4

Rockville, Maryland 20852 NRC Resident Inspector Sequoyah Nuclear Plant 2600 Igou Ferry Road Soddy Daisy, Tennessee 37379 q

Mr. B. A. Wilson, Project Chief s

U.S. Nuclear Regulatory Comission Region II 101 Marietta Street, NW, Suit-2900 Atlanta, Georgia 30323 I

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ENCLOSURE l.!

SQN Eagle:21, Unit.1 Six-Month Report-Period June 17 through December 16, 1990 Equipment / System Failuree During the period of June:17 through December 16, 1990, the fol'1owing problems:

occurred, j

Failure 1 l

The test sequencer processo.- (TSP) failed-five times on'the following--

l racks.

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RACK DATE 4

1-R-13 6/24/90 1

1-R-3 7/17/90 l

1-R-7 9/1/90-1 1-R-7 10/22/90

R-8 10/25/90

The TSP' lock-ups were identified by the receipt of a channel set failure =

alarm in the main control room,:with no corresponding bistable trips.

The rack diagnostic lightsLindicate that the' TSP has stopped functioning. -The loop calculation processor (LCP) remained operable.

Action Takent-The TSP was reset and returned to service.

DranetzJ11n'e Anitore were-l connected to all-four protection sets on Units 1'and'2 to monitor line'to

-j ground-disturbances. Main-control room and' switchyard-logs vere reviewed q

for similarities, ' but'-none -were found. ' TSP -and. LCP status sheets were d

developed for maintenance planners such that-"as found" board conditionsT l

-can be recorded before reset. Westinghouse Electric Corporation', and-Intel Corporation are' preparing to update-Sequoyah'a' racks with Revision 3 Intal processors.

Causes-Westinghouse is evaluating whether a ground-mat or power-spike irregularity is potentially the problem:

Westinghouse-is'also pursuing'a possible anomaly in the Revision 2' Intel Microprocessor 86ard 80286,--

which caused lock-ups in another application..-Westinghouse.has built a test circuit for-:their prototype in Pittsburgh that has-causedLlock-up of the processor, thereby linking the TSP and'LCP lock-ups to-the previously identified intel problem.

Failure 2 During this same period, one LCP lock-up occurred on August 26, 1990,--in:

Rack 5.

This event caused all channels in Rack 5 to trip: and become inoperable. -A half-trip condition was created,for several7 reactor protection and-engineered safety features:-(ESP) without an-actual trip 4

condition present. The. LCP and TSP were reset and all channels were; returned'to. service, however, as'a precaution,:the LCP was replaced and returned to Westinghouse for' diagnostic evaluation =.: -This LCP board-has L

operated in Weatinghouse's' test bed in Pittsburg, Pennsylvania-without 8

any.fallures. This event may have'been caused by similar conditions'that created the TSP lock-ups' described earlier.

For: this 'eason, the came actions were taken.-and the-same possible cause is considered applicable as described :for the TSP Llock-ups above.

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Failure.

1 The 12-volt powe _ supply failed low (0-volt-directbcurrent).and' caused'a l

' TSP failure. -The LCP-did not fail and the rack ~re' maine'dLoperable.

The power' supply was-. replaced and the TSP was reset lto return'the TSPito::

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service. The power' supply _was; returned to: Westinghouse;for analysis and<

Q repair. o As - of this; date, 'the cause-ofe f ailure has1not been' determined. _ _

J This is the.first= failure ofia. power supply and'is' considered an=1solated:

case. Furtherfactions'will belpursuedLas necessarytbased on thel j

Weatinghouse failure analysis.

4 Failure 4 Two surveillance; injection response (SIR); bus' cables failed during this period. The-failures oecurred:during.surveillancectestLmode activities.

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The' failures-would.not_ allow? the testisigna1 injection to be performed,:

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associated' with surveillance i test only. _ The LCP was unaf fectedlby1 the_-

a failures, and all Eagle safety: functions remained operable.

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.The SIR bus. cables lwere replaced'and-the surveillanceltesting was' satisfactorily completed. Westinghouse-has eva1 Hated the failures, 3

reviewed their.' manufacturing process,.andidetermineditheifailurestare-not gene: ic.

