ML17325A260

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LER 87-007-00:on 870714,ESF Reactor Trip Occurred Due to Undervoltage of Reactor Coolant Buses.Caused by Failure of Main Generator Voltage Control Sys.Failed & Suspected Components of Sys replaced.W/870813 Ltr
ML17325A260
Person / Time
Site: Cook American Electric Power icon.png
Issue date: 08/13/1987
From: SAMPSON J R, SMITH W G
AMERICAN ELECTRIC POWER SERVICE CORP., INDIANA MICHIGAN POWER CO. (FORMERLY INDIANA & MICHIG
To:
NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM)
References
LER-87-007-01, LER-87-7-1, NUDOCS 8708180184
Download: ML17325A260 (8)


Text

REGULAYINFORNATION DISTRIBUTIO SYSTEM(RIDS)ACCESSION NBR:8708180184 DOC.DATE:87/08/13NOTARIZED:

NODOCKETFAGIL:50-316DonaldC.CookNuclearPoeerPlant'nit2iIndiana&05000316AUTH.MANEAUTHORAFFILIATION SAMPSONeJ.R.Indiana&MichiganElectricCo.SMITHS'.G.Indiana&MichiganElectricCo.RECIP.NAMERECIPIENTAFFILIATION

SUBJECT:

LER87-007-00:

on870714'SF reactortripoccurredduetoundervoltage ofreactorcoolantbusses.Causedbgfailureofmaingenerator voltagecontrolsos.Failed&suspected components ofsosreplaced.

W/870813ltr.DISTRIBUTION CODE:IE22DCOPIESRECEIVED:

LTRENCLSIZE:TITLE:50.73LicenseeEventReport(LER)>IncidentRptietc.NOTES:RECIPIENT IDCODE/NANE PD3-3LAWIGGINGTON DCOPIESLTTRENCL1111RECIPIENT IDCODE/NANE PD3-3PDCOPIESLTTRENCL11INTERNAL:

ACRSNICHELSON AEOD/DOAAEOD/DSP/PQAB DEDRONRR/DEST/ADS NRR/DEST/ELB NRR/DEST/MEB NRR/DEST/PSB NRR/DEST/SGB NRR/DLPG/GAB NRR/DREP/RAB NRR/PMAS/ILRB RESDEPYGIRES/DE/EIB EXTERNAL:

EG&GGROf<iNLPDRNSICHARRIS'11221110111111111111111155111ACRSNOELLERAEOD/DSP/NAS AEOD/DSP/TPAB NRR/DEST/ADE NRR/DEST/CEB NRR/DEST/

ICSBNRR/DEST/NTB NRR/DEBT/RSB NRR/DLPG/HFB NRR/DOEA/EAB RlhhDREPBGFILE02RFORDSJRGN3FILE01HSTLOBBYWARDNRCPDRNSICMAYST'2211110111'1111-122111111111TOTALNUMBEROFCOPIESREQUIRED:

LTTR44ENCL42 r.~NRCFOrm3dd(943)LICENSEEEVENTREPORT(LER)U.S.NUCLEARREOULATORY COMMISSION APPROVEDOMBNO.31504104EXPIRES:SI31lddFACILITYNAMEPID.C.CookNuclearPlant,Unit2DOCKETNUMBER(2)PAE3l050003161oFESFActuation (ReactorTrip)DuetoUndervoltage oftheReactorCoolantPumBussesasaResultofCEVENTDATE(5)LERNUMBER(5)REPORTDATE(7)OTHERFACILITIES INVOLVED(5)MONTHDAY'9EARYEARSEOUENTrAI NUMBEtlf<<r<<<<REVISION

.>>TdNUMBERMONTHOAYYEARFACILITYNAMESDOCKETNUMBER(El 050000714878700700138705000OPERATINO MODE(9)POWERLEYEL080$<<@$.PgP.Exnan)pr)Q<<R;

<<r<<rr20.402(B) 20.406(s)

(1)(i)20.405(sI(1I(6)20.405(s)

(I)(ill)20.405(sI(I)IIv)20.405(s)

(1I(v)20.405(c) 50M(c)(1) 50.35(c)(2)60.73(s)(2)(I)50.73(s)(2)(Q) 60.73(s)(2)(ill)LICENSEECONTACTFORTHISLER(12)60.73(s)(2)(iv)50.73(s)(2 I(v)50.73(s)(2)(rd)50,73(s)(2)(vill)IA)50.73(s)(2)(rlii)(BI 60.73(s)(2)(x)

THISREPORTISSUBMITTED PURSUANTT0THEAEOUIREMENTS OF10CFRII:IChecfroneormoreofthefollory'np)

