ML17249A911

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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  Constellation icon.png
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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~Jlili$1illliiI!1<rlivi<piivl ROCHESTER GASANDELECTRICCORPORATION rl~~Oos~Oo89EASTAVENUE,ROCHESTER, N.Y.L4649LEONO.iVHITE,JR.VICCPRCSIDCNT TCLCPHOVC iPCiCOOCria546-2700April30,1980Mr.BoyceH.Grier,DirectorU.S.NuclearRegulatory Commission OfficeofInspection andEnforcement RegionI651ParkAvenueKingofPrussia,Pennsylvania 19406

Subject:

ResponsetoIEBulletinNo.'80-04o

DearMr.Grier.:

EnclosedisourresponsetoIEBulletinNo.80-04.ThisbulletinwasreceivedonFebruary8,1980.Sincerely, XC:OfficeofInspection andEnforcement DivisionofReactorOperations Inspection U.S.NuclearRegulatory Commission Washington, D.C.20555

ResonsetoIEBulletin80-04Request1.IResponse1.Reviewthecontainment pressureresponseanalysistodetermine ifthepotential forcontainment overpressure foramainsteamlinebreakinsidecontainment includedtheimpactofrunoutflowfromtheauxiliary feedwater systemandtheimpactofotherenergysources,suchascontinuation offeedwater orcondensate flow.Inyourreview,consider.

yourabilitytodetectandisolatethedamagedsteamgenerator fromthesesourcesandtheabilityofthepumpstoremainoperableafterextendedoperation at,runoutflow.AlthoughtheGinnapost-steamline breakcontainment pressureanalysisintheFSARdidnotincludetheeffectsofauxiliary feedwater flowtotheaffectedsteamgenerator, itisimportant torecognize thattheevaluation alsodidnotincludethebenefitsofpassiveandactiveheatsinksinsidecontainment.

Continued feedwater/condensate additiontothesteamgenerator willnotoccur,since,thesafetyinjection signal(generated byavarietyofprocessparameters, including highsteamlineflow,highcontainment

pressure, andlowpressurizer pressure) willclosethefeedwater controlvalvesandstopthefeedwater pumps.Theadditionofmaximumauxiliary feedwater flowtothebrokensteamgenerator willeventually requireoperatoractionto1)realignflowtotheintactgenerator, 2)terminate auxiliary feedwater flowtothebrokengenerators.

Positiveinformation isavailable totheoperatortodetermine whichistheaffectedsteamgenerator.

Steamgenerator levelinstrumentation islocatedinsidecontainment andsteamgenerator pressureislocatedoutsidecontain-mentwhereit.wouldnotbeaffectedbytheaccidentenvironment, insidecontainment.

Itisexpectedthat,throughpropertrainingandbyuseoftheemergency procedures, theoperators willbecapableofquicklyrecognizing thesteamlinebreak,andwillperformtheproperoperations.

Thereissubstantial timeavailable fortheoperatortoperformthetwosafetyfunctions notedabove.TheSEPSafeShutdownreviewconcluded following theirsitevisitinJune1978thatonesteamgenerator wouldnotboildryforoverthirtyminutes.Thusthereissubstantial timetoalignflowtotheintactsteamgenerator.

Thetermination ofauxiliary feedwater flowtotheaffectedsteamgenerator, underthepessimistic circumstances, wouldrequiremorerapidaction(butstilleasilywithinthecapability oftheoperators) tomaintaincontainment

pressurebelowdesignpressure.

Theanalysispresented inAttachment 1concludes that,assumingminimumsafeguards for.containment cooling,auxiliary feedwater flowwouldhavetobeterminated inabout26minutes.Withmaximumsafeguards, thistimewouldbeextendedtoabout44minutes.Thereisnoneedtoconsidertheoperation oftheauxiliary feedwater pumpsatrunoutflow.Theturbine-driven pumpsarecontrolled bya'overnor, andwillnot,exceedabout400gpm.Themotordrivenpumpflowiscontrolled bytheAFWcontrolvalves,whichreceiveanautomatic throttlesignalto200gpmfromtheirflowcontrollers.

