RadiationTrainingCourse核輻射基礎(chǔ)知識(shí)天然輻射RadiationistheemissionofenergyfromanatomintheformofeitheranelectromagneticwaveoraparticletravellingathighspeedTheatomemitsthisenergytoreachamorestable(i.e.lowerenergy)state輻射是原子通過發(fā)射電磁波或粒子而釋放能量的過程。原子通過釋放能量從而達(dá)到穩(wěn)定的狀態(tài)。

原子AnAtomhasanucleusaroundwhichelectronsorbit原子由原子核與核外電子構(gòu)成NucleusElectron原子(2)Thenucleuscontainsneutronsandprotons原子核包含中子與質(zhì)子NeutronProtonElectron原子(3)Theprotonseachcarryapositive(+)chargeTheneutronsareneutral(nocharge)質(zhì)子帶一個(gè)單位正電荷，中子不帶電，而電子帶一個(gè)單位負(fù)電荷。NeutronProtonElectron++Theelectronseachcarryanegative(-)charge,sotheatomisneutraloverallsincethenumbersofneutronsandelectronsareequal原子(4)Thenumberofprotonsistermedtheatomicnumber,ZThenumberofneutronsandprotonsistermedthemassnumber,A質(zhì)子數(shù)決定原子序數(shù)Z，中子和質(zhì)子數(shù)之和決定質(zhì)量數(shù)AInthisexample,thereare2protons,sotheatomicnumberis2Therearealso2neutrons,sothemassnumber,A

is4原子(5)Theatomicnumber,Zdependsonthechemicalelement原子序數(shù)Z決定元素的化學(xué)性質(zhì)Z=1Z=3Z=2HydrogenHeliumLithiumHHeLi同位素(1)Isotopesareatomsofthesamechemicalelement(sameatomicnumber,Z),butwithdifferentnumbersofneutrons(differentmassnumber,A),forexample,isotopesofhydrogen,HZ=1Z=1Z=1HydrogenDeuteriumTritium1H2HA=1A=3A=23H同位素(2)Isotopesarewritten:Asthenameofthechemicalelement,followedbytheMassNumber(A),e.g.Uranium-235Or

U23592Symbolforchemicalelement

AtomicNumber,ZMassNumber,ATypesofAtomicRadiationAlphaparticle(α)Betaparticle(β)Gammaradiation(γ)NeutronsThereareothertypesofradiationbuttheyarebeyondthescopeofthistrainingcourseAlphaParticlesAnα-particleisanucleusofaheliumatom,ejectedathighspeedbydisintegrationofthenucleusofalarger(heavier)atomItconsistsof2neutronsand2protonsItcarriesadoublepositivechargeα粒子是由重核衰變產(chǎn)生的，由2個(gè)中子與2個(gè)質(zhì)子組成，帶2個(gè)單位正電荷。++He42αBetaParticlesAβ-particleisanelectronejectedathighspeedfromadisintegratingatomItcarriesasinglenegativechargeβ粒子是由原子核產(chǎn)生的高速電子，帶1個(gè)單位負(fù)電荷-β0-1GammaRadiationAγ

-rayisapulseofhighfrequencyelectromagneticradiationejectedfromthenucleusofadisintegratingatomItcarriesnoelectricalcharge

