ML080560615

Millstone, Unit 3 - Response to Request for Additional Information Regarding Stretch Power Uprate License Amendment Request Revised and Supplemental Responses to Questions AFPB-07-0007 & AFPB-07-0008

ML080560615
Person / Time
Site:	Millstone
Issue date:	02/25/2008
From:	Bischof G T Dominion Nuclear Connecticut
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
07-0799A
Download: ML080560615 (7)

Text

Dominion Nuclear Connecticut, Inc.\lillS10IlC Power Station!\(Il)l'J l.Trv Road\\.u,!<l1l!.CT February 25.2008U.S.NuclearRegulatoryCommissionAttention:DocumentControlDeskOneWhiteFlintNorth11555RockvillePikeRockville,MD20852-2378SerialNo.:

NLOS/MAE:DocketNo.:LicenseNo.:

07-0799A R1 50-423 NPF-49 DOMINION NUCLEAR CONNECTICUT, INC.MILLSTONE POWER STATIONUNIT3 RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION REGARDING STRETCH POWER UPRATE LICENSE AMENDMENT REQUEST REVISED AND SUPPLEMENTAL RESPONSES TO QUESTIONS AFPB-07-0007 AND AFPB-07-0008DominionNuclearConnecticut,Inc.(DNC)submittedastretchpowerupratelicense amendmentrequest(LAR)forMillstonePowerStationUnit3(MPS3)inlettersdatedJuly13,2007(SerialNos.07-0450and07-0450A),andsupplementedthesubmittalbylettersdated September12,2007(SerialNo.07-0450B)andDecember13,2007(SerialNo.07-0450C).TheNRC staffforwardedrequestsforadditionalinformation(RAls)inOctober29,2007,November26,2007,December14,2007,andDecember20,2007letters.DNCrespondedtotheRAlsinlettersdatedNovember19,2007(SerialNo.07-0751), December17,2007(SerialNo.07-0799),January10,2008(SerialNos.07-0834,07-0834A,07-0834C,and07-0834F),January11,2008(SerialNos.07-0834B,07-0834E,07-0834G,and07-0834H),January14,2008(SerialNo.07-0834D),January18,2008(SerialNos.07-0846,07-0846A,07-0846B,07-0846C,and07-0846D)andJanuary31,2008(SerialNo.

07-08341).InaconferencecallwiththeNRCstaffonJanuary24,2008,theNRC staff requestedadditionalclarificationtotheresponsetoRAIQuestion AFPB-07-0007providedinDNC'sDecember17,2007letter.TheresponsetoRAIQuestionAFPB-07-0007hasbeenrevisedandisprovidedintheattachmenttothisletter.ThisrevisedresponsesupersedestheDecember17,2007responsetoRAIQuestion07-AFPB-0007initsentirety.

ONe'sDecember17,2007letteralsocontainedaresponsetoRAIQuestion07-AFPB-0008.Thatresponsecommittedtoprovidingtheresultsoftheupdatedcontrolroomfireanalysisby February 29,2008.AsupplementalresponsetoRAIQuestion 07-AFPB-0008whichcontainstheupdatedcontrolroomfireanalysisisalsoprovidedintheattachmenttothisletter.TheinformationprovidedbythisletterdoesnotaffecttheconclusionsofthesignificanthazardsconsiderationdiscussionintheDecember13,2007DNCletter(SerialNo.

07-0450C).

SerialNo.07-0799ADocketNo.50-423Supp.Resp,SPUPage2of3Shouldyouhaveanyquestionsinregardtothissubmittal,pleasecontactMs.MargaretEarleat804-273-2768.

Sincerely,VicePresident-NuclearEngineering COMMONWEALTH OF VIRGINIA COUNTY OF HENRICO The foregoing document was acknowledgedbeforeme,inandforthe County and Commonwealth aforesaid,todaybyGeraldT.Bischof,whoisVice President-Nuclear Engineering of Dominion Nuclear Connecticut, Inc.Hehas affirmedbeforemethatheisduly authorized to executeandfilethe foregoing document in behalfofthat Company,andthatthe statementsinthe documentaretruetothebestofhis knowledgeandbelief.

