RadiationTrainingCourse核辐射基础知识

（优选）RadiationTrainingCourse核辐射基础知识当前1页，总共54页。天然辐射RadiationistheemissionofenergyfromanatomintheformofeitheranelectromagneticwaveoraparticletravellingathighspeedTheatomemitsthisenergytoreachamorestable(i.e.lowerenergy)state辐射是原子通过发射电磁波或粒子而释放能量的过程。原子通过释放能量从而达到稳定的状态。

当前2页，总共54页。原子AnAtomhasanucleusaroundwhichelectronsorbit原子由原子核与核外电子构成NucleusElectron当前3页，总共54页。原子(2)Thenucleuscontainsneutronsandprotons原子核包含中子与质子NeutronProtonElectron当前4页，总共54页。原子(3)Theprotonseachcarryapositive(+)chargeTheneutronsareneutral(nocharge)质子带一个单位正电荷，中子不带电，而电子带一个单位负电荷。NeutronProtonElectron++Theelectronseachcarryanegative(-)charge,sotheatomisneutraloverallsincethenumbersofneutronsandelectronsareequal当前5页，总共54页。原子(4)Thenumberofprotonsistermedtheatomicnumber,ZThenumberofneutronsandprotonsistermedthemassnumber,A质子数决定原子序数Z，中子和质子数之和决定质量数AInthisexample,thereare2protons,sotheatomicnumberis2Therearealso2neutrons,sothemassnumber,A

is4当前6页，总共54页。原子(5)Theatomicnumber,Zdependsonthechemicalelement原子序数Z决定元素的化学性质Z=1Z=3Z=2HydrogenHeliumLithiumHHeLi当前7页，总共54页。同位素(1)Isotopesareatomsofthesamechemicalelement(sameatomicnumber,Z),butwithdifferentnumbersofneutrons(differentmassnumber,A),forexample,isotopesofhydrogen,HZ=1Z=1Z=1HydrogenDeuteriumTritium1H2HA=1A=3A=23H当前8页，总共54页。同位素(2)Isotopesarewritten:Asthenameofthechemicalelement,followedbytheMassNumber(A),e.g.Uranium-235Or

U23592Symbolforchemicalelement

AtomicNumber,ZMassNumber,A当前9页，总共54页。TypesofAtomicRadiationAlphaparticle(α)Betaparticle(β)Gammaradiation(γ)NeutronsThereareothertypesofradiationbuttheyarebeyondthescopeofthistrainingcourse当前10页，总共54页。AlphaParticlesAnα-particleisanucleusofaheliumatom,ejectedathighspeedbydisintegrationofthenucleusofalarger(heavier)atomItconsistsof2neutronsand2protonsItcarriesadoublepositivechargeα粒子是由重核衰变产生的，由2个中子与2个质子组成，带2个单位正电荷。++He42α当前11页，总共54页。BetaParticlesAβ-particleisanelectronejectedathighspeedfromadisintegratingatomItcarriesasinglenegativechargeβ粒子是由原子核产生的高速电子，带1个单位负电荷-β0-1当前12页，总共54页。GammaRadiationAγ

-rayisapulseofhighfrequencyelectromagneticradiationejectedfromthenucleusofadisintegratingatomItcarriesnoelectricalcharge

