核反应堆工程核反应堆工程 (11).ppt
Nuclear Engineering ReactorIntroduction of Space Nuclear Power1Overview1BackgroundDesignfeatures23Typicalspacereactorsystems4Summary2Background3MannedLandingonMars（theUSA）Spaceexplorationprogram（Russia）Unmannedbaseonthemoon（Japan）Inthebitterlycold,radiation-rich,poorlylitenvironmentsoftheouterplanets,onlyarugged,solar-independentpowersourcehasthewherewithaltosurviveandfunctionforlongperiodsoftime.Thedevelopmentanduseofnuclearpowerinspacehasenabledthehumanracetoextenditsvisionintoregionsthatwouldnothavebeenpossiblewithnon-nuclearpowersources.Withthespreadingoftheresearchresultsofspacescienceandapplications,spacesciencehasbecomeoneoftheimportantmotiveforcesforthedevelopmentofeconomy and society.4BackgroundNuclearpowerIndependently of sunlight.Nuclearreactorscanmass less thansolarcellsofequivalentcapacity.Nuclearpowerconceptsthatcanpowerbothlife support andpropulsionsystemsmayreducebothcost and flight time.ChemicalpowerSolarpowerAdvantageSpaceStation30kWPlanetarysurface40kW20MWDeepspaceexploration100kWOverview1BackgroundDesign features23Typicalspacereactorsystems4Summary5Design requirements6Space environmentSpace environment：VacuumenvironmentandlowcorrosivenessLowambientpressure.HighrequirementsforcompressionresistanceandsealingExtremetemperature.Equipmentinsulationandheatdissipation.Design requirements:Design requirements:Long-termreliableLightweightandsmallsizeRadiationprotectionandnuclearsafetySimplifieddesignrequiresmorerigorouscontrolandsafety7ClassificationRTG:RadioisotopeThermoelectricGeneratorRHU:RadioisotopeHeatUnitTEC:ThermionicEnergyConvertorAMTEC:AlkaliMetalThermaltoElectricConverterOverview1BackgroundDesignfeatures23Typical space reactor systems4Summary89Typical systemsSNAP-10ASP-100pForalmost55years,spacenuclearpowersourceshaveprovedtobesafe,reliable,sturdy,long-livedsourcesofelectricalpower.pSince1961,theU.S.hassuccessfullylaunched42nuclearpowersources(41radioisotopethermoelectricgeneratorsandonenuclearreactor)on24spacemissionsalongwithhundredsofradioisotopeheaterunits(RHUs).pRussiahasalsosuccessfullydevelopedfourmaintypesofSpaceNuclearReactors,haslaunchedmorethan35satellitesequippedwithNuclearreactors.CORECORECONVCONVERSIERSIONONSHIELDSHIELDELECTELECTLOADLOADHEAT HEAT REAJECTIONREAJECTIONBUKTOPAZ-10Typical systemsFission Surface Power(FSP)11pSystem Concepts for Affordable Fission Surface PowerTypical systems FSPpTheproposedFSPsystemusesalow temperature,uranium dioxide-fueled,liquid metal-cooledfissionreactorcoupledtofree-pistonStirlingconverters.pTheconceptwasdeterminedbya12monthNASA/DOEstudythatexamineddesignoptionsanddevelopmentstrategiesbasedonaffordability and risk.UndertheVisionforExploration,NASAisevaluatingoptionsforhumanmissionstotheMoonandMars.Lunar missionsareexpectedtobeginintheearly2020s.Mars missionsmayoccurlater,possiblyinthe2030s.12pReactor-Converter CombinationpAmatrixofsystemconcepts,asshownintable,wasgeneratedbyselectingreactor fuel,primary coolant,power conversion type,andradiator coolant.pTheaffordabilitygoalledtoadecisionbythegovernmentteamtolimitreactorfuel-cladtemperatureto900K tominimizefuelandmaterialdevelopmentcostsandmaximizetheuseofexistingtechnology.Typical systems FSP13pReactor-Converter CombinationTypical systems FSP14pPreliminary Reference ConceptAsampleofthescreeningstudyresultsisprovidedinfigureshowinga comparison of reactor thermal power and radiator area