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1)InadvertentOpeningofaSteamGeneratorSafetyValveorAtmosphericDumpValve2)Post-TripReturntoPowerforSteamSystemPipingFailures(SteamLineBreaks)3)PressurizerPressureDecreaseEvents(InadvertentOpeningofthePressurizerPowerOperatedReliefValves-PORVs)4)SmallPrimaryLineBreakOutsideContainment(LetdownLineBreak)5)SteamGeneratorTubeRuptureEventOftheaboveDBEs,theNSSSsimulationoftheInadvertentOpeningofthePressurizerPORVswasterminatedbeforetheRCSpressurestabilizes.Thisisduetothefactthatthepost-tripNSSSbehaviorforthiseventfallswithinthespectrumofconsideredLOCAsandisnotofanyinterestwithrespecttotheDNBcriterionofthisanalysis.AsaLOCA,thepost-tripNSSSbehaviorofthiseventiswithinthedomainaddressedinSection2.0ofthisreport.ReviewoftheremainingDBEswasperformedtodeterminewhetherthecalculatedminimumRCSpressureisbelowthecurrentSITminimumsetpointpressureof570psig(585psia).ThissurveyshowsthattheminimumRCSpressureduringanyoftheaboveDBEsis661psig(676psia)whichoccursduringtheInadvertentOpeningofaSteamGeneratorSafetyValveorAtmosphericlumpValveevent.ForthePost-TripReturntoPowerHotZeroPowerSteamLineBreakEvent,theminimumRCSpressureat300seconds(theendofsimulationtime)is668psig(683psia)andessentiallystable.Theminimumcalculatedpressuresfor,thesetwoeventsarestillabovethecurrentSITminimumsetpointpressureof570psig,resultinginnodeliveryofSITinventorytotheRCS.Sincenoneofthenon-LOCAeventsresultedinorcreditedthedeliveryofSITinventory,adecreaseintheminimumSITsetpointpressurewillhavenoadverseimpactontheresultsandconclusionsoftheseevents.52 0yU Insummary,areviewofSt.LucieUnit2non-LOCAOesignBasisEventsanalysesshowsthatnocreditforSITinjectionintotheRCSwastakenbytheseanalysesinordertoshowacceptableconsequences.Therefore,thereductionoftheSITminimumsetpointpressurehasnoimpactonthenon-LOCAsafetyanalyses.53 EUIUIU,UkIl't$,UJ+'ICtU'U~4IP;P.$qu TABLE4.1-1ST.LUCIEUNIT2,DESIGNBASISEVENTSCONSIDEREDINTHECYCLE2SAFETYANALYSISIncreaseInHeatRemovalByTheSecondarySystemA.B.C.~D.E*DecreaseinFeedwaterTemperatureIncreaseinFeedwaterFlowIncreasedHainSteamFlowInadvertentOpeningofaSteamGeneratorSafetyValveorAtmosphericDumpValveSteamSystemPipingFailuresl.InsideContainmentPre-Trip2.OutsideContainmentPre-TripPowerExcursions3.Post-TripReturntoPower2.3.4.5.6.7.DecreaseInHeatRemovalByTheSecondarySystemA.LossofExternalLoadB.TurbineTripC.LossofCondenserVacuumD.LossofNormalACPowerE.LossofNormalFeedwaterF.*FeedwaterSystemPipeBreaksDecreaseInReactorCoolantFlowrateA.PartialLossofForcedReactorCoolantFlowB.TotalLossofForcedReactorCoolantFlowC.*SingleReactorCoolantPumpShaftSeizure/ShearedShaftReactivityAndPowerDistributionAnomaliesA.UncontrolledCEAMithdrawalfromaSubcriticalorLowPowerConditionB.UncontrolledCEAMithdrawalatPower'.C.CEADropD.CVCSMalfunction(InadvertentBoronDilution)E.StartupofanInactiveReactorCoolantSystemPumpF.*.ControlElementAssemblyEjectionIncreaseInReactorCoolantSystemInventoryA.CVCSMalfunctionB.InadvertentOperationoftheECCSDuringPowerOperationDecreaseInReactorCoolantSystemInventory~A.PressurizerPressureDecreaseEvents~B.SmallPrimaryLineBreakOutsideContainment~C.*SteamGeneratorTubeRuptureHiscellaneousA.AsymmetricSteamGeneratorEventsddddd*Postulat'edAccidents54 E+tRghk! | 1)InadvertentOpeningofaSteamGeneratorSafetyValveorAtmosphericDumpValve2)Post-TripReturntoPowerforSteamSystemPipingFailures(SteamLineBreaks)3)PressurizerPressureDecreaseEvents(InadvertentOpeningofthePressurizerPowerOperatedReliefValves-PORVs)4)SmallPrimaryLineBreakOutsideContainment(LetdownLineBreak)5)SteamGeneratorTubeRuptureEventOftheaboveDBEs,theNSSSsimulationoftheInadvertentOpeningofthePressurizerPORVswasterminatedbeforetheRCSpressurestabilizes.Thisisduetothefactthatthepost-tripNSSSbehaviorforthiseventfallswithinthespectrumofconsideredLOCAsandisnotofanyinterestwithrespecttotheDNBcriterionofthisanalysis.AsaLOCA,thepost-tripNSSSbehaviorofthiseventiswithinthedomainaddressedinSection2.0ofthisreport.ReviewoftheremainingDBEswasperformedtodeterminewhetherthecalculatedminimumRCSpressureisbelowthecurrentSITminimumsetpointpressureof570psig(585psia).ThissurveyshowsthattheminimumRCSpressureduringanyoftheaboveDBEsis661psig(676psia)whichoccursduringtheInadvertentOpeningofaSteamGeneratorSafetyValveorAtmosphericlumpValveevent.ForthePost-TripReturntoPowerHotZeroPowerSteamLineBreakEvent,theminimumRCSpressureat300seconds(theendofsimulationtime)is668psig(683psia)andessentiallystable.Theminimumcalculatedpressuresfor,thesetwoeventsarestillabovethecurrentSITminimumsetpointpressureof570psig,resultinginnodeliveryofSITinventorytotheRCS.Sincenoneofthenon-LOCAeventsresultedinorcreditedthedeliveryofSITinventory,adecreaseintheminimumSITsetpointpressurewillhavenoadverseimpactontheresultsandconclusionsoftheseevents.52 0yU Insummary,areviewofSt.LucieUnit2non-LOCAOesignBasisEventsanalysesshowsthatnocreditforSITinjectionintotheRCSwastakenbytheseanalysesinordertoshowacceptableconsequences.Therefore,thereductionoftheSITminimumsetpointpressurehasnoimpactonthenon-LOCAsafetyanalyses.53 EUIUIU,UkIl't$,UJ+'ICtU'U~4IP;P.$qu TABLE4.1-1ST.LUCIEUNIT2,DESIGNBASISEVENTSCONSIDEREDINTHECYCLE2SAFETYANALYSISIncreaseInHeatRemovalByTheSecondarySystemA.B.C.~D.E*DecreaseinFeedwaterTemperatureIncreaseinFeedwaterFlowIncreasedHainSteamFlowInadvertentOpeningofaSteamGeneratorSafetyValveorAtmosphericDumpValveSteamSystemPipingFailuresl.InsideContainmentPre-Trip2.OutsideContainmentPre-TripPowerExcursions3.Post-TripReturntoPower2.3.4.5.6.7.DecreaseInHeatRemovalByTheSecondarySystemA.LossofExternalLoadB.TurbineTripC.LossofCondenserVacuumD.LossofNormalACPowerE.LossofNormalFeedwaterF.*FeedwaterSystemPipeBreaksDecreaseInReactorCoolantFlowrateA.PartialLossofForcedReactorCoolantFlowB.TotalLossofForcedReactorCoolantFlowC.*SingleReactorCoolantPumpShaftSeizure/ShearedShaftReactivityAndPowerDistributionAnomaliesA.UncontrolledCEAMithdrawalfromaSubcriticalorLowPowerConditionB.UncontrolledCEAMithdrawalatPower'.C.CEADropD.CVCSMalfunction(InadvertentBoronDilution)E.StartupofanInactiveReactorCoolantSystemPumpF.*.ControlElementAssemblyEjectionIncreaseInReactorCoolantSystemInventoryA.CVCSMalfunctionB.InadvertentOperationoftheECCSDuringPowerOperationDecreaseInReactorCoolantSystemInventory~A.PressurizerPressureDecreaseEvents~B.SmallPrimaryLineBreakOutsideContainment~C.*SteamGeneratorTubeRuptureHiscellaneousA.AsymmetricSteamGeneratorEventsddddd*Postulat'edAccidents54 E+tRghk! | ||
4.2SttoacoutEventAnassessmentwasmadeofthevalidityofthestationblackoutevent-documentedinSection15.10oftheFSAR(Reference9)withregardtotheimpactofreducingtheminimumSITpressuresetpoint.Inthisassessment,theresultspresentedinReference9areusedtodemonstratethateven'ithdelayedSITdischargeintotheRCSresultingfromloweringtheSITsetpointto500psigsufficientliquidinventoryremainsintheRCStopreventvoidingintheRCSloopandlossofnaturalcirculation.Therefore,.thisassessmentshowsthattheconclusionspresentedinReference9regardingmaintainingprimarynaturalcirculationudcoresubcriticalityareunchangedwiththereducedSITpressuresetpointof500pslg~TheinitialconditionsforthereferenceanalysisareforCycle1,andthereforedonotincludesteamgeneratortubepluggingandstretchreactorcorepowerlevelwhichhaveoccurredsincetheCycle1analysis.Inthereferenceanalysis,creditistakenforoperatoractiontomaintainatleast10'Fprimarysystemsubcoolinginthehotlegs.FortheCycle1analysis,subcoolingensurescondensationof.bubblesproducedinthecore,restrictsvoidformationduetoinventorylosstothereactorvesselupperheadandpressurizer,andmaintainsnaturalcirculation.Inthisassessment,theeffectsoftubepluggingandpowerupgradeonthecalculatedmassandenergybalancesareassumedtobeoffsetbythedifferenceinsteamgeneratorsecondaryoperationthatwouldberequiredtomaintainthespecified'hotlegsubcooling.Thatis,assumingoperatoractionsfollowthesame"no-load"temperatureprogram,theRCSinventoryataparticularRCSpressurefortheCycle1analysiswillbeverysimilartotheRCSinventoryatthesame.RCSpressurecalculatedwithtubepluggingandstretchpower.Inarevisedanalysis,thetimingorsequenceofeventswouldbedifferentfromtheCycle1analysisduetothedynamiceffectsofincreasedpowerandreducedsteamgeneratorheattransferarea,butcreditingoperatoractiontomaintainthesamelevelofsubcooling(i.e.,thesametemperature)inthehotlegsresultsinacomparableRCSinventoryandpressurerelationship.Therefore,arevisedstation55 ra~<eiw4~s blackoutanalysisisnotrequiredfortheassessmentdiscussedbelow,whichusestheRCSinventoryandpressurerelationshipintheCycle1referenceanalysistoshowthatvoidinginthehotlegswouldnotbecalculatedtooccurwithareducedSITpressuresetpoint.TheReference9stationblackouteventanalysiswasperformedusingtheCESEC-IIIcomputercode,seeReference10.ThisreferenceanalysiscreditedSITdischargetotheRCSatabout12540secondsaftereventinitiation,whichwasbasedonaSITpressuresetpointof568psig.UsingtheReference9calculatedresults,Table4.2-1presentstheprimarycoolantmassesinthepressurizer,reactorvesselupperhead,.andremainderoftheRCSforthetimeperiodbetween12000and14000seconds.ColumnsAand8ofTable4.2-1showthatthetimeof12000secondsrepresentsacalculatedconditionintheRCSbeforetheSITpressuresetpointisreached(RCSpressureof632.9psig).Similarly,thetimeof14000secondsisacalculatedconditionintheRCSwhentheprimarypressureisbelowthereducedSITpressuresetpoiptof500psig(RCSpressureof496.6psig).Therefore,thereferenceanalysisindicatesthatthetimedelayinSITdischargeresultingfromreducingthepressuresetpointisroughly1460seconds.ThedatainColumnsAthroughHofTable4.2-1,istakenfromtheCESECoutputeditsfortheReference9analysis.ColumnIinTable4.2-1isthemassofliquidintheRCSexcludingtheupperheadandthepressurizer.Thisisobtainedbysubtractingtheupperheadmass(ColumnG)fromtotalRCSmasswithoutpressurizermass(ColumnF).ThetotalRCSmass'(ColumnJ)includingtheupperheadandthepressurizermassesisobtainedbyaddingthevaluesofColumnsE(pressurizermass)andF(massofRCSplussurgeline).ThevaluesatthebottomofeachcolumninTable4.2-1arethemassdifferencesbetween12000and14000seconds.Table4.2-1showsthatfrom12000to14000seconds,11824.4ibm(ColumnC)wasaddedtotheRCSviaSITdischargeinthereferenceanalysis.Duringthesametimeperiod,1118ibm(ColumnD)leakedoutofthesystem.Therefore,basedonthedifferencebetweeninventoryaddedandinventorylost,thenetmassadditiontotheRCSis10706.4ibm.However,Table4.2-1alsoshowsthatCESECdeterminesforthistimeperiodthatthetotal56 44.vo'1V'4'd~!