ML17320A414
| ML17320A414 | |
| Person / Time | |
|---|---|
| Site: | Cook  |
| Issue date: | 02/28/1983 |
| From: | INDIANA MICHIGAN POWER CO. (FORMERLY INDIANA & MICHIG |
| To: | |
| Shared Package | |
| ML17320A413 | List: |
| References | |
| AEP:NRC:0745B, AEP:NRC:745B, NUDOCS 8303080145 | |
| Download: ML17320A414 (23) | |
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ATTACHMENT NO.1TOAEP:NRC:0745B DONALDC.COOKNUCLEARPLANTUNITNOS.1AND2SUMMARYOFNEWANDSPENTFUELSTORAGEARRAYCRITICALITY SAFETYANALYSES8303080145 830888PDR*DOCK080003g8PPDR
~~
~~1.0SU!%MROFCRITYANALYSISK)RDC.QXKENTHJELRACKCriticality offuelassemblies inthespentfuelstoragerackisprevented bythedesignoftherackwhichlimitsfuelassemblyinteracticn.
Thisisdonebyfixingthezunianseparaticn betweenassemblies andinserting neutronpoisonbetweenassanblies.
Thedesignbasisforpreventinp criticality outsidethereactoristhat,including uncertainties, thereisa95percentprobability ata95percentconfidence levelthattheeffective multiplication factor(Kff)ofthefuelassarhlyarraywillbelessthan0.95asreccamended inANSIN210-1976 andin"NK'.PositicnforRevi~andAcceptance ofSpentBzelStorageandHandlingApplication."
Xnmeetingthisdesignbasis,scmeoftheconditions assumedare:fresh15x15Nestinghouse cptinuzed fuelassemblies (OFA)of4.05w/oU-235arestored,thepoolwaterhasadensityof1.0gm/cm,thestoragearrayisinfiniteinlateralandaxialextentwhichisnarcreactivethantheactualfinitearray,mechanical andmethodbiasesanduncert-~ties areincluded, theminimumpoisonloadingisused,ardforscmeaccidentconditions creditforthedissolved boroninthepoolwateristaken.Thedesignrrathodwhichinsuresthecriticality safetyoffuelassemblies inthespentfuelstoragerackusestheAMPXsystemofcodesfbrcross-section generation andKENOXVforreactivity determinaticn.
Asetof27criticalexperiments hasbeenanalyzedusingtheabovemthcdtodenanstrate itsapplicability tocriti-calityanalysisaxxltoestablish themethodbiasandvariability whicharethenincluded'n thereactivity analysisoftherack.Thresultoftheaboveconsiderations isthatthenucleardesignoftherackwillgreettherequirements ofNRCguidelines andcriteria.
2-0CRITICALITY AISEORD.C.CXXKSPRG'UELCK2-1NEVZIKNNJLTIPLICATIOH FACIORCriticality offuelassemblies inthespentfuelstoragerackisprevented bythedesignoftherackwhichlimitsfuelassemblyinteraction.
'IhisisGonebyfixingtheminimumseparation betweenassemblies anRinserting neutrcnpoiscnbetweenassemblies.
Thedesignbasisforpreventing criticality outsidethereactoristhat,including uncertainties, thereisa95percentprobability ata95percentconfidence levelthattheeffective multiplication factor(Kff)ofthefuelassemblyarraywillbelessthan0.95aseffreccmnended inANSI5210-1976 andin"NRCPositionforReviewandAcceptance ofSpentFuelStorageandHandlingApplications".
Thefollowing aretheconditions thatareassumedinmeetingthisdesignbasis.2.2NORMALSZORAGEa.'Ihefuelassemblycontainsthehighestenrichment authorized withoutanycontrolrodsaranynoncantained burnablepoiscnandisat.itsnostreactivepointinlife.Criticality analysesweredonefarWestinghouse 15x15optimized fuelassanbly(OFA)withanenrichment of4.05w/o.'Ihefollowing
'ssemblyparameters werenadeled:NumberofFuelRodsperassemblyRodZirc-4CladO.D.CladThickness FuelPelletO.D.BmlPelletDensityFuelPelletDishy~RdPitchNurrberZirc-4GuideTubesGuideTubeO.D.GuideTubeThickness 2040-422"0-0243"0.3659"955Theoretical 1.190%0.5630"Square210.546"0-017" Theassliesareconservatively reeledwithwaterreplacing theassemblygridvoluman2noU-234orU-236inthefuelpellet..NoU-235burnupisassumed.b.Thestoragecellnanin-Q.gecmetryisshcamcnFigurel.c.'Ihemoderator ispurewateratthetemperature withinthedesignlimitsofthepoolwhichyieldsthelargestreactivity.