forthevariouspowerconversionoptionsassuminga900Kpumped-NaKreactorheatsource.Typical systems FSP15pPreliminary Reference ConceptThereactorislocated at the bottom of a 2 m excavation withanupperplugshieldprotectingtheequipmentabovefromdirectradiation.pThereactor(Rx)producesapproximately175 kWt withapeakcladtemperatureof900KanddeliversheatedNaKat890Ktoapairofintermediateheatexchangers(IHX)viatwo,redundantprimarypumps.Typical systems FSP16pSystem SchematicpTheIHXisaNaK-to-NaKheatexchangerthatisolatestheprimaryNaKfromtheStirlingconvertersandpermitstheNaKinterfacetemperaturestobeoptimizedfortheStirling,whiletheprimaryNaKconditionscanbetailoredforthereactor.pEachintermediateNaKloopincludesredundantpumpsandservices two Stirling convertersatasupplytemperatureof880K.12kWedual-opposedstirlingconvertorconceptHeatrejectionandradiatorpanelconceptsTypical systems FSP17pTheaverageStirlinghot-endtemperatureis830K.EachStirlingconverterhasadedicatedcoolingloopwitha400K waterexittemperature.pTheeffectiveradiatortemperatureis380K.Typical systems FSP18pReactor and ShieldpThereactorcoolantisa78 percent Na,22 percent K mixturethatcanmoreeasilybemaintainedasaliquidpriortostartupbecauseofitsrelativelylow262Kfreezingtemperature.pThepeakfuelburn-upisestimatedat1.3at.%forthe8 yr designlife.Reactivitycontrolisprovidedbysix radial beryllium(Be)reflector drums.pTheouterstainlesssteelvesselisdodecagon-shapedfortightpackagingwiththeradialreflectors.Typical systems FSP19pReactor and ShieldTheshieldconsistsofboron-carbide(B4C)inastainlesssteelcontainerprovidingbothneutronandgammaattenuationAthinnerradialshield,asshowninfigure,mayalsobeneededtoreduceneutronleakagethroughtheregolith.Typical systems FSP20pReference concept mass summarySystemmassscalingforemplacedandlandedconfigurations.Typical systems FSP21Typical systemsDOE-Naval Reactors Program Prometheus22pDOE-Naval Reactors Program Prometheus(USA)PrometheuspProjectPrometheuswasestablishedin2003withagoalofdevelopingthe first nuclear reactor-powered propulsion system for a spaceship and demonstratingthatitcanbeoperatedsafelyandreliablyforciviliandeep-spaceexplorationmissions.pTheinitialapplicationofspacefissionpowerevaluatedwastheJupiterIceMoonsOrbiter(JIMO).The goal of the Prometheus Project:pDevelopingaspaceshipforexplorationmissionsoftheouter solar system pProvidingunprecedented amounts of on-board electrical power and energy toincreasespacecraftmaneuverability,enablehigh-capabilityinstruments,provideexpandedmissiondesignTypical systems23pDOE-Naval Reactors Program Prometheus(USA)Thefeasibilityassessmentresultwereusedtoselectfiveconcepts:pDirectcycle,gas-cooledreactorwithaBraytonenergyconversionsystempHeatpipe-cooledreactorwithaBraytonenergyconversionsystempLiquidlithium-cooledreactorwithaBraytonenergyconversionsystempLiquidlithium-cooledreactorwithathermoelectricenergyconversionsystempLowertemperature,liquidmetalcooledreasctorwithaStirlingenergyenergyconversionsystemPrometheusTypical systems24pDOE-Naval Reactors Program Prometheus(USA)pThegas reactor system wasjudgedtohave the best prospect tomeetmissionrequirementswithintheexpecteddevelopmenttimeframe.Useofaninert gas coolantsimplifiesengineeringdevelopmenttesting.pBrayton technology isjudgedtoberelativelymaturewithanexistingengineeringandmanufacturingbase,andaBraytonsystemhasfewercomponentsrequiringdevelopmentrelativetotheotherconceptsconsidered.pAgasBraytonsystemisextensibletosurfacemissions.SpaceshipandModulesParameterValuePower1MWth185kWeFullPowerYears15FuelUO2CladMaterialMo-47.5ReSystemPressure(MPa)2CoolantHe-Xe(31.5g/mol)VesselMaterialAlloy-617ShieldMaterialBe-B4C-WPrometheusTypical