ŽN't'll RCSmassincreasedby16899ibm(lastentryinColumnJ).ThisdiscrepancybetweentheintegratedinventorybalanceandthesummationoftotalRCSinventory(6192.6ibmintotalinventorygain)isaresultoftheCESECcomputercodenumericalintegrationscheme.Forconservatism,thelowervalueoftotalRCSmassisusedinthisassessmentoftheimpactofthereducedSITpressuresetpoint.Table4.2-1showsthatthe'otalmassofpressurizerandupperheadinventoryat14000secondsis24559ibm(13670ibmfromColumnEplus10889ibmfromColumnG).ReducingthismassbythetotalintegratedSITdischargeof11824.4ibm(ColumnC)andbythe6192.6ibmwhichwasaddedbythecodenumericalscheme,produces6542ibm.Thisisthehypotheticaltotalmassinthepressurizerandtheupperheadat14000secondswithouttheSITinventory.Reducingthishypotheticaltotalmassbythemassofsteamproducesthetotalmassofliquidinthepressurizerandupperhead.ThesteammassesinthepressurizerandupperheadaredeterminedusingtheRCSparametersat12400secondsinthereferenceanalysisbecausethisisthelastsetofinformationnotinfluencedbySITdischarge.Thisselectionof12400seconds'isconservativerelativetolatertimesinthereferenceanalysisbecausetheCESEC-IIIcalculationshowsareductioninvapormassasRCSpressuredecreases,aslongassubcoolinginthehotlegsismaintained.Therefore,themassofsteamthatexistsinthereactorvesselupperheadandpressurizeratthistimeprovidesaconservativeestimatefortheamountofsteamthatwoul'dexistwhentheRCSpressuredecreasestotheSITsetpointpressureof500psig.FromtheCESECmajoreditat12400seconds,themassofsteaminthepressurizeris1829.0ibm.Themassofsteaminthereactorvesselupperheadat12400secondis1339.5ibmwhichisbasedon(1)atotalupperheadvolumeof1165.4ft,(2)avoidfractionof0.86547(ColumnHat12400seconds),and(3)asteamspecificvolumeof0.753ft/ibmatasaturatedpressureof598.2psig(Column8at12400seconds).Subtractingthesteammassofthepressurizerandupperhead(3168.5ibm)fromthetotalmassoftheseregions(6542ibm)showsthatapproximately3373.5ibmofliquidwouldstillremainintheseregionsat14000seconds57 AyA9) withoutanySITinventoryenteringtheRCS.ColumnBofTable4.2-1indicatesthatwiththereducedpressuresetpointof500psig,theSITswillhavedischargedatsometimepriorto14000seconds.Therefore,itisconcludedthatRCSliquidinventorywouldstillbeenoughsothatsomeliquidremainedintheupperheadandthepressurizer.ThismeansnovoidingwouldhavebeenintroducedintheRCSloops.Restrictingvoidingtotheupperheadin.theanalysisistheresultofassumingoperatoractiontomaintainatleast10'Fsubcoolinginthehotlegsbyopeningtheatmosphericdumpvalvestoreducethesecondarysystempressureandtemperature.Theincreasedheatremovalinthesteamgeneratorscausedbythelargertemperaturedifferenceacrossthesteamgeneratortubesreducestheprimarysystemtemperature.Sincethesizeofthevoidisdeterminedtoremainconfinedbytheupperheadandpressurizer,naturalcirculationinthehotlegsismaintained.DischargeofboratedwaterfromtheSITspreventsadditionalvoiggrowth.Hence,theconclusionsoftheReference9analysisregarding'maintainingnaturalcirculationintheRCSforthefirstfourhoursoftheeventareunchanged.ItshouldbenotedthattheReference9calculationdidnotcredittheboroncontentsoftheSITsforthereactivitycalculations.Therefore,theconclusionsoftheReference9analysiswithrespecttomaintainingcoresubcriticalityarenotaffectedbytheSITspressuresetpointchangeinthisevaluation.Also,thisevaluationconservativelyusedthelowerRCSinventorycalculationfromCESECandassumednoSITdischargethrough14000seconds,wheretheprimarypressureisbelowtheSITpressuresetpoint.58 tlflegr'tI~,p TABLE4.2-1STATIONBLACKOUTEVENTINVENTORYSUMMARYTIMEPRESSINTEGRATEDPSIGSIT,lbmINTEGRATEDLEAK,lbmPZRRCSIncUPHMASS,lbmMASS,lbmUPPERHEADMASS,IbmUPPERHEADVOIDFRACTCESECTHERMAL-HYDRAULICSUMMARYRCSw/oUPHRCSTOTALMASS,IbmMASS,Ibm12000632.9122001240012600622,3598.2559.112800549.713000544.513200539.10.00.00.02352.13707.94411.15226.510215A7.5710E+034.4990E+0510332.88.6070E+034.4880E+0510445.48.3660E+034.4890E+0510560.84.8990E+034.5580E+05106786.0010E+034.5660Et0510790.27.7420E+034.5570Et0510899A9.3640Et034.5510E+058.5076E+039.0452E+039.1083E+038.3772E+038.7643E+039.2671E+039.7185E+038.7677E-01441392.48.6696E-01439754.88.6547E-018.7782E-018.7086E-01439791.7447422.8447835.78.6196E-01446432.98.5398E-01445381.5457471457407457266460699462601463442464464134001360013800531.5508.1501.26259.99964.311092.611005.21.0760E+044.5520E+0511115.61.0350E<044.6120E+0511226.61.1840E+044.6140E>051.0093E+041.0127Et041.0396E+048.4734E-018.4657E-018.4185E-0144510745107345100448596047155047324014000496.611824.411333.41.3670E+044.6070E+051.0889E+048.3328E-01449811474370DIFF11824.411186.0990E+03.1.0800E+042.3814E+038418.616899DESCRIPTIONOFCOLUMNHEADINGSA)TIME(SECONDS)B)RCSPRESSURE(PSIG)C)INTEGRATEDSITDISCHARGE(LBM)D)INTEGRATEDLEAKFROMRCS,TOTALEDFORTHETWOSIMULATEDLEAKS(LBM)E)TOTALPRESSURIZERMASS,PRESSURIZERLIQUIDPLUSSTEAMMASS(LBM)F)MASSOFRCSPLUSSURGELINE(LBM)G)MASSINTHEUPPERHEAD(LBM)H)UPPERHEADVOIDFRACTIONI)MASSINTHERCSLOOP,EXCLUDINGMASSOFPRESSURIZERANDUPPERHEAD(LBM)OBTAINEDBYSUBTRACTINGCOLUMNGFROMFJ)TOTALRCSMASS,INCLUDINGTHEPRESSURIZERANDUPPERHEADMASSES(LBM)OBTAINEDBYADDINGCOLUMNSEANDFDIFF:THELASTROWPROVIDESTHEMASSDIFFERENCEBETWEEN14000AND12000SECONDSFOREACHPARAMETER 0CVI"lJI This'eportprovidesthetechnicalbasisfortheengineeringevaluationwhichdemonstratesthatareductionofSITpressureminimumoperatingsetpointfrom570psigto500psigforSt.LucieUnit2Cycle6continuestomeettheacceptancecriteriaforECCSperformanceasdefinedbyIOCFR50.46.ThisreportincludesthesupportinginformationandanalyticalresultsforSBLOCA,LBLOCA,non-LOCAdesignbasistransientsandthestationblackoutevent.Thecontainmentpeakpressureanalysiswasnotexaminedbythisstudy,however,thereductionofSITpressureminimumoperatingsetpointto500psigdoesnotadverselyaffectthecontainmentpeakpressurebecausethetotalmassandenergyreleasedtothecontainmentfromtheprimarysystemintheanalysisisnotchangedandbecausetheSITdischargeslessthanonesecondlateratthelowersetpoint.ReducingthetechnicalspecificationLCOvalueto500psigprovidesadditionaldifferentialpressuremarginbetweentheSIToperatingpressureandtheSITreliefvalvepressuresetpoint(669psig).Thisadditionalmarginlessensthepotentialforchallengesto'heSITreliefvalveandconcurrentreliefvalveleakagethathaveimpactedSt.LucieUnit2plantavailability.,60 Nl'O'Lgj'It'd CENP0-137,"CalculativeMethodsfortheCESmallBreakLOCAEvalu'ationModel,"CombustionEngineeringProprietaryReport,August1974,(Proprietary).CENP0-137,"CalculativeMethods.fortheCESmallBreakLOCAEvaluationModel,"Supplement1,January1977,(Proprietary).AcceptanceCriteriaforEmergencyCoreCoolingSystemforLight-WaterCooledNuclearPowerReactors,FederalRegister,Vol.39,No.3-Friday,January4,1974.Letter,E.L.Trapp(C-E)toW.L.Parks,(FPLL),"St.LucieUnit2.Cycle6ReloadSafetyEvaluation(RSE)Report,"F2-90-035,July6,1990.CENPD-133,Supplement1,"CEFLASH-4AS,AComputerProgramforReactorBlowdownAnalysisoftheSmallBreakLoss-of-CoolantAccident,"August1974,(Proprietary).CENP0-133,Supplement3,"CEFLASH-4AS,AComputerProgramforReactorBlowdownAnalysisoftheSmallBreakLoss-of-CoolantAccident,"January1977,(Proprietary).CENP0-134,"COMPERC-II,AProgramforEmergencyRefill-RefloodoftheCore,"April1974,(Proprietary).CENPD-134,Supplement1,"COMPERC-II,AProgramforEmergencyRefill-RefloodoftheCore(Modification),"December1974,(Proprietary).CENPD-134,Supplement2,"COMPERC-II,AProgramforEmergencyRefill-RefloodoftheCore,"June1985,(Proprietary).CENPD-135,"STRIKIN-II,ACylindricalGeometryFuelRodHeatTransferProgram,"April1974,(Proprietary).CENP0-135,Supplement2,"STRIKIN-II,ACylindricalGeometryFuelRodHeatTransferProgram(Modification),"February1975(Proprietary).CENP0-135,Supplement4,"STRIKIN-II,ACylindricalGeometryFuelRodHeatTransferProgram,"August1976,(Proprietary).CENP0-135,Supplement5,"STRIKIN-II,ACylindricalGeometry'uelRodHeatTransferProgram,"April1977,(Proprietary).61 PI1~ | 4.2SttoacoutEventAnassessmentwasmadeofthevalidityofthestationblackoutevent-documentedinSection15.10oftheFSAR(Reference9)withregardtotheimpactofreducingtheminimumSITpressuresetpoint.Inthisassessment,theresultspresentedinReference9areusedtodemonstratethateven'ithdelayedSITdischargeintotheRCSresultingfromloweringtheSITsetpointto500psigsufficientliquidinventoryremainsintheRCStopreventvoidingintheRCSloopandlossofnaturalcirculation.Therefore,.thisassessmentshowsthattheconclusionspresentedinReference9regardingmaintainingprimarynaturalcirculationudcoresubcriticalityareunchangedwiththereducedSITpressuresetpointof500pslg~TheinitialconditionsforthereferenceanalysisareforCycle1,andthereforedonotincludesteamgeneratortubepluggingandstretchreactorcorepowerlevelwhichhaveoccurredsincetheCycle1analysis.Inthereferenceanalysis,creditistakenforoperatoractiontomaintainatleast10'Fprimarysystemsubcoolinginthehotlegs.FortheCycle1analysis,subcoolingensurescondensationof.bubblesproducedinthecore,restrictsvoidformationduetoinventorylosstothereactorvesselupperheadandpressurizer,andmaintainsnaturalcirculation.Inthisassessment,theeffectsoftubepluggingandpowerupgradeonthecalculatedmassandenergybalancesareassumedtobeoffsetbythedifferenceinsteamgeneratorsecondaryoperationthatwouldberequiredtomaintainthespecified'hotlegsubcooling.Thatis,assumingoperatoractionsfollowthesame"no-load"temperatureprogram,theRCSinventoryataparticularRCSpressurefortheCycle1analysiswillbeverysimilartotheRCSinventoryatthesame.RCSpressurecalculatedwithtubepluggingandstretchpower.Inarevisedanalysis,thetimingorsequenceofeventswouldbedifferentfromtheCycle1analysisduetothedynamiceffectsofincreasedpowerandreducedsteamgeneratorheattransferarea,butcreditingoperatoractiontomaintainthesamelevelofsubcooling(i.e.,thesametemperature)inthehotlegsresultsinacomparableRCSinventoryandpressurerelationship.Therefore,arevisedstation55 ra~<eiw4~s blackoutanalysisisnotrequiredfortheassessmentdiscussedbelow,whichusestheRCSinventoryandpressurerelationshipintheCycle1referenceanalysistoshowthatvoidinginthehotlegswouldnotbecalculatedtooccurwithareducedSITpressuresetpoint.TheReference9stationblackouteventanalysiswasperformedusingtheCESEC-IIIcomputercode,seeReference10.ThisreferenceanalysiscreditedSITdischargetotheRCSatabout12540secondsaftereventinitiation,whichwasbasedonaSITpressuresetpointof568psig.UsingtheReference9calculatedresults,Table4.2-1presentstheprimarycoolantmassesinthepressurizer,reactorvesselupperhead,.andremainderoftheRCSforthetimeperiodbetween12000and14000seconds.ColumnsAand8ofTable4.2-1showthatthetimeof12000secondsrepresentsacalculatedconditionintheRCSbeforetheSITpressuresetpointisreached(RCSpressureof632.9psig).Similarly,thetimeof14000secondsisacalculatedconditionintheRCSwhentheprimarypressureisbelowthereducedSITpressuresetpoiptof500psig(RCSpressureof496.6psig).Therefore,thereferenceanalysisindicatesthatthetimedelayinSITdischargeresultingfromreducingthepressuresetpointisroughly1460seconds.ThedatainColumnsAthroughHofTable4.2-1,istakenfromtheCESECoutputeditsfortheReference9analysis.ColumnIinTable4.2-1isthemassofliquidintheRCSexcludingtheupperheadandthepressurizer.Thisisobtainedbysubtractingtheupperheadmass(ColumnG)fromtotalRCSmasswithoutpressurizermass(ColumnF).ThetotalRCSmass'(ColumnJ)includingtheupperheadandthepressurizermassesisobtainedbyaddingthevaluesofColumnsE(pressurizermass)andF(massofRCSplussurgeline).ThevaluesatthebottomofeachcolumninTable4.2-1arethemassdifferencesbetween12000and14000seconds.Table4.2-1showsthatfrom12000to14000seconds,11824.4ibm(ColumnC)wasaddedtotheRCSviaSITdischargeinthereferenceanalysis.Duringthesametimeperiod,1118ibm(ColumnD)leakedoutofthesystem.Therefore,basedonthedifferencebetweeninventoryaddedandinventorylost,thenetmassadditiontotheRCSis10706.4ibm.However,Table4.2-1alsoshowsthatCESECdeterminesforthistimeperiodthatthetotal56 44.vo'1V'4'd~!