γ射線是由原子核衰變產(chǎn)生的高能電磁波，不帶電γX-RadiationAnX-rayisapulseofhighfrequencyelectromagneticradiationejectedfromanatomwhenanorbitalelectrondropsfromahigh-energy(‘excited’)statetoalower-energystateItcarriesnoelectricalchargeX射線是核外電子由高能態(tài)躍遷到低能態(tài)時(shí)產(chǎn)生的電磁波，不帶電NeutronsNeutronsareemittedfromthenucleusasaresultofradioactivedecayofsomeunstableatoms:‘Fissionproducts’formedjustafteraheavyatom,suchasUranium,hasbeensplit(‘fissioned’)ThisoccursmainlyinnuclearreactorsandatomicweaponexplosionsSomeveryheavyisotopesshowaprocessknown‘spontaneousfission’;theyemitneutrons(examplesareplutonium-240,andcalifornium-252)Certainradioisotopesourcesaredesignedtoemitneutrons,forexampleamericium-241mixedwithberylliumNeutronscarrynoelectricalcharge中子是不穩(wěn)定的原子核衰變時(shí)產(chǎn)生的，不帶電輻射的穿透性(1)Alphaparticlesarenotverypenetrating.Theyarestoppedby:Afewcm/2–3inchesofairAsheetofpaperorathinfoilofaluminiumThedeadlayerofhumanskinHOWEVERAlphaparticlesinsidethebodydepositalloftheirenergyinaverysmallvolumeofhumantissueInthissituation,theyareabout20timesmoredamagingthanγ-radiationAlpha粒子的穿透能力很弱，一張紙或人的皮膚就可以阻止Alpha粒子，空氣中的射程也只有幾個(gè)cm.但是，Alpha粒子在人體組織中的內(nèi)照射危害約是Gamma射線的20倍。輻射的穿透性(2)Beta(β)particlesaremorepenetratingthanα-particlesTheyarestoppedby:Severalfeetofair(range~12feet/MeVβ-particleenergy)Afewcm(~2”)ofaluminiumorafewmm(~?”ofsteel)β-particlescanirradiatethegrowinglayersofhumanskinPlasticandaluminiumareusefulshieldingmaterialsBeta粒子的穿透性比Alpha粒子強(qiáng)。Beta粒子可以穿透人的皮膚，其在空氣中的射程約幾十cm,在鋁中的射程為幾個(gè)cm。通常我們用塑料或鋁來屏蔽Beta粒子。輻射的穿透性(3)Gamma(γ)andX-raysareverypenetratingTheycantravellongdistances(miles)inairandothermaterialsTheyarenotabsorbedcompletely,buttheirintensitycanbegreatlyreducedby:20feet(6metres)ofwaterSeveralfeet(2-3m)ofconcrete4”(10cm)ofleadγ-radiationpassesthroughthehumanbodyGamma射線和X射線的穿透能力很強(qiáng)，其在空氣中的射程可達(dá)幾公里，在鉛中的射程達(dá)幾個(gè)cm，可以穿過人體。通常用鉛來屏蔽Gamma射線。輻射的穿透性(4)Neutronscantravelhundredsofyards(~km)inairTheyrequirespecialshieldingusingmaterialscontaininglightelements,suchashydrogen,orcertainelementsthatabsorborscatterneutrons.Examples:Water,HeavyWater,Polyethylene,cadmium,concrete中子在空氣中的射程可達(dá)數(shù)公里，通常用輕核素來屏蔽中子，例如水，塑料，水泥等。輻射的穿透性(5)PaperPlasticorAluminiumSteel,leadorconcreteαβγ輻射與放射性RadiationisthestreamofparticlesorraysbeingemittedbyasourceofradioactivityRadioactivityistheprocessofgivingoffradiation輻射是放射源發(fā)射出粒子或射線束，放射性是發(fā)出輻射的過程SourceRadiation放射性衰變(1)RecallthattheatomicnucleuscontainsneutronsandprotonsNeutronProtonElectron放射性衰變(2)Byemittinganα-particleNucleusloses2protons+2neutronsByemittingaβ-particleNucleusgainsaprotonByemittingaseriesofα-particlesand

β-particles,thenucleuscanachievethemoststableconfigurationParentNucleus‘Daughter’Nucleusα-particleRadioactiveDecayofUranium-238半衰期Thehalf-lifeofaradioisotopeisthetimetakenforhalfoftheatomsinasampletohavedecayedThehalf-lifecanvaryoverahugerange;itisfixedforaparticularradioisotope.Theshorterthehalf-life,themore‘a(chǎn)ctive’thesamplewillbe半衰期是指樣品中放射原子數(shù)量從開始衰變到一半時(shí)所用的時(shí)間。TypicalRadioactiveHalf-LivesUranium-2384.5billionyearsCarbon-145730yearsRadium-2261600yearsCaesium-13730yearsCobalt-605.3yearsPolonium-210138daysPhosphorous-302.55minutesHelium-60.82seconds放射性衰變圖放射性單位1Becquerel(Bq)=1disintegrationpersecondAVERYSMALLQUANTITYSIUnits1Curie(Ci)=37billiondisintegrationspersecond=37billionBecquerels(37GBq)ANENORMOUSQUANTITY!USUnitsRelativeMagnitudesofNumbersNUMBERSGREATERTHAN1NUMBERSLESSTHAN110121,000,000,000,000teraT10-10.1decid1091,000,000,000gigaG10-20.01centic1061,000,000megaM10-30.001millim1031,000kilok10-60.000001microμ102100hectoh10-90.000000001nanon10011110-120.000000000001picop輻射能量αandβparticles,andγ-andX-radiationcanbeemittedwithdifferentenergies,dependingonthenucleustheyoriginatedinTheseenergiesarecharacteristicoftheisotopeoforiginα

或β

粒子,γ或X射線的能量是由放射性核素決定的。Withspecialinstrumentation,thisfeaturecanbeusedtoidentifytheisotopespresentinanunknownradioactivesampleTheenergyofaparticleorradiationismeasuredinelectronvolts(eV),withprefixesofkilo(x1000)ormega(x1,000,000)