γ射线是由原子核衰变产生的高能电磁波，不带电γ当前13页，总共54页。X-RadiationAnX-rayisapulseofhighfrequencyelectromagneticradiationejectedfromanatomwhenanorbitalelectrondropsfromahigh-energy(‘excited’)statetoalower-energystateItcarriesnoelectricalchargeX射线是核外电子由高能态跃迁到低能态时产生的电磁波，不带电当前14页，总共54页。NeutronsNeutronsareemittedfromthenucleusasaresultofradioactivedecayofsomeunstableatoms:‘Fissionproducts’formedjustafteraheavyatom,suchasUranium,hasbeensplit(‘fissioned’)ThisoccursmainlyinnuclearreactorsandatomicweaponexplosionsSomeveryheavyisotopesshowaprocessknown‘spontaneousfission’;theyemitneutrons(examplesareplutonium-240,andcalifornium-252)Certainradioisotopesourcesaredesignedtoemitneutrons,forexampleamericium-241mixedwithberylliumNeutronscarrynoelectricalcharge中子是不稳定的原子核衰变时产生的，不带电当前15页，总共54页。辐射的穿透性(1)Alphaparticlesarenotverypenetrating.Theyarestoppedby:Afewcm/2–3inchesofairAsheetofpaperorathinfoilofaluminiumThedeadlayerofhumanskinHOWEVERAlphaparticlesinsidethebodydepositalloftheirenergyinaverysmallvolumeofhumantissueInthissituation,theyareabout20timesmoredamagingthanγ-radiationAlpha粒子的穿透能力很弱，一张纸或人的皮肤就可以阻止Alpha粒子，空气中的射程也只有几个cm.但是，Alpha粒子在人体组织中的内照射危害约是Gamma射线的20倍。当前16页，总共54页。辐射的穿透性(2)Beta(β)particlesaremorepenetratingthanα-particlesTheyarestoppedby:Severalfeetofair(range~12feet/MeVβ-particleenergy)Afewcm(~2”)ofaluminiumorafewmm(~⅛”ofsteel)β-particlescanirradiatethegrowinglayersofhumanskinPlasticandaluminiumareusefulshieldingmaterialsBeta粒子的穿透性比Alpha粒子强。Beta粒子可以穿透人的皮肤，其在空气中的射程约几十cm,在铝中的射程为几个cm。通常我们用塑料或铝来屏蔽Beta粒子。当前17页，总共54页。辐射的穿透性(3)Gamma(γ)andX-raysareverypenetratingTheycantravellongdistances(miles)inairandothermaterialsTheyarenotabsorbedcompletely,buttheirintensitycanbegreatlyreducedby:20feet(6metres)ofwaterSeveralfeet(2-3m)ofconcrete4”(10cm)ofleadγ-radiationpassesthroughthehumanbodyGamma射线和X射线的穿透能力很强，其在空气中的射程可达几公里，在铅中的射程达几个cm，可以穿过人体。通常用铅来屏蔽Gamma射线。当前18页，总共54页。辐射的穿透性(4)Neutronscantravelhundredsofyards(~km)inairTheyrequirespecialshieldingusingmaterialscontaininglightelements,suchashydrogen,orcertainelementsthatabsorborscatterneutrons.Examples:Water,HeavyWater,Polyethylene,cadmium,concrete中子在空气中的射程可达数公里，通常用轻核素来屏蔽中子，例如水，塑料，水泥等。当前19页，总共54页。辐射的穿透性(5)PaperPlasticorAluminiumSteel,leadorconcreteαβγ当前20页，总共54页。辐射与放射性RadiationisthestreamofparticlesorraysbeingemittedbyasourceofradioactivityRadioactivityistheprocessofgivingoffradiation辐射是放射源发射出粒子或射线束，放射性是发出辐射的过程SourceRadiation当前21页，总共54页。放射性衰变(1)RecallthattheatomicnucleuscontainsneutronsandprotonsNeutronProtonElectron当前22页，总共54页。放射性衰变(2)Byemittinganα-particleNucleusloses2protons+2neutronsByemittingaβ-particleNucleusgainsaprotonByemittingaseriesofα-particlesand

β-particles,thenucleuscanachievethemoststableconfigurationParentNucleus‘Daughter’Nucleusα-particle当前23页，总共54页。RadioactiveDecayofUranium-238当前24页，总共54页。半衰期Thehalf-lifeofaradioisotopeisthetimetakenforhalfoftheatomsinasampletohavedecayedThehalf-lifecanvaryoverahugerange;itisfixedforaparticularradioisotope.Theshorterthehalf-life,themore‘active’thesamplewillbe半衰期是指样品中放射原子数量从开始衰变到一半时所用的时间。TypicalRadioactiveHalf-LivesUranium-2384.5billionyearsCarbon-145730yearsRadium-2261600yearsCaesium-13730yearsCobalt-605.3yearsPolonium-210138daysPhosphorous-302.55minutesHelium-60.82seconds当前25页，总共54页。放射性衰变图当前26页，总共54页。放射性单位1Becquerel(Bq)=1disintegrationpersecondAVERYSMALLQUANTITYSIUnits1Curie(Ci)=37billiondisintegrationspersecond=37billionBecquerels(37GBq)ANENORMOUSQUANTITY!USUnits当前27页，总共54页。RelativeMagnitudesofNumbersNUMBERSGREATERTHAN1NUMBERSLESSTHAN110121,000,000,000,000teraT10-10.1decid1091,000,000,000gigaG10-20.01centic1061,000,000megaM10-30.001millim1031,000kilok10-60.000001microµ102100hectoh10-90.000000001nanon10011110-120.000000000001picop当前28页，总共54页。辐射能量αandβparticles,andγ-andX-radiationcanbeemittedwithdifferentenergies,dependingonthenucleustheyoriginatedinTheseenergiesarecharacteristicoftheisotopeoforiginα

或β

粒子,γ或X射线的能量是由放射性核素决定的。Withspecialinstrumentation,thisfeaturecanbeusedtoidentifytheisotopespresentinanunknownradioactivesampleTheenergyofaparticleorradiationismeasuredinelectronvolts(eV),withprefixesofkilo(x1000)ormega(x1,000,000)

hencekeV,MeV,etc.Thehighertheenergy,thefastertheparticleistravellingandthemorepenetratingtheradiation当前29页，总共54页。UnitsofRadiation:Radiation‘Dose’As,ittravelsthroughair,oranyothermedium,abeamofradiation,oraradiationparticle,losessomeorallofitsenergybytransferringittothemediumJustas,forexample,amicrowaveovenradiatesmicrowaveswhichareabsorbedbysomethingyouwanttocook,raisingthetemperature当前30页，总共54页。UnitsofRadiation:Radiation‘Dose’(2)Theenergytransferredtotheair,orothermaterialthattheradiationtravelsthrough,causesariseintemperaturewhichcanbemeasured,althoughitisverysmallThisENERGYABSORBEDbythematerialistermedtheABSORBEDDOSEUnits (USA): Rad RadiationAbsorbedDose (SI): Gray (Gy) 1Gy=100rads=100cGy当前31页，总共54页。UnitsofRadiation:Radiation‘Dose’(3)TheintensityofaradiationbeamistherateatwhichenergyisdeliveredThisistheabsorbeddoseperunitoftime,orDOSERATEUsually,thisisexpressedasdoseperhour,butBEWARE!insomeaccident,medicalormilitarysituations,weusedoseperSECONDABSORBEDDOSERATE:DOSE/TIME