ŽN't'll RCSmassincreasedby16899ibm(lastentryinColumnJ).ThisdiscrepancybetweentheintegratedinventorybalanceandthesummationoftotalRCSinventory(6192.6ibmintotalinventorygain)isaresultoftheCESECcomputercodenumericalintegrationscheme.Forconservatism,thelowervalueoftotalRCSmassisusedinthisassessmentoftheimpactofthereducedSITpressuresetpoint.Table4.2-1showsthatthe'otalmassofpressurizerandupperheadinventoryat14000secondsis24559ibm(13670ibmfromColumnEplus10889ibmfromColumnG).ReducingthismassbythetotalintegratedSITdischargeof11824.4ibm(ColumnC)andbythe6192.6ibmwhichwasaddedbythecodenumericalscheme,produces6542ibm.Thisisthehypotheticaltotalmassinthepressurizerandtheupperheadat14000secondswithouttheSITinventory.Reducingthishypotheticaltotalmassbythemassofsteamproducesthetotalmassofliquidinthepressurizerandupperhead.ThesteammassesinthepressurizerandupperheadaredeterminedusingtheRCSparametersat12400secondsinthereferenceanalysisbecausethisisthelastsetofinformationnotinfluencedbySITdischarge.Thisselectionof12400seconds'isconservativerelativetolatertimesinthereferenceanalysisbecausetheCESEC-IIIcalculationshowsareductioninvapormassasRCSpressuredecreases,aslongassubcoolinginthehotlegsismaintained.Therefore,themassofsteamthatexistsinthereactorvesselupperheadandpressurizeratthistimeprovidesaconservativeestimatefortheamountofsteamthatwoul'dexistwhentheRCSpressuredecreasestotheSITsetpointpressureof500psig.FromtheCESECmajoreditat12400seconds,themassofsteaminthepressurizeris1829.0ibm.Themassofsteaminthereactorvesselupperheadat12400secondis1339.5ibmwhichisbasedon(1)atotalupperheadvolumeof1165.4ft,(2)avoidfractionof0.86547(ColumnHat12400seconds),and(3)asteamspecificvolumeof0.753ft/ibmatasaturatedpressureof598.2psig(Column8at12400seconds).Subtractingthesteammassofthepressurizerandupperhead(3168.5ibm)fromthetotalmassoftheseregions(6542ibm)showsthatapproximately3373.5ibmofliquidwouldstillremainintheseregionsat14000seconds57 AyA9) withoutanySITinventoryenteringtheRCS.ColumnBofTable4.2-1indicatesthatwiththereducedpressuresetpointof500psig,theSITswillhavedischargedatsometimepriorto14000seconds.Therefore,itisconcludedthatRCSliquidinventorywouldstillbeenoughsothatsomeliquidremainedintheupperheadandthepressurizer.ThismeansnovoidingwouldhavebeenintroducedintheRCSloops.Restrictingvoidingtotheupperheadin.theanalysisistheresultofassumingoperatoractiontomaintainatleast10'Fsubcoolinginthehotlegsbyopeningtheatmosphericdumpvalvestoreducethesecondarysystempressureandtemperature.Theincreasedheatremovalinthesteamgeneratorscausedbythelargertemperaturedifferenceacrossthesteamgeneratortubesreducestheprimarysystemtemperature.Sincethesizeofthevoidisdeterminedtoremainconfinedbytheupperheadandpressurizer,naturalcirculationinthehotlegsismaintained.DischargeofboratedwaterfromtheSITspreventsadditionalvoiggrowth.Hence,theconclusionsoftheReference9analysisregarding'maintainingnaturalcirculationintheRCSforthefirstfourhoursoftheeventareunchanged.ItshouldbenotedthattheReference9calculationdidnotcredittheboroncontentsoftheSITsforthereactivitycalculations.Therefore,theconclusionsoftheReference9analysiswithrespecttomaintainingcoresubcriticalityarenotaffectedbytheSITspressuresetpointchangeinthisevaluation.Also,thisevaluationconservativelyusedthelowerRCSinventorycalculationfromCESECandassumednoSITdischargethrough14000seconds,wheretheprimarypressureisbelowtheSITpressuresetpoint.58 tlflegr'tI~,p TABLE4.2-1STATIONBLACKOUTEVENTINVENTORYSUMMARYTIMEPRESSINTEGRATEDPSIGSIT,lbmINTEGRATEDLEAK,lbmPZRRCSIncUPHMASS,lbmMASS,lbmUPPERHEADMASS,IbmUPPERHEADVOIDFRACTCESECTHERMAL-HYDRAULICSUMMARYRCSw/oUPHRCSTOTALMASS,IbmMASS,Ibm12000632.9122001240012600622,3598.2559.112800549.713000544.513200539.10.00.00.02352.13707.94411.15226.510215A7.5710E+034.4990E+0510332.88.6070E+034.4880E+0510445.48.3660E+034.4890E+0510560.84.8990E+034.5580E+05106786.0010E+034.5660Et0510790.27.7420E+034.5570Et0510899A9.3640Et034.5510E+058.5076E+039.0452E+039.1083E+038.3772E+038.7643E+039.2671E+039.7185E+038.7677E-01441392.48.6696E-01439754.88.6547E-018.7782E-018.7086E-01439791.7447422.8447835.78.6196E-01446432.98.5398E-01445381.5457471457407457266460699462601463442464464134001360013800531.5508.1501.26259.99964.311092.611005.21.0760E+044.5520E+0511115.61.0350E<044.6120E+0511226.61.1840E+044.6140E>051.0093E+041.0127Et041.0396E+048.4734E-018.4657E-018.4185E-0144510745107345100448596047155047324014000496.611824.411333.41.3670E+044.6070E+051.0889E+048.3328E-01449811474370DIFF11824.411186.0990E+03.1.0800E+042.3814E+038418.616899DESCRIPTIONOFCOLUMNHEADINGSA)TIME(SECONDS)B)RCSPRESSURE(PSIG)C)INTEGRATEDSITDISCHARGE(LBM)D)INTEGRATEDLEAKFROMRCS,TOTALEDFORTHETWOSIMULATEDLEAKS(LBM)E)TOTALPRESSURIZERMASS,PRESSURIZERLIQUIDPLUSSTEAMMASS(LBM)F)MASSOFRCSPLUSSURGELINE(LBM)G)MASSINTHEUPPERHEAD(LBM)H)UPPERHEADVOIDFRACTIONI)MASSINTHERCSLOOP,EXCLUDINGMASSOFPRESSURIZERANDUPPERHEAD(LBM)OBTAINEDBYSUBTRACTINGCOLUMNGFROMFJ)TOTALRCSMASS,INCLUDINGTHEPRESSURIZERANDUPPERHEADMASSES(LBM)OBTAINEDBYADDINGCOLUMNSEANDFDIFF:THELASTROWPROVIDESTHEMASSDIFFERENCEBETWEEN14000AND12000SECONDSFOREACHPARAMETER 0CVI"lJI This'eportprovidesthetechnicalbasisfortheengineeringevaluationwhichdemonstratesthatareductionofSITpressureminimumoperatingsetpointfrom570psigto500psigforSt.LucieUnit2Cycle6continuestomeettheacceptancecriteriaforECCSperformanceasdefinedbyIOCFR50.46.ThisreportincludesthesupportinginformationandanalyticalresultsforSBLOCA,LBLOCA,non-LOCAdesignbasistransientsandthestationblackoutevent.Thecontainmentpeakpressureanalysiswasnotexaminedbythisstudy,however,thereductionofSITpressureminimumoperatingsetpointto500psigdoesnotadverselyaffectthecontainmentpeakpressurebecausethetotalmassandenergyreleasedtothecontainmentfromtheprimarysystemintheanalysisisnotchangedandbecausetheSITdischargeslessthanonesecondlateratthelowersetpoint.ReducingthetechnicalspecificationLCOvalueto500psigprovidesadditionaldifferentialpressuremarginbetweentheSIToperatingpressureandtheSITreliefvalvepressuresetpoint(669psig).Thisadditionalmarginlessensthepotentialforchallengesto'heSITreliefvalveandconcurrentreliefvalveleakagethathaveimpactedSt.LucieUnit2plantavailability.,60 Nl'O'Lgj'It'd CENP0-137,"CalculativeMethodsfortheCESmallBreakLOCAEvalu'ationModel,"CombustionEngineeringProprietaryReport,August1974,(Proprietary).CENP0-137,"CalculativeMethods.fortheCESmallBreakLOCAEvaluationModel,"Supplement1,January1977,(Proprietary).AcceptanceCriteriaforEmergencyCoreCoolingSystemforLight-WaterCooledNuclearPowerReactors,FederalRegister,Vol.39,No.3-Friday,January4,1974.Letter,E.L.Trapp(C-E)toW.L.Parks,(FPLL),"St.LucieUnit2.Cycle6ReloadSafetyEvaluation(RSE)Report,"F2-90-035,July6,1990.CENPD-133,Supplement1,"CEFLASH-4AS,AComputerProgramforReactorBlowdownAnalysisoftheSmallBreakLoss-of-CoolantAccident,"August1974,(Proprietary).CENP0-133,Supplement3,"CEFLASH-4AS,AComputerProgramforReactorBlowdownAnalysisoftheSmallBreakLoss-of-CoolantAccident,"January1977,(Proprietary).CENP0-134,"COMPERC-II,AProgramforEmergencyRefill-RefloodoftheCore,"April1974,(Proprietary).CENPD-134,Supplement1,"COMPERC-II,AProgramforEmergencyRefill-RefloodoftheCore(Modification),"December1974,(Proprietary).CENPD-134,Supplement2,"COMPERC-II,AProgramforEmergencyRefill-RefloodoftheCore,"June1985,(Proprietary).CENPD-135,"STRIKIN-II,ACylindricalGeometryFuelRodHeatTransferProgram,"April1974,(Proprietary).CENP0-135,Supplement2,"STRIKIN-II,ACylindricalGeometryFuelRodHeatTransferProgram(Modification),"February1975(Proprietary).CENP0-135,Supplement4,"STRIKIN-II,ACylindricalGeometryFuelRodHeatTransferProgram,"August1976,(Proprietary).CENP0-135,Supplement5,"STRIKIN-II,ACylindricalGeometry'uelRodHeatTransferProgram,"April1977,(Proprietary).61 PI1~ | ||
7.CENPD-138,"PARCH-AFORTRAN-IVDigitalProgramtoEvaluatePoolBoiling,AxialRodandCoolantHeatup,"August1974,(Proprietary).CENPD-138,SupplementI,"PARCH,AFORTRAN-IVDigitalProgramtoEvaluatePoolBoiling,AxialRodandCoolantHeatup,"(Hodification),February1975,(Proprietary).8.CENPD-138,Supplement2-P,January1977,(Proprietary).Letter,E.L.Trapp(C-E)toJ.L.Perryman(FPKL),"ResultsofCE'sLargeBreakLOCA,ReevaluationforSt.LucieUnit2BasedonCE'sNew(1986)EvaluationModel,"F2-CE-R-137,April10,1987.9.FPEL,"St.LuciePlantUnit2,FSAR,"AmendmentNo.1,April1986.10.C-ETopicalReport,CENPD-107,"CESEC-DigitalSimulationofaCombustionEng'ineeringNuclearSteamSupplySystem,"April1974.C-ETopicalReport,"CESEC-DigitalSimulationofaCombustionEngineeringNuclearSteamSupplySystem,"Enclosure1-PtoLD-82-001,January6,1982.62 5 | 7.CENPD-138,"PARCH-AFORTRAN-IVDigitalProgramtoEvaluatePoolBoiling,AxialRodandCoolantHeatup,"August1974,(Proprietary).CENPD-138,SupplementI,"PARCH,AFORTRAN-IVDigitalProgramtoEvaluatePoolBoiling,AxialRodandCoolantHeatup,"(Hodification),February1975,(Proprietary).8.CENPD-138,Supplement2-P,January1977,(Proprietary).Letter,E.L.Trapp(C-E)toJ.L.Perryman(FPKL),"ResultsofCE'sLargeBreakLOCA,ReevaluationforSt.LucieUnit2BasedonCE'sNew(1986)EvaluationModel,"F2-CE-R-137,April10,1987.9.FPEL,"St.LuciePlantUnit2,FSAR,"AmendmentNo.1,April1986.10.C-ETopicalReport,CENPD-107,"CESEC-DigitalSimulationofaCombustionEng'ineeringNuclearSteamSupplySystem,"April1974.C-ETopicalReport,"CESEC-DigitalSimulationofaCombustionEngineeringNuclearSteamSupplySystem,"Enclosure1-PtoLD-82-001,January6,1982.62 5}} | ||
}} |
Revision as of 15:55, 18 May 2018
ML17227A389 | |
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Site: | Saint Lucie |
Issue date: | 04/21/1992 |
From: | FLORIDA POWER & LIGHT CO. |
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ML17227A388 | List: |
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Text
~~~~St.LucieUnit2DocketNo.50-389ProposedLicenseAmendmentSafetIn'ectionTankMinimumPressureReductionATTACHMENT1St.LucieUnit2Marked-upTechnicalSpecificationPage3/45-1'F204230201920421PDRADOCK05000289PPDR 3t'0';5-"'tNGBCY'OttE~CNRINGSYSTEMSECCS3/4.5.1SAFETYINJECTIONTANKSiV.~sLIMITINGCONDITIONFOROPERATION~I3.5;1EachReactorCoolantSystemsafetyinjectiontankshallbeOPERABLEwith:a.:The,isolationvalve..open,b.Acontainedboratedwatervolumeofbetween1420and1556cubicfeet,I~A'<'c.Aboronconcentrationofbetween1720and2100ppmofboron,andI~d.AniItrogcn~cover.-pressureofbetween@'nd'650psig.APPIICABILITY:MOOES1;2,3",and4".Sob.ACTION:Withonesafetyinjectiontankinoperable,exceptasaresultofaclosedisolationvalve,restoretheinsuperable.tanktoQPERA8LE.')atuaAwithin1"ho'uh,or.be'in.af;ljastHdTsTACIBY'withinthenext;6'o'ursandinHOTSHUTDOWN"wi4hirithefollowing6hours.+th'one,'sat'etying'ectiontang,inoperabIe'.due,.'to)gei~1atlqnvalvebetngchas'ed,either,.iaeedfgCqty,open,'he"isolatian.vieer.Pe,.inatleast'HOTSTANDB'(within1'ouran4tjein'OT,SHUTGGMtfmithinthenext.12hours...SURVEILLANCE.REUIREMENTS.:~l4.5;,l-..lIEachsafari@;injectiontankshallbedemonstrated.OPFRABI.E;...a.Atleastonceper12hoursby:l.Verifying(bytheabsenceofalarms)thecontainedboratedwatervolumeand.nitrogencoverpressureinthetanks,and2;"Verifying'hat'eachsafetyinjectiontankisolationvalveisopen.thpressurZerpress'ut"e,'..cfihaterIthaiorequalto1750psia.'henpressur-izerpressureis1'essthan1750psia",atleastthreesafetyinjection.tanksshallbeOPERABLE,eachwithaminimumpressureof.,235psigandamaximumpressureof650psigandacontained'atervol'umeofbetween1250and1556cubicfeetwitha.boronconcentrationofbetween,1720and2100ppmofboron.Withallfours'afetyinjectiontariks'OPERAHL'E,eachtankshallhaveaminimumpressureof235psiganda.maximumpressureof650.psiganteacaqtaiqed.watervolumeofBetween833'nd.'1556cubicfeetwithaboihconcentratianofbetween1720and2100ppmofb'oron.InMODE4withpressuriziirpressUrelessthan276psia,thesafe.'yinjectiontanksmaybeisolated.ST.LUCIE"UNIT23/45"1IAmendmentNo.40 0$P St.LucieUnit2DocketNo.50-389ProposedLicenseAmendmentSafetInectionTankMinimumPressureReductionATTACHMENT2SAFETY"ANALYSISIntroductionTheproposedchangetotheSt.LucieUnit2,TechnicalSpecificationsreducesthesafetyinjectiontank(SIT)minimumpressurefrom570psigto500psig.TheproposedchangemodifiesTechnicalSpecification3.5.1.d,SafetyInjectionTanks,forSt.LucieUnit2.TheproposedchangeprovidesthebenefitofagreaterdifferentialpressuremarginbetweentheSIToperatingpressureandtheSITreliefvalvepressuresetpoint(669psig).ReducingtheSITLimitingConditionforOperation(LCO)to500psigmeanstheminimumSITpressurewouldbeapproximately75percentofthere'liefvalvepressuresetpointwhichrepresentsa10percentincreaseinmarginwhencomparedtocurrentconditions.ThisadditionalmarginlessensthepotentialforSITreliefvalveleakagethathasimpactedplantavailabilityinthepast.DiscussionTheSITsensurethatasufficientvolumeofboratedwaterwillbeimmediatelyforcedintothereactorcorethrougheachofthecoldlegsintheeventthereactorcoolantsystem(RCS)pressurefallsbelowthepressureoftheSITs.ThisinitialsurgeofwaterintothecoreprovidestheinitialcoolingmechanismduringlargeRCSpiperuptures.ThelimitsonSITvolume,boronconcentration,andpressureensuretheassumptionsusedforSITinjectioninthesafetyanalysisaremet.Bycomparison,St.LucieUnit1SITnitrogencoverpressureisnormallysetbetween220psigand225psig,andtheUnit1TechnicalSpecificationsrequiretheSITpressuretobebetween200psigand250psig.St.LucieUnit1has14x14fuelassemblyarraywhileSt.LucieUnit2hasa16x16fuel.ThehigherpressureoftheSt.LucieUnit2safetyinjectiontankswasemployedtogainadditionalLOCAmarginabovethemargingainedbythefuelassemblyarraychange.