Acknowledgedbeforemethis J 5 or-JldJ/JLril.j

,2006 My Commission Expires:doLo..//!Lk1:L..:MtlLNotaryPublicCommitmentsmadeinthisletter:None Attachmentcc:U.S.NuclearRegulatoryCommissionRegionI Regional Administrator475AllendaleRoadKingofPrussia,PA19406-1415 Mr.J.G.LambU.S.NuclearRegulatoryCommissionOneWhiteFlintNorth11555RockvillePikeMailStop 0-8B1ARockville,MD20852-2738 VICKI L.HULL NoIaIY PuDIC COINftOn*..-of.....,....COIMIIlllon al.lO,e Ms.C.J.Sanders Project Manager U.S.NuclearRegulatoryCommissionOneWhiteFlintNorth11555RockvillePikeMailStop 0-8B3Rockville,MD20852-2738 NRC Senior Resident InspectorMillstonePowerStation DirectorBureauofAir ManagementMonitoringandRadiationDivision DepartmentofEnvironmentalProtection79ElmStreetHartford,CT06106-5127SerialNo.07-0799ADocketNo.50-423Supp.Resp,SPUPage3of3 SerialNo.07

-0799A Docket No.50-423 ATTACHMENT LICENSE AMENDMENT REQUEST STRETCH POWER UPRATE LICENSE AMENDMENT REQUEST RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION REVISED AND SUPPLEMENTAL RESPONSES TO QUESTIONS AFPB-07-0007 AND AFPB-07-0008 MILLSTONE POWER STATIONUNIT3 DOMINION NUCLEAR CONNECTICUT, INC.

SerialNo.07-0799ADocketNo.50-423Attachment,Page1of3 NRC Question AFPB-07-0007 LAR Attachment5,Section2.5.1.4.2.3.4,"SafeShutdownEvaluations,"statesthat"...thesafe-shutdownanalysisidentifiesfire-inducedfailuresthataffecttheplantandtheoperatoractionsthatcanbeusedtocompensateforthesefailures..."Discusstheresponsetime,includinganyassumptions,especiallythoseofapotentially non-conservativenature,whichmayhavebeenmadeindeterminingthattheoperatormanualactionscanconfidentlybeaccomplishedwithintheavailabletime.RevisedONC ResponseAsdescribedinLARSection2.5.1.4.2.3.4,therevisedanalysesperformedatSPUconditionsforbothControlRoomFireTransientandChargingCubicleFire TransientconfirmsthatSPUdoesnotimpacttherequiredoperatoractiontimes.Theassumptionsforcriticaloperatoractionsusedinpre-SPUandpost-SPUanalysesremainthesamefortheControlRoomFireTransient.Thecritical operator actionsassumedfollowingthereactortripfromthecontrolroomandinitiationofmainsteamisolation(MSI)signalfromthecontrolroomareletdownisolationandchargingflowrestoration.Specifically,theanalysisassumes15minutesforletdownisolationand30minutesfortherestorationofchargingflowfromtheeventinitiation.Theresponsetimesfortheseassumedactiontimeshavebeenvalidatedforcurrentpowerlevelsandarewellwithintheassumedoperatoractiontimes.TheseresponsetimesarenotimpactedforpostSPUconditions.Notethattheresponsetimeforthemanualinitiationofauxiliary feedwaterisdiscussed in AFPB-07-0008.

Operatorinitiationtimeofauxiliaryfeedwaterflowisnotaparameterusedintheabovestatedanalysis.ThecurrentanalysisfortheChargingCubicleFireTransientwasperformedusingtheTREATmodel.Thereareseveraloperatoractionsthatoccuratspecifictimes throughoutthetransientthatarecriticalinmaintainingpressurizerlevelonscale.Specifically,thecurrentanalysisassumesletdownisolationin5minutes,reactortripin10minutes,closureoftheMSIvalves(MSIVs)in 11minutesandsecuringthe pressurizerheatersin15minutes.TherevisedanalysisforSPUconditionswasperformedusingtheNOTRUMPmodel.Theassumedcritical operatoractiontimesremainthesameasthepre-SPUconditions.ItisnotedthattheSPUanalysisassumed695seconds(11.6minutes)forMSIVclosure.ThisprovidesasmallincreaseinmarginforoperatoractionthatisunrelatedtoSPU.Theseanalysisassumptionsareboundingwithrespecttothefireshutdownprocedureofrecord.