(1173.71(B)73.71(c)OTHERISpeclfylnAprtrectINfowendInText,NIICform366AINAMEJ.R.Sampson-Safet6Assessment SuerinteTELEPHONE NUMBERAREACODE616465-590 COMPLETEONELINEFOREACHCOMPONENT FAILUREOESCRIBEO INTHISREPORT(13ICAUSESYSTEMCOMPONENT MANUFAC.TURERREPORTABLE

'@'P,CAUSESYSTEMx>gjcQ.yg<<>S>>rTONPROSr.',<<,rrrrCOMPONENT MANUFAC.TUREREPORTABLETONPADSXEXELUJX34553%@$i"'6"4CR3455NrrMArXEL773455N3455N'.je~P~Nx4+>>~~KKM SUPPLEMENTAL REPORTEXPFCTED(14)YESIlfyer,complereEXPECTEDS(fphtlSSION OATEIXNoABSTRACTILlmittote00rpecer,Ie.,epproxlmerely llfteentlnplespecstypevrritren finer)(15)EXPECTEDSUBMISSIONDATE(15)MONTHDAYYEAROnJuly14,1987,at0707hours,anEngineered SafetyFeaturesActuation (ReactorTrip)occurredduetoundervoltage ofthereactorcoolantpumpbusses.Theundervoltage condition wastheresultofthefailureofthemaingenerator voltagecontrolsystem.TheUnitwasstabilized inMode3(HotStandby)atapproximately 0755hours,July14,1987.Noabnormalreactortripsequenceresponses werenoted.TheNRCwasnotifiedoftheeventviatheENSat0815hours,July14,1987.Post-event testingofthevoltagecontrolsystemcomponents revealedtwofailedpowersupplies(automatic andmanual),andsixfailedSCRModules.Allfailed/suspected components werereplaced.

Investigation regarding industryexperience withBrownBoverivoltagecontrolsystemsindicates thatthefailureswhichoccurredareconsistent withthoseexperienced atotherplantsandisnotaresultofoperatorerrororlackofmaintenance.

Evaluation astothenecessity fortheredesignofthevoltagecontrolsystem,viathePlantModification progra'm, continues however,nospecificpreventive measureshavebeenidentified todate.8708180184 870813PDRADOCI(r0500031(EI 8PDRNRCForm3dd(9d3)

NRCForm366A(()4)3)LICENSEEETREPORT(LER)TEXTCONTINUAU.S.NUCLEARREGULATORY COMMISSION APPROVEDOMBNO.3150-0104 EXPIRES:8/31/88FACILITYNAME(1)DOCKETNUMBER(2)LERNUMBER(6)YEAR8'jets'EGUENTIAL 4.NUMSE4REVISIONNOMEE4PAGE(3)D.C.CookNuclearPlant,Unit2ppppp31TEXT/FIINvoEPEcoirroqoiaEoooaANPenelHRCForm355AB/((1)870070002oF0Conditions PriortoOccurrence Unit2inMode1(poweroperations) at80percentReactorThermalPower.DescritionofEventOnJuly14,1987,at0707hours,anEngineered Actuation (ReactorTripSequence) occurreddueofthereactorcoolantpumpbusses(EIIS/EA).

condition wastheresultofthefailureofthevoltage.controlsystem(EIIS/EL)

.SafetyFeaturestoundervoltage Theundervoltage maingenerator Atapproximately 0637hours,July14,1987,theincomingUnit,Supervisor (Utility-Licensed Operator) noticedthattheoutputfromthemaingenerator automatic voltageregulator (EIIS/EL-RG) wasnotnulledwiththemanualvoltageregulator (EIIS/EL-RG).

Theautomatic regulator wascurrently inserviceandhadbeenoperating atthelowestvalueofthevoltagebandthroughout thepreviousshift.WhentheUnitSupervisor adjustedthemanualregulator tomatchtheautomatic

setpoint, themaingenerator voltageandexcitercurrentindication dippedmomentarily andreturnedtonormal[theadjustment.

shouldhavehadnoeffectonthemaingenerator (EIIS/EL-GEN)].

Hethenrequested thataReactorOperator(RO)(Utility-Licensed Operator) bepostedat.theregulator tomonitortheindication.

TheROreviewedthegenerator panelstatuswiththeincomingUnit,Supervisor andnoticedthat.thegenerator outputvoltagewasslightlybelowtheminimumoftheoperating band.TheROincreased theautomatic regulator torestorethegenerator outputvoltagetothebottomoftheoperating band.Fortheremaining periodpriortothetripsequence, thevolt-amps

reactive, generator fieldtemperature, andtoalesserdegreethegenerator outputvoltageindication showedunstablebehavior.