4)kd4<<+oliey'g<)4'II1$'I~tl~J"AJ
~~~~~~~~~Section6.3.3.1oftheSt.LucieUpdatedFinalSafetyAnalysisReport(UFSAR)liststhefollowingEmergencyCoreCoolingSystem(ECCS)designcriteriafrom10CFR50.46:(1)Thecalculatedmaximum-fuelelementtemperatureshallnotexceed2200'F.(2)Thecalculatedtotaloxidationofthecladdingshallnowhereexceed17percentofthetotalcladdingthicknessbeforeoxidation.(3)Thecalculatedtotalamountofhydrogengeneratedfromthechemicalreactionofthecladdingwithwaterorsteamshallnotexceed1percentofthehypotheticalamountthatwouldbegeneratedifallthemetalinthecladdingcylinderssurroundingthefuel,excludingthecladdingsurroundingtheplenumvolume,weretoreact.(4)Calculatedchangesincoregeometryshallbesuchthatthe.coreremainsamenabletocooling.(5)AfteranycalculatedsuccessfulinitialoperationoftheECCS,thecalculatedcoretemperatureshallbemaintainedatanacceptablylowvalueanddecayheatshallberemovedfortheextendedperiodoftimerequiredbythelong-livedradioactivityremaininginthecore.Attachment4istheTechnicalEvaluation,ReductionofSafetyInjectionTankPressureMinimumSetpointforSt.LucieUnit2NuclearPowerP2ant,preparedbyABBCombustionEngineering.ItprovidesthejustificationforadecreaseintheSt.LucieUnit2minimumSITpressurefrom570psig.to500psig.TechnicaljustificationforoperationofSt.Lucie"Cycle"7"'ata-reducedSITminimumoperatingpressureof500psigisprovidedbyECCSperformanceevaluationsofthesmallbreakloss-of-coolantaccident(SBLOCA).Sincethelargebreakloss-of-coolantaccident(LBLOCA)analysisofrecordwasperformedwith,anSITpressureof200psig,theproposedminimumSITpressureof500psigisbounded.Theseperformanceevaluationsdemonstrateacceptableconformancewith10CFR.50.46.Areviewofthenon-LOCAdesignbasesevents,in'ttachment4,showsthat=noneoftheseanalysescalculateor-creditSITinjectionintotheRCS.Therefore,thereductionofSIT-minimumoperatingpressuresetpointhasnoimpactonpostulatednon-LOCAdesignbasesevents.Althoughthestationblackoutevent(SBO)isoutsidethedesignbasesforUnit2,ananalysiswasperformedasaconditionoflicenseattherequestoftheNRC.ThisanalysisappearsasSection15.10oftheUFSAR.Attachment4provides'technical lt40ll'laf'J)()')fyj~'~)(j<<,g~,v'3y's.lQ%Ua~~4m+p~~gA4=v~4<.$&j~'N~4sra~~tlg~4 evaluationoftheSBOeventattheproposedminimumoperatingpressureof500psig.This.evaluationdemonstratesthattheoriginalconclusionspresentedinSection15.10.5oftheUFSARhavenotbeenadverselyaffected.TheslightincreaseinthedifferentialpressurebetweentheRCSandSITsmayhavetwoopposingeffectsonbackleakagefromtheRCSintotheSITs.First,theincreaseddifferentialpressurewilltendtoseatthecheckvalvesmorefirmly,andthusmaycauseaslightdecreaseintheprobabilityofbackleakageintotheSITs.Second,theslightincreaseindifferentialpressurebetweentheRCSandtheSITsmayslightlyincreasetherateofbackleakageintotheSITs,shouldbackleakageoccur.Suchback-leakagewouldaffecttherequiredSITboronconcentrationandlevel.Thereisnohistoryofback-leakageintotheSITsatSt.LucieUnit2orUnit1.AsachangeinlevelwouldalerttheoperatorstoanyaccompanyingreductioninboronconcentrationintheSITs,thereisessentiallynoprobabilityofsuchbackleakagecontributingtoanevent.Therefore,thereductionofSITminimumpressurewillhavenosignificanteffectontheprobabilityorconsequencesofback-leakagefromtheRCSintotheSITs.CONCLUSIONeTheacceptabilityoftheproposedreductionoftheSITminimumoperatingpressuredependsontheimpactonthepostulatedSBLOCA,thepostulatedLBLOCA,andthepostulatedSBO.TheSBLOCAlimitingbreaksizeandassociatedpeakcladdingtemperaturestronglydependontheSITpressure.ReducingtheSITminimumoperatingpressureto500psigforSt.LucieUnit2increasestheSBLOCAlimitingbreaksizefrom0.0375ft2to0.0450ftandincreasesthepeakcladdingtemperaturefrom1771'Fto1905'F.ThisanalyticalevaluationforSBLOCAwasperformedusingABBCombustionEngineering'sNRCapprovedproprietarysmallbreakevaluationmodel,CalculativeMethodsfortheCESmallBreakLOCAEvaluationModel,CENPD-137(P),datedAugust1974andCENPD-137(P)Supplement1,datedJanuary1977.Theanalysiswasperformedconsistentwiththerequirementsof10CFR50AppendixK.Thisanalysisdemonstratedacceptableconformancewith10CFR50.46.TheLBLOCAanalysisofrecordisforcycle3whichboundslatercycles.TheLBLOCAanalysiswasredoneforcycle2whenthecorepowerwasincreasedfrom2560MWtto2700MWt.-TheLBLOCAanalysiswasredoneagainforcycle3withrevisedsteamgeneratortubeplugginglimits.ThisLBLOCAanalysiswasperformedwithaSITpressureof200psig,aconditionwhichconservativelycoversthe500psigSITpressureusedintheSBLOCAanalysis.ThepeakcladdingtemperaturefortheLBLOCAanalysisis2107'F.TheSBLOCAanalysiswithreducedSITminimumpressureremainslessthanthecurrentLBLOCApeakcladdingtemperatureofrecord.Therefore,the
'I~i~/+t,4Jk4~e~A%"Pg(.I-l*4flf"%~a LBLOCAcalculationremainsthe.limitinganalysisof..recordforECCSperformanceevaluation.ThisLBLOCAanalysisalsoshowsacceptable.conformancetothe10CFR50.46acceptancecriteriaforECCSperformanceinsupportofthereducedvalueofSITminimumpressureof500psig.Attachment4includesareviewofSBO,which.isoutsidethedesignbasisforSt.LucieUnit2butispartofthelicensingbasis.TheSBOeventpostulatesafourhourtimeperiodforrestoringACpowerduringwhichprimarysubcoolingandnaturalcirculationmustbemaintained.TheSBOanalysisinUFSARSection15.10creditssomeSITinjectionlateinthetransient.Anassessmentofthisanalysis,.concludedthattheproposedreductionintheminimumSITpressurewoulddelaytheSITdischarge.However,sufficientinventoryremainsintheRCSthroughtheSBOtopreventvoidingintheRCSloopandthustopreventalossofnaturalcirculation.TheconclusionspresentedintheUFSARregardingmaintainingnaturalcirculationandcoresubcriticalityareunchanged.Therefore,thereductionoftheSITminimumpressuresetpointto.-500'sighasnoimpactontheSBOevent.Non-LOCAdesignbaseseventshavebeenreviewedtoevaluatetheimpactofdecreasingtheSITminimumpressureto500psiginAttachment4.ForSt.LucieUnit2,noneofthenon-LOCAeventscalculateorcreditSITinjectionintotheRCS.Therefore,thereductioninSITminimumoperatingpressuresetpointhasnoimpact,onotherpostulatednon-LOCAsafetyanalyses.
0~'.V4yJIsJV.'4Vt("~<k!4i~~+~.Ih.~
~~~~St.LucieUnit2DocketNo.50-389ProposedLicenseAmendmentSafetIn'ectionTankMinimumPressureReductionATTACHMENT3DETERMINATIONOFNOSIGNIFICANTHAZARDSCONSIDERATIONThestandardsusedtoarriveatadeterminationthatarequestforamendmentinvolvesanosignificanthazardsconsiderationareincludedintheCommissionsregulation,10CFR50.92,whichstatesthatnosignificanthazardsconsiderationsareinvolvediftheoperationofthefacilityinaccordancewiththeproposedamendmentwouldnot(1)involveasignificantincreaseintheprobabilityorconsequencesofanaccidentpreviouslyevaluated;or(2)createthepossibilityofanewordifferentkindofaccidentfromanyaccidentpreviouslyevaluated;or(3)involveasignificantreductioninamarginofsafety.Eachstandardisdiscussedasfollows:(1)Operationofthefacilityinaccordancewiththeproposedamendmentwouldnotinvolveasignificantincreaseintheprobabilityorconsequencesofanaccidentpreviouslyevaluated.Reducingthesafetyinjectiontank(SIT)minimumpressuredoesnotinvolveasignificantincreaseintheprobabilityofa-.loss-of-coolantaccident-(LOCA),-since-the-SITs--are--passivesystemsandhavenoeffectonthereactorcoolantsystem(RCS)untilafterthedepressurizationoftheRCSduetoaLOCA.ReducingtheSITminimumpressureto500psigforSt.LucieUnit2increasesthesmallbreakloss-of-coolant(SBLOCA)limitingbreaksizefrom0.0375ftto0.0450ftandincreasespeakcladdingtemperaturefrom1771'Fto1905'Fforthenewlimitingbreaksize.Thecalculatedpeakcladdingtemperature(1905'F)fortheSBLOCAanalysiswithreducedSITminimumpressureremainslessthanthecurrentlarge'.breakloss-of-.coolant(LBLOCA),analysis.peakcladding.temperature.of.2107'F..ThisLBLOCAanalysiswasperformedassumingaSITpressureof200psig,aconditionwhichconservativelycoverstheproposedminimumSITpressureof500psig.Therefore,althoughtheconsequencesofaSBLOCAareincreasedslightly,theLBLOCAcalculationremainsthelimitinganalysisofrecordforemergencycorecoolingsystem(ECCS)performanceevaluation.