hencekeV,MeV,etc.Thehighertheenergy,thefastertheparticleistravellingandthemorepenetratingtheradiationUnitsofRadiation:Radiation‘Dose’As,ittravelsthroughair,oranyothermedium,abeamofradiation,oraradiationparticle,losessomeorallofitsenergybytransferringittothemediumJustas,forexample,amicrowaveovenradiatesmicrowaveswhichareabsorbedbysomethingyouwanttocook,raisingthetemperatureUnitsofRadiation:Radiation‘Dose’(2)Theenergytransferredtotheair,orothermaterialthattheradiationtravelsthrough,causesariseintemperaturewhichcanbemeasured,althoughitisverysmallThisENERGYABSORBEDbythematerialistermedtheABSORBEDDOSEUnits (USA): Rad RadiationAbsorbedDose (SI): Gray (Gy) 1Gy=100rads=100cGyUnitsofRadiation:Radiation‘Dose’(3)TheintensityofaradiationbeamistherateatwhichenergyisdeliveredThisistheabsorbeddoseperunitoftime,orDOSERATEUsually,thisisexpressedasdoseperhour,butBEWARE!insomeaccident,medicalormilitarysituations,weusedoseperSECONDABSORBEDDOSERATE:DOSE/TIME

1Gy/h=100rads/h=100cGy/hUnitsofRadiation:Radiation‘Dose’(4)Thusfar,wehavebeenconsideringabsorbedradiationdoseinAIR,oranotherMEDIUMHowever,wearemoreinterestedinmeasuringthesignificanceofradiationtohumansTheabsorbeddoseismultipliedbyaweightingfactorwhichtakestheestimatedbiologicaleffectoftheabsorbedradiationintoaccountThisnewquantityisknownasWhataboutremsandSieverts?DOSEEQUIVALENTUnitsofRadiation:DoseEquivalentDOSEEQUIVALENTHABSORBEDDOSE,DxQUALITYFACTOR,QUnitsofRadiation:DoseEquivalent(2)DxQ=HGyxQ=SvradxQ=remUnitsofRadiation:DoseEquivalent(3)DxQ=HGyxQ=SvradxQ=remQUALITYFACTORS:X-RAYS,BETA,GAMMA 1Alpha 20ForX-RAYS,BETA,GAMMA:1Gy=1Sv=100remWhyareweconcernedaboutradiation?Whyareweconcernedaboutradiation?放射性對(duì)人的影響Photo:USDoD/DoEPublicDomainCANCERSTERILITYMUTATIONSRADIATIONSICKNESS輻射的生物效應(yīng)(1)RADIATIONCAUSESIONIZATIONCellNucleusγ-ray+-+-OH.H.輻射引起細(xì)胞的DNA鏈斷裂，產(chǎn)生自由基輻射的生物效應(yīng)(2)DamagedCellDamagedcelldiesCellrepairsitselfDamagedcellreplicatesMUTATION輻射的生物效應(yīng)(3)EARLYEFFECTSTemporarychangeinbloodcount臨時(shí)改變血球計(jì)數(shù)Sterility不育癥Nausea&Vomiting惡心和嘔吐Radiationburns輻射灼傷AcuteRadiationSyndrome急性輻射綜合癥Death死亡DELAYEDEFFECTSCataracts白內(nèi)障Leukaemia,othercancers白血病，其他癌癥Lifeshortening壽命縮短Geneticeffects遺傳效應(yīng)Hormesis(improvedhealth)興奮效應(yīng)（改善健康）Nothingatall無影響輻射的生物效應(yīng)(4)Radiationhasthegreatesteffectonthosepartsofthebodywherecellsaredividingquickly:SexorgansStomachliningSkin輻射對(duì)性器官，胃，皮膚等影響較大Radiationhaslesseffectonthoseorganswherecellsarerenewedmoreslowly:MuscleBoneNerve輻射對(duì)肌肉，骨骼，神經(jīng)等影響較小Whathappenswithveryhighradiationdoses?Dose(Sv)SurvivalTimeModeofDemise550%chanceofsurvival5to10Weeks-monthsInfection感染10to100Days-weeksGastrointestinalcollapse胃腸道塌陷>100Hours-daysCentralNervousSystemFailure中樞系統(tǒng)衰竭…andatslightlylowerdoses?Dose(Sv)Effect0.15Temporarysterility暫時(shí)不育0.5Cataractformation白內(nèi)障的形成3Erythema(skinreddening)，Hairloss紅斑（皮膚發(fā)紅），脫發(fā)5Drydesquamation干性脫皮10to20Moistdesquamation濕性脫皮HealthEffectsversusRadiationDose0.11101001,00010,000mSv101001,00010,000100,0001,000,000mremNote:thisscaleisinmilliSieverts(mSv);toconvertthistomicroSieverts(μSv),multiplyby1,000(add3zero’s)ormultiplymilliremscaleby10(add1zero)AnnualdoselimitforamemberofthePublicinEUAverageannualdosefromnaturalbackgroundradiationAnnualdoselimitforaradiationworkerinEU5-yeardoselimitforaradiationworkerinEUChangesinbloodcountvisibleafterasingledoseClinicalsymptomsofearlypathologyLethaldosebeyondtherapy*Typicaldosefromatrans-AtlanticcommercialflightRadiationDosesfromVariousS