ML17037C333

Nine Mile Point Unit 1 - Letter Responding to the March 21, 1972 Letter Requesting Additional Information Regarding Proposed Changes to the Technical Specifications and Bases

ML17037C333
Person / Time
Site:	Nine Mile Point
Issue date:	04/21/1972
From:	Brosnan T J Niagara Mohawk Power Corp
To:	Skovholt D J US Atomic Energy Commission (AEC)
References
Download: ML17037C333 (24)

Text

s'eA."".C..DXSTaRBDTXCi'l:.(.3, PAR'0DOCK""TY~.T"".,XAL (T'""OKER FORa'}IieCONTROLNO;2218PRO~!:NiagaraMohawkPowerCorp.Syracuse, N.Y.13202T.J.BrosnanTO:Mr.Skovholt,DA7."GPDCC:4-21-2ORiG1sied.DAYER!.C'~Hasbls(4-24-2'-XOTfERCCa'asssORP7.Oe~f~%RS"".iTAZCPDRSFNTLOCALPDRxCLASS:U/PROPINFOINPUTNOCYSRZC'D40cysrec'dDOC(ETNO:50-220ECrreourltrdtd.3-21-72,transtheDa-SCRIPTION' ollowing:

ENCLOSURES:

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g%C~ltI5~@6h~NIAGARA~MOHAWKGOOERIKBOULEVARD WEST9YRACU92, H<Y.I3202ApriI2I,l972llyhCe5Mr.DonaIdJ.SkovhoItAssistantDirectorforReactorOperationsDivisionofReactorLicensing UnitedStatesAtomicEnergyCommission Washington, D.C.20545

DearMr.Skovholt:

IIJ,,Re;:'ocketNo'.'50-220LicenseDPR-l7Wesubmittheadditional information requested inyourletterofMarch2I,l972regaldingproposed'hanges totheTechnical Specifications andBasesfortheNineMile.PointNuclearStation.Since,testingofthenewreliefvalvesetpoints.requiresdeinerting andaccesstothedrywell,Weplan,subjecttoyourapproval, tomakethesechangesandperformthenecessary testingduringthecurrentstationoutage.Inadditiontodataonoperational transients, yourletteralsorequested information onthepostulated controlroddropaccident.

Acompletereanalysis ofthisaccidentwillbeforthcoming intheverynearfuturefromtheGeneralElectricCompanyasaTopicalReportgenerictoboilingwaterreactors.

0Verytrulyyours,J.BrosnanVicePreient'andChiefEngineer.

Enclosures oI'.,~~-Q0yc~IIyC

't0Cgl$1/I811'YrP QuestionNo.1Youstatethatimprovedanalytical techniques available atGeneralElectricCompanycausedyoutoadopttheproposedrevisedscramreactive.ty curve,butnoinformation regarding thesetechniques wasprovided.

Describetheanalytical techniques usedpreviously, thechangesbeingmadetotheanalytical model,andthebasisforconsidering thechangeanimprovement.

AnswerNo.1Theimprovedanalytical techniques whichcausedadoptionofanewscramreactivity curveinclude:(a)(b)(c)Arevisedpowershapingphilosophy hasbeenfollowedwhichresultsinaflatteraxialpowerdistribution (lowerlinealheatgeneration rates)particularly atend-of-cycle.

Thepowershapinghasbeenaccomplished bymanagement ofcontrolrodpatternsthroughout theoperating cycleinaccordance withtheHalingprinciple.

Althoughnotpresently

,incorporated infuelatNineMilePoint,theuseofaxialshapedgadolinia mayalsobeusedinthefuturetofurtherflattenthepowerdistribution.

Anewlatticecodeforcalculation ofbundlek'shasreplacedthe2'odeloriginally'used forNineMilePointfuel.Theuseofthenewlatticecode,asfurtherdescribed herein,alsoresultsinaflattening oftheaxialpowerdistribution.

)IMoredetailhasbeenincorporated intothemodelforcalculation ofscramreactivity.

Thechangesdescribed in(b)and(c)havetheeffectofdecreasing thepeakaxialpowerandmovingthepeakawayfromthebottomofthecoreasanequilibrium fuelcycleisapproached.