TheLBLOCAanalysisofrecordisforcycle3whichhasbeenshowntoboundlatercycles.ThisLBLOCAanalysisalsoshowsacceptableconformanceto10CFR50.46,AcceptanceCriteriaforECCSperformanceforlightwaternuclearpowerreactors,insupportoftheproposedminimumSITpressureof500psig.ThisECCSperformanceevaluationforSt.LucieUnit2wasperformedconsistentwithNRCapprovedmethodologyand10CFR50AppendixKcriteria.TheLBLOCAanalysiswasperformedassumingaSITpressureof200psig,therefore,thereisnoincreaseintheconsequencesofaLBLOCAduetoreducingtheminimumSITpressureto500psig.Non-LOCAdesignbasiseventshavebeenreviewedtoevaluatetheimpactofdecreasingtheminimumSITpressureto500psig.ForSt.LucieUnit2,noneofthenon-LOCAeventscalculateorcreditSITinjectionintotheRCS,sincenoneofthenon-LOCAaccidentsresultinRCSdepressurizationbelowtheSITmaximumpressuresetpoint.Therefore,thereductionoftheSITminimumpressuresetpointhasnoincreaseintheconsequences.ofnon-LOCAdesignbaseseventsduetoreducingtheminimumSITpressureto500psig.Thestationblackoutevent,(SBO),whichispresentedinSection15.10.5oftheUFSAR,hasbeenreviewedtoevaluatetheimpactofdecreasingtheSITminimumpressureto500psig.WiththeSITpressurereducedto500psig,SITinjectionisinitiatedpriortotheoccurrenceofvoidingintheRCSloops,thuspreventingalossofnaturalcirculation.Therefore,reducingtheSt.LucieUnit2TechnicalSpecificationlimitforSITminimumnitrogencoverpressurefrom570psigto500psigdoesnotinvolveasignificantincreaseintheprobability.or*.consequences=='of-.an=-.accidentpreviouslyevaluated.(2)Useofthemodifiedspecificationwouldnotcreatethepossibilityofanewordifferentkindofaccidentfromanypreviouslyevaluated.TherearenoadditionalfailuremodesfortheSITsduetoreducingthenitrogencoverpressurefrom570psigto.500.psig.TheSITs"are-passive"systemsandhave-no.effect-on-the,RCSuntilafterthedepressurxzationof-.the-RCS.,dueto.a.LOCA.Therefore,reducingtheSt.LucieUnit2TechnicalSpecificationlimitforSITminimumnitrogencoverpressurefrom570psigto500psigdoesnotcreatethepossibilityofanewordifferentkindofaccidentfromanypreviouslyevaluated.
~Qe~JiltP'JIp~,q~~4~V'1%f'"k (3)Useofthemodifiedspecificationwouldnotinvolveasignificantreductioninamarginofsafety.TheSBLOCAanalysiswiththeSITpressureof500psigsatisfiesthecriteriaof10CFR50.46andremainsboundedbytheLBLOCAanalysisofrecord.TheLBLOCAanalysiswas.performedassuminga.SITpressureof200psig.ReviewoftheSBOanalysiswiththeSITpressureof500psigdemonstratesthattheoriginalconclusions,presentedinUFSARSection15.10.5,havenotbeenadverselyaffected.Therefore,reducingtheSt.LucieUnit2TechnicalSpecificationlimitforSITminimumnitrogencoverpressurefrom560psigto500psigdoesnotinvolveasignificantreductioninamarginofsafety.Basedontheabove,wehavedeterminedthattheproposedamendmentdoesnot(1)involveasignificantincreaseintheprobabilityorconsequencesofanaccidentpreviouslyevaluated,(2)createtheprobabilityofanew-ordifferentkindofaccidentfromanypreviouslyevaluated,or(3)involveasignificantreductioninamarginofsafety;andthereforedoesnotinvolveasignificanthazardsconsideration.
+I
~~~~St.LucieUnit2DocketNo.50-389,ProposedLicenseAmendmentSafetIn'ectionTankMinimumPressureReductionATTACHMENT4TECHNICALEVALUATIONREDUCTIONOFSAFETYINJECTIONTANKPRESSUREMINIMUMSETPOINTFORST.LUCIEUNIT2 4PgKlp OPS-92-0385ENCLOSURE1TECHNjtCALJUS'IXFICATIONforREDUCTIONOFSAFETYINJECTIONTMWPRESSURESETPOINTTO500PSIGforST;LUCIEVI.'GT2NUCLEARPOWERPLANTPreparedforFloridaPower4Light'yOperationsAnalysisABBCombustionEngineeringNuclearServicesMARCH1992CombustionEngineering,Inc.JLItItr<IrIeASEABROWNBOVERI pff'i'iL~VIl4tIrv'EC.BPtP ThisreportprovidestechnicaljustificationforadecreaseintheSt.LucieUnit2minimumoperatingsafetyinjectiontank(SIT)pressurefrom570psigto500psig.ReducingthisTechnicalSpecificationLimitingConditionforOperation(LCO)valueprovidesagreaterdifferentialpressuremarginbetweentheSIToperatingpressureandtheSITreliefvalvepressuresetpoint(669psig).Thisadditionalmarginlessens.thepotentialforchallengestotheSITreliefvalveandconcurrentreliefvalveleakagesthathaveimpactedSt.LucieUnit2availability'nthepast.TechnicaljustificationforoperationofSt.LucieUnit2Cycle6atthereducedSITminimumpressureof500psigisprovidedbyECCSperformanceevaluationsofthesmallbreakloss-of-coolantaccident.ReducingtheSITminimumoperatingpressureto500psigincreasestheSBLOCAlimitingbreaksizefrom0.0375ftto0.045ftandincreasesthepeakcladdingtemperaturefrom1771'Fto1905'F.ThisincreasedPCTforSBLOCAremainslessthanthelimitingECCSperformanceanalysislargebreakLOCAPCTof2107'F.TheLBLOCAanalysiswasperformedwithaminimumSITpressureof200psig,therefore,theLBLOCAcalculatedresultsalreadyconservativelycoveroperationataminimumSITpressureof500psig.TheseECCSperformanceevaluationsdemonstrateacceptableconformancewith10CFR50.46.Areviewofthenon-LOCAdesignbasiseventsshowsthatnoneofthesesafetyanalysescreditSITinjectionintotheRCStomeettheacceptancecriteria.Therefore,thereductionoftheSITminimumopeFatingpressuresetpointhasnoadverseimpactonthenon-LOCAdesignbasisevents.AnassessmentoftheStationBlackoutEventshowsthatevenwithdelayedSITactuationduetothereducedminimumoperatingpressuresetpoint,primaryreactorcoolantsubcoolinginthehotlegsandreactorcoolantsystemnaturalcirculationaremaintainedthroughouttheassumedfourhourtimeperiodforrestoringACpowerduringthispostulatedevent.
ll SECTIONPAGE"ANNXcjf'fABLKYof~coNTEN$832.1IntroductionandSummary2.2MethodofAnalysis2.3Results2.4Conclusions5Y@7%NNCCVN9KNQMxYNN9%NNNC64.1Non-LOCADesignBasisEvents4.2StationBlackoutEvent'X~AXNKNNS485151556061 I'4AQitfiQ'r ThisreportprovidestechnicaljustificationforadecreaseintheSt.LucieUnit2minimumoperatingsafetyinjectiontank(SIT)pressurefrom570psigto500psig.ReducingthisTechnicalSpecificationLimitingConditionforOperation(LCO)valueprovidesagreaterdifferentialpressuremarginbetweentheSIToperatingpressureandtheSITreliefvalvepressuresetpoint(669'sig).ReducingtheLCOto500psigmeans'hattheminimumSITpressureforoperationwouldberoughly75%ofthereliefvalvepressuresetpointwhichrepresentsa1(Nincreaseinmargincomparedtocurrentconditions.ThisadditionalmarginlessensthepotentialforchallengestotheSITreliefvalveandconcurrentreliefvalveleakagethathaveimpactedSt.LucieUnit2availabilityinthepast.ThisreportislimitedtotheengineeringevaluationnecessarytojustifytheplantchangetoreducetheSITminimumoperatingpressuresetpointfrom570psigto500psig.Thisreportdoesnotinclude(1)anevaluationoftherelatedinstrument(loop)inaccuraciesoruncertainties,(2)PC/H,technicalspecification,FSARorrelatedchangepackages,or(3)addressingchangesintheSITmaximumoperatingpressuresetpoint.Primarily,thisreportaddressestheimpactofreducingthetechnicalspecification,LCOonminimumSITpressureforthepostulatedsmallbreakloss-of-coolantaccident(SBLOCA).TheSBLOCAlimitingbreaksizeandassociatedpeakcladdingtemperature(PCT)stronglydependontheSITpressure.ReducingtheSITminimumoperatingpressureto500psigforSt.LucieUnitfincreasestheSBLOCAlimitingbreaksizefrom0.0375ftto0.045ftandincreasesthePCTfrom1771'Fto1905'F.ThisanalyticalevaluationforSBLOCAwasperformedusingABBCombustionEngineering'sNRCapprovedsmallbreakevaluationmodeldescribedinReference1.Thisanalysisdemonstratesacceptableconformancewith10CFR50.46whichpresentstheAcceptanceCriteriaforEmergencyCoreCoolingSystems(ECCS)forLightWaterNuclearPowerReactors(Reference2).ThecalculatedPCT(1905'F)fortheSBLOCAanalysiswithreducedSITminimumoperatingpressureremainslessthanthecurrentlargebreakloss-
~IIU'L)lq%l of-coolantaccident(LBLOCA)PCTofrecord.ThePCTfortheLBLOCAanalysisis2107'F.ThisLBLOCAanalysiswasperformedwithaSIToperatingpressureof200psig,aconditionwhichconservativelycoversthe500psigSITpressureusedintheSBLOCAanalysis.Therefore,theLBLOCAcalculationremainsthelimitinganalysisofrecordforECCSperformanceevaluation.TheLBLOCAanalysisofrecordisforCycle3whichhasbeenshowntoboundlatercyclesthroughCycle6.ThisLBLOCAanalysisalsoshowsacceptableconformanceto10CFR50.46AcceptanceCriteriaforECCSperformanceinsupportofthereducedvalueofSITminimumoperatingpressureof500psig.ThisLBLOCAECCSperformanceevaluationforSt.LucieUnit2Cycle6wasperformedatapowerlevelof2754NMt(2700HMtplus2Xuncertainty)andatapeaklinearheatgenerationrate(PLHGR)of13kw/ft.Thisreportincludesareviewofthenon-LOCAdesignbasiseventstoIevaluatethepotentialimpactofdecreasingtheLCOforSITminimumpressureto500psig.ForSt.LucieUnit2,noneofthenon-LOCAeventscreditSITinjectionintothereactorcoolantsystem.Therefore,thereductionoftheSITminimumoperatingpressuresetpointhasnoadverseimpactonthenon-LOCAdesignbasiseventanalyses.ThisreportincludesanassessmentofthevalidityofthestationblackouteventdocumentedinSection15.10oftheFSAR(Reference9)withregardtotheimpactofreducingtheminimumSITpressuresetpoint.Inthisassessment,theresultspresentedinReference9areusedtodemonstratethatevenwithdelayedSITdischargeintotheRCSresultingfromloweringtheSITsetpointto500psig,sufficientliquidinventoryremainsintheRCStopreventvoidingintheRCSloopandlossofnaturalcirculation.Therefore,thisassessmentshowsthattheconclusionspresentedinReference9regardingmaintainingprimarynaturalcirculationandcoresubcriticalityforthefourhourdurationofthepostulatedeventareunchangedwiththereducedSITpressuresetpointof500psig.
