ML17309A406
| ML17309A406 | |
| Person / Time | |
|---|---|
| Site: | Ginna  |
| Issue date: | 07/07/1988 |
| From: | SNOW B A ROCHESTER GAS & ELECTRIC CORP. |
| To: | STAHLE C NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM), Office of Nuclear Reactor Regulation |
| References | |
| IEB-88-004, IEB-88-4, IEIN-87-059, IEIN-87-59, NUDOCS 8807130187 | |
| Download: ML17309A406 (30) | |
Text
ROCHESTERGASANDELECTRICCORPORATION~89EASTAVENUE.ROCHESTER,N.Y.14649-0001July7,1988U.S.NuclearRegulatoryCommissionDocumentControlDeskAttn:Mr.CarlStahlePWRProjectDirectorateNo.1Washington,D.C.20555
Subject:
ResponsetoNRCBulletin88-04PotentialSafety-RelatedPumpLossR.E.GinnaNuclearPowerPlantDocketNo.50-244
DearMr.Stahle:
ThesubjectBulletinrequestedlicenseestodeterminewhetherconditionsmayexistwhichcouldpotentiallycausesafety-relatedpumpdamageduetoparalleloperation.Damagewouldbetheresultofoverheatingcausedbythepumpoperatingdeadheaded.TheBulletinalsorequestedanevaluationoftheadequacyoftheminimumrecirculationflowduringoperation,testing,andaccidentconditionsconsideringthelargesttimespentinthesemodesandthecumulativeeffectsonthepumpoverthelifctimeoftheplant.RG&EwasinitiallynotifiedoftheseconcernsbyWestinghouseElectricCorporation,whichwasfollowedbyNRCInformationNotice87-59.RESIDUALHEATREMOVALANDSAFETYINJE~ONSYSTEMSTheresultsofourevaluationsperformedandtestsrunsubsequenttothesenotificationshaveindicatedthattheresidualheatremoval(RHR)pumps,whichalsoserveasthelowheadsafetyinjectionpumps,wouldbesusceptibletotheconditiondescribedintheBulletinforthreereasons:1)TheRHRsystemutilizesaminimumflowbypasslinewhichiscommontobothpumps.2)Theminiflowpipingisconfiguredsuchthataninteractionbetweenthetwopumpsisnotprecludedduringparalleloperation.3)TheRHRpumpdesignischaracterizedbyahead-capacitycurvewhichhasarelativelyflatshapeatlowflows.
Thethreehighheadsafetyinjection(SI)pumpsareeachprovidedwithaminimumflowrecirculationlinewhichislocatedupstreamofeachdischargelinecheckvalve.Therefore,eachSIpumpwillreceiveaminimumflowindependentoftheotherpumpsandarenotsusceptibletotheparalleloperationconcerndescribedinthesubjectBulletin.Theexistingminimumflow(designedfor30gpm)wasbasedonshorttermoperationand.limitingthetemperatureriseofthepumpinternalfluid.Thissystemhasbeenre-evaluatedassetforthinAttachmentA.Baseduponourreviewofperiodicandspecialtestdata,andthepumpdesignsandoperationalmodes,wehaveconcludedthatthesizingoftheminimumflowbypasslinesforboththeRHRandSIpumpscouldbeconsideredadequatetoprovidepumpprotectionforshorttermoperationintheminimumflowmode,forwhichtheselineswereintended.However,theparalleloperationconcernfortheRHRpumpsnecessitatedcorrectiveactionwhichwastakenonaninterimbasisbyproceduralstepsandwillbetakenforthelongertermbyaplantmodification.Thesafetyinjectionsystemrecirculationsystemisalsoundergoingaredesignforaplannedplantmodificationforthepurposeofde-sensitizingthesafetyinjectionpumpstothepotentialforlongtermweardegradationcausedbymonthlyperiodictestsinthelowflowmode.ThisplannedmodificationisbeingcombinedwithapreviousmodificationcommitmentmadeinresponsetoIEBulletin86-03,PotentialFailureofMultipleECCSPumpsDuetoSingleFailureofAirOperatedValveinMinimumFlowRecirculationLine,submittedinourletterdatedJanuary8,1987.HardwaremodificationsforbothRHRandSIsystemsareplannedduringour1989annualmaintenanceandrefuelingoutage.FortheRHRsystem,aredesignisunderwaywhichwillprovideeachRHRpumpwithaminimumflowrecirculationlinewhichisindependentoftheoppositetrain.Thelineisbeingsizedtoprovidesufficientrecirculationflowwhenthepumpdischargepathisisolated.Intheinterim,procedureshavebeenmodifiedwhichrequiresecuringoneRHRpumpiftwopumpsareoperatingwithacombinedflowlessthan1200gpm.Thisflowwasdeterminedasaconservativevalueabovewhichsufficientflowwouldbeguaranteedthroughtheweakerpumpwhenthepumpsoperateinparallel.FortheSIsystem,theplannedmodificationwillrequireadditionallargerdiameterrecirculationpipingwithapressurebreakdownorificeineachseparateline,sizedtoallow100gpmorabout25%ofbestefficiencypoint(BEP)offlow.Eachofthesedesignshadtheobjectiveofprovidingsufficientrecirculationflowconsistentwithpumpmanufacturerrecommendationswithoutreductionintheinjectedflowdeliveryduringaccidentconditionsusedinthesafetyanalysisreport.
AnevaluationoftheSIandRHRrecirculationredesignsandjustificationforcontinuedoperationissetforthinAttachmentsAandB.AUXILIARYFEEDWATERSYSTEMSTheauxiliaryfeedwaterpumpshavealsobeenevaluatedrelativetotheBulletin88-04concerns.TheGinnaStationmainauxiliaryfeedwatersystemconsistsoftwo1009ocapacitymotordrivenpumpsandone200%,capacityturbinedrivenpump.Twoadditionalstandbyauxiliaryfeedwaterpumps,each100%capacity,arealsoinstalledinaseparatebuildingasabackuptothemainauxiliaryfeedwaterpumps.Eachofthesepumpsisprovidedwithanautomaticallycontrolledminimumflowrecirculationsystemsizedandperiodicallytestedtoensurethatsufficientminimumflowwillbeprovidedunderallaccidentandnormaloperatingconditions.IthasbeendeterminedthattheminimumflowconcernsraisedinBulletin88-04havebeenadequatelyaddressedinthe'designandtestingofthesesystemsatGinna.AnevaluationoftherecirculationsystemsforthesepumpsissetforthinAttachmentC.Therearenoothersafety-relatedpumpswhicharesusceptibletotheBulletin88-04concer'ns.Asrequiredbyparagraph5of.thesubjectbulletin,awrittenresponsedescribingtheactionstakenwillbeprovidedwithin30daysfollowingcompletionoftheplannedplantmodificationsdescribedinAttachmentsAandB.Asrequiredbyparagraph6ofthesubjectbulletin,thisresponsetothebulletinandourevaluationssetforthinAttachmentsAthroughCwillbemaintainedatGinnaStationforaminimumoftwoyears.Verytrulyyours,'ruceA.SnowSuperintendentNuclearProductionSubscribedandsworntobeforemethis7thdayofJuly,1988.NotaryPublicLYNNJ.HAUCKNotaryPrrtraeintheStateoiNewYorkMONROECOUNTYCommissionExpiresiVov.30.l9R5 AttachmentsxcU.S.NuclearRegulatoryCommissionRegionI475AllendaleRoadKingofPrussia,PA19406xc:GinnaSeniorResidentInspector