Aconservative valueof1.0gm/cmisusedforthedensityofwater-Nodissolved borcnisincludedinthewater.d.Thennunalcasecalculation isinfiniteinlateralandaxialextent.e.Credit,istakenfortheneutronabsorption infulllengthstructural materials arxlinsolidmaterials addedspecifically forneutronabsorption.
'Iheminimumpoisonloading(0.02gm-B10/an)isassumedinthepoisonedcellwalls.Abiasisincludedinthereactivity calculation toaccountfortheB4Cparticleselfshielding.
g.Abias,withanuncert-~ty isincludedtoaccountforthefactthattheD.C.Cookrackshaverandemcellsclosertogetherthanfortherarninal'design.
Theminimumgapbetweenadjacentcellsmaybeassmallas0.953",canparedtothenaninalgapof1.139".IThe.calculation mthoduncertainty andbiasisdiscussed in'ection2.4.2.3POSHJLATED ACCXDEHIS IRx;taccidentconditions willmtresultinanincreaseinKffofefftherack.Examplesarethelossofcoolingsystans(reactivity decreases withdecreasing waterdensity)anddroppingafuel 0assemblycntopoftherack.(therackstructure pertinent forcriticality isnotdeformedandtheassemblyhasmrethaneightinchesofwaterseparatirg it,frantheactivefuelintherackwhichprecludes interaction)
.Hmmver,accidents canbepostulated whichauldincreasereactivity suchasinadvertent drcpofanassemblybetweentheoutsideperiph-eryoftherackandthepealwall.'Iherefore, foraccidentcondi-tions,thedoublecontingency principle ofAHSN16.1-1975 isa~lied.'Ihisstatesthatitshallrequiretwounlikely, inde-pendent,concurrent eventstoproduceacriticality accident.
Thus,foraccidentconditions, the-presenceofsolubleboroninthestoragegxilwatercanbeassumedasarealistic initialcccxiitim.
Thepresenceoftheapproxinately 2000pgnboroninthepoolwaterwilldecreasereactivity bynarcthan3(Sb,k.Inperspective, thisisnarcnegativereactivity thanispresentinthepoisonedcellwalls,(i.e.,24%b,k).Therefore, Kfffartherackwouldbelesseffthan0.95evenifthecellwallswereunpoisoned-
'IhusKeff~0-95canbeeasilymetforpostulated accidents, sinceanyreactivity increasewillbemuchlessthanthenegativeworthofthedissolved Porfuelstorageapplications, waterisusuallypresent.~ever,accidental criticality whenfuelassemblies arestoredinthedryccndition isalsoaccounted for.Parthiscase,possiblesourcesofnaderaticn, suchasthosethat'ould ariseduringfirefightingcperations, areincludedintheanalysis.
This"optinaxn naderation" accidentisnotaprobleminpoisonedfuelstorageracks.'Xhepresenceofpoisonplatesraravestheconditions necessary far"optionnxderation" sothatKffcontinually de-"33creasesasrraderator densitydecreases frcm1.0gm/cmto0.0gm/aninpoiscnrackdesigns.
Figure2showsthebehaviorofKffasafunctionofmoderator
'ffdensityfaratypicalPNRpoisonedspentfuelstoragerack.12.4MEZHODH)RCRITICALI'IY ANALYSIS'Ihecalculation aathodandcross-section va1uesareverifiedbycanpariscn withcriticalexperiment dataforassemblies similartothosefor~chtheracks'aredesigned.
'Ihisbenchmarking dataissufficient1y diversetoestablish thatthemethodbiasanduncer-taintywillapplytorackcna9itions whichincludestrongneutronabsorbers, largewatergapsanilearrxderator densities.
Thedesignmthodwhichensuresthecriticality safetyoffuelassemblies inthespentfuelstoragerackusestheAMPXsystanofcodesC'forcross-section generation andKEHOIVforreactiv-C33itydeterminaticn.
The218energygroupcross-section, librarythatistheccrmenstart~pointfarallcross-sections usedfarthebenchnarks andthestoragerackisgenerat,ed frunENDF/8-XV data.'IheNITAWLprogram3includes, inthislibrary,theshelf-shielded resonance cross-sections thatareappropriate foreachparticular geanetxy.