hlyPI'i,<<\
2.1IntroductionandSummarThissectionpresentstheresultsoftheECCSperformanceevaluationfortheSmallBreakLoss-of-CoolantAccident(SBLOCA)forSt.LucieUnit2,Cycle6,withtheminimumoperatingsafetyinjectiontank(SIT)pressuredecreasedfrom570psigto500psig.ThisECCSperformanceevaluationdemonstratesconformancewith10CFR50.46whichpresentstheAcceptanceCriteriaforEmergencyCoreCoolingSystems(ECCS)forLightWaterNuclearPowerReactors(Reference2).Theevaluationwith500psigminimumoperatingSITpressuredemonstratesacceptableSBLOCAECCSperformanceforSt.LucieUnit2.Sections2.2,2.3,and2.4presentthemethodofanalysis,results,andconclusions,respectively.2.2HethodofAnalsisThecalculationsreportedinthissectionwereperformedusingABBCombustionEngineering'sNRCapprovedsmallbreakevaluationmodeldescribedinReference1.ThismethodofanalysisisthesameasthatusedfortheSt.LucieUnit2Cycle6SBLOCAECCSperformanceanalysis(Reference3).AcompleteevaluationofSBLOCAinvolvestheuseoffourcomputercodes.BlowdownhydraulicsarecalculatedusingtheCEFLASH-4AScomputercode(Reference~RefloodhydraulicsarecalculatedusingtheCOHPERC-IIcode(Reference5).FuelrodtemperaturesandcladdingoxidationpercentagesarecalculatedusingtheSTRIKIN-II(Reference6)andPARCH(Reference7)codes.DetailsoftheinterfacingofthesecodesarediscussedinReference1.FortheECCSperformanceevaluationwiththereducedSITpressure,onlytheCEFLASH-4ASandPARCHcodeswereneededfortheanalysis.LoweringtheSITpressurewhilekeepingallotherparametersandmethodsthesameresultsinachangeinthelimitingbreaksizeandachangeinthe f~'i4t~tt'vf'4A' calculatedPCT.TheCEFLASH-4AScodeisusedtoprovideprimarysystemthermal-hydraulicsforaspectrumofbreaksizestoidentifythenewlimitingbreaksizeandthePARCHcodeprovidesthehotrodheat-upcalculationsduringthecoreboil-offperiodofthetransient.Forlicensingcalculations,thelimitingbreaksizeistypicallythelargestbreakforwhichthecladdingtemperatureheat-upduringcoreboil-offuncoveryisreversedwithonlyHPSIdeliverytotheprimarysystemandwithoutSITdischarge.Inthisanalysis,PCToccursjustafterabriefmomentarydischargefromtheSITswhichisfollowedbyHPSIdrivenrepressurizationandcorerecovery.ForSBLOCA,theCOHPERC-IIcodeisusedtoanalyzethecorehydraulicresponse(recovery)followingcontinuousSITdischarge.TheEvaluationModelmethodologyinReferenceIforanalyzingcorerefloodfollowingSITdischargeusingCOHPERC-IIassumesthatcontinuousSITinjectioncausesallsteaminthecoretwo-phasefluidtocondense.ThisconditiondoesnotapplyforthebreaksizesofthisstudywhereSITdischargeisbriefandnotcontinuous.forthebreaksizesinthisSBLOCAstudy,corerefloodfromHPSIdeliveryandbriefdischargefromtheSITsisanalyzedadequatelywiththeCEFLASH-4AScodewhichgivesboththethermalandhydraulicresponseofthecorerefloodperiod.Therefore,analysisofcorerefloodusingtheCOHPERC-IIcodeisnotneededforthelimitedrangeofbreaksizesinthisstudy.IntheABBC-EmethodologyforSBLOCA,theSTRIKIN-IIcodeisusedtoanalyzethehotrodthermalresponseduringtheperiodofforcedconvectionwhendeparturefromnucleateboilingmayoccur.ForthebreaksizesofthisSBLOCAstudy,acladdingtemperatureincreaseduringtheforcedconvectionperiodduetodeparturefromnucleateboilingdoesnot,usuallyoccur,asindicatedbythe0.0375ftbreakresultsfromtheanalysisperformedforCycle6inReference3.SincethePCTcalculatedwiththePARCHcodeoccursduringtheboil-offuncoveryperiodofthetransient,analysisoftheearlyblowdownhotrodresponseusingtheSTRIKIN-IIcodeisnotneededforthelimitedrangeofbreaksizesinthisECCSevaluation.Also,theearlyblowdownhotrodresponsehasanegligibleinfluenceontheboil-offuncoveryperiodwhendeparturefromnucleateboilingdoesnotoccur.
71eplI;YC4' 1"TheECCSanalysisassumptionsforthisanalysiswithreducedSITpressureareunchangedfromtheevaluationmodelassumptions(Reference1).TheworstsinglefailureforanalysisofSBLOCAisthefailureofoneoftheemergencydieselgeneratorstostart.Thisfailureresultsintheminimumsafetyinje'ctionavailabletocoolthecore.Therefore,basedonthisassumption,thefollowinginjectionpumpswerecreditedintheSBLOCAanalysis:'a~b.C.d.oneHighPressureSafetyInjection(HPSI)pumponeLowPressureSafetyInjection(LPSI)pumponeChargingpumpfourSafetyInjectionTanksForbreaksinthepumpdischargeleg,itisalsoassumedthatallsafetyinjectionflowdeliveredtothebrokencoldlegspillsoutthebreak.Thisresultsinthefollowingreducedinjectionflowdeliveredtothecore:'a~b.C.d.75%oftheflowfromoneHPSIpump50XoftheflowfromoneLPSIpump4ÃoftheflowfromoneChargingpump(basedonworstflowsplit)10ÃoftheflowfromthreeSafetyInjectionTanksAsdescribedinReference1,theSBLOCAanalysesassumethatoffsitepowerislostuponreactortrip.Asaresult,thesafetyinjectionpumpswereassumedtostartaftera30seconddelay(fordieselgeneratorstartupandloadsequenqjgg)followingasafetyinjectionactuationsignal.TheECCSperformanceanalysisconsideredaspectrumofcoldlegbreaksinthereactorcoolantpumpdischargeleg.Asdemonstratedinpreviousanalyses,dischargelegbreaksaremorelimitingthanotherbreaklocations.ThespectrumofbreakswereselectedtoshowthenewlimitingbreaksizeresultingfromthereductioninSITpressure.
I'tJ Thepreviouslimitingbreaksize,0.0375ft,isnotinfluencedbythereducedSITpressure,sincethecladdingtemperatureheat-upisreversedbyHPSIdeliveryalone.LargerbreaksizesdependonSITdischargetoreversethefuelcladdingheat-up.ByreducingSITpressure,theselargerbreaksizes'ustwaitforthereactorcoolantsystempressuretodecreasetothelowerSITsetpointpressurebeforereceivingSITdischargetotheprimarysystem.Theselargerbreaksizesdepressurizemorerapidly,loseinventoryoutthebreakatagreaterrate,andexperiencegreaterratesofcoolantflashing.But,theselargerbreaksizesalsoreceivemoreHPSIdeliverytotheprimarysystemwiththelowerprimarysystempressurepriortoSITdischarge.Whiletheselargerbreaksizecaseswaitfor.SITactuationatthelowerpressuresetpoint,thecladdingcontinuestoheat-uptohighertemperatures.EventuallyHPSIdeliveryatthelowerprimarysystempressurewillbegreaterthantheinventorylossbyflashing,coreboil-off,andspillageoutthebreakandwillreversethecladdingheat-upjustpriortoornearthemomentofSITdischarge,thusestablishinganewlimitingbreaksize.BriefSITdischargetotheRCScanoccurjustpriortoreachingthetimeofpeakcladdingtemperatureandmaythroughitsimpactonthecoretwo-.phasemixturelevelterminatethecladdingtemperatureriseand/ormaycausethecoreaxialelevationofpeaktemperaturetochangetothenexthighestnode.Thenewlimitingbreaksizeidentifiedbythisanalysisisthe0.045ftcoldlegbreak.2.3ResultsTheanalysisdemonstratedthe0.045ftbreaktobethelimitingsmallbreakwithapeakcladdingtemperatureof1905'Fandamaximumcladdingoxidationpercentageoflessthan7%.TheresultsaresummarizedinTable2.3-1.ThetimesatwhichsignificanteventsintheperformanceoftheECCSoccurredforeachbreaksizearelistedinTable2.3-2.Table2.3-3providesalistofthesignificantparametersandinitialconditionsused,intheanalysis.
PP4a$I,/kCi,'~klj"'IA"k,.i~l ThetransientvaluesofparameterswhichmostdirectlyaffectfuelrodperformanceareshowninFigures2.3-1through2.3-4(seeTables2.3-4and2.3-5).Thefollowingparametersaregraphicallypresentedforeachbreaksize:(a)NormalizedTotalCorePower(b)InnerVesselPressure(c)BreakFlowRate'd)InnerVesselInletFlowRate(e)InnerVesselTwo-PhaseMixtureLevel(f)HotSpotHeatTransferCoefficient(g)CoolantTemperatureatHotSpot(h)HotSpotCladdingSurfaceTemperatureFigure2.3-5summarizesthepeakcladdingtemperatureresultsofthespectrumanalysis.The0.045ftbreakwasdeterminedtobethelimitingsmallbreak.Forbreakssmallerthan0.045ftcoreuncoverybeginslaterwhenthefissionproductdecayheatgenerationislessand,hence,thedepthofuncoverywillbeless.forbreaksgreaterthan0.045fthmtheresultingsystemdepressurizationrateisfastersuchthatthecladdingtemperatureriseisterminatedearlyinthetransientbySafetyInjectionTanksactuation.2.4ConclusionsBasedontheresultsofananalysisofaspectrumofsmallbreaksinthecoldlegatthereactorpumpdischargewiththeminimumoperatingpressureofthesafetyinjectiontanksreducedfrom570psigto500psig,itis'concludedthatoperationofSt.LucieUnit2Cycle6isacceptable.Theresultsofthelimiting0.045ftsmallbreakresultedinapeakcladdingtemperatureof1905'Fandamaximumcladdingoxidationpercentageoflessthan7%,demonstratingtheSBLOCAECCSperformancetobelesslimitingthanthatforthelargebreakLOCAperformanceresultsgiveninSection3.0.
Avs*
Table2.3-1St.LucieUnit2FuelRodPerformanceSummarySmallBreakLOCASpectrumwithSafetyInjectionTankPressureof500psigBreakSize(ft)PeakCladTemperatureaxial('F)location"'eakLocalCladOxidationaxialP)location"HotRodCladOxidation"'1o)0.0375ft/PD0.0400ft/PD0.0450ft/PD(0.0500ft/PD17710.9018360.9519050.9518410.855.240.906.730.906.690.904.610.90<0.65<0.81<0.77<0.53(a)Hotrodoxidationvaluesaregivenasaconservativeindicationofcore-wideoxidation(b)PDatPumpDischarge(c)Axiallocationgivenasafractionofactivecoreheight10
~~
Table2.3-2St.LucieUnit2TimesofInterestforSmallBreakLOCASpectrumwithSafetyInjectionTankPressureof500psig(secondsafterbreak)BreakSize(ft)HPSI'"'umpOnLPSISI~~PumpOnTanksOnHotSpotPeakCladTemp.Occurs0.0375ft/PD0.0400ft/PD0.0450ft/PD0.0500ft/PD130120110100(a)(a)(a)(a)28072408203217632261.22351.72034.31776.2(a)CalculationterminatedbeforetimeofLPSIpumpactivation.(b)"PumpOn"and"TanksOn"aremeanttoindicate"RCSInjectionBegins"
Table2.3-3St.LucieUnit2SmallBreakECCSPerformanceAnalysisSignificantParametersandInitialConditionsarameterCorePowerLevelat102KofNominal(MWt)CoreAverageLinearHeatRateat102KofNominal(kw/ft)PeakLinearHeatGenerationRate(PLHGR)HotAssembly,HotChannel(kw/ft)CoreInletTemperature('F)CoreOutletTemperature('F)SystemFlowRate(ibm/hr)CoreFlowRate(ibm/hr)NumberofTubesPluggedPerSteamGenerator~SafetyInjectionTank(SIT)GasPressure(psig)moderatorTemperatureCoefficient(dp/'F)AxialShapeIndex(ASIU)Low'ressurizerPressureTripSetpoint(psia)ISafetyInjectionActuationSignalSetpoint(psia)HighPressureSafetyInjectionPumpShutoffHead(psia)Values27544.9015.0552.0603.8136.1xlO(1)131.1xlO1250500(2)+0.2xlO-0.151650.01500.01214(1)SystemFlowrateconsistentwith363,000gpm(2)LBLOCAusesSITGasPressureof200psig12 r.yy4~
Table2.3-4St.LucieUnit2SmallBreakLOCASpectrumI'eSieandLocation0.0375ftBreakinPumpDischargeLeg0.0400ftBreakinPumpDischargeLeg0.0450ft.BreakinPumpDischargeLeg0.0500ftBreakinPumpDischargeLegAbbreviation0.0375ft/PD0.0400ft/PD0.0450ft/PD0.0500ft/PD~Fiures2.3-12.3-22.3-32.3-413