ATTACHMENTAEvaluation.ofSafetyInjectionRecirculationSystemand,JustificationforContinuedrationReference(a):LetterURGE-87-670fromS.P.Swigert(Westinghouse)toS.M.Spector(RG&E),datedDecember8,1987Reference(b):AgingandServiceWearofAuxiliaryFeedwaterPumpsforPWRNuclearPowerPlants,Volume1,OperatingExperienceandFailureIdentification,NUREG/CR-4597-VldatedJuly1986NRCBulletin88-04requestedanevaluationoftwoconditionswhich,ifexisting,couldresultindamageorfailureofsafety-relatedpumps.First,theconcernexiststhatwhentwopumpsareoperatedinparallel,theweakerpumpmaybedeadheadedbythestrongerpumpwhenthepumpsareoperatingintheminimumflowmode.Second,theconcernexiststhattheamountofminimumflowmaynotbeadequatetoprecludepumpdamageorfailureifevenasinglepumpisoperating.Shouldeitheroftheseconditionsexist,theplannedshorttermandlongtermmodificationsaretobeidentifiedaswellasthejustificationforcontinuedoperation.R.E.Ginnautilizesatwo-loopWestinghousedesignedreactorcoolantsystemandhasthreehighheadsafetyinjectionpumpsTheexistingsafetyinjectionsystemisdepictedonFigure6.3-1oftheUFSAR.AlinediagramdepictingthepresentSIrecirculationsystemisalsoshownonFigureA-1ofthisattachment.Eachsafetyinjectionpumpisprovidedwitha3/4-inchlinecontainingapressurebreakdownorifice,acheckvalveandalockedopenmanualvalve.Thedischargelinesfromthe"A"pumpand"B"pumphavetrainseparation,leadingtotheRCSloop"B"andloop"A"coldlegs,respectively.The"C"pumpisaswingpumpthatensuresdeliverytobothtrainswillexistintheeventthateitherthe"A"or"B"pumpfailstostart.Whenallthreepumpsareoperating,theflowfromthe"C"pumpisdirectedtobothtrains.The3/4-inchlinesfromthethreepumpsjoinandforma1-inchlinewhicheventuallyleads'backtotheRWST.However,asnotedinWestinghouseletter,Reference(a),theplacementoftheorificeupstreamofthisjunctionreducesthepressurelowenoughsothataweakerpumpwillnotbepreventedfromdeliveringitsminimumflow.Theorificeintheindividualrecirculationlineessentiallydesensitizesthesystemtostrong/weakpumpminiflowconcerns.Sincethe3/4-inchrecirculationlinesarelocatedupstreamofthepump'sdischargecheckvalves,andthefactthatanorificeislocatedineachminiflowline,theoperatingpressureofastrongerpumprunninginparalleldoesnothavethepotentialtopreventrecirculationflowthroughthisline,anddeadheadtheotherpump.
AsshownonUFSARFigure15.6-12,duringtheinjectionphaseSIflowwillbepumpedintotheRCScoldlegswhenpressuredropsbelow1400psia.Ofthebreaksizesrequiredtobeanalyzedinsection15.6oftheUFSAR,onlyabreaksizebelow4-inchdiameterwouldresultintheRCSremainingabove1400psiaforanyappreciabletime.The4-inchbreaktransientwasthesmallestsizeanalyzedandresultedintheRCSpressurefallingto1400psiainapproximately20seconds.Theelapsedtimetogeneratethesafetyinjectionsignal,actuatethestartsequenceandbringthepumpstofullspeedisontheorderof20seconds(assuminglossofoffsitepower).Ifoffsitepowerremainsavailable,theSIpumpswouldbebroughtuptospeedin10seconds,sothatpotentiallyapumpmightexpecttooperatewiththedesignedrecirculationcapacityforonly10secondsbeforethepumpdischargepressurewouldovercomethesystempressure.Therefore,forthebreaksizesanalyzed,representingtheboundingcases,thepumpswouldnotbeexpectedtooperateforanappreciabletimeintherecirculationmode.Forprimarysystembreakssmallerthan4-inchdiameter,secondarysidesteambreaks,steamgeneratortuberupture,rodejectionaccident,oraninadvertentSIsignal,thesafetyinjectionpumpsmaybecalledupontooperateintheminimumrecirculationflowmodeforshortperiodsoftime.Procedurereviewandtrainingonthe:-ulatorconservativelyhasshownthattheoperatingtimeinthe."irculationflowmodewill'otexceed60minutes.Thedesignedminimumflowis30gpmatshutoff,i.e.,whenthedischargevalveisclosed,30gpmrecirculatescontinuouslythroughthepump.Th'erearenoautomaticvalvesintheindividualrecirculationlines,sothateachlineisalwaysopen.ThesafetyinjectionpumpsareWorthingtonCorporation,horizontal,11stage,centrifugalpumpsdrivenbyWestinghouse350hp,3600SRPM,A.C.motors.Theminimumflowrecirculationsystemforthesafetyinjectionpumpswasdesignedtoprovidepumpprotectionforshorttermoperationandwasbasedonlimitingtheheatriseoftheinternalfluidwithinthepumptoacceptablevalues.Consideringtheboricacidstoragetanksasthesourceofwaterforthepumpsandtheheattracingapplied,thecalculatedtemperatureriseis40F.Thisiswellwithinestablishedlimitsgiventheoperatingconditionsandthedesignbasis.Theallowabletemperaturerisetosaturationconditionsisover100F.Thedesignofthepumpprovidesforprocessfluidcoolingforthemechanicalseals,usingseparatesealwaterheatexchangers,usingcomponentcoolingwaterandservicewaterjacketcoolingforthepumpballthrustbearing.Althoughthevalueof30gpm(orabout7%ofbestefficiencypoint;BEP)wouldbeconsideredlowusingcurrentguidelinesofminimumflowdesign,RG&Econsidersitaconditionallyacceptablevaluebasedonthefollowing:1)Itprovidespumpprotectionforshorttermoperationonly2)Demonstratedperformanceofthesepumpsduringperiodictestingatlowflowssubstantiatesacceptability.A-2 tTrendsinminimumowdesignphilosophyand,moreimportantly,developmentsintheeffectsofsuctionrecirculationonpumphydraulicperformanceandimpellerweardegradationinthelongterm,hasledpumpmanufacturerstorecommendsignificantlyhighervaluesofrecirculationflow.Theserecommendationsareconsistentfromtheperspectivethat1)oftenthespecifieddesignoperatingconditionsanddurationisnot,orcannot,bewelldefinedand,2)themanufacturershavenocontrolovertheusers'perationofthepump,yetriskliabilitybyassociationifthecomponentsuffersprematuredegradation.Consequently,minimumflowrecommendationsfromthemanufacturers,unlessotherwisenoted,applytocontinuouslongtermoperationandareontheorderof25:ofBEP,dependingonpumpparameterssuchaspumpedwatertemperature,rotatingspeed,singleormulti-stagedesign,horizontalandverticalmounting,wearingringmaterials,pumpspecificspeed,brakehorsepower,suctionconditions,andothers.Operationintherecirculationmodefor24hoursperdayorsomefinitenumberofhourspermonth,perhapsontheorderof100hourspermonth,hasthepotentialtocauseaggravatedimpellerdamageandprematureinternalwearifampleflowisnotprovided.Quantifyingtheoperatingtimetothedegreeofanticipatedwearcanonlybedeterminedempirically.Areportonagingandservicewearofauxiliaryfeedwaterpumps,Reference(b),makesreferencetotheeffectsofsuctionrecirculationandcausesofinternalwear.Basedonthisreasoning,themanufacturerhasnowrecommendedanominalvalueof1/3ofBEP(150gpm)forcontinuousoperation,andseatedthatoperationatlowerflowsisafunctionofownerrelatedexperience.Whilethistrendofprovidingminimumflowrecommendationsbasedonlongtermoperationisinthebestinterestoftheownersandsuppliers,attheexpenseofoversizingthepumpsandrelatedcomponents,earlierdesigns,whichproducedminimumflowconsistentwithshorttermoperation,canbeshowntobeadequate.RG&E'sexperiencewiththeSXpumpperformanceduringperiodictestinghasbeenexcellent.Therehavenotbeenanymaintenanceproblemsassociatedwiththepumps.Monthlylowflowperiodictestsareperformedatessentiallythesameconditionsastherecirculationmodeofoperation.ProcedurePT-2.1specifiesoperationofeachpumpwithflowthrougha3/4-inchtestlinewiththeflowthrottledto53gpm(TechnicalSpecificationvaluesetinSection4.5.2.1).Thisrepresentstheonlyflowthroughthepumpduringthetest,becausethemanualvalveintherecirculationlineisclosedduringtesting.Thevalueof53gpmisnotjudgedtorepresentasignificantincreaseinflowover-thevalueof30gpm,whichisthedesignedflowthroughtherecirculationline.Asameansofsubstantiatingthis,aspecialtestwasconductedonApril6,1988.Duringthistest,valvealignmentswereslightlymodifiedfromthestandardperiodictestprocedureinordertooperatethe"A"pumpwithaminimumflowof30gpmthroughthetestlineandcomparethepumpoperationandvibrationwiththatforaflowof53gpmaswellasaflowinexcessof100gpm*.AsummaryoftestresultsisincludedonpageA-5.