TheNordheimIntegralTreatment isused.Energyandspatialweighting ofcross-sections isperformed bytheXSDRNPMexp;amC23whichisaane-Lunensional Stransport theorycode.Thesemulti-groupcross-section setsarethenusedasinputtoKENOIVwhichE33isathree-dimensional MonteCarlotheoryprogramdesignedforreactivity calculations.
Asetof27criticalexperiments hasbeenanalyzedusingtheabovemethodtodemonstrate itsapplicability tocriticality analysisandtoestablish themethodbiasandvariability.
'Iheexperiments rangefrcnwatermoderated, oxidefuelarraysseparated byvariousmaterials (Boral,steelandmter)thatsimulateGRfuelshippingandstorageconditions
'todry,harderspe~~uraru.unmetalC4,53.cylinderarrayswithvariousinterspersed materials (Plexiglass,
~C63 steelardairthatdeaenstrate t¹wideeofapplicability ofthemthod.Theresultsandscnadescriptive factsabouteachofthe27bench-Vmarkcriticalexperiments aregiveninTable1.TheaverageKffofeffthebenchmarks is0.9998whichdenanstrates thatthereisnobiasassociated withthemethcd.Thestandarddeviation oftheKffeffvaluesis0.0057dk.The95/95onesidedtolerance limitfactorfor27valuesis2.26.Thus,thereisa95percent.probability witha95rpercentconfidence levelthattheuncertainty inreactivity, duetothemethod,isnotgreaterthan0.0136,k.
'Thetotaluncertainty (TU)istobeaddedtoacriticality calcula-txcnxs.~=E(ks)method
+(~)~~al+(ks)~h3where(ks)~~is0.013asdiscussed above,(ks),~isthestatistical uncertainty associated withtheparticular KENOcalculation heirs.used,(ks)~isthestatistical uncert-unty associated withrandangapreduction betweenadjacentstoragecells.Forasinglecanitisfourrithatreactivity doesnotincreasesignificantly becausetheincreaseinreactivity duetothewatergapreduction ononesideofthecanisoffsetbythedecreaseinreactivity duetotheincreased watergaponthecppositesideofthiscan.Theanalysis, fortheeffectofmchanicaltolerances, 1xxmer,assumsa"worst"caseofarackccmgosedofanarrayofgroupsoffourcanswherethewatergapbetweenthefourcansisreducedto0.953inch.KEGcalculations usingthisminimumgapresultinabiasof0-002lldk ard.a95K/95Kuncert-sty of0.00454.Scnenechanical tolerances areratincludedintheanalysisbecauseworstcaseassumptions areusedinthencminalcaseanalysis.
Anexampleofthisiseccentric assenibly position.
Calculations were performed whis~thatthemastreavecxnxU.tion istheassemblycenteredinthecanw'hichisassumedintherxminalcase.Thefinalresultoftheuncm~inty analysisisthatthecriticality designcriteriaaremtwhenthecalculated effective multiplication factor,plusthetotaluncm~ty(1U)anRanybiases,islessthan0.95.Thesemethodsconformwith'ANSI N18.2-1973, "NuclearSafetyCriteriafcrtheDesignofStationary Pressurized WaterReactorPlants",MSX5210-1976, "DesignCbjectives forLNRSpent&elStorageFacilities atNuclearPoorerStations",
'Validation ofCalculational MethodsforNuclearCriticality Safety";HRC1StandardReviewPlan,ardtheNECGuidance, "NRCPositicnfor'Revim
- andAcceptance ofSpentKeelStorageandHandlingApplications".
2.5CRITICALI'IY RESULTSThespentfuelstoragecellisshowninFi,gurel.'IheminismmBloadieinthepoisonedcellwallsis0.02gm-B/cm.Thesensi-102,t'vityofstorage1tt'mKfftoU-235~ientofthefelassembly, thestoragelatticepitch,andBloadinginthepoisonplatesasrequested bytheNRCforprisonracksisgiveninFigures3~Forrmrmaloperation andusingtherrathoddescribed intheabovesections, theKfffartherackisdetexmined inthefollcwing effmanner.:~+B~+B~+B~+221/2 where:K.al=amninalcaseKEHOKffKffbiastoaccountforthefactthatmchanical efftolerances canresultinwatergapsbetweenpoisonplateslessthanncminalB~=m~biasdetermined frcmbenchmark crit.icalccnpari-sonsB=biastoaccountforpoisonparticleself-shielding ks~~=95/95uncertainty inthencaunalcaeKENTKffks~.=95/95uncertainty inthecalculation duetoKENOanalysisofmech-mical tolerances ks~~=95/95uncertainty inthemethodbiasSubstituting calculated values,theresultsarethefolly'Lng:
Kff092837++00211+00+0025+t(006494)+(004539)22eff+(.013)3=.9482SinceKffislessthan0.95including uncertainties ata95/95effprobability/confidence level,theacceptance criteriafarcritical-ityismt.26ACCEPI'ANCE CRITERIAFORCRITICALITY Theneutrcnmultiplicaticn factorinspentfuelpoolsshallbelessthanorecyalto0.95,including a11uncertainties, underallconditions.
