Introduction
Variousmaterialsusedinnuclearengineering(oratomicenergyengineering).Nuclearengineeringincludestwotypes:
①Reactorengineeringbasedonnuclearfissionreactionandatomicbomb;
②Fusionreactorengineeringbasedonnuclearfusionreactionandhydrogenbomb.
Butpeopleusuallysaythatnuclearmaterialsmainlyrefertomaterialsusedinvariouspartsofthereactor,sotheyarealsocalledreactormaterials.Thisisbecausethedevelopmentofnuclearreactorshasbecomemoremature.Aboutathousandreactorshavebeenputintooperationaroundtheworld,andfusionreactorsarestillintheresearchstage.Reactormaterialsincludenuclearfuelthatundergoesfissionofnuclearenergyunderneutronbombardment,claddingmaterialsofnuclearfuelelements,coolants,neutronmoderatormaterials(moderators),control(rod)materialsthatstronglyabsorbneutrons,andpreventneutronleakageThereflective(layer)materialtotheoutsideofthereactor.
Reactormaterials
Materialsusedtobuildreactors,includingnuclearfuel,coolantmaterials,moderatingmaterials,structuralmaterials,controlmaterials,shieldingmaterials,etc.,haveformedamaterialsystem.Inadditiontothepropertiesofgeneralengineeringmaterials,reactormaterialsshouldalsohavegoodnuclearphysicalproperties,aswellasthecharacteristicsofbeingwellcompatiblewiththereactorenvironment.
Theresearchonreactormaterialsmainlyfocusesontheirnuclearphysicalproperties,radiationeffects,chemicalcompatibility,etc.,aswellasperformancestudiesrelatedtovariousapplications.Thiskindofresearchhasgreatlybroadenedthedevelopmentandapplicationofmaterialsscienceandtechnology.
Coolantmaterial
Theworkingmediummaterialusedtoderivetheheatgeneratedbythefissionofthereactorcoreismainlygaseousandliquid.Commonliquidcoolantmaterialsincludewater,heavywaterandliquidmetals-sodium,sodiumpotassiumalloy,bismuth,lead-bismuthalloyandsoon.Commongascoolantmaterialsincludecarbondioxide(CO2),air,andhelium(He).(SeeReactorCoolantMaterials)
Moderatormaterials
Materialsusedinthermalneutronreactorstoslowfissionneutronsintothermalneutrons,alsoknownasmoderators,Moderator(seeNeutronModeration).Commonlyusedmoderatormaterialsaresolidandliquid.Thesolid-statemoderatormaterialsincludegraphite,berylliumandberylliumoxide.Commonlyusedliquidmoderatormaterialsarelightwaterandheavywater,inadditiontoorganicmoderatormaterials.Forslowingdownmaterials,inadditiontohavingexcellentnuclearproperties,theyarealsorequiredtohavegoodengineeringperformance.(Seereactormoderatormaterials)
Structuralmaterials
Reactorstructuralmaterialsincludecorestructuralmaterials,fuel(rod)claddingmaterials,reactorpressurevessels,drivingmechanismmaterials,etc.Whenselectingstructuralmaterialsforcommercialreactors,thestrength,toughness,corrosionresistance,andtheresistanceofferriticsteeltoradiationembrittlementshouldbeconsidered.Nuclear-gradehigh-toughnesslow-alloysteel,stainlesssteel,basealloys,etc.arewidelyusedasmaterialsforreactorcorestructureandreactorpressurevesselmaterials.Zirconiumalloysarewidelyusedinfuel(rod)claddingmaterialsandfuelassemblystructuralmaterials.
Controlmaterials
Materialsusedtomanufacturecontrolelementsforcontrollingreactorreactivity.Suchmaterialshavestrongneutronabsorptionproperties.Suchmaterialsincludehafnium,silver-indium-cadmiumalloys,boron-containingmaterialsandrareearthmaterialsinsamarium,erbium,europium,gadolinium,andsomeoftheiroxidesandcarbides.(Seereactorcontrolmaterials)
Shieldingmaterials
Thematerialsusedinthereactorstructuretoattenuatevariousraysandavoidradiationdamagetostaffandequipment,mainlyincludeLead,iron,heavyconcrete,waterandothermaterials.