Reviewofthisdataandperiodictestdataoverthepastseveralyearsindicatesthatthereisnoappreciabledifferenceinpumpvibrationlevelsrelativetoflowsfrom30gpmto100gpm.Thevaluesrecordedforeachofthe3pumpsaretypicalofthoseseenduringmonthlyperiodictesting,andareconsistent(orlowerthan)the-referencedvaluesestablishedduringtheinitialtestprogramforthesepumps.Thevibrationlevelsarewellwithintheacceptablerangeof0to1mils.Testingofthesafetyinjectionpumpsduringmonthlyperiodictestingrequireslowflowoperationforperiodsgenerallyof30minutesto1hour.Thepumpsmayalsobeoperatedatlowflowsforbriefperiodstomaintainaccumulatorlevelorforrefillingtheaccumulatorswhendrainedduringrefuelingshutdowns.Thetotaloperatingtimeforthe3pumpscombinedforthefirst18yearsofplantoperationhasbeenapproximately600hours.The"C"pumphasloggedthemostnumberofhours,280.Therefore,continuedplantoperationutilizingthepresentrecirculationsystemdoesnotcreateaconditionwhichisoutsideoftheoriginaldesignbasis,forthesystemnordoesitrepresentanunacceptableconditionintermsofpumpprotectionforthemaximumdurationthatthepumpswouldbeexpectedtooperateintherecirculationmode.Thebasisforcontinuedopera:isthattheminimumrecirculationflowpipingdesignw~...individuallinesbranchedoffthepumpdischargelineupstreamofthecheckvalveandanorificeplacedineachindividualrecirculationlinepreventsastrong/weakpumpinteraction.Also,thetestresultsconductedforthefirst18yearsofplantoperationdemonstratethatpumpperformance,asreflectedbyvibrationmeasurements,isnotsignificantlydifferentbetween30gpmand100gpm,thelatterrepresentingabout25tofBEP.Theremainderofthisevaluationisintendedtofocusontheplannedplantmodificationtoprovideincreasedpumprecirculationcapacity.Thebasisforthismodificationistoreducethepotentialforpumpinternalacceleratedwearasaresultoflowflowoperationandtherequiredperiodictesting.Thegreatmajorityofpumpoperatinghourshavetodateoccurredduringlowflowoperation.Operationofthepumpsduringanyofthepostulatedaccidentconditionswillnotresultinoperationinminimumflowmodeformorethan1hour,duetoproceduralSItermination.Byinstallingnewresizedrecirculationpipingpresentlyplannedtorecirculate100gpmwhenthepumpoperatesatshutoff,apositivelongtermeffect,althoughunquantified,isexpectedoverthelifeofthepumps.Themodificationwillprovidethecapabilitytoperformperiodictestsat150gpm."Existingflowmeterinthetestlineis70gpmfullscale.Duringthetesting,thethrottlevalvewasfullopenandindicatedinexcessoffullscale.Combinedwithaflowofabout30gpmthroughtherecirculationline,theflowwasdeterminedtobeinexcessof100gpm.A-4 ttSUMMARYOFTESTRESULTSFORSPECIALMINIMUMFLOWTESTCONDUCTEDON"A"SAFETYINJECTIONPUMP30~i"A"SIPUMPFLOW53c3pm)100~mAcceptableRangeat53~mReferenceValuesat53~mDevelopedpressure,psigVibration,milsIBVerticalIBHorizontalOBVerticalOBHorizontal14460.0570'840.190.1514430.060.0880.180.1414130.0480.0820.170.1351420-14810-1mils0-1mils0-1mils0-1mils14520.0550.090.240.11Developedpressure,psig"B"PUMP953GPM1457AcceptableRaneat1420-1493ReferenceValuesat1464Vibration,milsIBVerticalIBHorizontalOBVerticalOBHorizontal0.0520.0960.120.110-1milsO-lmils0-1mils0-1mils0.0650.120.210.11Developedpressure,psig"C"PUMP953GPM1459Acceptable1420-1488ReferenceValuesat1459Vibration,milsIBVerticalIBHorizontalOBVerticalOBHorizontal0.0810.170.0880.140-1mils0-1mils0-1milsO-lmils0'950.160.350.16IB=Inboard(coupling)endOB=OutboardA-5 Therecirculationrateof100gpmrepresentsavalueof25%ofBEP.Thisvaluewasselectedbaseduponfourcriteria:1)Thevalueapproachedthemanufacturer'srecommendationsforlongtermoperation,reducinghydraulicanddynamicforcesimposedonthepump.Themanufacturerrecommended150gpmforlongtermoperation,butmadenoexplicitrecommendationforshortertermoperation.sinceitisdependentuponownerexperience.Theproposedmodificationwillenabletestingat150gpm./2)Thevaluewas*consideredthemaximumrecirculationflowwhichwillstillallowtherequiredSIdeliverytotheRCSunderallaccidentconditions.TherequireddeliverycurveispresentedintheUFSARFigure15.6-12.3)Thevaluewillreducethecalculatedpumpedfluidtemperatureincreasethroughthepumpfourfold,i.e.,toa10Ftemperaturerise.4)Thevaluewillincreasetheoperatinglifeofthepumpballbearingsbyreducingthebearingloadsduringperiodictesting.Thepresentperiodictestingisconductedusingaparatetestlinewiththerecirculationlinesisolated.Thetestflowisadjustedto53gpmandpumpperformanceismonitoredinaccordancewithASMESectionXIArticleIWP-3100,withoneexceptionasdiscussedbelow.Inordertodeterminetheeffectofincreasedrecirculationflowoverthatoftheexistingsystem,30gpmperpump,ahydraulicmodelusingtheKYPIPEcomputercodefortheECCSsystemhasbeendeveloped.Thepumpmanufacturer,WorthingtonCorporation,doesnotrecommendbearingtemperaturemeasurementsatlowflowsasagoodindicationofbearingcondition.Vibrationreadingsprovideabetterindicationoftheircondition.Atlowflows,bearingtemperaturemeasurementsareexpectedtobehigherduetoincreasedaxialandradialthrustloadsinthisregion.Thetemperatureriseofthepumpedfluidisalsogreater,andthisheatisconductedtothebearingsthroughthepumpshaft.Thesefactorstypicallyresultedinbearingstabilizationtimebeingextendedbeyondthatwhichwouldbenormallyexpectedforthepumpatitsrated,flowcondition.Stabilizationundertheselowflowconditionsduringpreviousperiodictestsoccurredtypicallyafterabout1hour,andsometimes2hours.Retestswerenotuncommonduetotemperaturesexceedingthe160Fimposedlimit,whichwas,infact,themanufacturer'srecommendedlimitattheratedconditionof300gpm.A-6 Ithasalsobeenshownthatbearingstabilizationtemperatureanddurationisdependentonotherfactors,suchasambientairtemperatureandthrustbearinghousingcoolingwatertemperature(servicewater).Thiswasconfirmedduringaseriesoftestsperformedoneachofthe3pumpsduringthewinterof1981andthewinterandsummerof1982.Consequently,itisnotpossibletoobtainrepeatable,consistentandmeaningfulresultsrelatabletobearingcondition.Obtainingthisonlymarginallyusefuldatawasoutweighedbythenegativeimpactofsubjectingthepumptounnecessarilyhighloadsinthelowflowtestconditionforextendedperiodsoftimeeachmonth.Overall,thiswasviewedashavingadetrimentaleffectonbearinglife,andultimatelypumpserviceability.Consequently,'bearingstabilizationtestswerediscontinuedinJanuary1983.Stabilizationtemperaturewasnotnoticeablychanged.bytestflowsbetween50to80gpm.Thetestingperformedin1981and1982didconfirmthatthebearingtemperatureswillstabilizeinthelowflowmodeandnotreachunacceptablelevelsconsideringthedesignlaketemperatureof80Fforsummeroperation.Theproposedmodificationwillallowaflowduringtestinginexcessofthe150gpmrecommendedbythemanufacturerforcontinuousoperationbycombiningthemodifiedrecirculationlineflowandexistingtestlineflow.Nearlydoublingtheflowfrom80gpmto150gpmwillplacethepumpinanoperatingregionwhereresidualaxialthrustcanbeexpected.tob.