Table2.3-5St.LucieUnit2VariablesPlottedasaFunctionofTimeforEachSmallBreakLOCAintheSpectrumVariableFigureNormalizedTotalCorePowerInnerVesselPressureBreakFlowRateInnerVesselInletFl'owRateInnerVesselTwo-PhaseHixtureLevelHeatTransferCoefficientatHotSpotCoolantTemperatureatHotSpotHotSpotCladdingSurfaceTemperatureI*RefertoFigures2.3-1Athrough2.3-4H.14 lt~i~=~vus~a~4t~W~'Iu
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4000032000FJ24000~16000I-O~~80000-80000100020003000TIME(SECONDS)40005000FLORIDAPOWER8cLIGHTCO.St.LucieP.NuclearPowerPlantINNERVESSELINLETFLOWRATE0.0450FT28REAKINPUMPDISCHARGELEGFigure8.3-3034 4032LLIP-24OC016OTOPOFCOREOMOFCORE00100020003000(sEcowos)40005000FLORIDAPOWER8cLIGHTCO.St.Lucie2NuclearPoorerPlantINNERVESSELTWO-PHASEMIXTURELEVEL0.0450FT2BREAKINPUMPDISCHARGELEGFigure2.8-0E35 J4(~rEp4BPlt~t 100000IIj0000I-LLIOIJJO10001001010100020003000VIMEtSECONDS)40005000FLORIDAPOWER8cLIGHTCO.St.Lucie8NuclearPowerPlantHEATTRANSFERCOEFFICIENTATHOTSPOT0.0450FT2BREAKINPUMPDISCHARGELEGFigure2.S-SF36 gIt 140012001000LJJ5800LIJ6004002000100020003000TIME(SECONDS)40005000FLORIDAPOWER8cLIGHTCO.St.Lucie?NuclearPapererPlantCOOLANTTEMPERATUREATHOTSPOT0.0450FT2BREAKINPUMPDISCHARGELEGFigure2.3-3G37
~IW~VI"PI~~~~lW%~
22001900IJJ~1600I-~1300<C.K1000Ci7004000100020003000TIME(SECONDS)40005000FLORIDAPOWER8cLIGHTCO.St.Lucie8NuclearPowerPlantHOTSPOTCLADDINGSURFACETEMPERATURE0.0450FT2BREAKINPUMPDISCHARGELEGFigure2.3-3H38 I',g,1I(~,
O1.00OOo0.75CiN~0.50O0.2500'100020003000TIME(SECONDS)40005000FLORIDAPOWER8cLIGHTCO.St.Lucie2NuclearPowerPlantCOREPOWER0.0500FT2BREAKINPUMPDISCHARGELEGFigure2.3-4A39
'4~le~
240020001600wl20080040000100020003000TIME(SECONDS)40005000FLORIDAPOWER8cLIGHTCO.St.Lucie2NuclearPowerPlantINNERVESSELPRESSURE0.0500FT2BREAKINPUMPDISCHARGELEGFigure2.3-484p I'
1200j000800600O4002000100020003000TIME(SECONDS)40005000FLORIDAPOWER8cLIGHTCO.St.LucieP.NuclearPowerPlantBREAKFLOWRATE0.0500FT2BREAKINPUMPDISCHARGELEGFigure2.8-4C
~h0l~0'-~
4000032000~24000mw1600080000010002000000(sEcoNDs)40005000FLORIDAPOWER8cLIGHTCO.St.Lucie2NuclearPowerPlantINNERVESSELINLETFLOWRATE0.0500FT2BREAKINPUMPDISCHARGELEGFigure2.8-4D42
&tsla, 4032IJJP-24>CW016OTOPOFCOREBOMOFCORE00100020003000TIME(SECONDS)40005000FLORIDAPOWER8c'LIGHTCO.St.Lucie8NuclearPowerPlantINNERVESSELTWO-PHASEMIXTURELEVEL0.0500FT2BREAKINPUMPDISCHARGELEGFigure2.0-4E43 I,~RlI'LIeMOM,aa 10000010000tsJV44bJOC3QLJJ(A'L1000100l001000200030004000(sEcoNDs)5000FLORIDAPOWER8cLIGHTCO.St.Lucie2NuclearPowerPlantHEATTRANSFERCOEFFICIENTATHOTSPOT0.0500FT2BREAKINPUMPDISCHARGELEGFigure2.3-4F44 IAPII 12001000800IJJ600<002000010002000300040005000TIMEt',SECONOS)FLORIDAPOWER8cLIGHTCO.St.Lucie8NuclearPoorerPlantCOOLANTTEMPERATUREATHOTSPOT0.0500FT2BREAKINPUMPDISCHARGELEGFigure2.8-4G45 a4llII~~1If 22001900~1600I-~]300IJJ~10000O700400010002000300040005000TIME(SECONDS)FLORIDAPOWER8cLIGHTCO.St.Lucie2NuclearPowerPlantHOTSPOTCIADDINGSURFACETEMPERATURE0.0500FT2BREAKINPUMPDISCHARGELEGFigure2.8-4H46
~84f 22002000LIJCi~1800LYI-~16000C3K~14OO120010000.03790.04000.04250.04500.0475BREAKAREA(SQFT)0.0500FLORIDAPOWER8cLIGHTCO.St.Lucie8NuclearPowerPlantPEAKCLADDINGTEMPERATUREVERSUSBREAKAREAFigure2\3547
~tri,s1fpVJCar4"k>k, Thelargebreakloss-of-coolantaccident(LBLOCA)analysisofrecordforSt.LucieUnit2isforCycle3(Reference8).TheCycle3analysishasboundedlatercycles,namely,Cycles4,5,and6,becauseallcurrentcycle-specificinputdatahasbeenshowntobethesameorlessseverethantheCycle3data.TheCycle3inputdataandresultsofReference8,whichapplyconservativelytoCycle6arepresentedinTables3.0-1and3.0-2,respectively.TheresultsofthisECCSperformanceevaluationdemonstrateapeakcladdingtemperaturenotinexcessof2107'F,apeaklocalcl'addingoxidationpercentage.of7.62K,andapeakcore-widecladdingoxidationpercentageoflessthan0.7%,comparedtotheECCSacceptancecriteriaof2200'F,17K,and1%,respectively.TheseresultswerebasedonaninitialSITpressureof200psig,aconditionalreadymoreadverseforECCSperformancethanthe500psigSITminimumpressureanalyzedforSBLOCAinSection2.0.Therefore,theCycle3LBLOCAresultsapplyconservativelytoCycle6withaminimumSIToperatingpressureof500psig.Inconclusion,operationofSt.LucieUnit2Cycle6withaminimumSITpressureof500psigatacorepowerlevelof2754NWt(102Kof2700HWt)andapeaklinearheatgenerationrateof13.0kw/ftisinconformancewith10CFR50.46.48
~ParameteTable3.0-1St.LucieUnit2LargeBreakECCSPerformanceAnalysisSignificantParametersandInitialConditionsaluesCorePowerLevelat102%ofNominal(HWt)CoreAverageLinearHeatRateat102KofNominal(kw/ft)PeakLinearHeatGenerationRate(PLHGR)HotAssembly,HotChannel(kw/ft)PeakLinear,HeatGenerationRate(PLHGR)HotAssembly,AverageChannel(kw/ft)CoreInletTemperature('F)CoreOutletTemperature('F)SystemFlowRate(ibm/hr)CoreFlowRate(ibm/hr)GapConductanceatPLHGR'(Btu/hr-ft-'F)FuelCenterlineTemperatureatPLHGR'('F)FuelAverageTemperatureatPLHGR'('F)HotRodGasPressure(psia)'aHotRodBurnup(NWD/HTU)NumberofTubesPluggedPerSteamGeneratorAugmentationFactorSafetyInjectionTank(SIT)GasPressure(psig)InitialContainmentTemperature('F)27544.9013.011.57552.0603.8136.lx10(1)131.lxl0146032962102'118103814301.00200(3)90(1)SystemFlowrateconsistentwith363,000gpm(2)STRIKIN-IIvaluesathotrodburnupwhichyieldhighestPCT(3)SBLOCAandnon-LOCAuseSITGasPressureof500-650psig49 t>>
Table3.0-2St.LucieUnit2ResultsforLimitingBreakSize(0.6DfG/PD)~ParametePeakCladdingTemperature('F)TimeofPeakCladdingTemperature(seconds)TimeofCladdingRupture(seconds)PeakLocalCladdingOxidation(5)TotalCore-MideCladdingOxidationP)Value<210726644.747.62<0.7050 f"lh.lIRIP[
ThissectionpresentstheassessmentofotherDesignBasisEvents(DBEs)andthestationblackouteventregardingthereductionoftheSITminimumoperatingpressuresetpoint.Section4.1reviewsthenon-LOCADBEstodeterminewhethertheSITinventorywascreditedinanyoftheseeventsfortheSt.LucieUnit2safetyanalysesofrecord.Section4.2assessesthestationblackoutevent.StationblackoutisoutsidethedesignbasisforSt.LucieUnit2butispartofthelicensingbasis.Thestationblackouteventpostulatesafourhourtimeperi'odforrestoringACpowerduringwhichprimarysubcoolingandnaturalcirculationmustbemaintained.ThestationblackouteventdoescreditSITinventoryformaintainingnaturalcirculation.4.1Non-LOCADesinBasisEventsThenon-LOCADesignBasisEvents(DBEs)werereviewedtodeterminewhethertheSafetyInjectionTankinventorywascreditedintheSt.LucieUnit2safetyanalysesofrecord.Inaddition,theimpactofdecreasingtheSITgaspressureontheresultsofthenon-LOCAeventswasevaluated.TheSITswillinjectduringseveredepressurizationevents,releasinghighlyboratedliquidinventoryintotheRCS.Theboratedliquidinsertsnegativereactivityinthecore,enhancingtheshutdownmarginandmitigatingapossiblereturntocriticality.DecreasingtheSITpressure(actuationsetpoint)woulddelaythepossibleintroductionoftheboratedinventoryintotheRCSandcouldreducethemargintocriticality.Table4.1-1presentsalistoftheSt.LucieUnit2non-LOCADBEs.DBEswhichresultinaseveredepressurizationareidentifiedinthisTablebyarrowsintheleftmargin.Theseareeventsduringwhichthereactorcoolantsystem(RCS)pressuredecreasesbelowthesafetyinjectionactuationsignal(SIAS)setpointandtheHPSIpumpsshutoffhead.Thenon-LOCADBEsresultinginsuchasevereRCSdepressurizationare:51 Jj~kP4I'~tgOttCQglpk,tlI0~~
1)InadvertentOpeningofaSteamGeneratorSafetyValveorAtmosphericDumpValve2)Post-TripReturntoPowerforSteamSystemPipingFailures(SteamLineBreaks)3)PressurizerPressureDecreaseEvents(InadvertentOpeningofthePressurizerPowerOperatedReliefValves-PORVs)4)SmallPrimaryLineBreakOutsideContainment(LetdownLineBreak)5)SteamGeneratorTubeRuptureEventOftheaboveDBEs,theNSSSsimulationoftheInadvertentOpeningofthePressurizerPORVswasterminatedbeforetheRCSpressurestabilizes.Thisisduetothefactthatthepost-tripNSSSbehaviorforthiseventfallswithinthespectrumofconsideredLOCAsandisnotofanyinterestwithrespecttotheDNBcriterionofthisanalysis.AsaLOCA,thepost-tripNSSSbehaviorofthiseventiswithinthedomainaddressedinSection2.0ofthisreport.ReviewoftheremainingDBEswasperformedtodeterminewhetherthecalculatedminimumRCSpressureisbelowthecurrentSITminimumsetpointpressureof570psig(585psia).ThissurveyshowsthattheminimumRCSpressureduringanyoftheaboveDBEsis661psig(676psia)whichoccursduringtheInadvertentOpeningofaSteamGeneratorSafetyValveorAtmosphericlumpValveevent.ForthePost-TripReturntoPowerHotZeroPowerSteamLineBreakEvent,theminimumRCSpressureat300seconds(theendofsimulationtime)is668psig(683psia)andessentiallystable.Theminimumcalculatedpressuresfor,thesetwoeventsarestillabovethecurrentSITminimumsetpointpressureof570psig,resultinginnodeliveryofSITinventorytotheRCS.Sincenoneofthenon-LOCAeventsresultedinorcreditedthedeliveryofSITinventory,adecreaseintheminimumSITsetpointpressurewillhavenoadverseimpactontheresultsandconclusionsoftheseevents.52 0yU Insummary,areviewofSt.LucieUnit2non-LOCAOesignBasisEventsanalysesshowsthatnocreditforSITinjectionintotheRCSwastakenbytheseanalysesinordertoshowacceptableconsequences.Therefore,thereductionoftheSITminimumsetpointpressurehasnoimpactonthenon-LOCAsafetyanalyses.53 EUIUIU,UkIl't$,UJ+'ICtU'U~4IP;P.$qu TABLE4.1-1ST.LUCIEUNIT2,DESIGNBASISEVENTSCONSIDEREDINTHECYCLE2SAFETYANALYSISIncreaseInHeatRemovalByTheSecondarySystemA.B.C.~D.E*DecreaseinFeedwaterTemperatureIncreaseinFeedwaterFlowIncreasedHainSteamFlowInadvertentOpeningofaSteamGeneratorSafetyValveorAtmosphericDumpValveSteamSystemPipingFailuresl.InsideContainmentPre-Trip2.OutsideContainmentPre-TripPowerExcursions3.Post-TripReturntoPower2.3.4.5.6.7.DecreaseInHeatRemovalByTheSecondarySystemA.LossofExternalLoadB.TurbineTripC.LossofCondenserVacuumD.LossofNormalACPowerE.LossofNormalFeedwaterF.*FeedwaterSystemPipeBreaksDecreaseInReactorCoolantFlowrateA.PartialLossofForcedReactorCoolantFlowB.TotalLossofForcedReactorCoolantFlowC.*SingleReactorCoolantPumpShaftSeizure/ShearedShaftReactivityAndPowerDistributionAnomaliesA.UncontrolledCEAMithdrawalfromaSubcriticalorLowPowerConditionB.UncontrolledCEAMithdrawalatPower'.C.CEADropD.CVCSMalfunction(InadvertentBoronDilution)E.StartupofanInactiveReactorCoolantSystemPumpF.*.ControlElementAssemblyEjectionIncreaseInReactorCoolantSystemInventoryA.CVCSMalfunctionB.InadvertentOperationoftheECCSDuringPowerOperationDecreaseInReactorCoolantSystemInventory~A.PressurizerPressureDecreaseEvents~B.SmallPrimaryLineBreakOutsideContainment~C.*SteamGeneratorTubeRuptureHiscellaneousA.AsymmetricSteamGeneratorEventsddddd*Postulat'edAccidents54 E+tRghk!
