ML17264A281

Proposed Tech Specs Re Changes to Current RCS Pressure & Temp Limits for Heatup,Cooldown,Criticality & Hydrostatic Testing

ML17264A281
Person / Time
Site:	Ginna
Issue date:	12/08/1995
From:	ROCHESTER GAS & ELECTRIC CORP.
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ML17264A280	List: ML17264A279 ML17264A281 ML17309A594
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NUDOCS 9512120159
Download: ML17264A281 (17)

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f%xlJt'7)QQhe.~creactorcoolantpumpinasingleloopisstartedwiththeRCStemperatureasmuchas50Flowerthanthesteamgeneratorsecondarysidetemperature.Thisresultsinasuddenheatinputtoawater-solidRCSfromthesteamgenerators,creating.th,::*',,-,,"-!::,,!,i,,::!,-*,.I"-.'Ie,",d"::,',i--.i~(:j::-..:::,:::,::,;.,::-lisRs-:-:-e,~:,::::e'.::::~egcetici'os+Žii"he.",.'.ttFet'iiinarl5ls"so',itis'ttiiette"teeciitation"ttRe.";ssfiitj~iii'Jeeorottj'~mp~sg~totthi~RC8~7he.',sePondÃscenar]Nsithe'.s~multaneous~f~soatlF~%Wt.eKHR:Pisolationofletdown,andfailureofthenormalchargingflowcontrolstothefullflowcondition.'thser.'men'eke.'agl6e,"8lniir'iatRe",'f.0'e~'e'oosfdeiNtfonl'dept.dl'n'nIOct~thejfeot!OototJLiitetircie"wKihCi'.reiiTtettiottetb7gMeCh'ni~ate'tieCF!5%eiifiie'!,;X!Sgi,Ih.:--:-::"j~li:~t:.:.isW!i!!ii!--!i!!::.-..!-,,!l%VT:-:-I-'-!I,-:~i-:I,::"la'iiiTheresultingmassinjection/letdownmismatchcausesanincreasingpressuretransient.3.2LTOPSSetpointDeterminationRochesterGasandElectricandBabcock&WilcoxNuclearTechnology(BWNT)havedevelopedthefollowingmethodologywhichisemployedtodeterminePORVsetpointsformitigationoftheLTOPSdesignbasiscoldoverpressurizationtransients.ThismethodologymaximizestheavailableoperatingmarginforsetpointselectionwhilemaintaininganappropriatelevelofprotectioninsupportofreactorvesselandRHRSystemintegrity.3.2.iParametersConsideredTheselectionofproperLTOPSsetpointforactuatingthePORVsrequirestheconsiderationofnumeroussystemparametersincluding:a.Volumeofreactorcoolantinvolvedintransient9512120159951208PDRADOCK05000244'PPDR3-2 b.RCSpressuresignaltransmissiondelayc.Volumetriccapacityofthereliefvalvesversusopeningposition,includingthepotentialforcriticalflowd.Stroketimeofthereliefvalves(open&close)e.InitialtemperatureandpressureoftheRCSandsteamgeneratorf..MassinputrateintoRCSg.Temperatureofinjectedfluidh.HeattransfercharacteristicsofthesteamgeneratorsInitialtemperatureasymmetrybetweenRCSandsteamgeneratorj~k.secondarywaterIMassofsteamgeneratorsecondarywaterRCPstartupdynamics10CFR50,AppendixG'4'ressure/temperaturecharacteristicsofthereactorvessele~~(ti/><m.PressurizerPORVpiping/structuralanalysislimitationsn.DynamicandstaticpressuredifferencesthroughouttheRCSandRHRSo.RHRSystempressurelimitsp.LoopassymetryforRCPstartcasesqf:,:;,:.::-:,:,':;::;qettqmetttiqqe'etteiitttet.oii::.emeeetqteqetidltiqqeqtidergvlit&e'ttie::t'TOP"'8-:-*--::::iiia!:----K-.-ei---!-"-:"'--I:-:"dT!0".~A:-:-'-iii:::It'!:-ll.aetp'oftTheseparametersaremodelledintheBWNTRELAP5/MOD2-BSWcomputercode(Ref.19)whichcalculatesthemaximumandminimumsystempressures.3.2.2PressureLimitsSelectionThefunctionoftheLTOPSistoprotectthereactorvesselfromfastpropagatingbrittlefracture.ThishasbeenimplementedbychoosingaLTOPSsetpointwhichpreventsexceedingthelimitsprescribedbytheapplicablepressure/temperaturecharacteristicforthespecificreactorvesselmaterialinaccordancewithrulesgiveninAppendixGto10CFR50"'.TheLTOPSdesignbasistakescreditforthefact3-3