-:educed.Sincethevalueof150gpmrepresentsaflowjudgedacceptableforlongtermoperation,thisconditioncanbeviewedasanimprovementtooverallbearinglife.TheKYPIPEcomputercodehasbeenverifiedagainstactualplantdatatakeninMarch1971whichwasperformedbyWestinghousetore-evaluatethecapabilityofthesafetyinjectionsystem.Theplannedrecirculationsystemwillconsistofasinglerecirculationlinesizedfor100gpmforeachpumpwithpressurebreakdownfloworifice,checkvalveandmanualvalve.Thisconfigurationwaspreferredasitrepresentsapassivetypesystemwithnoactivecomponents,andthereforemeetsthesingleactivefailurecriteria.Itrepresentsamorereliableoptionthantheotheractive/passiveparallelpathsystemsconsideredwhichwouldrequirecontrolsystemswithairand/orelectricalinterfaces.AschematicoftheplannedsystemisdepictedonFigureA-2..ThecriteriausedtoestablishthemaximumallowablerecirculationflowwasthedeliverycurveshownonFigure15.6-12oftheUFSAR(attachedFigureA-3).Thehydraulicmodelisconservativeforthefollowingreasons:a)Theexistingpumpperformancecurvewasdegraded5percenttoevaluatetheabilityofthesafetyinjectionsystemtomeettheUFSARSIdeliverycurve.PeriodictestprocedurePT-2.1containsactionrequirementswhenthepumpperformancedegrades3-o-4%ofthereferencepressure.A-7
(~b)ThehydraulicmodelpredictslessSIfowthanthatwhichwasactuallymeasuredduringthefullflowtestingperformed.inMarch1971.c)ThehydraulicmodelassumedtheminimumSIsuctionheadforallrangesofSIflow.minimumsuctionheadisequivalenttotheRWSTlevel,thepointatwhichtheSIsuctionistransferredtothecontainmentviatheRHRpumps.pumpThe15'tpumpsumpd)ThedeterminationoftheresultantSIdeliverycurve,utilizingthemodified(100gpm)recirculationflow,wasbaseduponthehighestresistanceflowpath(pump"C"deliverytolooplIAll)TheresultantsafetyinjectiondeliverycurveexceedstherequirementshownonFigure15.6-12oftheUFSAR(attachedFigureA-3),utilizingtheproposedrecirculationdesignwhichwillallow100gpmrecirculationflowatshutoff.Inordertoreducevelocitiestoacceptablevalues,eachrecirculationlinewillbeincreasedfrom3/4-inchtol-inch,andtherecirculationmanifoldlinewillincreasefrom1-inchto2-inch.Theexisting1-inchmanifoldlinecontains2airoperatedvalvesinseries.Duringthesumprecirculationmode,therecirculationmanifoldlineisisolatedtoprecluderadioactivecontaminationoftheRWST.Currentlythese2valves,AOV897andAOV898,aremechanicallyblockedopentopreventclosureonlossofairsupply.ClosurewouldblockofftheminiflowprotectionforallthreeSIpumps.Theymustbemanuallyunblockedandclosedpriortotheinitiationofthesumprecirculationphase.AspreviouslyreportedunderRG&E'sresponsetoIEBulletin86-03,RG&Eplanstoreplacethesevalves.'PThecriteriausedforthereplacementvalvesis1)toensurethatnosingleactivefailurewouldpreventtherecirculationlinefromremainingopenforpumpprotection,2)toensurethatnosingleactivefailurewillpreventtherecirculationlinetobeisolatedpriortothesumprecirculationphase,and3)thatvalvemanipulationcanbeperformedfromtheControlRoom.Thepresentschedulecallsforthenewrecirculationpiping,valvesandcontrolstobeinstalledduringthe1989refuelingoutage,withpre-operationaltestingandthemodificationturnedoverforusebytheendof1989.A-8 FIGUREA-1.SISMINIFLOWRECIRCLATIONSYSTEM3/4'.O.RESTERKlltieORIFICE(IYP)IMAwiFoLDLINE.3/4'.O.~8973/4'.O.098RltSTSlPOPAREACTOf1LOOP,8eASISIPlNPCRllSTslRNpeI]RFACIORLOS'THROTTL'CVALVETESTLIREI FIGUREA-2MODIFICATIONSCHEMATICMRFLlMIMARYPFICPu~p9PO~Pl00GRILOORIFICE2'/i3/4'eLO3/i'3/4'QISIR.OITESTLCP3/4'OAY~~wrrcxaLOLESSCSPLY2'ESTLCOPLOjOPTIONAI)SIRlOA(TYPIC'LE%%:Dllllt8Ll%llllEQlIRCÃlIEIlllHlGISTIl8LMAlOEml18%Rf%ÃFIEO%VLI%AIOEmJIP%N1IHSTlLLfD>0RvST
~II>II~IIIIIIII'~IIliII~I~e00~II~
ae~~ATTACHMENTBEvaluationoftheResidualHeatRemoval(RHR)RecirculationSstemand.JustificationforContinuedration
Reference:
(a)FlowMeasurementEnineerinHandbook,R.W.Miller,McGrawHillBookCompany,NewYork,1983,Chapter4NRCBulletin88-04requestedanevaluationoftwoconditionswhich,ifexisting,couldresultindamageorfailureofsafety-relatedpumps.First,theconcernexiststhatwhentwopumpsareoperatedinparallel,theweakerpumpmaybedeadheadedbythestrongerpumpwhenthepumpsareoperatingintheminimumflowmode.Second,theconcernexiststhattheamountofminimumflowmaynotbeadequatetoprecludepumpdamageorfailureifevenasinglepumpisoperating.Shouldeitheroftheseconditionsexist,theplannedshorttermandlongterm-modificationsaretobeidentifiedaswellasthejustificationforcontinuedoperation.TheRHRpumpsatR.E.Ginnaserveastheresidualheatremovalpumpsusedduringnormalplantcooldown,heatupandrefuelingaswellasthelowheadsafetyinjectionpumps,functioningaspartoftheemergencycorecoolingsystem(ECCS).Thereare4modesduringwhichtheRHRpumpsareplacedinoperation:1)Lowheadsafetyinjection(LHSI)aspartoftheECCS,withpumpstakingsuctionfromtherefuelingwaterstoragetank(RWST).ThisistheinjectionphaseandrepresentsthenormalplantalignmentuponreceiptofanSIsignal.2)Lowheadsafetyinjection(LHSI)aspartoftheECCS,withpumpstakingsuctionfromthecontainmentsump.ThisrepresentstherecirculationphasefollowingdepletionofRWSTto15%level.3)Residualheatremovalmodeduringplantcooldownandduringrefuelingoperations.TheRHRpumpstakesuctionfromtheRCSloop"A"hotleganddischargebacktotheRCStoloop"B"coldleg.DuringthismodeRCSpressureandtemperaturearebelow350psigand350F.Pumpoperabilitytestingisalsoconductedmonthlyduringshutdownsatapumpflowof700gpm.