Generally, theacceptance criteriaforpostulated accidentcondi-tionscanbeKff<0.98becauseoftheaccuracyofthemethodsusedeff-Icoupledwiththelearprobability ofoccurrence.
Barinstance, inANSIH210-1976 theacceptance criteriaforthe"optionmcderation" condition isKff0.98.~ever,forstoragepools,whichcontaindissolved bore+,theuseofrealistic, initialconditions ensuresthatKff<<0.95forpostulated accidents asdiscussed inSectioneff2.3.Thus,forsimplicity, theacceptance criteriafarallcondi-tionswillbeKff<0.95.eff 3.0CRI1LITYANALYSISFORO.C.COOKIFUELRACK3.1NEUTRONMULTIPLICATION FACTORCriticality offuelassemblies inthenewfuelstoragerackisprevented bythedesignoftherackwhichlimitsfuelassemblyinteraction.
Thisisdonebyfixingtheminimumseparation betweenassemblies totakeadvantage ofneutronabsorption inwaterandstainless steel.Thedesignbasisforpreventing criticality outsidethereactoristhat,including uncertainties, thereisa95percentprobability ata95per-centconfidence levelthattheeffective multiplication factor(Kff)ofthefuelassemblyarraywillbelessthan0.98asrecommended inANSIN18.2-1973.
'hefollowing aretheconditions thatareassumedinmeetingthisdesignbasisfortheD.C.Cooknewfuelstorageracks.3.2NORMALSTORAGEa.Thefuelassemblycontainsthehighestenrichment authorized withoutanycontrolrodsoranynoncontained burnablepoisonandisatitsmostreactivepointinlife.BecausetheWestinghouse 17xl7and15xl5areverysimilarneutronically
,onlythe17x17willbeexamined.
Sufficient marginwillbemaintained to,coveranyreac-tivitydifferences.
Theenrichment ofthe17x17Westinghouse stan-dardfuelassemblyis4.5w/oU-235withnodepletion orfissionproductbuildup.Theassemblyisconservatively modeledwiththeassemblygridvolumeremovedandnoU-234andU-236inthefuelpellet.b.Thearrayiseitherinfiniteinlateralextentorissurrounded byaconservatively chosenreflector, whichever isappropriate forthedesign.Thenominalcasecalculation isinfiniteinlateralandaxialextent.Calculations showthatthe'inite rackislessreac-tivethanthenominalcaseinfiniterack.Therefore, thenominalcaseofaninfinitearrayofcellsisaconservative assumption.
2407F:6 c.Nechanica1 uncpieties andbiasesduetomac!ica1to1erances Iduringconstruction aretreatedbyeitherusing"worstcase"condi-tionsorbyperforming sensitivity studiestoobtaintheappropriate values.The~temsincludedintheanalysisare:-stainless steelthickness
-cellID-center-to-center spacing-asymmetric assemblypositionThecalculation methoduncertainty andbiasisdiscussed inSec-tion4.d.Creditistakenfortheneutronabsorption infulllengthstainless steelstructural material.
3.3POSTULATED ACCIDENTS Mostaccidentconditions willnotresultinanincreaseinKeffoftherack.Anexampleisthedroppingofafuelassemblyontopoftherack(therackstructure pertinent forcriticality isnotdeformedandtheassemblyhasmorethaneightinchesseparating itfromthe.activefuelintherestoftherackwhichprecludes interaction).
However,accidents canbepostulated (underfloodedconditions) whichwouldincreasereactivity suchasinadvertent dropofanassemblybe-tweentheoutsideperiphery oftherackandpoolwall.Therefore, foraccidentconditions;-=the doublecontigency principle ofANSN16.1-1975 isapplied.Thisstatesthatitisunnecessary toassumetwounlikely, independent, concurrent eventstoensureprotection againstacriti-calityaccident.