Theseeffects,inturn,reducetheinitialrateofreactivity insertedbyascrambecauseoftheincreased timeintervalbetweenthescraminihtionandthepointwherethecontrolbladesenterthehighpowerregionofthecore.Therevisedpowershapingphilosophy isdirectedtowardmaintaining arelatively constantpowerdistribution throughout eachfuelcycle.Carefu1manage-mentofcontrolrodpatternsduringpoweroperation inaccordance withtheHalingprinciple willresultinminimumpeakingattheend-of-cycle withallcontrolrodsoutofcore.Haling,R.K.,"Operating StrategyMaintaining anOptimumPowerDistribution Throughout Life",TID-7672, p.205,(September, l963)AECDocket50-298,BrownsFerryStation,SafetyAnalysisReport,VolumeI,pp.II-6-2AECDocket50-220,NineMilePointNuclearStation,FinalSafetyAnalysisReport,VolumeI,pp.IV-22-24 I%~Ilii 1-2Thenewerlatticecoderesultsinanimprovedcalculation ofk~'s.Asignificant difference inthekpredicted byeachlatticemodelcanbeseenbyexamination ofthecurvesinFigure1-1.Thenewlatticecode'predicts higherk~'sathighvoidandlowerk~'satlowervoidconditions relativetotheolderlatticecode.Thisresultsinalowerpredicted peakpoweratthebottomofthecorewhichreducestheinitialrateofscramreactivity.

6Thebasicrefinements intheanalytical techniques forevaluation ofthescramreactivity curvecharacteristics referredto'n(c)aboveincludethefollowing changes:(a)Anincreaseinthenumberofpromptneutrongroupsfrom1.5to3.(b)Anincreaseinthenumberofaxialnodes.(c)Replacement ofthetimeconstantpreviously usedtorelateheatfluxtovoidswithatransient thermalhydraulic modelsimilartothatusedinblowdowntransient analyses.

(d)Addingtheabilitytorepresent cross-section databasedontypicalexposureandvoidhistory.(e)Animprovedfinitedi.fference representation ojtheone-dimensional timedependent fewgroupneutrondiffusion equations.

8 2-1QuestionNo.2Describethedataandmeasurements obtainedatNineMilePointfromreactoroperations andteststhatsupportuseofthenewanalytical techniques.

AnswerNo.2Themanagement ofcontrolrodpatternsatNineMilePointhasenabledthecoretodevelopandmaintainanaxialpowerdistribution and,therefore, anexposuredistribution, consistent withtheobjective ofminimizing powerpeakingthroughout eachoperating cycle.Figure2-1comparestheexposuredistribution calculated fromNineMilePointreactoroperation asofJanuary,1972,withthe"target"exposuredistribution derivedfromtheHalingprinciple.

The"target"exposuredistribution hasbeencomputedforanallrodsoutcondition priortoremovalofcontrolcurtains, itdoesnotrepresent theequilibrium end-of-cycle condition.

Confirmation ofthenewlatticecodeiseve,denced bytheabilityofthiscode,inconjunction withagobal3-Dsimulator<

)topredictpowerdistributions androdinventory.

Figure2-2comparesthenormalized predicted rodinventory toactualrodinventory duringtheoperating periodjustpriortothecurrentstationshutdown.

Xnaddition, comgarisops ofpredicted andobserveddatahavebeenmadeforvariousotherreactors<

)(>whicharealsoapplicable totheNineMilePointreactorindemonstrating thegeneraladequacyofthebasiccomputermodelemployedforthesecalculations.

Crowther, R.L.andet.al.,"ThreeDimensional BNRSimulation" (TED-4500),

Proceedings ofConference onEffective UseofComputers inNuclearindustry, Knoxville, Tennessee, April21-23,1969.,Fuller,E.D.,"PhysicsofOperating BoilingWaterReactors,"

NuclearApplications andTechnology, Volume19,pp.622-633,(November, 1970).

3-1QuestionNo.3Theeffectofpartialrefuelings onthescramreactivity curvehasnotbeenpresented.

Pleasedefinetherelationship ofthepresentcoreloadingwiththescramreactivity curveanddescribetheeffectonthescramreactivity fromapproaching anequilibrium fuelloading,including theexpectedoperational controlrodpatterns.

AnswerNo.3Thescramreactivity curveusedintheanalysispresented inourletterofFebruary28,1972,wasaconservative estimateofanendcondition forafuelcycleapproximating theequilibrium fuelloading.Additional calculations havebeenmadeofaconservative scramreactivity curvetypicaloftheperiodimmediately following removalofcontrolcurtains'.