4)Testmode.MonthlyperiodictestingisperformedinaccordancewithASMESectionXIArticleIWP-3100duringnormalplantoperation.PumpsareoperatedseparatelyandtakesuctionfromtheRWSTanddischargethroughtheminiflowrecirculationlineandbacktothepumpsuction.TheRHRsystemconfigurationisshownonFigure5.4-7oftheUFSAR.Thepumpsdischargeintoparallelpathseachwithacheckvalve,residualheatexchanger,andcontrolvalveinprimarily8-inchpiping.Thedischargelinesmergeintoacommon10-inchsectionofpipingwhichleadsinsidecontainment.This10-inchlinedirectstheflowthroughtwomotoroperated,valvestotheloop"B"coldleg.ThesenormallyclosedvalvesareopenedfornormalRHRoperationduringplantcooldown.Two6-inchbranchlinesleadingtothereactorvessel,areautomaticallyalignedforlowheadsafetyinjectionuponreceivinganSIsignal.A2-inchminiflowrecirculationlinebranchesoffthe10-inchcommondischargelineandleadstoasectionof10inchRHRsuctionpipingwhichsplitsandleadsbacktoeachoftheRHRpumps.'heminiflowrecirculationlinecontainsamanualglobevalveandflowmeterFI-628.Theminiflowlineisalwaysopen.ThisminiflowlineservesbothpumpsandprovidestheneededflowthroughthepumpswhentheRCSpressureexceedsRHRpumpshutoffhead.Thesystemisdesignedtoprovide200gpmminimumflowwithonepumprunningor100gpmperpumpifoperatedinparallel.WestinghouseinitiallynotifiedRG&EofapotentialconcernforthoseplantsthathadacommonrecirculationlineandidentifiedR.E.Ginnaasaplantthatwaspotentiallyaffected(WestinghouseletterstoRG&EdatedOctober26,1987,November30,1987andDecember8,1987).NRCInformationNotice87-59datedNovember17,1987wasissuedidentifyingtheconcernswhichwereagaindocumentedinNRCBulletin88-04datedMay5,1988.RG&EinitiatedaCorrectiveActionReport(CAR1828)followingreceiptoftheinitialWestinghousecorrespondence.TheRHRpumpsaresinglestage,horizontal,coupledcentrifugalpumps,Model6-SVC,manufacturedbyPacificPumpDivisiondrivenbyWestinghouseElectricCorporation200hpA.C.motors.Thepumpsareratedfor1560gpmat280ft.totalheadat1770rpm.Reviewofthemanufacturer'sinitialpumpperformancecurvesindicatedthatthepumpsarewellmatchedforparalleloperation,however,duetotheflatnessofthecurvesatlowflowswhichistypicalofpumpswithlowspecificspeedsuchasthese,smalldifferencesintheactualpumptotaldevelopedheadorsystemresistancecancauselargedifferencesintheindividualpump'soperatingflow.AreviewofseveralmonthsofperiodictestdataperformedintheApril-September1987timeframedemonstratedthatthedifferencebetweenthetwopumps'evelopedpressurewasabout1or2psiatthe200gpmflowrate.Theimpactofthiswasthen.evaluated.B-2 TheRHRsystemcontainsoneflowmeter(FZ-626)locatedinthe10-inchcommondischargeline,whichmeasuresthetotalflowfrombothRHRlegs,therefore,confirmationoftheactualflowfromeachpumpduringparallellowflowoperationnecessitatedaspecialtest.Twotestswereconducted,onDecember16,1987andDecember22,1987,duringwhichanultrasonictypeflowmeterwasinstalledonthe>>B>>RHRdischargeleg.ByrecordingsimultaneouslytheflowontheminiflowrecirculationlineflowmeterFZ-628andtheultrasonicflowmeterinthe>>B>>pumpleg,flowinbothlegsoftheRHRpipingwasdetermined.Pumpbearinghousingvibration,casingvibration,sealwaterpipingtemperature,casingtemperatureandmotorcurrentwerealsomonitoredandrecordedduringthetest.Thetestingdeterminedthatwithbothpumpsoperatinginparallelatatotalflowof200gpm,the>>A>>pumpreceivedonlyabout5gpmandwas,therefore,essentiallydeadheaded.Operationintheparallelmodewasterminated51/2minutesafterstart.Thetotaldischargepressureconfirmedthe>>A>>pumptobeonly2psilessthanthe>>B>>pumpat200gpmwheneachpumpoperatedseparately.Basedupontheshapeofthehead-capacitycurve,however,forthesepumps,a2psidifferencewouldresultinthetotalflowwithbothpumpsoperatinginparallelrequiredtobeabout500gpmbeforetheweaker>>A>>pumpwouldbeabletoovercometheheadatthisoperatingpoint.Znordertomorecloselyestablishtheoperationallimitationswhileinparallel,areviewwasmadeofalargersampleofmonthlyperiodictestdata.Thistes'tingisconductedduringnormalplantoperationutilizingtheminiflowrecirculationline.Theflowrateissetat200gpmbythrottlingmanualglobevalve822B.Eachpumpistestedseparately.Dataoverthelast24monthshasbeentrendedtoestablishthedifferencebetweenthedifferentialpressuresofthe>>A>>and>>B>>pumpsconsideringthepressuregagerepeatability.Thesamedischargepressuregage,PI-629,isusedfortestingeachpump.Suctionpressureisdeterminedbyanelevationheadcalculationbased.onRWSTwaterlevel.Testingisdoneonbothpumpssequentiallyusingthesameprocedure.Thesamepersonnelperformedthetestingonthe>>A>>aswellas>>B>>pump,hence,gagereadingsareexpectedtobeconsistentforaparticularmonthlytest.Sincethesamegageisused,thecalibrationandbiaserrorofthegagewouldremainunchangedforaparticularmonthlytest,andnotbeafactorindeterminingthedifferenceindifferentialpressuresbetweenpumps>>A>>and>>B>>.Thetrending,therefore,providesthebasisfordeterminationofthemeanvalueofthepressuredifferenceandstandarddeviationofthedata.Thetrendingshowsthatthemeanvalueforthedifferenceindifferentialpressuresis1.76psi~Thedatapointsreviewedoverthelast24monthsofperiodictestingindicatethatthepressureindicatorproducesreasonablyrepeatablepressurevalues.Theaccuracyofthevalues,thatis,theclosenesstothetruevalue,whichincludestheeffectsofbothprecisionandbiaserror,is+1.6%forthe>>A>>pumpdataand+1.2:forthe>>B>>pumpdata.BydeterminingthedifferenceB-3