Noalarmsoccurreduntilsecondsbeforethetripsequence.

Following thetripsequence[openingofthereactortripbreakers(EIIS/JE-BKR),

insertion ofthereactorcontrolrods(EIIS/AA-ROD),

feedwater isolation (EIIS/JB),

automatic startingofthemotor-drivenandturbine-driven auxiliary feedwater pumps(EIIS/BA-P)]

operations personnel immediately implemented thespecialEmergency Operating Procedure, 1OHP-4023.E-O, toverifyproperresponseoftheautomatic protection system(EIIS/JC) andtoassessplantconditions forinitiating appropriate recoveryactions.Therewasnoautomatic ormanualactuation oftheintermediate headsafetyinjection system(EIIS/BQ)

.NACFOAM366A(84)3)oU.S.GPO:1988 0.824538/455

NRCForm366A(94)31LICENSEEETREPORT(LER)TEXTCONTINUAU.S.NUCLEARREGULATORY COMMISSION APPROVEDOMBNO.3150&104EXPIRES:8/31/88FACILITYNAME(I)DOCKETNUMBER(2)YEARLERNUMBER(6)WSEOUENTIAL NUMEERNUMBERPAGE(3)D.C.CookNuclearPlant,Unit20s00031687TEXT/SmoteEPooo)rnrqrr)or/,

rroo/Ar/orro/HRC Forrrr35549/(IT)-007-003oF05Thevoltagetransient wasalsodetectedbytheT21Dsafeguards bus(train"A")undervoltage relays(EIIS/EA-27) whichstartedtheCDemergency dieselgenerator (EIIS/EK-DG) andinitiated loadsheddingofthe"A"trainsafeguards busses.TheRB"trainbusseswereapproximately 70to100voltshigherthanthe"A"trainbussesimmediately priortothetrip-consequently theloadsheddingactuation logicforthe"BRtrainwasnotsatisfied, andtheABemergency dieselgenerator didnot,automatically start.TheEastcentrifugal chargingpump(EIIS/CB-P) hadbeenoperating andwasnotrestoredduringblackoutloadsequencing (asperdesign).Operators manuallystartedtheWestcentrifugal chargingpumptorestorereactorcoolantpumpsealinjection (EIIS/CB) andopenedIM0-911,chargingpumpsuctionfromtherefueling waterstoragetank(EIIS/CB-TK),

torestorepressurizer levelandtocleartheletdownisolation (whichoccurred, asdesigned, duetothelossoftheEastcentrifugal chargingpump).Theloadshedalsode-energized thelightingtransformers (EIIS/FF-XFMR),

isolating plantlightingandoutlets(EIIS/FF-OUT).

Otherlightingtransformer loadslostincluded; theanalogrodpositionindication (EIIS/AA-XF) andtherodbottomlights(EIIS/AA-IL),

chartdrivesforthenarrowrangeandwiderangereactorcoolanttemperature recorder(EIIS/JC-TR),

maingenerator megawattrecorderchartdrive(EIIS/EL-XR),

normalcontrolroomlighting(EIIS/FF)E andtheABemergency dieselgenerator recorderchartdrive(EIIS/EK-XR).

Theloadsheddingsequenceexperienced wasinaccordance withundervoltage protection system(EIIS/EA)design.

Powerwasmanuallly restoredtothelightingtransformers within30minutes.TheABemergency dieselgenerator wasmanuallystarted45secondsafterthetrip,butwasneverloaded.Bothemergency dieselsweresecuredafteroffsitepowerwasestablished tothe"A"trainsafeguards busses.TheUnitwasstabilized inMode3(hotstandby)atapproximately 0755hours,July14,1987.TheNRCwasnotifiedoftheeventviatheENSat0815hours,July14,1987.Withtheexception ofthefailureofthemaingenerator voltagecontrolsystem,therewerenoinoperative structures, components, orsystemsthatcontributed tothisevent.CauseofEventThecauseoftheeventwasdetermined tobethefailureofthemaingenerator automatic voltageregulator powersupplyconcurrent withthefailureofthemanualvoltageregulator powersupply.Post-event testingofvoltagecontrolsystemcomponents revealedsixfailedSCRmodules,inadditiontothetwofailedpowersupplies(automatic and.manual).Intermittent failuresofthemaingenerator automatic voltageregulator pulseamplifier andpulsedrivercircuitboardsaretheprobablecauseoftheSCRmodulefailures.