TheseresultsareshowninFigure3-3.alongwithcurves'usedinpreviousanalyses.

Allofthesescramreactivity curvesareconservatively basedonascramtimeof5secondsfor90percentinsertion; acondition whichdoesnotexistatthisstation.'Figure3-1indicates therewillbeagradualreduction intheinitialscramreactivity insertion rateasthecoreapproaches anequilibrium condition.

Figure3-2showsanaxialcontrolrodpositionandtheresultant relativeaxialpowerdistribution whichistypicalofexpectedreactorperformance following thecurtainremoval.Otheraxialcontrolrodfractions havebeenexaminedwhichresultinascramreactivity insertion rateclosetothatcorresponding tobeginning oflife.Thesepatternsresultinhighaxialpowerpeakingwhichisnotconsistent withcurrentdesirestolimittotalpeakingfactors,and,therefore, heatfluxtothoserequiredtoachieveoptimumfuelperformance.

li 4-1QuestionNo.4Youranalysessupporting theproposedchangesdonotincludeconsideration ofthecontrolroddropaccident.

Thechangeinslopeofthescramreactivity curvewouldindicateanincreased rateofreactivity insertion intheeventofacontrolroddropaccident.

Provideacompletereanalysis ofthisaccident, including consideration ofthevalidityoftheassumedmaximumreactivity worthofthecontrolrodinvolvedinthedropaccident.

Yourattention isdirectedtoaletterdatedMarch8,1972,toMr.A.P.BrayoftheGeneralElectricCompany'rom Mr.R.S.Boyd',DivisionofReactorLicensing.

Acopyofthisletterisenclosedforyourconvenience.

AnswerNo.4Reanalysis ofthecontrolroddropaccidentasoutlinedinMr.RogerS.Boyd'sMarch8,1972,lettertoMr.P.A.BrayisnowbeingpreparedbyGeneralElectricandwillbesubmitted totheCommission asaTopicalReportintheverynearfutuxe.TheStation's Technical Specifications (3.1.]b(3)

)requirethataprescribed controlrodwithdrawal sequencebeadheredtoduringplantstartupsinorder'tolimitmaximumrodworth.Specifically, whentherodworthminimizer isnotoperable, asecondlicensedoperatororqualified technical stationemployeeshallverifythattheoperatoratthereactorconsoleisfollowing theprescribed rodwithdrawal sequence.

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FIGURE1NINENILEPOINTKC(HOT)VERSUSPERCENTINCHANNELVOIDSINITI'ALfUEL-UNCONTROLLED CURTAINS-ZERO EXPOSURE~OLDLATTICECODENEWLATTICECODE1020.304050PERCENTINCHANNELVOIDS607080

FIGURE2-1NINEMILEPOINTREACTOR'XIALEXPOSUREDISTRIBUTION 1.81.61.4DISTRIBUTION,AT6059MMD/T0.80.6,/ITARGETDISTRIBUTION (PRIOR.TOCURTAINREMOVAL)'.4'.2.00'OTTOM246-.8,10'1214;,AXIALNODES161820,2224261TOP

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FIGURE2-2NINENILEPOINTRODINVENTORY.

VS.EXPOSURESEQUENCEA-3900OBSERCALCULATED RODVEDRODINVENTORY INVENTORYC)I-C/)C)O;OMh~UJCACAClEDCLC)CYIC)I-C)I-'00FDI-C)CO500400CD300200,1002,700600'0,500060007000EXPOSURE, MWD/T8000 0'rl t~FIGURE3-lNINEMILEPOINTSCRAMREACTIVITY CURVES-40G(ENDOFCYCLE)EQUILIBRIUM FUELLOADIN-300I-o'20I-,-10BEGINNING OFLIFE///////////////AFTERCURTAINREMOVAL////r00'3TIME(SECONDS) 5 Ay

'.0'IGURENINEMILEPOINT-TYPICALCONTROLFRACTIONANDRELATIVEPOWERVERSUSAXIALPOSITION,(AFTERCURTAINREMOVAL)0.50.4.1.510cn'D0.3CDOClCDCDCYCD.O0.2OCrAXIALCONTROLRODPOSITIONS AXIALPOWER0.50.1AXIALCONTROLRODPOSITROLRODSINSERTEDATAXIALNODETIPN-CONTOTALNUMBEROFCONTROLRODS1290,0.0'2468'10,12141618202224AXIALNODEBOTTOMTOP 0"r>>4('L