Nuclearfuel
Itreferstothematerialthatcanproducefissionorfusionnuclearreactionandreleasehugenuclearenergy.Nuclearfuelcanbedividedintotwocategories:fissionfuelandfusionfuel(orthermonuclearfuel).Fissionfuelmainlyreferstofissilenuclidessuchasuranium235,plutonium239anduranium233.Inaddition,becauseuranium238andthorium232areimportantrawmaterialsthatcanbeconvertedintofissilenuclides,andtheycanalsofissionundercertainconditions,theyarealsocustomarilycallednuclearfuels.Fusionfuelcontainshydrogenisotopessuchasdeuterium,tritium,lithium6,anditscompounds.
Nuclearengineeringmaterialsrefertovariousspecialmaterialsusedinreactorsandnuclearfuelcyclesandnucleartechnology,suchasreactorstructuralmaterials,componentcladdingmaterials,reactorcontrolmaterials,moderators,coolants,andshieldingmaterialsandmanymore.Forexample,specialaluminumalloy,beryllium,specialstainlesssteel,specialceramics,polymermaterials,etc.
Non-nuclearfuel
referstonuclidesthatcanundergochainreactionsafterabsorbingneutronsorconvertiblematerialsthatcannewlygeneratefissilenuclides.Theneutron-inducedfissionenergythresholdof235U,239pu,and233Uiszero.Theyarecalledfissilenuclides,whicharenuclearfuelsthatcanbeusedinthermalneutronreactors.After232Thand238Uabsorbneutrons,newfissilematerials233Uand239pucanbegenerated.232Thand238Uarecalledconvertiblematerials.238Uand232Tharerichinresources,providingabroadsourceofmaterialsfortheuseofnuclearenergy.Nuclearmaterialsareallradionuclides,andcaremustbetakentoprotectthemwhenusingthem.StrictcontrolandmanagementofPu,233U,and235Uwithanenrichmentdegreeofmorethan20%shallbeimplementedtopreventthetheftoftheabove-mentionedspecialnuclearmaterialsandtheiruseintheillegalproductionofnuclearweapons.
Safetyassuranceproceduresapplytoalllinksofthefuelcycle,includingfuelmanufacturing,powergeneration,fuelreprocessing,storageandtransportation.Nuclearmaterialsmustbeplacedinprotectedareaswithmultiplephysicalbarriers,andcomprehensivecontrolandstatisticsmustbeimplementedtopreventlossandproliferation.
Development
DatashowsthatasofJanuary2011,thereareatotalof442nuclearpowerplantsinoperationworldwide.TheInternationalAtomicEnergyAgencypredictsthatby2030,therewillbeabout300morenuclearpowerplantsoperatinggloballythaninJanuary2011.TheWorldNuclearEnergyAssociationpredictsthatby2015,theworldmaystartconstructionofanuclearpowerplantwithaninstalledcapacityofabout1,000megawattseveryfivedaysonaverage.
Asoftheendof2010,mycountry’sinstallednuclearpowercapacityexceeded10millionkilowatts,reaching10.82millionkilowatts,andthescaleof26unitsunderconstructionreached29.14millionkilowatts.Accordingtothecalculationof40millionkilowattsinthe"TwelfthFive-YearPlan",theconstructionperiodofnuclearpowerisgenerally5years.By2020,mycountry'snuclearpowergeneratingunitswillbecloseto80millionkilowatts.Itisestimatedthatthetotalinvestmentinthenuclearpowermarketwillreach980billionyuanfrom2011to2020,andtheaverageannualinvestmentwillbecloseto100billionyuan.
ThenuclearleakcausedbytheearthquakeinJapanwillundoubtedlycausedomesticconcernsaboutnuclearpowersafety.TheanalysisbelievesthatJapan’snuclearleakagewillincreasedomesticconcernsaboutnuclearsafetyandaffectthecountry’sfuturenuclearpowerplanning,buttheoverallnuclearpowerdevelopmentstrategyof"activedevelopment"willnotbefundamentallychanged.