'I'inpressurereadingsandaccountingfortwostandarddeviations,theadjustedpressuredifferencewasdeterminedtobe3.76psiforanalysispurposes(Referencea).Ananalysisofthelossesduetopipingandcomponentsshowsthattheheadlossinthe"B"pumpand"A"pumpdischargesectionsofpipinguptothejunctionpointofthetwoloopsiswithin0.2feetofwateroressentiallyequivalentatthe200gpmflowrate.Theheadlossencompassedpipingandcomponentlossessuchaselbows,reducers,heatexchangers,andvalvesaswellaselevationheadlosses.Therefore,thedifferenceinpumpdifferentialpressuresrecordedisduetoindividualpumpcharacteristics,notdifferencesintheindividualRHRdischargelineresistances.Thepurposeofthedatareviewandtrendingwastoestablishavalueforthedifferenceofpumpdevelopedpressurewhichwouldprovidethebasisforestablishingoperatinglimitationsforparallelpumpoperation.Thisadjustedpressuredifferenceresultedinaconditionwherebythetotalflowwithbothpumpsoperatinginparallelwouldneedtobeabout700gpmbeforetheweaker"A"pumpwouldbeassured,ofovercomingtheheadattheoperatingpoint.FollowingRG&EnotificationoftheminiflowconcernbyWestinghouse,calculationswereperformedtodeterminethefollowing:1)Thecalculatedtemperature=riseinthefluidwithinthecriticalareasinternaltothepumpversustheflowratethroughthepump.2)Thetimetosaturationofthewaterwithinthecriticalinternalareasofthepumpafterbeingstartedinthedeadheadedcondition.TheRHRpumpsarenormallyalignedtotheRWSTwhichismaintainedataminimumwatervolumebyTechnicalSpecification,therefore,theelevationheadabovetheRHRpumpsuctioncenterlineisknown.Themaximumwatertemperatureof80FfortheRWSTwasusedinthecalculations.Thevolumeofwaterwithinthepumpwasobtainedwiththehelpofthemanufacturer.Thetemperatureriseversuspumpflowcurvewasplottedwiththeresultsthata40gpmflowwouldproducea10Friseanda20gpmflowwouldproducea21Friseintheinternalfluid.Theresultsalsoindicatedthatifstartedinadeadheadedcondition,theinternalfluidcouldreachsaturationconditionsin6.7minutes,assumingnoheatlossesfromthepump,noheatlossduetothecomponentcoolingwaterjacketcoolingwhichisprovidedaroundthepumpcasingcover,andallthepumpbrakehorsepowerisconvertedimmediatelyintoheatupofthepumpfluid.B-4
~~~Theminiflowrecirculationlinewasoriginallysizedbaseduponpumpinternaltemperatureriseandwasintendedtoprovidepumpprotectionagainstoperationintherecircmodeforshortperiodsoftime.Thecapacityoftheminiflowlineisinexcessof200gpmwithonepumpoperating,sinceV-822Brequiressomethrottlinginordertoachievethisflow.Consequently,forparalleloperation,ifbothpumpsweretoequallysharethisflow(asistheidealconditioninparalleloperation),eachpumpwoulddeliver100gpm.Baseduponthisandthecalculatedtemperaturerisecurve,theminiflowlinewasadequatelysizedandwouldresultinatemperatureriseofonly3.9F.Regardingthe6.7minutestosaturationtime,duringthespecialtestrunonDecember22,1987the"A"pumpwasdeterminedtobeessentiallydeadheadedfor5.5minuteswhilethepumpparametersweremonitored.Sealreturnpipingsurfacetemperatureandcasingsurfacetemperatureweremonitored.Thesealreturntemperaturedidnotshowanoticeableincrease.Thecasingsurfacetemperatureindicated85Fwhenthepumpwassecured.Bearinghousingvibrationatthehighestlocation(inboardendvertical)increasedfrom0.75mils(normal)to1.2mils(deadheaded).Casingvibrationincreasedfrom0.20mils(normal)to0.32mils(deadheaded)onthe"A"pump.Ingeneral,thetrendinthebearinghousingvibrationlevelswasanincreaseof10-20%asflowwasreducedfrom200gpmto50gpm.Onthe"A"pump,whichwasinfactdeadheadedduringthe51/2minutespan,thevibrationincreasedfrom0.80milsat50gpmto1.2mils(inboardvertical)or50%,yet,theselevelsthemselvesaretypicalfortheequipmentandarewithintheacceptedstandards.Consequently,testdatarecordedintherangeof200gpmto50gpmdidnotindicateasignificantincreaseinpumpvibration,orothermonitoredparameters,althoughthecasingtemperaturedidindicatethefluidtemperaturewasincreasing,aswouldbeexpected.Basedupontheforegoingsummaryofeventsandinformation,allprocedureswhichrequireoperationoftheRHRpumpshavebeenchangedtorequirethatwhentwopumpsarerunningandthetotalflowindicatedonflowindicatorFI-626islessthan1200gpm,onepumpisstopped.Conversely,ifonepumpisrunningwithgreaterthanorequalto1200gpm,thesecondpumpisstartedifavailable.ItisacceptabletostopanRHRpumpbecauseasinglepumpwillprovideallrequiredaccidentflow.Theseproceduralmodificationshavebeenmadeasaninterimmeasurejustifyingcontinuedoperationuntilaplannedplantmodificationcanbeinstalledwhichwillprovideaseparateandindependentrecirculationflowloopforeachpump.Additionally,anoperatoraidtaghasbeenplacedontheFI-626indicatorintheControlRoomwhichidentifiesthisoperatinglimitation.Trainingontheseprocedurechangesisbeingprovidedtotheoperatorsonanongoingbasis.Theprocedurechangeshavebeeninsertedintheimmediateactionstepsoftheemergencyprocedures.MonitoringthistripandrestartcriteriaisperformedonacontinualbasisB-5 asrequiredontheprocedurefoldoutpage.Combinedwiththeoperatortrainingandtheoperatoraidtag,ahighconfidenceexiststhatoperationofthepumpsinparallelataconditionwhichcouldresultinoverheatingordamagewillnotoccur.Thesetpointof1200gpmhasbeenchosentoaccountforinstrumentuncertaintyandtoprovideanacceptableflowsplitduringparalleloperation.Utilizingtheperiodictestdata,it.hasbeendeterminedthattotalflowsaboveabout700gpmwillensurethattheweakerpumpwillovercometheoperatinghead.Consideringtheeffectsofinstrumentuncertaintyofapproximately3%,whichwouldresultinanadditionalrequired,marginof130gpm,thevalueof1200gpmwillensurethatbothpumpswilldeliveranadequateflowwhileoperatinginparallel.Ithasbeendeterminedthatanindicatedflowrateof1200gpmonFI-626intheControlRoomwouldresultinnolessthan1070gpmtotalflowconsideringthemostlimitinginstrumentuncertainty.Ifthiswerethecase,the"A"pumpwouldreceive300gpmandthe"B"pump770gpm.Anactualtotalflowof1200gpmwouldbesplitsuchthatthe"A"pumpwoulddeliver390gpmandthe"B"pump810gpm.Therefore,thesetpointprovidesaflowsplitwherebytheweaker"A"pumpreceivesnominallyabout20percentofBEPflowandanamountconsistentwithcurrentmanufacturer'srecommendations.Thepumpmanufacturer,PacificPumpDivision,hasrecommendedarecirculationflowof100gpmperpumpforshortdurationsupto30minutes.Therecommendedvalueforintermediaterangeoperation,thatof100hourspermonth,is260gpm(15%ofBEP)andlongtermcontinuousoperationavalueof520gpm(30%ofBEP)isrecommended.ThemajorityofoperatingtimeforthepumpsisspentintheRHRmodeduringplantheatup,cooldown,andrefuelingoperations.OneorbothRHRpumpsoperateforatotalofabout1000hoursperyearintheRHRmode.'heprecisetimesplitbetweenthe"A"pumpand"B"pumphasnotbeendetermined.Operationinthetestmodeof200gpmisperformedmonthlyexceptduringannualrefuelingshutdownswhentheyaretestedat700gpm.Thiswouldamounttoadurationontheorderof25hoursperyear(orless)orabout5'tofthetotaloperatingtime(assuming500hoursperpump).Sincethe200gpmvalueissufficientlyclosetotherecommendedvalueof260gpmrecommendedbythemanufacturerforoperationupto1200hoursperyear(100hourspermonth),theapproximately25hoursspentat200gpmwillnotresultinacceleratedwearonthepumpinternals.AsafetyanalysiswasperformedwhichsupportedtheproceduralmodificationswhichrequiresecuringoneRHRpumpasdescribedabove.ParallellowflowoperationofRHRpumpsatGinnamayoccurduring:B-6 