SerialNo.07-0799ADocketNo.50-423Attachment,Page2of3 NRC Question AFPB-07-0008 LAR Attachment5,Section2.5.1.4.2.3.7,"OperatorActionsRequiredFollowingaFire" states that"...[an]analysiswasperformedtodeterminethesteam generatordryouttimeatthesupportstretchpoweruprate(SPU)powerlevel;theresultsshowedadryouttime of approximately37minutes.Therefore,therecontinuestobeadequatetimefortheoperatortomanuallyinitiateauxiliaryfeedwatertothesteamgenerators(SGs)atSPUconditions..."Discusstheresponsetime,includinganyassumptionsthatmayhavebeenmadeindeterminingthattheoperatormanualactionscanconfidentlybeaccomplishedbeforeSGdryout.ONCInitial ResponseThefollowingresponsewasprovidedinDNCletterdatedDecember17,2007,(SerialNo.07-0799):"TheMP3BTP9.5-1ComplianceReportcontainsinformationonprioritizationofoperatoractions.Oneofthemanualactionsgivenhighpriorityisauxiliary feedwater(AFW)initiationtoaminimumoftwoSteamGenerators(SGs)forthefireshutdownscenariorequiringcontrolroomevacuation(i.e.,CB-8,9, 11A1B fires).In Attachment5,Section2.5.1.4.2.3.7oftheLAR,thesteamgeneratordry-outtimeisstatedas approximately37minutes.DuringvalidationandverificationoftheresponsetothisRAI,itwasidentifiedthattherewasanerrorintheSPUlicensesubmittal.Thecorrectsteamgeneratordry-outtimeforSPUconditionsis34.67minutesbasedonthecitedanalysis.Thisvalueisobtainedfromananalysisthatusedaveryconservativereactortriptime.MP3BTP9.5-1ComplianceReport(Section6.1.1)statesthatAFWflowcanbeinitiatedwithin1O-minutestoaminimumoftwosteamgenerators.ItwasrecentlyidentifiedthattheinitiationofAFWflowwouldoccuratapproximately27minutesforthelimitingfire scenario.Evenwithadecreaseinsteamgeneratordry-outtimeandanincreaseintheAFWflowinitiationtime,basedontheavailabilityofthelargecapacityturbinedriven AFW pump, preliminaryanalysishasshownthatthemarginbetween27minutesand34.67minutesisstill sufficienttoassurethatallBTP9.5-1criteriawillbemet.Inordertoprovideabetterestimateofthesteamgeneratordry-outtimeaswellasprovidemorecomplete documentationthatallBTP9.5-1criteriacanbemet,anupdatetothecontrolroomfireanalysisisinprogress.ResultsoftheupdatedcontrolroomfireanalysiswillbeprovidedtoyoubyFebruary29,2008."

SerialNo.07-0799ADocketNo.50-423Attachment,Page3of3 ONe Supplemental Response:AscommittedtointheDNCresponsetoRAIAFPB-07-0008(DNCletter07-0799datedDecember17,2007),athermalhydraulicanalysishasbeenperformedforthefireshutdownscenariorequiringcontrolroomevacuation(i.e.,CB-8,CB-9, CB-11A1B fires),whichassumesadelayedauxiliaryfeedwater(AFW)initiationtimeof31.5minutes(30minutesplus90secondturbinedrivenAFWpumpstarttime)toaminimumoftwosteamgenerators(SGs).AsstatedinDNCinitialresponse,theoperatoractiontoinitiateAFWflowfromtheauxiliaryshutdownpaneltoatleasttwoSGshasbeenestimatedtooccurinapproximately27minutesforthelimitingfirescenariobaseduponourcurrentfireshutdownprocedures.Inordertoprovidemargin,thisAFWinitiationtimewillbereducedtolessthan21.5minutes(20minutesplus90secondturbinedrivenAFWpumpstarttime)priortoimplementationoftheSPU,bymakingchangestothefireshutdownprocedureanddesigncompliancereport.TheanalysisshowsthatthelevelinthetwosteamgeneratorsbeginstorecoverimmediatelyafterreceivingAFWflowat31.5minutes.SecondarysteamingshiftspreferentiallytothetwosteamgeneratorsnotreceivingAFWflow.InventoryinthetwosteamgeneratorsnotreceivingAFWflowcontinuestodecreaseuntildryoutintherangeof45minutes.EventhoughtheanalysisconservativelyassumesnoAFWflowtotwooftheSGsbecauseoftheclosureoftwooftheAFWcontrolvalvesduetopotentialhotshorts,thecurrentfireshutdowndesign/procedurecallsfordenergizingtheAFWsolenoidoperatedcontrolvalvescausingthemtofailopen.Thisactionwilloccurbeforethe45minutedryouttime.Thus,completingthisactionwithin45minuteswillassurenoneofthesteamgeneratorswilldryout.TheminimumAFWflowrateandoperatoractiontimeassumedintheanalysisaresufficienttoremovedecayheatandpreventSGdryout.