Apotential singlefailureoftheflowcontroller tocontrol.flowto200gpmisnotconsidered aworst-case singlefailureintermsofnetenergyadditiontothecontainment, sincetheoperation ofallcontainment coolingsafeguards (vs.theminimumsafeguards assumedinthisevaluation) wouldresultinasubstantial increaseinenergyremovalfromcontainment.

Request2.Reviewyouranalysisofthereactivity increasewhichresultsfromamainsteamlinebreakinsideor"outsidecontainment.

Thisreviewshouldconsiderthereactorcooldownrateandthepotential forthereactortoreturntopowerwiththemostreactivecontrolrodinthefullywithdrawn position.

Ifyourpreviousanalysisdidnotconsiderallpotential watersources(suchasthoselistedin1above)andifthereactivity increaseisgreaterthanpreviousanalysisindicated thereportofth'isreviewshouldinclude:aITheboundaryconditions fortheanalysis, e.g.,theendoflifeshutdownmargin,themoderator temperature coefficient, powerlevelandtheneteffectoftheassociated steamgenerator waterinventory onthereactorsystemcooling,etc.,b.Themostrestrictive singleactivefailureinthesafetyinjection systemandtheeffectofthatfailureondelayingthedeliveryofhighconcentration boricacidsolutiontothereactorcoolantsystem,cTheeffectofextendedwatersupplytotheaffectedsteamgenerator onthecorecriticality andreturntopower,

d.Thehotchannelfactorscorresponding tothemostreactiverodinthefullywithdrawn'osition attheendoflife,andtheMinimumDeparture fromNucleateBoilingRatio(MDNBR)valuesfortheanalyzedtransient.

Response2.Westinghouse ElectricCorporation performed theoriginalsteambreakanalysisforGinnaasreportedintheFSARandareanalysis submitted totheNRCinSeptember 1975.Westinghouse hasreviewedtheassumptions madeformainandauxiliary feedwater flowastheyapplytolicensing basissteamlinebreaktransients.

Severaloftherelevantassumptions usedinallcoretransient analysesfollow,andarefurtherexplained intheGinnaFSAR.1.Thereactorisassumedinitially tobeathotshutdownconditions, attheminimumallowable shutdownmargin.2.FortheCondition IVbreaks,i.e.,double-ended ruptureofamainsteampipe,fullmainfeedwater isassumedfromthebeginning ofthetransient ataveryconservative coldtemperature.

3.Allauxiliary feedwater pumpsareinitially assumedtobeoperating, inadditiontothemainfeedwater.

Theflowisequivalent totheratedflowofallpumpsatthesteamgenerator designpressure.

4Feedwater isassumedtocontinueatitsinitialflowrateuntilfeedwater isolation iscomplete, approximately 10secondsafterthebreakoccurs,whileauxiliary feedwater isassumedtocontinueatitsinitialflow'rate.5.Mainfeedwater flowiscompletely terminated following feedwater isolation.

Basedonthemannerinwhichtheanalysisisperformed

~forWestinghouse plants,thecoretransient resultsareveryinsensitive toauxiliary feedwater flow.Thefirstminuteofthetransient isdominated entirelybythesteamflowcontribution toprimary-secondary heattransfer, whichistheforcingfunctionforboththereactivity andthermal-hydraulic transients inthecore.Theeffectofauxiliary feedwater runout(orfailureofrunoutprotection whereapplicable) isminimal.Greaterfeedwater flowduringthelargesteamline breaksservestoreducesecondary pressures, accelerating theautomatic safeguards actions,i.e.steamline isolation, feedwater isolation andsafetyinjection.

Theassumptions described aboveare

therefore appropriate andconservative fortheshort-term aspectofthesteamline breaktransient.

Theauxiliary feedwater flowbecomesa-dominant factorindetermining thedurationand,magnitude ofthesteamflowtransient'uring laterstagesinthetransient.

