ML17249A911

Forwards Response to IE Bulletin 80-04. Analysis of PWR Main Steam Line Break W/Continued Feedwater Addition. Auxiliary Feedwater Flow Becomes Dominant Factor in Determining Duration & Magnitude of Steam Flow Transient

ML17249A911
Person / Time
Site:	Ginna, Sterling
Issue date:	04/30/1980
From:	WHITE L D ROCHESTER GAS & ELECTRIC CORP.
To:	GRIER B H NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
References
IEB-80-04, IEB-80-4, NUDOCS 8005210684
Download: ML17249A911 (16)

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I/ix/'Qllj~gslÃl/I~Jlili$1illliiI!1<rlivi<piivlROCHESTERGASANDELECTRICCORPORATIONrl~~Oos~Oo89EASTAVENUE,ROCHESTER,N.Y.L4649LEONO.iVHITE,JR.VICCPRCSIDCNTTCLCPHOVCiPCiCOOCria546-2700April30,1980Mr.BoyceH.Grier,DirectorU.S.NuclearRegulatoryCommissionOfficeofInspectionandEnforcementRegionI651ParkAvenueKingofPrussia,Pennsylvania19406

Subject:

ResponsetoIEBulletinNo.'80-04o

DearMr.Grier.:

EnclosedisourresponsetoIEBulletinNo.80-04.ThisbulletinwasreceivedonFebruary8,1980.Sincerely,XC:OfficeofInspectionandEnforcementDivisionofReactorOperationsInspectionU.S.NuclearRegulatoryCommissionWashington,D.C.20555

ResonsetoIEBulletin80-04Request1.IResponse1.Reviewthecontainmentpressureresponseanalysistodetermineifthepotentialforcontainmentoverpressureforamainsteamlinebreakinsidecontainmentincludedtheimpactofrunoutflowfromtheauxiliaryfeedwatersystemandtheimpactofotherenergysources,suchascontinuationoffeedwaterorcondensateflow.Inyourreview,consider.yourabilitytodetectandisolatethedamagedsteamgeneratorfromthesesourcesandtheabilityofthepumpstoremainoperableafterextendedoperationat,runoutflow.AlthoughtheGinnapost-steamlinebreakcontainmentpressureanalysisintheFSARdidnotincludetheeffectsofauxiliaryfeedwaterflowtotheaffectedsteamgenerator,itisimportanttorecognizethattheevaluationalsodidnotincludethebenefitsofpassiveandactiveheatsinksinsidecontainment.Continuedfeedwater/condensateadditiontothesteamgeneratorwillnotoccur,since,thesafetyinjectionsignal(generatedbyavarietyofprocessparameters,includinghighsteamlineflow,highcontainmentpressure,andlowpressurizerpressure)willclosethefeedwatercontrolvalvesandstopthefeedwaterpumps.Theadditionofmaximumauxiliaryfeedwaterflowtothebrokensteamgeneratorwilleventuallyrequireoperatoractionto1)realignflowtotheintactgenerator,2)terminateauxiliaryfeedwaterflowtothebrokengenerators.Positiveinformationisavailabletotheoperatortodeterminewhichistheaffectedsteamgenerator.Steamgeneratorlevelinstrumentationislocatedinsidecontainmentandsteamgeneratorpressureislocatedoutsidecontain-mentwhereit.wouldnotbeaffectedbytheaccidentenvironment,insidecontainment.Itisexpectedthat,throughpropertrainingandbyuseoftheemergencyprocedures,theoperatorswillbecapableofquicklyrecognizingthesteamlinebreak,andwillperformtheproperoperations.Thereissubstantialtimeavailablefortheoperatortoperformthetwosafetyfunctionsnotedabove.TheSEPSafeShutdownreviewconcludedfollowingtheirsitevisitinJune1978thatonesteamgeneratorwouldnotboildryforoverthirtyminutes.Thusthereissubstantialtimetoalignflowtotheintactsteamgenerator.Theterminationofauxiliaryfeedwaterflowtotheaffectedsteamgenerator,underthepessimisticcircumstances,wouldrequiremorerapidaction(butstilleasilywithinthecapabilityoftheoperators)tomaintaincontainment