1Gy/h=100rads/h=100cGy/h当前32页，总共54页。UnitsofRadiation:Radiation‘Dose’(4)Thusfar,wehavebeenconsideringabsorbedradiationdoseinAIR,oranotherMEDIUMHowever,wearemoreinterestedinmeasuringthesignificanceofradiationtohumansTheabsorbeddoseismultipliedbyaweightingfactor

whichtakestheestimatedbiologicaleffectoftheabsorbedradiationintoaccountThisnewquantityisknownasWhataboutremsandSieverts?DOSEEQUIVALENT当前33页，总共54页。UnitsofRadiation:DoseEquivalentDOSEEQUIVALENTHABSORBEDDOSE,DxQUALITYFACTOR,Q当前34页，总共54页。UnitsofRadiation:DoseEquivalent(2)DxQ

=HGyxQ=SvradxQ=rem当前35页，总共54页。UnitsofRadiation:DoseEquivalent(3)DxQ=HGyxQ=SvradxQ=remQUALITYFACTORS:X-RAYS,BETA,GAMMA 1Alpha 20ForX-RAYS,BETA,GAMMA:1Gy=1Sv=100rem当前36页，总共54页。Whyareweconcernedaboutradiation?Whyareweconcernedaboutradiation?当前37页，总共54页。放射性对人的影响Photo:USDoD/DoEPublicDomainCANCERSTERILITYMUTATIONSRADIATIONSICKNESS当前38页，总共54页。辐射的生物效应(1)RADIATIONCAUSESIONIZATIONCellNucleusγ-ray+-+-OH.H.辐射引起细胞的DNA链断裂，产生自由基当前39页，总共54页。辐射的生物效应(2)DamagedCellDamagedcelldiesCellrepairsitselfDamagedcellreplicatesMUTATION当前40页，总共54页。辐射的生物效应(3)EARLYEFFECTSTemporarychangeinbloodcount临时改变血球计数Sterility不育症Nausea&Vomiting恶心和呕吐Radiationburns辐射灼伤AcuteRadiationSyndrome急性辐射综合症Death死亡DELAYEDEFFECTSCataracts白内障Leukaemia,othercancers白血病，其他癌症Lifeshortening寿命缩短Geneticeffects遗传效应Hormesis(improvedhealth)兴奋效应（改善健康）Nothingatall无影响当前41页，总共54页。辐射的生物效应(4)Radiationhasthegreatesteffectonthosepartsofthebodywherecellsaredividingquickly:SexorgansStomachliningSkin辐射对性器官，胃，皮肤等影响较大Radiationhaslesseffectonthoseorganswherecellsarerenewedmoreslowly:MuscleBoneNerve辐射对肌肉，骨骼，神经等影响较小当前42页，总共54页。Whathappenswithveryhighradiationdoses?Dose(Sv)SurvivalTimeModeofDemise550%chanceofsurvival5to10Weeks-monthsInfection感染10to100Days-weeksGastrointestinalcollapse胃肠道塌陷>100Hours-daysCentralNervousSystemFailure中枢系统衰竭当前43页，总共54页。…andatslightlylowerdoses?Dose(Sv)Effect0.15Temporarysterility暂时不育0.5Cataractformation白内障的形成3Erythema(skinreddening)，Hairloss红斑（皮肤发红），脱发5Drydesquamation干性脱皮10to20Moistdesquamation湿性脱皮当前44页，总共54页。HealthEffectsversusRadiationDose0.11101001,00010,000mSv101001,00010,000100,0001,000,000mremNote:thisscaleisinmilliSieverts(mSv);toconvertthistomicroSieverts(µSv),multiplyby1,000(add3zero’s)ormultiplymilliremscaleby10(add1zero)AnnualdoselimitforamemberofthePublicinEUAverageannualdosefromnaturalbackgroundradiationAnnualdoselimitforaradiationworkerinEU5-yeardoselimitforaradiationworkerinEUChangesinbloodcountvisibleafterasingledoseClinicalsymptomsofearlypathologyLethaldosebeyondtherapy*Typicaldosefromatrans-Atlanticcommercialflight当前45页，总共54页。RadiationDosesfromVariousSourcesTypicaldistributionofaverageindividualexposureTotal2to3mSv/person/yearSource:AREVA当前46页，总共54页。ExamplesofNaturalRadioactivityRainWater:0.3to1