Thus,foraccidentconditions, theabsenceofwaterin-thestoragepoolcanbeassumedasarealistic initialcondition sinceassumingitspresencewouldbeasecondunlikelyevent.2407F:6 Theabsenceofwatinthestoragepoolguarantee subcriticality forenrichments lessthan5w/o.Thusanypostulated accidents otherE13thantheintroduction ofwaterintothestorageareawillnotprecludethepoolfrommeetingtheKeff<0.98limit.Becausethemostlimitingaccidentistheintroduction ofmoderation intothestoragepool,thisaccidentwillbeconsidered indetermining themaximumKffforthestoragepool.Forthisaccident, possibleeffsourcesofmoderation, suchasthosethatcouldariseduringfirefight-ingoperations, areincludedintheanalysis.
This"optimummoderation" accidentisnotaprobleminnewfuelstorageracksbecausephysically achievable waterdensities (caused,forinstance, bysprinklers, foamgenerators orfognozzles)areconsiderably toolow(<<0.01gm/cm)toyieldKvalueshigherthanfulldensitywater.Theoptimumachievable moderation occurswithwaterat1.0gm/cm.Pre-ferential waterdensityreduction betweencells(i.e.,boilingbetweencells)isprevented bytherackdesign.3.4METHODFORCRITICALITY ANALYSIS'IThemostimportant effectonreactivity ofthemechanical tolerances isthepossiblereduction inthecenter-to-center spacingbetweenadjacentassemblies.
-ThenominalgapbetweenadjacentcellsforD.C.Cookis11.0inches.Thedesignalsoguarantees thattheaveragecenter-to-center storagecellspacingforamoduleofcellswillbe21.0inches.(SeeFigure4).Therefore, anyreduction ofcell-to-cell gapononesideofacanwillproduceagapincreaseontheoppositesideofthecan-TheKENOmodelforthegapreduction analysisconsistsofaninfinitearrayofclustersof4cellswiththegapbetweenadjacentcellsineachclus-terreducedto10.97inches.Anothercenter-to-center spacingreduction canbecausedbytheasym-metricassemblypositionwithinthestoragecell.Theinsidedimensions ofanominalstoragecellaresuchthatifafuelassemblyisloadedintothecornerofthecell,theassemblycenterline willbedisplaced J2407F:6 only0.284inchesfQthecellcenterline.
Thisnsthatadjacentasymmetric fuelassemblies wouldhavetheircenter-to-center distancereducedby0.568inchesfromthenominal.Analysisshowsthatthecombinedeffectoftheworstmechanical toler-ancesandtheasymnetric assemblypositioning mayincreasereactivity by0.00lhk.Thiswillbetreatedasabiasalthoughtheindividual devi-ationswillberandom.Thefinalresultoftheuncertainty analysisisthatthecriticality designcriteriaaremetwhenthecalculated effective multiplication factor,plusthetotaluncertainty (TU)andanybiases,islessthan0.98.ThesemethodsconformwithANSIN18,2-1973, "NuclearSafetyCriteriafortheDesignofStationary Pressurized WaterReactorPlants",Section5.7,FuelHandlingSystem;ANSIN16.9-1975, "Yalidation ofCalculational MethodsforNuclearCriticality Safety".3.5CRITICALITY ANALYSISFORRACKDESIGNFornormaloperation andusingthemethodintheabovesection,theKfffortherackisdetermined inthefollowing manner.effIK=K'+B+B+effnominalmechmethodnominalmethod~Where:nominalnominalcaseKENOKeffmechKffbiastoaccountforthefactthatmechanical efftolerances canresultinspacingsbetweenassemblies lessthannominal2407F:6 Bmethodme~biasdetermined frombenchmcritica1compari-Isonsnominal95/95uncertainty inthenominalcaseKENOKffks=95/95uncertainty inthemethodbiasSubstituting calculated valuesintheorderlistedabove,theresultis:Kff=0.9189+0.0010+0.0+f.(.0062)