4.2SttoacoutEventAnassessmentwasmadeofthevalidityofthestationblackoutevent-documentedinSection15.10oftheFSAR(Reference9)withregardtotheimpactofreducingtheminimumSITpressuresetpoint.Inthisassessment,theresultspresentedinReference9areusedtodemonstratethateven'ithdelayedSITdischargeintotheRCSresultingfromloweringtheSITsetpointto500psigsufficientliquidinventoryremainsintheRCStopreventvoidingintheRCSloopandlossofnaturalcirculation.Therefore,.thisassessmentshowsthattheconclusionspresentedinReference9regardingmaintainingprimarynaturalcirculationudcoresubcriticalityareunchangedwiththereducedSITpressuresetpointof500pslg~TheinitialconditionsforthereferenceanalysisareforCycle1,andthereforedonotincludesteamgeneratortubepluggingandstretchreactorcorepowerlevelwhichhaveoccurredsincetheCycle1analysis.Inthereferenceanalysis,creditistakenforoperatoractiontomaintainatleast10'Fprimarysystemsubcoolinginthehotlegs.FortheCycle1analysis,subcoolingensurescondensationof.bubblesproducedinthecore,restrictsvoidformationduetoinventorylosstothereactorvesselupperheadandpressurizer,andmaintainsnaturalcirculation.Inthisassessment,theeffectsoftubepluggingandpowerupgradeonthecalculatedmassandenergybalancesareassumedtobeoffsetbythedifferenceinsteamgeneratorsecondaryoperationthatwouldberequiredtomaintainthespecified'hotlegsubcooling.Thatis,assumingoperatoractionsfollowthesame"no-load"temperatureprogram,theRCSinventoryataparticularRCSpressurefortheCycle1analysiswillbeverysimilartotheRCSinventoryatthesame.RCSpressurecalculatedwithtubepluggingandstretchpower.Inarevisedanalysis,thetimingorsequenceofeventswouldbedifferentfromtheCycle1analysisduetothedynamiceffectsofincreasedpowerandreducedsteamgeneratorheattransferarea,butcreditingoperatoractiontomaintainthesamelevelofsubcooling(i.e.,thesametemperature)inthehotlegsresultsinacomparableRCSinventoryandpressurerelationship.Therefore,arevisedstation55 ra~<eiw4~s blackoutanalysisisnotrequiredfortheassessmentdiscussedbelow,whichusestheRCSinventoryandpressurerelationshipintheCycle1referenceanalysistoshowthatvoidinginthehotlegswouldnotbecalculatedtooccurwithareducedSITpressuresetpoint.TheReference9stationblackouteventanalysiswasperformedusingtheCESEC-IIIcomputercode,seeReference10.ThisreferenceanalysiscreditedSITdischargetotheRCSatabout12540secondsaftereventinitiation,whichwasbasedonaSITpressuresetpointof568psig.UsingtheReference9calculatedresults,Table4.2-1presentstheprimarycoolantmassesinthepressurizer,reactorvesselupperhead,.andremainderoftheRCSforthetimeperiodbetween12000and14000seconds.ColumnsAand8ofTable4.2-1showthatthetimeof12000secondsrepresentsacalculatedconditionintheRCSbeforetheSITpressuresetpointisreached(RCSpressureof632.9psig).Similarly,thetimeof14000secondsisacalculatedconditionintheRCSwhentheprimarypressureisbelowthereducedSITpressuresetpoiptof500psig(RCSpressureof496.6psig).Therefore,thereferenceanalysisindicatesthatthetimedelayinSITdischargeresultingfromreducingthepressuresetpointisroughly1460seconds.ThedatainColumnsAthroughHofTable4.2-1,istakenfromtheCESECoutputeditsfortheReference9analysis.ColumnIinTable4.2-1isthemassofliquidintheRCSexcludingtheupperheadandthepressurizer.Thisisobtainedbysubtractingtheupperheadmass(ColumnG)fromtotalRCSmasswithoutpressurizermass(ColumnF).ThetotalRCSmass'(ColumnJ)includingtheupperheadandthepressurizermassesisobtainedbyaddingthevaluesofColumnsE(pressurizermass)andF(massofRCSplussurgeline).ThevaluesatthebottomofeachcolumninTable4.2-1arethemassdifferencesbetween12000and14000seconds.Table4.2-1showsthatfrom12000to14000seconds,11824.4ibm(ColumnC)wasaddedtotheRCSviaSITdischargeinthereferenceanalysis.Duringthesametimeperiod,1118ibm(ColumnD)leakedoutofthesystem.Therefore,basedonthedifferencebetweeninventoryaddedandinventorylost,thenetmassadditiontotheRCSis10706.4ibm.However,Table4.2-1alsoshowsthatCESECdeterminesforthistimeperiodthatthetotal56 44.vo'1V'4'd~!ŽN't'll RCSmassincreasedby16899ibm(lastentryinColumnJ).ThisdiscrepancybetweentheintegratedinventorybalanceandthesummationoftotalRCSinventory(6192.6ibmintotalinventorygain)isaresultoftheCESECcomputercodenumericalintegrationscheme.Forconservatism,thelowervalueoftotalRCSmassisusedinthisassessmentoftheimpactofthereducedSITpressuresetpoint.Table4.2-1showsthatthe'otalmassofpressurizerandupperheadinventoryat14000secondsis24559ibm(13670ibmfromColumnEplus10889ibmfromColumnG).ReducingthismassbythetotalintegratedSITdischargeof11824.4ibm(ColumnC)andbythe6192.6ibmwhichwasaddedbythecodenumericalscheme,produces6542ibm.Thisisthehypotheticaltotalmassinthepressurizerandtheupperheadat14000secondswithouttheSITinventory.Reducingthishypotheticaltotalmassbythemassofsteamproducesthetotalmassofliquidinthepressurizerandupperhead.ThesteammassesinthepressurizerandupperheadaredeterminedusingtheRCSparametersat12400secondsinthereferenceanalysisbecausethisisthelastsetofinformationnotinfluencedbySITdischarge.Thisselectionof12400seconds'isconservativerelativetolatertimesinthereferenceanalysisbecausetheCESEC-IIIcalculationshowsareductioninvapormassasRCSpressuredecreases,aslongassubcoolinginthehotlegsismaintained.Therefore,themassofsteamthatexistsinthereactorvesselupperheadandpressurizeratthistimeprovidesaconservativeestimatefortheamountofsteamthatwoul'dexistwhentheRCSpressuredecreasestotheSITsetpointpressureof500psig.FromtheCESECmajoreditat12400seconds,themassofsteaminthepressurizeris1829.0ibm.Themassofsteaminthereactorvesselupperheadat12400secondis1339.5ibmwhichisbasedon(1)atotalupperheadvolumeof1165.4ft,(2)avoidfractionof0.86547(ColumnHat12400seconds),and(3)asteamspecificvolumeof0.753ft/ibmatasaturatedpressureof598.2psig(Column8at12400seconds).Subtractingthesteammassofthepressurizerandupperhead(3168.5ibm)fromthetotalmassoftheseregions(6542ibm)showsthatapproximately3373.5ibmofliquidwouldstillremainintheseregionsat14000seconds57 AyA9) withoutanySITinventoryenteringtheRCS.ColumnBofTable4.2-1indicatesthatwiththereducedpressuresetpointof500psig,theSITswillhavedischargedatsometimepriorto14000seconds.Therefore,itisconcludedthatRCSliquidinventorywouldstillbeenoughsothatsomeliquidremainedintheupperheadandthepressurizer.ThismeansnovoidingwouldhavebeenintroducedintheRCSloops.Restrictingvoidingtotheupperheadin.theanalysisistheresultofassumingoperatoractiontomaintainatleast10'Fsubcoolinginthehotlegsbyopeningtheatmosphericdumpvalvestoreducethesecondarysystempressureandtemperature.Theincreasedheatremovalinthesteamgeneratorscausedbythelargertemperaturedifferenceacrossthesteamgeneratortubesreducestheprimarysystemtemperature.Sincethesizeofthevoidisdeterminedtoremainconfinedbytheupperheadandpressurizer,naturalcirculationinthehotlegsismaintained.DischargeofboratedwaterfromtheSITspreventsadditionalvoiggrowth.Hence,theconclusionsoftheReference9analysisregarding'maintainingnaturalcirculationintheRCSforthefirstfourhoursoftheeventareunchanged.ItshouldbenotedthattheReference9calculationdidnotcredittheboroncontentsoftheSITsforthereactivitycalculations.Therefore,theconclusionsoftheReference9analysiswithrespecttomaintainingcoresubcriticalityarenotaffectedbytheSITspressuresetpointchangeinthisevaluation.Also,thisevaluationconservativelyusedthelowerRCSinventorycalculationfromCESECandassumednoSITdischargethrough14000seconds,wheretheprimarypressureisbelowtheSITpressuresetpoint.58 tlflegr'tI~,p TABLE4.2-1STATIONBLACKOUTEVENTINVENTORYSUMMARYTIMEPRESSINTEGRATEDPSIGSIT,lbmINTEGRATEDLEAK,lbmPZRRCSIncUPHMASS,lbmMASS,lbmUPPERHEADMASS,IbmUPPERHEADVOIDFRACTCESECTHERMAL-HYDRAULICSUMMARYRCSw/oUPHRCSTOTALMASS,IbmMASS,Ibm12000632.9122001240012600622,3598.2559.112800549.713000544.513200539.10.00.00.02352.13707.94411.15226.510215A7.5710E+034.4990E+0510332.88.6070E+034.4880E+0510445.48.3660E+034.4890E+0510560.84.8990E+034.5580E+05106786.0010E+034.5660Et0510790.27.7420E+034.5570Et0510899A9.3640Et034.5510E+058.5076E+039.0452E+039.1083E+038.3772E+038.7643E+039.2671E+039.7185E+038.7677E-01441392.48.6696E-01439754.88.6547E-018.7782E-018.7086E-01439791.7447422.8447835.78.6196E-01446432.98.5398E-01445381.5457471457407457266460699462601463442464464134001360013800531.5508.1501.26259.99964.311092.611005.21.0760E+044.5520E+0511115.61.0350E<044.6120E+0511226.61.1840E+044.6140E>051.0093E+041.0127Et041.0396E+048.4734E-018.4657E-018.4185E-0144510745107345100448596047155047324014000496.611824.411333.41.3670E+044.6070E+051.0889E+048.3328E-01449811474370DIFF11824.411186.0990E+03.1.0800E+042.3814E+038418.616899DESCRIPTIONOFCOLUMNHEADINGSA)TIME(SECONDS)B)RCSPRESSURE(PSIG)C)INTEGRATEDSITDISCHARGE(LBM)D)INTEGRATEDLEAKFROMRCS,TOTALEDFORTHETWOSIMULATEDLEAKS(LBM)E)TOTALPRESSURIZERMASS,PRESSURIZERLIQUIDPLUSSTEAMMASS(LBM)F)MASSOFRCSPLUSSURGELINE(LBM)G)MASSINTHEUPPERHEAD(LBM)H)UPPERHEADVOIDFRACTIONI)MASSINTHERCSLOOP,EXCLUDINGMASSOFPRESSURIZERANDUPPERHEAD(LBM)OBTAINEDBYSUBTRACTINGCOLUMNGFROMFJ)TOTALRCSMASS,INCLUDINGTHEPRESSURIZERANDUPPERHEADMASSES(LBM)OBTAINEDBYADDINGCOLUMNSEANDFDIFF:THELASTROWPROVIDESTHEMASSDIFFERENCEBETWEEN14000AND12000SECONDSFOREACHPARAMETER 0CVI"lJI This'eportprovidesthetechnicalbasisfortheengineeringevaluationwhichdemonstratesthatareductionofSITpressureminimumoperatingsetpointfrom570psigto500psigforSt.LucieUnit2Cycle6continuestomeettheacceptancecriteriaforECCSperformanceasdefinedbyIOCFR50.46.ThisreportincludesthesupportinginformationandanalyticalresultsforSBLOCA,LBLOCA,non-LOCAdesignbasistransientsandthestationblackoutevent.Thecontainmentpeakpressureanalysiswasnotexaminedbythisstudy,however,thereductionofSITpressureminimumoperatingsetpointto500psigdoesnotadverselyaffectthecontainmentpeakpressurebecausethetotalmassandenergyreleasedtothecontainmentfromtheprimarysystemintheanalysisisnotchangedandbecausetheSITdischargeslessthanonesecondlateratthelowersetpoint.ReducingthetechnicalspecificationLCOvalueto500psigprovidesadditionaldifferentialpressuremarginbetweentheSIToperatingpressureandtheSITreliefvalvepressuresetpoint(669psig).Thisadditionalmarginlessensthepotentialforchallengesto'heSITreliefvalveandconcurrentreliefvalveleakagethathaveimpactedSt.LucieUnit2plantavailability.,60 Nl'O'Lgj'It'd CENP0-137,"CalculativeMethodsfortheCESmallBreakLOCAEvalu'ationModel,"CombustionEngineeringProprietaryReport,August1974,(Proprietary).CENP0-137,"CalculativeMethods.fortheCESmallBreakLOCAEvaluationModel,"Supplement1,January1977,(Proprietary).AcceptanceCriteriaforEmergencyCoreCoolingSystemforLight-WaterCooledNuclearPowerReactors,FederalRegister,Vol.39,No.3-Friday,January4,1974.Letter,E.L.Trapp(C-E)toW.L.Parks,(FPLL),"St.LucieUnit2.Cycle6ReloadSafetyEvaluation(RSE)Report,"F2-90-035,July6,1990.CENPD-133,Supplement1,"CEFLASH-4AS,AComputerProgramforReactorBlowdownAnalysisoftheSmallBreakLoss-of-CoolantAccident,"August1974,(Proprietary).CENP0-133,Supplement3,"CEFLASH-4AS,AComputerProgramforReactorBlowdownAnalysisoftheSmallBreakLoss-of-CoolantAccident,"January1977,(Proprietary).CENP0-134,"COMPERC-II,AProgramforEmergencyRefill-RefloodoftheCore,"April1974,(Proprietary).CENPD-134,Supplement1,"COMPERC-II,AProgramforEmergencyRefill-RefloodoftheCore(Modification),"December1974,(Proprietary).CENPD-134,Supplement2,"COMPERC-II,AProgramforEmergencyRefill-RefloodoftheCore,"June1985,(Proprietary).CENPD-135,"STRIKIN-II,ACylindricalGeometryFuelRodHeatTransferProgram,"April1974,(Proprietary).CENP0-135,Supplement2,"STRIKIN-II,ACylindricalGeometryFuelRodHeatTransferProgram(Modification),"February1975(Proprietary).CENP0-135,Supplement4,"STRIKIN-II,ACylindricalGeometryFuelRodHeatTransferProgram,"August1976,(Proprietary).CENP0-135,Supplement5,"STRIKIN-II,ACylindricalGeometry'uelRodHeatTransferProgram,"April1977,(Proprietary).61 PI1~
7.CENPD-138,"PARCH-AFORTRAN-IVDigitalProgramtoEvaluatePoolBoiling,AxialRodandCoolantHeatup,"August1974,(Proprietary).CENPD-138,SupplementI,"PARCH,AFORTRAN-IVDigitalProgramtoEvaluatePoolBoiling,AxialRodandCoolantHeatup,"(Hodification),February1975,(Proprietary).8.CENPD-138,Supplement2-P,January1977,(Proprietary).Letter,E.L.Trapp(C-E)toJ.L.Perryman(FPKL),"ResultsofCE'sLargeBreakLOCA,ReevaluationforSt.LucieUnit2BasedonCE'sNew(1986)EvaluationModel,"F2-CE-R-137,April10,1987.9.FPEL,"St.LuciePlantUnit2,FSAR,"AmendmentNo.1,April1986.10.C-ETopicalReport,CENPD-107,"CESEC-DigitalSimulationofaCombustionEng'ineeringNuclearSteamSupplySystem,"April1974.C-ETopicalReport,"CESEC-DigitalSimulationofaCombustionEngineeringNuclearSteamSupplySystem,"Enclosure1-PtoLD-82-001,January6,1982.62 5