NRCFORM366A(94)3)*U.S.GPO:1986-0.824 538/455 NRCForm3BBA(94)3)LICENSEEETREPORT(LER)TEXTCONTINUAT JU.S.NUCLEARREGULATORY COMMISSION APPROVEOOMBNO.3150-0104 EXPIRES:8/31/88FACILITYNAME(1)DOCKETNUMBER(2)LERNUMBER(8)SEQUENTIAL NUMBERREVISIONNUMBERPAGE(3)D.C.CookNuclearPlant,Unit2TEXT//Fmoro<<>>oo/4Er)U)or/,

I>>o////or>>/NRC

%%drm3654'4/(17)050003180070004"05AnalsisofEventThisEngineered SafetyFeaturesActuation, whichresultedinareactortripsequence, isreportable pursuant.

to10CFR50.73(a)(2)(iv).TheOperations SequenceMonitorfunctioned asdesigned.

Atimestudyofparameters monitored concluded thatallautomatic protection systemresponses; reactortrip,andresulting actuations, functioned properlyasaresultoftheEngineered SafetyFeaturesactuation.

Basedontheabove,itisconcluded thattheeventdidnotconstitute anunreviewed safetyquestionasdefinedin10CFR50.59(a)(2),nordiditadversely impacthealthandsafety.Corrective ActionsImmediate corrective actioninvolvedoperations personnel implementing plantprocedures toverifyproperresponseoftheautomatic protection systemandtoassessplantconditions forinitiating appropriate recoveryactions.Allfailed/suspected components werereplaced(automatic andmanualvoltageregulator powersupplies, sixSCRmodules,twopulsegenerator circuitboardsandtwopulseamplifier circuit.boards).Investigation regarding industryexperience withBrownboverivoltagecontrolsystemsindicates thatthefailureswhichoccurredareconsistent withthoseexperienced atotherplantsandisnot.theresultofoperatorerrororlackofmaintenance.

Evaluation astothenecessity fortheredesignofthevoltagecontrolsystem,viathePlantModification program,continues

-however,nospecificpreventive measureshavebeenidentified todate.NRCFORMSSEA(94)3)rrU.S.GPO;198B 0-B24538/455 NRCForm3BSA(843)LICENSEETREPORT(LER)TEXTCONTINUAU.S.NUCLEARREGULATORY COMMISSION APPROVEOOM8NO.3150-0I04 EXPIRES:8/31/88FACILITYNAMEll)DOCKETNUMBER(2)YEARLFRNUMBER(8)SEOUENTIAL NUMBER'.RSREVISIONNUMBERPAGE(3)D.C.CookNuclearPlant,Unit2TExT///'oroBPoco/Br/v/rorEIrroo//I/mr/NRc%%drrrr3()343/lIT)050003]870070005OF05FailedComonentIdentification PlantDescription:

Manufacturer:

Manufacturer IDNumber:EIISCode:Numberreplaced:

MainGenerator VoltageRegulator PowerSuppliesBrownBoveriVRCE1R39287116 AR103963R1 ND-'501BEL-UJX2PlantDescription:

Manufacturer:

Manufacturer IDnumber:EIISCode:NumberReplaced:

MainGenerator VoltageRegulator SCR(Thyristor Insert)ModuleBrownBoveri07060GR90075/4 GR0053P1EL-SCR6PlantDescription:

Manufacturer:

Manufacturer IDNumber:EIISCode:NumberReplaced:

MainGenerator VoltageRegulator PulseGenerator CircuitBoardBrownBoveriGT032ALGV455007P13 EL-772PlantDescription:

Manufacturer:

Manufacturer IDNumber:EIISCode:NumberReplaced:

MainGenerator VoltageRegulator PulseAmplifier CircuitBoardBrownBoveri07102A139046615RUT/RU10LGV455011P EL-AMP2PreviousSimilarEventsNoneNRCFORMSBBA(()43)*U.S.GPO.10854 524538/455

~eileenDIAMICNIGANEIECTDICCDAIEANYDonaldC.CookNuclearPlantP.O.8ox456,8ridgman, Michigan49166August13,1987UnitedStatesNuclearRegulatory Commission DocumentControlDeskWashington, D.C.20555Operating LicenseDPR-74DocketNo.50-316Document.

ControlManager:Inaccordance withthecriteriaestablished by10CFR50.73entitledLicenseeEventReortinSstem,thefollowing reportisbeingsubmitted:

87-007-00 Sincerely, W.G.Smith,Jr.PlantManager/afhAttachment cc:JohnE.DolanA.B.Davis,RegionIIIM.P.AlexichR.F.KroegerH.B.BruggerR.W.Jurgensen NRCResidentInspector R.C.CallenG.Charnoff, Esq.D.HahnINPOD.Wigginton, NRCPNSRCA.A.BlindDottieSherman,ANILibraryJ.G.Feinstein/B.

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