pressurebelowdesignpressure.TheanalysispresentedinAttachment1concludesthat,assumingminimumsafeguardsfor.containmentcooling,auxiliaryfeedwaterflowwouldhavetobeterminatedinabout26minutes.Withmaximumsafeguards,thistimewouldbeextendedtoabout44minutes.Thereisnoneedtoconsidertheoperationoftheauxiliaryfeedwaterpumpsatrunoutflow.Theturbine-drivenpumpsarecontrolledbya'overnor,andwillnot,exceedabout400gpm.ThemotordrivenpumpflowiscontrolledbytheAFWcontrolvalves,whichreceiveanautomaticthrottlesignalto200gpmfromtheirflowcontrollers.Apotentialsinglefailureoftheflowcontrollertocontrol.flowto200gpmisnotconsideredaworst-casesinglefailureintermsofnetenergyadditiontothecontainment,sincetheoperationofallcontainmentcoolingsafeguards(vs.theminimumsafeguardsassumedinthisevaluation)wouldresultinasubstantialincreaseinenergyremovalfromcontainment.Request2.Reviewyouranalysisofthereactivityincreasewhichresultsfromamainsteamlinebreakinsideor"outsidecontainment.Thisreviewshouldconsiderthereactorcooldownrateandthepotentialforthereactortoreturntopowerwiththemostreactivecontrolrodinthefullywithdrawnposition.Ifyourpreviousanalysisdidnotconsiderallpotentialwatersources(suchasthoselistedin1above)andifthereactivityincreaseisgreaterthanpreviousanalysisindicatedthereportofth'isreviewshouldinclude:aITheboundaryconditionsfortheanalysis,e.g.,theendoflifeshutdownmargin,themoderatortemperaturecoefficient,powerlevelandtheneteffectoftheassociatedsteamgeneratorwaterinventoryonthereactorsystemcooling,etc.,b.Themostrestrictivesingleactivefailureinthesafetyinjectionsystemandtheeffectofthatfailureondelayingthedeliveryofhighconcentrationboricacidsolutiontothereactorcoolantsystem,cTheeffectofextendedwatersupplytotheaffectedsteamgeneratoronthecorecriticalityandreturntopower,

d.Thehotchannelfactorscorrespondingtothemostreactiverodinthefullywithdrawn'ositionattheendoflife,andtheMinimumDeparturefromNucleateBoilingRatio(MDNBR)valuesfortheanalyzedtransient.Response2.WestinghouseElectricCorporationperformedtheoriginalsteambreakanalysisforGinnaasreportedintheFSARandareanalysissubmittedtotheNRCinSeptember1975.Westinghousehasreviewedtheassumptionsmadeformainandauxiliaryfeedwaterflowastheyapplytolicensingbasissteamlinebreaktransients.Severaloftherelevantassumptionsusedinallcoretransientanalysesfollow,andarefurtherexplainedintheGinnaFSAR.1.Thereactorisassumedinitiallytobeathotshutdownconditions,attheminimumallowableshutdownmargin.2.FortheConditionIVbreaks,i.e.,double-endedruptureofamainsteampipe,fullmainfeedwaterisassumedfromthebeginningofthetransientataveryconservativecoldtemperature.3.Allauxiliaryfeedwaterpumpsareinitiallyassumedtobeoperating,inadditiontothemainfeedwater.Theflowisequivalenttotheratedflowofallpumpsatthesteamgeneratordesignpressure.4Feedwaterisassumedtocontinueatitsinitialflowrateuntilfeedwaterisolationiscomplete,approximately10secondsafterthebreakoccurs,whileauxiliaryfeedwaterisassumedtocontinueatitsinitialflow'rate.5.Mainfeedwaterflowiscompletelyterminatedfollowingfeedwaterisolation.Basedonthemannerinwhichtheanalysisisperformed~forWestinghouseplants,thecoretransientresultsareveryinsensitivetoauxiliaryfeedwaterflow.Thefirstminuteofthetransientisdominatedentirelybythesteamflowcontributiontoprimary-secondaryheattransfer,whichistheforcingfunctionforboththereactivityandthermal-hydraulictransientsinthecore.Theeffectofauxiliaryfeedwaterrunout(orfailureofrunoutprotectionwhereapplicable)isminimal.Greaterfeedwaterflowduringthelargesteamlinebreaksservestoreducesecondarypressures,acceleratingtheautomaticsafeguardsactions,i.e.steamlineisolation,feedwaterisolationandsafetyinjection.Theassumptionsdescribedaboveare