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. Failure 5 n

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-A hijh-temperature cabinet alarm for11-R 5 wasEreceived-in th'e mainL 1

9ontrol: room.. The LCP remained:operabic,:and;all Eagle.fUnetions~were p.ntained for reactor protection and ESF; considerations.:

q Actions were taken to determine the rack; temperature andJit was!verifiedL to be normal.- Troubleshooting? reveal'ed?two pins in connector J2 were noti fully inserted.1 The pins were properly = installed and the alarm was?

. cleared.: This isi the first identification 'of ' pins ; that were not properly 1

4 inserted during onsite installation by theEvendor.

Thisfis1 considered:an-

"f; isolated case with no further corrective:actionsiat-this-time.,

l Failure 6 An Eagle partial trip (EPT) board failure occurred.in-1-R-10. One

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channel,of the board-failed causing:the. delta'T! turbine runb~ck alarm 4 C a

annunciate.. This condition only caused an? alarm! function fand all other_

1 Eagle functions were maintained.

_l The EPT board was replaced to resolve the erroneous alarm condition. : '1The i

+oard was returned torWestinghouseffor' analysis and warranty repair.7 The.

9 results--of this analysis will be evaluated tordetermine any:further:

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corrective actions that.are necessary.

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'l It should be noted that of the failures described 'above,' only the one LCP 4

lock-up disabled any safoty functions of-the Eagle 21 system.' All'other-s failures affected only, diagnostic functions or_ initiated-alarm functions without affecting any; vital operations of Eaglef21'.;

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Generic Concern It was determined that chrnnel trip functionsfcanJbe actuated!when'a' digital:

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-voltmeter le plugged into an analog test point: inia: protection 1 set'. lThis?is'a' j

t generic concern ~with the: Eagle 21 equipment.- This'hastonlyJoccurred onceLat:

7 Sequoyah on a Unit 2 Eagle 21 rack during-troubleshooting _ activities but has; i

the potential for occuring on.any rack.;

t Plugging a_ digital voltmeter (DVM).into thesanalog input test points.onjthe Eagle 21 racks may cause an input signal perturbation becauseiofH he; i

t capacitance of the DVM. "The DVM must-charge'or dischargefto the input,signalE 1

voltage icvel. The magnitude of the perturbation--is dependent on thef 1

difference between the initial DVM'voltageLand the'inputisignal'voltagei: The effect is transient and doesinot_cause signa 11 perturbation..The method;for simulating this occurrence was to short the DVM leads to discharge _the meter input before inserting the leads into the test 1 point. = Unpluggingtand; reinserting the meter did notJeause any_ perturbation;since'the meter was charged - to _ the : Input signal voltage l levels ETests.wereEperformed by:

Westinghouse with a John Fluke Manufactbring Incorporated Mode 118840A DVM to.

support the above'-identified appare't.cause.'

n Long-term corrective actions. are' currently-under Levaluationiand wil15 be -

i tracked under SequoyahtConditionLAdverse to-Quality Report (CAQR) SQP900479.

l Review for generic applicabilityrwillt also'be performed under jthis CAQR.?

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Interim corrective actions required tifying maintenance of the' potential problem.by issuing a maintenance manu,sment directive and! supplying l

1 maintenance planners with a caution statement thattis to becincluded in all Eagle 21 troubleshooting work activities ~. ; Caution tags.were alsotinstalled on the racks.

Additional Design Concern

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Westinghouse discovered the maximum-design: temperature on an integrated.

circuit '

less than the maximum: allowable cabinet temperature. :The circuit, involves Burr-Brown' direct-current to direct-current converter-that was environmentally qualified by Westinghouse;: This! circuit is used~on<three

-boards in each Eagle 1 rack.

This problem is being documentedLand resolved'by.the.CAQRl precess (CAQR SQP901522); A justification' for continued, operation -(J 10):has beenf 1

written to address the acceptability of operation with theytenperature concern-based on compensatory measurec to be:taken in the-event of an' Appendix R fire 4

resulting in loss of heating, venting, and air-conditienfag roolingito the; auxiliar*/ instrument room. 1These components will bw I clar.ed'by; Westinghouse during the Unit 1 Cycle.5 refueling outage,_and!Westir.ghouse has filed a 10; CFR Part 21 to notify itsicustomers of'this5 condition. The' Unit 2-direct-current to direct-currentJconverters'in question,have.already:been; i

replaced prior to the Cycle :S start-up.

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