ML18037A130

Summarizes Util Evaluations & Corrective Actions Re 910813 Declaration of Site Area Emergency Due to Loss of Control Room Annunciators W/Plant Transient,Per 910815 Confirmatory Action Ltr.Ups Logic Power Supply Modified

ML18037A130
Person / Time
Site:	Nine Mile Point
Issue date:	09/10/1991
From:	SYLVIA B R NIAGARA MOHAWK POWER CORP.
To:	MARTIN T T NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
References
CON-IIT07-603-91, CON-IIT7-603-91, CON-IIT7-603-92 CAL, NMP2L-1314, NUREG-1455, NUDOCS 9109160243
Download: ML18037A130 (6)

Text

~NIAGARA0MOHWfKNIAQAAAMOHAWKPOWKACOAPOAATlOM>"i1~'i4i'"'CAO.=.'~AC'=.4KA'"<i."=;<-'i'R".,>>'ic.>>'~Q7t>~IMr,ThomasT.MartinRegionalAdministrator,RegionIU.S.NuclearRegulatoryCommission475AllendaleRoadKingoiPrussia,PA19406Re:NineHilePointUnit2DocketNo.50-410NPF<<69

DearHr.Hartin:

OnAugust13,1991>NiagaraHohavkPaverCorporation'sNineMilePointUnit2NuclearStationdeclaredaSiteAreaEmergencyduetolossofcontrolroomannunciatorsvithaplanttransient.Thelossofcontrolroomannunciatorsresultedfromalossoffiven'on-safetyrelatedUninterruptiblePoverSupplies(UPS's)whenthe8phasemainstep-uptransformerfailed.?owervasrestoredtotheannunciatorswithin34minutesandasafeshutdownoitheNineMilePointUnit2reactorvasachieved,coldshutdownvasreachedafterapproximately14hours.Inresponsetothisevent,theNuclearRegulatoryCommissionissuedaConfirmatoryActionLetteronAugust13,1991dispatchinganAugmentedInspectionTeam(AIT).ThislettervassupersededbyaConfirmatoryActionLetterdatedAugust15,1991.TheNRCalsoupgradedtheinvestigationbyforminganIncidentInvestigationTeam(IXT).NiagaraMohawkcooperatedfullyviththeAITandtheIITandfollovedtheactionsoutlinedintheAugust,15,1991lettertosupporttheIITinvestigation.OnAugust30,1991youprovidedplanstoconductaspecialteaminspectiontosupportanNRCrestartdecision.ThisinspectionbeganonSeptember3,1991.ThislettersummarizesNiagaraMohavk'sevaluationsandcorrectiveactionsthathavebeentakensuchthatsaferestartandcontinuedsafeoperationoftheNineHiltPointUnit2NuclearStationvillbeassured.NiagaraMohawkimmediatelyestablishedanActionPlanandaRecoveryOrganizationreportingtotheExecutiveVicePresident,NuclearpriortotheendoftheSitebreaEmergency.TheRecoveryPlanconsistedofspecificproblemassessmentsintheareasofplantresponse,operatorresponse>emergencypreparedness<safetyandequipmentfailureanalysis>vhichincludedtheUninterruptiblePowerSupplies,maintransformersandtheelectrical

~~~Wai~~$gv~~~Ehftheassessmentreportsvererevieedby'e'theSitedistributionsystem,acoOperationsReviewCommittee,iaaraMohawkmet'-ithyouandyourstaff:oprovidea'3tYiiltionintotheAugustt.xeZrovidedanovervievoftheUPScircuitry,t..eneeprovheonoinassessmentoftheevent..re-starreareonessitemsoutagerestartassessmentitems,pre-startupemergencypreparednessiems,ationsfromtheSafetyAssessment;eresnitemsalongvithrecommendationrom'h'sutonvalvshavebeenhesecificre-startupassessmenttemsavdhiatedwiththeteeawatercorrectedandthelessonslearnednodhavebeenappxetos'scram.TheRCICflovcontrollermalfunctonchanehasalsobeenmadetoproitclosfeedvatersuctionvalvesaftersa.ehasbeenaddressedbycheckingthecoSomeairvasfoundintheflovtransmitterandremove..sacontributedtotheflovoscillationproblem.Thesystemvduringstartupatdifferentreactorpressures,asessmentcontainedasummaryvhichoutlineothesequencehPantspoeassessmenofeventsassociatedwiththe'aluatplantaniecosiandthatatotimeduringthevi'thintheboundsofcurrenttransientanalysisantateventwastheplantinanunsafecondition.onseandactionsduringandimmediatelyAnassessmentofOperatorResponseanaoliogteSaEmergyencfoundoperatoranstaapproprateteandcommendable.Operatortrainingvaseecoperatorsforeventsofthisnature.PrearednessactivitiesconcludedthattheheasentotheEmergencypnrocedures.Allpre-startupcorrectiveactionsheSiteAreaEmergencyvastimeyanvarAssmentreportprovidedtotheNRCidentifiedintheEmergencyPreparednessAssessmentreonAuust28,1991,arecomplete.8srearedtoprovideasafetyrevievoftheSiteAreaais.TheSafetyAsessmentoniuddthatyg-gatnotimeduringthiseventvavaathereanyreleaseoraoadThiSafetyAssessmentalsovasthehealthandsafetyofthepublicaffecte.stdesinimprovements.providedrecommendationsforpoststartupplantesgnmpilureAnalysis,separateassessmentreportsvorelectricaldistributionsystemandtfhkholddtht'B"hite-t.sformer.Thefhiitiotodtintransformer1betrasportedoffsiteforurterntherootcauseofthefault.Theelectricalstrhosactuatedandperformedtheirconcluetaddhttheprotectiverelayingschemosactuaintendedfunctiontoisolatethetransformerfault.

1V~I~~~~cornletedarootcauseeva~uationofthelossofthefivepiblPrSuppliesandtheirfailuretosafetyre~atedUnintperruptePowerausemtiwithDr.ThornsMyofthintenance{alternate1eNRConhtingNiagaraMohawkhasconcludedSeptembe4,1991.Aserthesimultaneoustripp'ppingoftheUPS'sisimpropethattherootcausefortatearutiblePowerSuppliesverenl'otdesigned-:oaccommoda1Cesgn..heuneph1o1hcircuitdoesnotactuateuntiAso,as11hiversupplysvitchingcircus'llusethelogictotrap.Aso,adithbd'hthearesultoidiscussionswiththeUPSvenor,inedtomitigateadegradedvoltagelogicbackupbatteriesverenotdesignetomcondition.41991meeting,NiagaraMohavkvkhastakenAdiscussedintheSeptemberstoreventrecurrenceofasimilarcommonmode'eTeUPSlogicpowersuppyrrectiveactionsnecessaryp1hasbeenmodifiedtomakhppou.nverteraneeliminatesthevulnerabityo1oiooftheUPS's.totransientsontheACsystemduringnormasassessedallerltotheSiteAreaEmergency,hasassekhithiseventandhastaenIeah1d11oeration.eavecactionsforcontinuedsafepdviththenormaiftionprovidedtotheNRCtartstarh'theEncidentinvestgatedioiddtoM.S,Vi1ttlddhNiHilPoiU'September10,1991NiagaraMohavkhasconcue8NuclearStationisreadyforrestart.Verytrulyyours,Exec.VicePresident-NuclearffiofNuclearReactorRegulationxc:Dr.T.E.Murley>Director,0ceoMr.R.A.CapraiFxo)ectDirector,NRRBinkman,SeniorProspectManager,NRREeh,RtorPro)ectsSectionNo.Eeh3.,Director,eacactorPro)ectsSectionHo.18M.D.R.Haverkamp,Chief,Reactorror~s~1Chief,ReactorOperationsaMr.J.E.Rosentha,DivisionoaeyDocumentControlDeskRecordsManagementBRS/NAS/krc001740GG