thatoverpressureeventsmostlikelyoccurduringisothermalconditionsintheRCS.Therefore,itisappropriatetoutilizethesteady-stateAppendixGlimit.Inaddition,theLTOPSalsoprovidesforanoperationalconsiderationtomaintaintheintegrityofthePORVpiping,andtoprotecttheRHRSystemfromoverpressureduringtheLTOPSdesignbasistransients.Atypicalcharacteristic10CFR50AppendixGcurveisshownbyFigure3.1wheretheallowablesystempressureincreaseswithincreasingtemperature.ThistypeofcurvesetsthenominalupperlimitonthepressurewhichshouldnotbeexceededduringRCSincreasingpressuretransientsbasedonreactorvesselmaterialproperties.SuperimposedonthiscurveisthePORVpipinglimitandRHRSystempressurelimitwhichisconservativelyused,forsetpointdevelopment,asthemaximumallowablepressureabovethetemperatureatwhichitintersectswiththe10CFR50AppendixGcurve.Whenareliefvalveisactuatedtomitigateanincreasingpressuretransient,thereleaseofavolumeofcoolantthroughthevalvewillcausethepressureincreasetobeslowedandreversedasdescribedbyFigure3,2.Thesystempressurethendecreases,asthereliefvalvereleasescoolant,untilaresetpressureisreachedwherethevalveissignalledtoclose.Notethatthepressurecontinuestodecreasebelowtheresetpressureasthevalverecloses.Thenominallowerlimitonthepressureduringthetransientistypicallyestablishedbasedsolelyonanoperationalconsiderationforthereactorcoolantpump¹1sealtomaintainanominaldifferentialpressureacrossthesealfacesforproperfilm-ridingperformance.Intheeventthattheavailablerangeisinsufficienttoconcurrentlyaccomodatetheupperandlowerpressurelimits,theupperpressurelimitsare'givenpreference.Thenominalupperlimit(basedontheminimumofthesteady-state10CFR50AppendixGrequirement,theRHRSystempressurelimit,andthePORVpipinglimitations)andthenomirlalRCP¹1sealperformancecriteriacreateapressurerangefromwhichthesetpointsforbothPORVsmaybeselectedasshownonp.d..e,',"p,',i*,'i!i'p!p"'f!'"'~i'ppp!,':'!pp'p'd'."phlowe~rereeeare!!i'pmletta"'::;!eeieat:.".:"POFitrieedtOlrite!:-:::top!-tapirp8er::::,":.rateotpoir:::-:,s'gal%%p":-I!~dip:-,idrp,::,~!*-::.!p-.':!:::-:::i'":r:.':!pi:,:wrpi.i::p":rd::!!ip--pp,-pP~i:::-:..-:",::,:,t-,:.id!-,-.!.Ii,::.:3-4 3.2.3MassInputConsiderationForaparticularmassinputtransienttotheRCS,thereliefvalvewillbesignalledtoopenataspecificpressuresetpoint.However,asshownonFigure3.2,therewillbeapressureovershootduringthedelaytimebeforethevalvestartstomoveandduringthetimethevalveismovingtothefullopenposition.Thisovershootisdependentonthedynamicsofthesystemandtheinputparameters,andresultsinamaximumsystempressuresomewhathigherthanthesetpressure.Similarlytherewillbeapressureundershoot,whilethevalveisrelieving,bothduetotheresetpressurebeingbelowthesetpointandtothedelayinstrokingthevalveclosed.Themaximumandminimumpressuresreached(P~andP~)inthetransientareafunctionoftheselectedsetpoint(P,)asshownonFigure3.3.Theshadedarearepresentsanoptimumrangefromwhichtoselectthesetpointbasedontheparticularmassinputcase.Severalmassinputcasesmayberunatvariousinputflowratestoboundtheallowablesetpointrange.3.2.4HeatInputConsiderationTheheatinputcaseis,donesimilarlytothemassinputcaseexceptthatthelocusoftransientpressurevaluesversusselectedsetpointsmaybedeterminedforseveralvaluesoftheinitialRCStemperature.Thisheatinputevaluationprovidesarangeofacceptablesetpointsdependentonthereactorcoolanttemperature,whereasthemassinputcaseislimitedtothemostrestrictivelowtemperatureconditiononly(i.e.themassinjectiontransientisnotsensitivetotemperature).TheshadedareaonFigure3.4describestheacceptablebandforaheatinputtransientfromwhichtoselectthesetpointforaparticularinitialreactorcoolanttemperature.IftheLTOPSisasinglesetpointsystem,themostlimitingresultisusedthroughout.3.2.5FinalSetpointSelection3-5 Bysuperimposingtheresultsofmultiplemassinputandheatinputcasesevaluated,(fromaseriesoffiguressuchas3.3and3.4)arangeofallowablePORVsetpointstosatisfybothconditionscanbedetermined.Forasinglesetpointsystem,themostlimittingsetpointischosen,withtheupperpressurelimitgivenprecedenceifbothlimitscannotbeaccomodated.~It~I~SgadCi<~~tt)oltalsc~i'sit~C.a.httTheselectionofthesetpointsforthePORVsconsiderstheuseofnominalupperandlowerpressurelimits.Theupperlimitsarespecifiedbytheminimumofthesteady-statecooldowncurveascalculatedinaccordancewithAppendixGto10CFR50'4'rthepeakRCSor:RHRSystempressurebaseduponpiping/structuralanalysisloads.Thelowerpressureextremeisspecifiedbythereactorcoolantpump¹1sealminimumdifferentialpressureperformancecriteria.'-:Aeeffgi'Atlas>'..!:p.-,-,--ej~:,-:.!::-!!...-...%:::,.::!:,;;.!',;!*.-:Br!s~jire~i:Laraaris!ate'na!toitt:ern'rr..adalagy,.',o6":efeena%%o~Acoouritrnd"ol':theretfeatr!i!:::.-.:,ir-.::-,::;:!.:,."r:-::-::!r'!!!:.:!!...!!!':::::::..-:!le!':!IBeuelojjmsprit,whichisalreadybasedonconservativepressurelimits(suchasasafetyfactorof2onpressurestress,~~use,,attn!ioWeiraoyodlttrLsroaare!end!'en".:sasarn!sdViT!'Nlaoiadi~t'~t~js~>detti:."situs~to:;::trrrttrnasatnstreatswea~ttt:hirtkand)sessdrsaussed':S!sotto'd~ot%%is!:repa~it-t3.3ApplicationofASMECodeCaseN-514ASMECodeCaseN-514""allowslowtemperatureoverpressureprotectionsystems(LTOP)tolimitthemaximumpressureinthereactorvesselto110%ofthepressuredeterminedtosatisfyAppendixG,paragraphG-2215,ofSectionXI3-6 oftheASMECode'".(Note,thatthesetpointselectionmethodologyasdiscussedinSection3.2.5specificallyutilizesthesteady-statecurve,)TheapplicationofASMECodeCaseN-514increasestheoperatingmargininthe,regionofthepressure-temperaturelimitcurveswheretheLTOPSsystemisenabled.CodeCaseN-514requiresLTOPStobeeffectiveatcoolanttemperatureslessthan200'ForatcoolanttemperaturescorrespondingtoareactorvesselmetaltemperaturelessthanRT>>+50'F,whicheveris,greater.RT>>,isthehighestadjustedreferencetemperatureforweldorbasemetalinthebeltlineregionatadistanceone-fourthofthevesselsectionthicknessfromthevesselinsidesurface,asdeterminedbyRegulatoryGuide1.99,Revision2.Althoughexpectedsoon,useofCodeCaseN-514hasnotyetbeenformallyapprovedbytheNRC.Intheinterim,anexemptiontotheregulationsmustbegrantedbytheNRCbeforeCodeCaseN-514canbeusedin'thedeterminationoftheLTOPSsetpoint(s)andenabletemperature.3-7