1.SAFETYINJECTION(INJECTIONPHASE)DuringtheECCSinjectionphase1of2RHRpumps,2of3highheadsafetyinjectionpumpsand1of2SIaccumulatorsareassumedtoinjectwater.2.SAFETYINJECTION(RECIRCULATIONPHASE)DuringtheECCSrecirculationphase,1of2'RHRpumpsandheatexchangerwillsatisfythelongtermcorecoolingrequirementsof10CFR50.46.3-RHRSYSTEMSOPERATIONDURINGAPLANTCOOLDOWNBELOW350PDuringRCScooldownbelow350F,only1of2RHRpumpsareprocedurallyoperatedatlow-flowconditionsprecludingRHRpumpdamage.Areviewofproceduresshowsthatatnotimedoproceduresusedtoinitiate,operate,orshutdowntheRHRsysteminthismodeofoperationrequireorrecommendtherunningofRHRpumpswiththedischargepathisolated.Additionally,therearenoautomaticisolationsignalsintheGinnaconfigurationthatwouldplacetheRHRpumpsinthepa'rallellow-flowoperatingmode.4.TESTMODEAreviewofperiodictestproceduresandrefuelingshutdownsurveillanceproceduresrevealedthatatnotimewouldtherebeparallellow-flowoperation.Therefore,forallanticipatednormaloperatingconditionsthepotentialforRHRpumpdamageislimited,suchthattheRHRpumpsavailabilityisassuredtothemaximumextentpossiblesuchthattheprovisionsof10CFR50AppendixAGDC34ResidualHeatRemovalaresatisfied.Inaddition,themarginofsafetyandperformanceoftheECCSasdescribedin10CFR50AppendixAGDC35aresatisfied.Theprocedurechangesareintendedasaninterimmeasure.Aplantmodificationdesignedtoaffectlongtermcorrectiveactionispresentlyunderway.Criticalpipingtie-insforthemodificationarescheduledtobeinstalledduringthe1989RefuelingandMaintenanceshutdown,withnewhardwareandpipinginstallation,testing,andthemodificationturnedoverforusebytheendof1989.Anewrecirculationsystemisbeingdesignedwhichwillensureanincreasedminimumflowcapacityconsistentwiththemanufacturer'recommendationsforintermediatetermoperationunderallanticipatednormalandaccidentconditions.TherequirementswillbemetwheneveroneorbothRHRpumpsareoperating.Thenewrecirculationcapacitywillnotpreventtherequireddeliverytothereactorvessel,asdefinedonFigure15.6-13oftheUFSAR,frombeingmet.B-7
~~~Throughtheuseofthe.computermodelKYPIPEdevelopedfortheECCSsystematGinna,theexistingsystemandproposedmodificationtotherecirculationsystemcanbeassessedandimpactonsystemdeliverydetermined.Theoptimumdesignhasnotasyetbeenfinalized.SincethecriteriarequiresanincreaseinrecirculationcapacitywhenthedischargepathisisolatedaswellassufficientcapacitytoensurethattheUFSARdeliverycurve(Figure15.6-13)ismet,arecirculationsystemwithfloworpressurecontrolcomponentsmaybenecessaryinlieuofapassivepressurebreakdownsystemasisnowemployed.ThesystemredesignoptionwhichisbeinggivenstrongconsiderationforimplementationatthistimeisdepictedonFigureB-1.Asrequiredbyparagraph5ofBulletin88-04,awrittenresponsedescribingtheactionstakenwillbeprovidedwithin30daysfollowingcompletionoftheplantmodification.AppropriateconservatismwillbeappliedtotheKYPIPEcomputercode.SufficientpumpperformancedegradationwillalsobeappliedinthemodelsothatpumpmaintenancewillbeperformedpriortosystemdeliveryrequirementsbeingreducedbelowtheacceptablelimitsestablishedintheUFSAR.Pumpdevelopedpressuremeasurementsinthemonthlyperiodictestprocedurescanbeusedtodictatewhencorrectiveactionwouldbewarranted.Additionally,theincreasedcapacityoftherecirculationsystemwillreducetoaminimumt"...possibilityofacceleratedwearduetooperationintheperiodtestmode.B-8 P1427IOB70%71188'00BP)IOIIFICEITYPICAL))HIHXA30704A)IP141710A709A711C8't3o3040~4509%NAXINHITVPlra.)LON'HOTLEB701P14010'"AMBI886FIGUREB-lRHRHINIHUHRECIRCULATIONFLOW
~~~rATTACHMENTCEVALUATIONOFRECIRCULATIONSYSTEMSFORAUXILIARYFEEDWATERSYSTEMReference(a):LetterfromJ.E.Maier(RGGE)toD.M.Crutchfield(NRC),
Subject:
NRCRequirementsforAuxiliaryFeedwaterSystems,datedJanuary8,1982Reference(b):LetterfromJ.E.Maier(RG&E)toD.M.Crutchfield(NRC),
Subject:
NRCRequirementsforAuxiliaryFeedwaterSystems,datedJune8,1981Reference(c):LetterfromL.D.White(RGGE)toD.M.Crutchfield(NRC),
Subject:
NRCRequirementsforAuxiliaryFeedwaterSystems,datedMay28,1980ThesesystemshavebeenevaluatedunderpreviousSystemati'cEvaluationProgram(SEP)TopicXandTMI-2TaskActionPlanItemsII.E.l(fromNUREG-0660).Aspartofthelatertask,thesepumpsunderwenta48hourendurancetestperformedatminimumflowconditions.Thesetestsdemonstratedcontinuedoperabilityandacceptabilityofcriticalparametersatlowflowconditionsbaseduponlimitsestablishedforthepumpsatratedconditions.Monthlyperiodictestsrequirethateachauxiliaryfeedwaterpumprecirculationsystemoperatesasdesigned.Eachpumpisprovidedwithaseparatelineequippedwithanautomaticairoperated(fail-open)valveandpressurebreakdownorifice.Theselinestieintoacommonlinewhichleadsbacktothetwo30,000galloncondensatestoragetanksforthemainauxiliaryfeedwatersystem.Thestandbyauxiliaryfeedwatersystemissimilarwiththecommonlineleadingbacktothe10,000galloncondensatesupplytank.*MAINAUXILIARYF19KMATERSYSTEMThesystemisdepictedonFigure10.5-1oftheUFSAR.Eachofthethreepumpsisprovidedwitha2-inchrecirculationline,automaticallycontrolledairoperatedvalve,andpressurebreakdownorifice.Thevalveisdesignedtofailtotheopenposition.The"A"motordrivenAFWpumpiscapableofdischarging200gpmtothe"A"steamgeneratorandthe"B"motordrivenAFWpump200gpmtothe"B"steamgenerator.TheturbinedrivenAFWpumpiscapableofprovidingatotalof400gpmtobothsteamgenerators.Bothmotordrivenpumpsautomaticallystartif1)eithersteamgeneratordecreasestoalow-lowlevelof17%,2)anSIsignalispresent,or3)tripofbothmainboilerfeedpumpsoccurs.Sinceeachmotordrivenpumpisalignedtoitssteamgenerator,aninteractioncannotoccurasdescribedinBulletin88-04.