+(.013)]=.9343effSinceKeffislessthan0.98including uncertainties ata95/95pro-bability/confidence level,theacceptance criteria'or criticality ismet.2407F:6 REFERENCES 1.M.E.FordIII,etal,"A218-Group NeutronCross-Section LibraryintheAMPXMasterInterface FormatforCriticality SafetyStudies,"
ORNL/CSD/TM-4 (July1976).2.N.M.Green,etal,"AMPX:AModularCodeSystemforGenerating CoupledMultigroup Neutron-Gamma Libraries fromENDF/B,"ORNL/TM-3706 (March1976).3.L.M.PetrieandN.F.Cross,"KENOIY-AnImprovedMonteCarloCriti-calityProgram,"
ORNL-4938 (November 1978).4.S.R.Bierman,etal,"Critical Separation BetweenSubcritical Clus-22tersof2.35wtXUOEnrichedUORodsinMaterwithFixedNeutronPoisons,"
BattellePacificNorthwest Laboratories PNL-2438(October1977)-5.S.R.Bierman,etal,"Critical Separation BetweenSubcritical Clus-tersof4.29wt'XUOEnrichedVORodsinMaterwithFixed22NeutronPoisons,"
BattellePacificNorthwest Laboratories PNL-2614(March1978).6.J.T.Thomas,"Critical Three-Dimensional ArraysofU(93.2)-MetalCylinders,"
NuclearScienceandEngineering, Volume52,pages350-359(1973).7.LetterNo.AEP:NRC:00105 datedNovember22,1978..2407F:6
BENCHMhBK CRETXCALEXPERIMIKIS 2~3~4~5~6.7~8.9~10.12.13.14.15.16.17.18.19.20.21.22.23~24.25'6.27.UmetalcylinersGeneralM2rodlatticeUO2rcdlatticeUO2rodlatticeUO2rodlatticeUO2rodlatticeUO2rcdlatticeU)2rodlatticeUO2rcdlatticeUO2rcdlatticeUO2lcdlatticeUO2rcdlatticeUO2rcdlatticeUO2rodlatticeUO2rodlatticeUO2rodlatticeUmetalcylinersUmetalcylinersUmetalcylinersUmetalcylinersUmetalcylinersUmetalcylinersUmetalcylinersUmetalcylinersUmetalcylinersUmetalcylinersUmetalcylinersEnrichment w/oV2352.352.352.352.352.352.352.352.352.352.352.354.294.294.294.2993.293.293.293.293.293.293.293.293.293.293.293.2Reflector waterwaterwaterwaterwaterwaterwaterwaterwaterwaterwaterwaterwaterwaterwaterbareparaffinbareparaffinbareparaffinbareparaffinbareparaffinbareSeparating Materialwaterwaterwaterwaterstainless steelstainless steelstainless steelstainless steelboralboralboralwaterstainless steelstainless steelboralairairairairairairplexiglass plexiglass plexiglass plexiglass steelplexiglass, steelCharacterizing Seation(cm)11.928.396.394.4610.4411.477.767.426.349-035.0510.649.768.086.7215.4323.8419.9736.4713.74'.23.4815.7424.4321.7427.9414-7416.671.004+0.993+1.005+0.994+1.005+0.992+0.992+1.004+1.005+0.992+1.001+0.999+0.999+0.998+0.998+0.998+1.006+1.005+1.001+1.005+1.005+1.010+1.006+0.999+0.994+1.000+0.996+.004.004.004.004.004.004.004.004.005.005.006.005.003.00$.004-003.004.003.004~003.005.003.003 tlIrI>++gI~iI~$IPw+IL~EiIIII FIGU2K~~VS.hVTERYiODERAQeffFORATYPICAL"POISONED" SPENTFUELSTORAGERACK'1.00.9eif0.80.70.6TYPEOFRACKC-C,10.25INCHPOISONLOADING,0.02gm-B/cm102FUEL,3.5M/0M17x1700.20.40.60.81.0MODERATOR DENSITY(gm/cm)~0-'
~I~IU.KerfASAFUt>CTIOH OFC-CSPACING,,POILOAOIt(GCttDEt<RICHNEhT FOltdSTItsut{OUSE 15x15OFAFUELFORO.C.COOKSPEtlT.FUELRACK1.0C-CSPACING.98POISONLOADING.96ENRICHiMENT.94.92.90.88~v<tsi3.55-Pn>>ck~pnO(/o)-4.0510.0-9P-"<<~~Q-C(-Q~z)-10.50.01-L,>~~y(~-8'/z-3-0.02Forenric'r,;-,.ant c~r.e,C-C=10.5",lo=ding=Forspacingcurve,w/o=4.05,loading=0.02Forloadingcurve,w/o=4.05,C-C=10.5"20.,02c.---B/cm,".Ia/,24.5511.00.03 FIGURE4STRUCTURE BARSINTERi'MEDIATELY SPACED(NOTINCLUDEDINKENOi%0EL)REFLECTIVE fANGLEIRONS(FULLLENGTH)0.25"0.25"~I,lFUELASSEMBLY17x17MSTD.8.432".I9.0"21.0"