In2009,theworld'sprovenuraniumreserveswere6.3milliontons.GlobaluraniumresourcesaremainlydistributedinAustralia,Kazakhstan,theUnitedStates,Brazil,Canada,SouthAfricaandothercountries,whilehigh-gradeuraniumminesaremainlylocatedinCanada.Atpresent,theworld'slargesturaniummineislocatedinCanada'sAthabascaBasin.AccordingtoWNAstatistics,globaluraniumproductionin2009was50,772tons.
In2009,mycountry'snaturaluraniumoutputwasnearly1,000tons,anditneededabout1,600tonsofnaturaluranium.In2010,mycountryneededabout1,900tonsofnaturaluranium.Asmycountry'snuclearpowerinstalledcapacitycontinuestoincrease,thedemandforuraniuminthenuclearpowerindustrywillcontinuetogrow,andtheprospectsformycountry'suraniummarketarepromising.Ifmycountry’sinstallednuclearpowercapacityis80millionkilowattsin2020,itwillneedabout14,000tonsofnaturaluraniumannually.
Asmycountry’snuclearpowerinstalledcapacityincreasesyearbyyear,ontheonehand,itbringsnewdemandforzirconiummaterials,andontheotherhand,thedemandforrenewalofzirconiummaterialsisalsoincreasingeveryyear.Thehighgrowthofnuclear-gradezirconiummaterialswillItwillcontinueuntil2020,anditisexpectedthatmycountry'szirconiumdemandwillreach1,200tonsin2020.
Assumingthat15%ofnuclearenergyprojectsbefore2020usefastreactors,accordingtothenuclear-gradesodiumconsumptionofmycountry’stestfastreactors(65MWconsumptionof350tons),thedomesticfastneutronreactorswillproducenearly56377tonsofnuclearGradesodiumdemand,2011-2020,theaverageannualnucleargradesodiumdemandis5337.7tons.
Domesticnuclearpower
Chinaisincreasingitsenergystructureadjustmentefforts.Itisurgenttoactivelydevelopcleanandhigh-qualityenergysuchasnuclearpower,windpower,andhydropower.China'senergystructureisstilldominatedbycoal,andtheproportionofcleanandhigh-qualityenergyisrelativelylow.ThetotalinstalledcapacityofnuclearpowerplantscurrentlybuiltandunderconstructioninChinais8.7millionkilowatts.ItisestimatedthatChina'sinstallednuclearpowercapacitywillbeapproximately20millionkilowattsby2010andapproximately40millionkilowattsin2020.By2050,accordingtoestimatesbydifferentdepartments,China’snuclearpowerinstalledcapacitycanbedividedintothreeoptions:high,mediumandlow:thehighoptionis360millionkilowatts(about30%ofChina’stotalinstalledpowercapacity),andthemediumoptionis240millionkilowatts(aboutItaccountsfor20%ofChina’stotalinstalledpowercapacity),andthelowoptionis120millionkilowatts(approximately10%ofChina’stotalinstalledpowercapacity).
TheNationalDevelopmentandReformCommissionofChinaisformulatingaplanforthedevelopmentofChina’snuclearpowerindustry.Itispreparingthatby2020,China’stotalinstalledpowercapacityisexpectedtobe900millionkWh,andnuclearpowerwillaccountfor4%ofthetotalpowercapacity,namelyItisChina'snuclearpowerthatwillbe36-40millionkilowattsin2020.Inotherwords,by2020,Chinawillbuild40million-kilowattnuclearpowerplantsequivalenttoDayaBay.
Fromtheperspectiveofthegeneraltrendofnuclearpowerdevelopment,China’snuclearpowerdevelopmenttechnicalandstrategicrouteshavelongbeenclearandarebeingimplemented.Thecurrentdevelopmentofpressurizedwaterreactors,themedium-termdevelopmentoffastneutronreactors,andthelong-termdevelopmentoffusionreactors.Specifically,inthenearfuture,thedevelopmentofthermalneutronreactornuclearpowerplants;inordertomakefulluseofuraniumresources,adoptthetechnicalrouteofuranium-plutoniumcycle,developfastbreederreactornuclearpowerplantsinthemedium-term;developfusionreactornuclearpowerplantsinthelong-term,soastobasically"forever"solveContradictioninenergydemand.