a(~tTherecirculationvalvesforthemotordrivenpumpsystemremaincloseduntilthedischargepressureinthedischargelinereachestheestablishedsetpoint.Recenttestsperformedonthepumpsdemonstratedthatthevalveswerefullyopenat,adischargeflowof80gpm(32%ofBEP).Therefore,thetotalflowthroughthepumpexceeds80gpm,sincetherecirculationlineisalsoopentoprovideadditionalflow.Theexistingperiodictestproceduresrequireverificationthattherecirculationvalveisfullyopenedwhentheflowthroughthedischargeisthrottledto50gpm,or20:ofBEP,whichisconsideredadequate.Therefore,theestablishedsetpointsprovidemarginoverandabovetheacceptablevalueof50gpm.Theperiodictestalsodemonstratesthattherecirculationvalveisfullyclosedwhenthedischargeflowreaches125gpm.Theperiodictestingalsoverifiesthatthevalvewillfailtoopenpositionwhenairisremoved.Themotordrivenpumpsaredesignedtoprovideaminimumof200gpmduringaccidentconditions.Thedischargevalvesareautomaticallythrottledtoachievethisflow.Thedischargevalvesareonlythrottledtolowerflowsduringplantstartupandlowpoweroperationorduringperiodictesting.Duringthesemodesofoperation,theflowisprocedurallycontrolledsothataminimumof50gpmisalwaysprovided.Sincetherecirculationvalveopensautomatically,aminimumflowthroughthislineprovidesassurancethatthepumpwillalwaysreceivearecirculationflow.TheturbinedrivenAFWpumpisalsoequippedwitha2-inchseparaterecirculationline,automaticairoperatedvalve(fail-open)andpressurebreakdownorifice.Inthissystemthevalveiscontrolledbyflowinthedischargeline,designedtoopenthevalveiftheflowdecreasesto100gpm.Periodictestingisperformedonamonthlybasisanddemonstratesthatthevalveisfullyopenat100gpm.Thisflowrepresents20%ofBEPandisthereforeadequate.Theturbinedrivenpumpwouldonlybethrottledbacktothe100gpmconditionduringtestmodes.Theturbinedrivenpumpisautomaticallystartedonalow-lowlevelof17%inbothsteamgenerators,oronlossofboth4160Vbuses11Aand11B.Allthreemainauxiliaryfeedwaterpumpsstartonlossofoffsitepower.Inthiscase,eachofthe"A"and"B"motordrivenpumpswouldberunninginparallelwiththeturbinedrivenpumpsupplyingwatertothe"A"and"B"steamgenerators,respectively.Sincethesepumps,areprovidedwithautomaticsystems,therecirculationvalveswouldopenintheunlikelyeventthatthedischargevalvesweretobethrottledback,therebyprovidingadequateflowforeachpump.Additionally,anorificeisinstalledineachminimumflowrecirculationlineupstreamofthecommonlinetie-insothatthestrong/weakpumpinteractionnotedinBulletin88-04isde-sensitized.C-2
~~~eMonthlyperiodictestingofthepumpsperfo'rmedatratedflowdemonstratesthatthedischargepressurelimitsandbearinghousingvibrationarewithintheboundsestablished.Thisdataistrendedandprovidesameansofdeterminingperformancechanges.The48hourendurancetestsonthemotordrivenAFWpumpswereconducted.onOctober9throughOctober11,1981("A"pump)andonNovember6throughNovember8,1981("B"pump).TestresultswerereportedinReference(a).Thetestwasrunintherecirculationmodeof50gpmduringthetest.The48hourendurancetestontheturbinedrivenAFWpumpwasperformedonMarch6throughMarch8,1981.TestresultswerereportedbyReference(b)anddemonstratedoperabilityandacceptabilityofcriticalparametersduringtherecirculationconditionatabout100gpm.Consequently,theconcernsraisedinBulletin88-04havebeenadequatelyaddressedinthedesignandaredemonstratedduringperiodictestingofthesystems.STANDBYAUXILIARYFEEDWATERPUMPThissystemisdepictedonFigure10.5-2oftheUFSAR.Eachofthepumpsisratedfor200gpm.Eachpumpisprovidedwitha1.5-inchrecirculationline,withautomaticflowcontrolledairoperatedvalveand,manufacturer-designedpressurebreakdownorifice.Thevalveisdesignedtofailintheopenposition.Thevalveisdesignedtoopenwhenthedischargeflowdecreasesto80gpm.EachpumpfeedsaseparatesteamgeneratorandparalleloperationasdescribedinBulletin88-04is,therefore,notaconcern.Therecirculationlinesmergetoacommonlinewhichleadsbacktothe10,000galloncondensatesupplytank.Thestandbyauxiliaryfeedwaterpumpsareprovidedonlyforuseifallthreeofthemainauxiliaryfeedwaterpumpswereunavailable,suchascertainsteamlinebreaksandunmitigatedfirescenarios.Thepumpsaremanuallyactuatedand.controlled.Therearenoknownmodesofoperationwherebythedischargevalveswouldbethrottledbackwiththesepumpsrunninginparallel.However,sincethecommonlinetie-inisdownstreamofeachorifice,thelineisde-sensitizedtothepossibleeffectsofthestrong/weakpumpinteractiondescribedinBulletin88-04.Periodictestingofthepumpsisperformedmonthlyanddemonstratesthateachpumps'evelopedpressureremainswithinestablishedlimitsandthatataflowof50gpmtherecirculationvalveisfullyopen.Testingalsoconfirmsthatthevalvefailstotheopenpositionwhenairisremoved.C-3 Thebest-efficiencypointofthepumpsis450gpmmakingtherecirculationflowof50gpmabout11%ofBEP.Pumptemperatureriseoftheinternalfluidatthisconditioniscalculatedtobeonly17.3F.Sincetheonlymodeofoperationwhichwillresultinthislowflowisthetestmode,thisvalueisacceptable.Thepumpsareoperatedinthismodeforbriefperiodsoftimeonly,inordertodemonstratethattherecirculationvalvefullyopens.The48hourendurancetestwasconductedonbothpumpsattherecirculationconditioninMarchandMay1980.TestresultswerereportedinReference(c)anddemonstratedoperabilityandacceptabilityofcriticalparameters.Consequently,theconcernsraisedinBulletin88-04havebeenadequatelyaddressedinthedesignandaredemonstratedduringperiodictestingofthepumps.C-4 P<~,vt'~
TABLE1DETAILEDTECHNICALSPECIFICATIONCHANGESLocationPage4.5-3Page4.5-3DescritionofChaneAdded450gpmat138psigforRHRpumps;addedsquarebracketsaround,200gpmand.140psigi.nTable4.5-1.Added.Note(1).Added150gpmat1356psigforSIpumps;addedsquarebracketsaround50gpmand1420psiginTable4.5-1.AddedNote(2).ReasonforChaneReducethepotentialforpumpacceleratedwear..duetolowflowoperationbyincreasingsurveillancetestflowequivalentto0heminimumflowrecommendedforcontinuousoperation.Page4.5-8Elaboratedthebasisfortheminimumdischargepressureandpumpdegradation.,AddedReference2.ClarifybasisinkeepingwithUFSARanalyses.Page4.5-9Nochange.Reformattedonpage.Page4.5-10ChangedReference2toReference3andReference3toReference4.Renumberreferences.Page4.5-11UpdatedReferencesasfollows:Reference(1)fromFSAR6.2toUFSAR6.3.5.2.rAddedReference(2),UFSARFigs.15.6-12&15.6-13.ChangedReference(2)toReference(3)andupdateditfromFSAR6.3toUFSAR6.5.1.2.4.UpdatethereferencesfromtheoriginalFSARtotheappropriatesectionoftheUFSAR.ChangedReference(3)toReference(4)andupdateditfromFSAR14.3.5toUFSAR6.4.3.1.