3.4EnableTemperatureforLTOPSTheenabletemperatureisthetemperaturebelowwhichtheLTOPSsystemisrequiredtobeoperable.ThedefinitionoftheenablingtemperaturecurrentlyapprovedandsupportedbytheNRCisdescribedinBranchTechnicalPositionRSB5-2"".ThispositiondefinestheenabletemperatureforLTOPsystemsasthewatertemperaturecorrespondingtoametaltemperatureofatleastRT>>+90'Fatthebeltlinelocation(1/4tor3/4t)thatiscontrollingintheAppendixGlimitcalculations.Thisdefinitionismostlybasedonmaterialpropertiesandfracturemechanics,withtheunderstandingthatmaterialtemperatures'ofRopy+90Fatthecriticallocationwillbewellup.thetransitioncurvefrombrittletoductileproperties,andthereforebrittlefractureofthevesselisnotexpected.TheASMECodeCaseN-514supportsanenabletemperatureofRTgpr+50For200F,whicheverisgreaterasdescribedinSection3.3.ThisdefinitionisalsosupportedbyWestinghouseandcanbeusedbyrequestinganexemptiontotheregulationsorwhenASMECodeCaseN-514isformallyapprovedbytheNRC.TheRC8coldlegtemperaturelimitationforstartinganRCPisthesamevalueastheLTOPSenabletemperaturetoensurethatthebasisoftheheatinjectiontransientisnotviolated.TheStandardTechnicalSpecifications(STS)prohibitstartinganRCPwhenany'CScoldlegtemperaturesislessthanorequaltotheLTOPSenabletemperatureunlessthesecondarysidewatertemperatureofeachsteamgeneratorislessthanorequalto50'FaboveeachoftheRCScoldlegtemperatures.3-8 Figure3.1TYPICALAPPENDIXGP/TCHARACTERISTICS(g2500~2000~~15000U0<O1000ClI-Q500O'F/HR100IMPOSEDPORVPIPINGLIMITIMPOSEDRHRSPIPINGLIMIT00100200300400500INDICATEDCOOLANTTEMPERATURE,'F3-9 Figure3.2,TYPICAL:PRESSURETRANSIEN7(3RELIEFVAVL'6CYQLEJ8EfP;OINX-RESETRIfrihr3-10 Figure3.3:(MASSINPUT)::'APPENDIX:GSIAXIMUMLIMIT:,'RCPTGal;:::,'ERFORMAt4R'CANNA".:::::ISETPOIN7RANGE:PORVSETPOINT)'.PSIGThemaximumpressurelimitistheminimumoftheAppendixGlimit,thePORVdischargepipingstructuralanalysislimit,ortheRHRsystemlimit3-11 Figure3.4:":.:SRTP:OINK:..'::DETERMlfNATION(HEAT:INPUT)'APPENDIX:GSIAXIMUMLIMIT"P.tAN:IIIRCP.N:SEAL:::P.NFQRMANcRCRlTERfA:::::::SETPOINTRANGE:FORVSETPOIN7):PSIGThemaximumpressurelimitistheminimumoftheAppendixGlimit,thePORVdischargepipingstructuralanalysislimit,ortheRHRsystemlimit3-12

4.0REFERENCES

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