thereforeappropriateandconservativefortheshort-termaspectofthesteamlinebreaktransient.Theauxiliaryfeedwaterflowbecomesa-dominantfactorindeterminingthedurationand,magnitudeofthesteamflowtransient'uringlaterstagesinthetransient.However,thelimitingportionofthetransientoccursduringthefirstminute,bothduetohighersteamflowsinherentlypresentearlyinthetransientandduetotheintroductionofborontothecoreviathesafetyinjectionsystem.Inconclusion,Westinghousehasevaluatedtheeffectofrunoutauxiliaryfeedwaterflowsinthecoretransientforsteamlinebreak,andbasedonthisevaluation,hasdeterminedthattheassumptionspresentlymadeareappropriateforuseasalicensingbasis.TheconcernsoutlinedintheintroductiontoIEBulletin80-04relativeto,1)limitingcoreconditionsoccurringduringportionsofthetransientwhereauxiliaryfeedwaterflowisarelevantcontributortoplantcooldown;and2)incompleteisolationofmainfeedwaterflow,arenotrepresentativeoftheWestinghouseNSSSdesignsandassociatedBalanceofPlantrequirements.ThemostlimitingsteamlinebreakdeterminedbyWestinghousewasanalyzedbyExxonNuclearCo.,Inc.andpresentedinXN-NF-77-40Supplement1,"PlantTransientAnalysisfortheR.E.GinnaUnit1NuclearPowerPlant,"March1980.Thistransientoccursathotzeropowerwithoutsidepoweravailableandthebreakoccurringattheexitofthesteamgenerator.TheExxonanalysisdoesnotspecificallyaccountforauxiliaryfeedwater.However,theSteamGeneratorheat.transfermodel,usingconstantheattransfercoefficients,co'ntinuestocalculateheattransferfromtheprimarytothesecondarysideafterthebrokensteamgeneratorhasbeenestimatedtobeempty.Ifauxiliaryflowwasspecificallyaccountedfor,itseffectwouldbenegligibleduringtheinitialportionofthetransientandwouldhaveminimaleffectduringlaterportionsofthetransientsincebythetimethebrokensteamgeneratorempties,thetotalsystemreactivityisnegativeandcorepowerisdecreasing.Theadditionalreactivityadditionassociatedwiththeslightcooldownduetorunoutflowismorethannegatedbytheboronreactivityinsertedbysafetyinjection.Therefore,theseverityofthetransientisnotincreased.

Request3.Ifthepotentialforcontainmentoverpressureexists:orthereactor-return-to-powerresponseworsens,provideaproposedcorrectiveaction.Iftheunitisoperating,provideadescriptionofanyinterimactionthatwillbetakenuntiltheproposedcorrectiveactioniscompleted.Response3.Sinceneitherthepotentialforcontainmentover-pressurizationnorthereactor-return-to-powerresponseworsensnocorrectiveactionisrequired.Request4.Within90daysofthedateofthisBulletin,completethereviewandevaluationrequiredbythisBulletinandprovideawrittenresponsedescribingyourreviewsandactionstakeninresponsetoeachitem.Response4.Thisattachmentprovidestherequired90dayresponsetoIEBulletinNo.80-04.

Attachment1'-ContainmentEnerBalanceThepurposeofthisevaluationistodeterminethelengthoftimeavailabletotheoperatortoterminate'AFWflowtothebrokensteamgeneratorfollowingasteamlinebreakinsidecontainment,.priortocontainmentpressureexceeding60psig.InitialConditionsandAssumtionsa.,ZOCAenergyreleasetocontainment(includescreditforcontainmentheatsinks):191.3x10BTU(takenfromTable'14.3.4-2ofFSAR).Resultsinpeakcontainmentpressureof53psig.b.Additionalenergytoreach60psig:16x10BTU(takenfromFig.14.3.4-3ofFSAR).C.Minimumsafeguardsheatremovalcapability(1spraypumpand2fancoolers)=55x10BTU/sec=3.3x106BTU/min.(takenfromFig.14.3.4-9of'theFSAR).d.Energyinputfrom600gpmtothebrokensteamIgenerator=600galx1180BTUmanibmx62.6~lbx1ft=5.91x10B'fU6ft7.68galmz.ne.Energyreleasedtocontainmentfromtheinitialsteamlinebreakaccidentblowdown=140x10BTU(takenfromFig.14.2.5-10oftheFSAR).

Calculationsl.Additionalenergywhichcouldbeabsorbedbycontainment,takingcreditforpassiveandminimumactivecontainment,heatsinksfollowingasteamlinebreak.(froma+b-2.eabove).(191.3+16)x10BTU-140x10BTU=67.3NBTU66Netenergyadditiontocontainmentfollowinginitialsteamlinebreakblowdown(fromd-cabove):(5.91x10BTU-3.3x10BTU)=2.61x10BTU666manmz.nmz.n3.OperatorActionTime=67.3NBTU2.61NBTU/man f"lg