systems25Thegas-cooledreactorBraytonsystemisdepictedinFigure.pThereactorconsistsofacorewithcylindricalfuelpinelementsarrangedwithinthecorestructureandareactorvesseltodirectcoolantflowandprovidestructuralsupportforthecoreandreactivitycontrols.Itusesasingle gas-cooled reactormountedattheforwardendofthespaceship.Aninertgas(He-Xegasmixture)isusedtocoolthecoreandtransportenergyaroundorthroughashadowshieldtotheBraytonenergyconversionsystem.PrometheusTypical systems26Thecoolanttemperaturesuppliedtotheplantfromthereactorislimitedto1150 Kinordertoallowtheuseofmoreconventionalmaterialsfortheplantandenergyconversionsystemandtoreducepressureloadingonthefuelelementcladding.SampleplantarrangementsandheatbalanceresultsareshowninFigure.PrometheusTypical systems27pFixed and movable reflector segmentsareusedtocontrolthefissionreactionratebychangingthefractionofneutronleakagethatisreflectedbackintothecore.pRemovable,neutron-absorbingsafetyrodskeepthereactorshutdownintheeventofalaunchortransportaccident.Reactorcontroldrivemechanismsareusedtomovethereflectorsandsafetyrods.pGasflowsdirectlyoverthefuelelementseitherinanopenlatticearrayorthroughchannelsinablockintowhichthefuelpinsareinserted.PrometheusTypical systems28Theelementsconsistofceramicfuelpellets,agasgaptoaccommodateswelling,acladdinglinertoimprovematerialcompatibility,andthecladdingwhichpreventsfissiongasescape.A fission gas plenum istypicallysituatedatoneendofeachfuelelementtoaccommodatethefissiongasreleasedfromthepelletswithout producing excessive clad strain duetogaspressureaccumulation.Theelementsareattachedtothesupportstructureatonlyoneendtoallowfordifferentialgrowthbetweenthefuelelementandthestructure.PrometheusTypical systems29pTheannular flow block geometry andopen lattice geometry wereevaluatedmorethantheotherconceptspriortoprojectrestructuring.pTheannularflowblockarrangementallowedformore controlled coolant distributionwithinthecorebutresultsinhigher reactor masses ascomparedtotheopenlatticedesigns.pTheopenlatticedesignshadtheleast mass butthelackofdefinedcoolant channelsmakesitmorechallengingtocontrolflowtospecificregionsofthecore.PrometheusTypical systems30pAmodular cermet design.Thecermetfuelsystemconsistsofarefractorymetalalloymatrixandsmallfuelparticles.pThisapproacheliminatestheneedforgas plena,improvesconductiveheattransfer,andcouldallowfortheabilitytocontrolcoolantflowtovariousregionsofthecore.pThedesignismoreaggressivethantheotherconceptsconsideredandrequiresoptimisticfabricationandperformancedesignassumptionstobemasscompetitive.ParametersValue(cm)FuelUO2FuelPinOD1.965FuelPelletOD1.819CladThickness0.051Pitch2.614FuelPinNumber(#)288SideReflectorThickness13VesselOD61.81VesselThickness0.48PrometheusTypical systems31pPros and Cons for Fuel Options PrometheusTypical systemsOverview1BackgroundDesignfeatures23Typicalspacereactorsystems4Summary3233Summary Beingtheonlysourcethatcanprovidelarge andlong-lastingpowerinthecurrentandnear-termfuture,thenuclear energy playsanimportantroleintheaerospacefield.Theresearchonspacenuclearreactoriscomprehensiveandthetechnologyisbecomingmature.Also,therearemanychallengesforthedevelopmentofspacenuclearreactors:Tooexpensive;Hightemperatureandirradiationresistantmaterialtechnology;Mass.