However,thelimitingportionofthetransient occursduringthefirstminute,bothduetohighersteamflowsinherently presentearlyinthetransient andduetotheintroduction ofborontothecoreviathesafetyinjection system.Inconclusion, Westinghouse hasevaluated theeffectofrunoutauxiliary feedwater flowsinthecoretransient forsteamline break,andbasedonthisevaluation, hasdetermined thattheassumptions presently madeareappropriate foruseasalicensing basis.Theconcernsoutlinedintheintroduction toIEBulletin80-04relativeto,1)limitingcoreconditions occurring duringportionsofthetransient whereauxiliary feedwater flowisarelevantcontributor toplantcooldown; and2)incomplete isolation ofmainfeedwater flow,arenotrepresentative oftheWestinghouse NSSSdesignsandassociated BalanceofPlantrequirements.

Themostlimitingsteamlinebreakdetermined byWestinghouse wasanalyzedbyExxonNuclearCo.,Inc.andpresented inXN-NF-77-40 Supplement 1,"PlantTransient AnalysisfortheR.E.GinnaUnit1NuclearPowerPlant,"March1980.Thistransient occursathotzeropowerwithoutsidepoweravailable andthebreakoccurring attheexitofthesteamgenerator.

TheExxonanalysisdoesnotspecifically accountforauxiliary feedwater.

However,theSteamGenerator heat.transfermodel,usingconstantheattransfercoefficients, co'ntinues tocalculate heattransferfromtheprimarytothesecondary sideafterthebrokensteamgenerator hasbeenestimated tobeempty.Ifauxiliary flowwasspecifically accounted for,itseffectwouldbenegligible duringtheinitialportionofthetransient andwouldhaveminimaleffectduringlaterportionsofthetransient sincebythetimethebrokensteamgenerator empties,thetotalsystemreactivity isnegativeandcorepowerisdecreasing.

Theadditional reactivity additionassociated withtheslightcooldownduetorunoutflowismorethannegatedbytheboronreactivity insertedbysafetyinjection.

Therefore, theseverityofthetransient isnotincreased.

Request3.Ifthepotential forcontainment overpressure exists:orthereactor-return-to-power responseworsens,provideaproposedcorrective action.Iftheunitisoperating, provideadescription ofanyinterimactionthatwillbetakenuntiltheproposedcorrective actioniscompleted.

Response3.Sinceneitherthepotential forcontainment over-pressurization northereactor-return-to-power responseworsensnocorrective actionisrequired.

Request4.Within90daysofthedateofthisBulletin, completethereviewandevaluation requiredbythisBulletinandprovideawrittenresponsedescribing yourreviewsandactionstakeninresponsetoeachitem.Response4.Thisattachment providestherequired90dayresponsetoIEBulletinNo.80-04.

Attachment 1'-Containment EnerBalanceThepurposeofthisevaluation istodetermine thelengthoftimeavailable totheoperatortoterminate'AFW flowtothebrokensteamgenerator following asteamlinebreakinsidecontainment,.prior tocontainment pressureexceeding 60psig.InitialConditions andAssumtionsa.,ZOCAenergyreleasetocontainment (includes creditforcontainment heatsinks):191.3x10BTU(takenfromTable'14.3.4-2 ofFSAR).Resultsinpeakcontainment pressureof53psig.b.Additional energytoreach60psig:16x10BTU(takenfromFig.14.3.4-3ofFSAR).C.Minimumsafeguards heatremovalcapability (1spraypumpand2fancoolers)=55x10BTU/sec=3.3x106BTU/min.(takenfromFig.14.3.4-9of'theFSAR).d.Energyinputfrom600gpmtothebrokensteamIgenerator

=600galx1180BTUmanibmx62.6~lbx1ft=5.91x10B'fU6ft7.68galmz.ne.Energyreleasedtocontainment fromtheinitialsteamlinebreakaccidentblowdown=140x10BTU(takenfromFig.14.2.5-10 oftheFSAR).

Calculations l.Additional energywhichcouldbeabsorbedbycontainment, takingcreditforpassiveandminimumactivecontainment, heatsinksfollowing asteamlinebreak.(froma+b-2.eabove).(191.3+16)x10BTU-140x10BTU=67.3NBTU66Netenergyadditiontocontainment following initialsteamlinebreakblowdown(fromd-cabove):(5.91x10BTU-3.3x10BTU)=2.61x10BTU666manmz.nmz.n3.OperatorActionTime=67.3NBTU2.61NBTU/man f"lg