What is Radiation? | ANSTO

This is the level of natural background radiation in Australia. Low exposure to ionising radiation at this background level is not harmful. Australia's level of ... Skiptomaincontent ANSTO Education Nuclearfacts Radiation ANSTOEducationNuclearfactsRadiationNuclearfacts-NuclearscienceRadiationRadioisotopesSynchrotronlightManagingwasteBenefitsofnuclearscienceNuclearmedicineandhealth Radiation Radiationcanbedescribedasenergyorparticlesfromasourcethattravelthroughspaceorothermediums. Light,heat,andthemicrowavesandradiowavesusedforwirelesscommunicationsareallformsofradiation. Radiationincludesparticlesandelectromagneticwavesthatareemittedbysomematerialsandcarryenergy.Thekindofradiationdiscussedbelowiscalledionisingradiationbecauseitcanproducechargedparticles(orions)inmatter.X-rays,gamma-rays,alphaparticles,beta particlesandneutronsareallexamplesofionisingradiation. Play Naturalbackgroundradiation Australiansareconstantlyexposedtoionisingradiationfromavarietyofnaturalandartificialsources. Thesunisamajorsourceofcosmicradiation,orradiationoriginatingfromspace.Airlineflightsandskiingathighaltitudesareactivitiesthatwillincreaseexposuretothiscosmicradiation.Manybuildingsalsoemitionisingradiationsimplybecausethematerialsthatwereusedtobuildthem,suchasclaybricksandgranite, arenaturallyradioactive. Averageexposurestobackgroundradiation InAustralia,peoplereceiveabout1,500to2,000μSvofionisingradiationeveryyear.ThisisthelevelofnaturalbackgroundradiationinAustralia.Lowexposuretoionisingradiationatthisbackgroundlevel isnotharmful. Australia'slevel ofnaturalbackgroundradiationisquitelowcomparedtomanyotherpartsoftheworld.Asatypicalexample,inthecountyofCornwall,UK,peoplereceiveabout7,800 μSvofionisingradiationeveryyear.Again,thislowlevelofbackgroundradiationisnotharmful. Passengersonhigh-altitudeflightsreceivemoreexposuretocosmicradiationthantheywouldexperienceatgroundlevel.Forexample,ifyouflewreturnfromSydneytoLosAngeles,youwouldreceiveanextra160 μSvofbackgroundradiationdose. Asgraniteemitsmoreradiationthanothermaterials,ahomewouldgranitetileswouldexposuretheoccupantstoanextra1,000 μSvofbackgroundradiationannually. SomemedicalX-raysandsimilarproceduresprovideradiationdoses,withatypicalX-rayorCTscanofyourheadexposingyouto2,600 μSvofionisingradiation. Duetoits highpotassiumcontent,eatingabananawillprovideyouwithadoseof0.1 μSvfromthenaturally-occurring potassium-40isotope.  Frequently-askedquestions Whatisthedifferencebetweenradiationandradioactivity? Aradioactiveatomisunstablebecauseitcontainsextraenergy,oranunbalancednumberofparticles,initsnucleus.Whenthisatom‘decays’toamorestableatom,itreleasestheextraenergyand/orparticlesasionisingradiation. Howisionisingradiationdifferentfromothertypesofradiation? Ionisingradiationcanejectelectronsoutofatoms(therebyionisingthem),eitherbydirectinteractionwiththeatomsorbyothermethods.Alphaandbetaparticles,aswellasX-raysandgammarays,areexamplesofdirectly-ionisingradiation,whileneutronscauseionisationbyindirectprocesses. Istheremorethanonekindofionisingradiation? Yes.InadditiontoX-rays,threearecommon.Theyarecalledalpha(α),beta(β)andgamma(ɣ)radiation.Alphaparticles(heliumnucleiconsistingoftwoprotonsandtwoneutrons)maybestoppedcompletelybyasheetofpaper,betaparticles(high-speedelectrons)canbestoppedbyperspex,whilegammarays(likeX-rays,butwithashorterwavelength)mayneedleadorconcretetoefficientlystopthem-butcanbestoppedbyanymaterialprovidingthereisenoughofit.Otherlesscommontypesofionisingradiationalsoexist. Willtheseionisingradiationsmakemeradioactive? No.Receivingionisingradiation,suchas ultravioletlightfromthesunorradiationfromadental/medicalX-ray, willnotmakeyouradioactive. Ifionisingradiationdoesnotmakethingsradioactive,howdoitemsbecomeradioactiveinareactor? Inareactortherearetrillionsoffreenuclearparticlescalledneutrons.Whenabsorbedbyamaterialtheymayconvertstableisotopesintounstableisotopesandtherebymakethematerialradioactive(i.e.theunstableisotopeswill emittheir ownradiation).Thisprocess ishowmedicalradioisotopesaremadeintheOPALmultipurposereactor. Doesradiationbuildsupinthebodyuntilitgetstoapointwhereitkillsyou? Ionisingradiationdoesnotbuildupinyourbodyanymorethanlightwhichfallsonyoubuildsupinyourbody.Theradiationthatreachesyouisgoneafractionofasecondlater. Radiationeffectsmayappearfollowingexposuretohighdosesinashorttime,suchashowabaddoseofsunburnresultsfromtoomuchexposuretosunlight(ultravioletradiation)tooquickly.Similarly,long-termexposuretoionisingradiationathighlevelsmaycausepermanentdamagetothebody. Ifradiationdoesnotbuildupwithinthebody,howdoesitharmaperson? Radiation,includingultravioletlightfromthesun,carriesenergywhichmaydamagelivingcellsbyionisingatomsinthosecells.Ifthedoseislow,orisdeliveredoveralongtime,thereisanopportunityforthebodycellstorepair.Unlessthedoseisquitehigh,thereisonlyaminisculechancethatsomecellsmayhavebeendamagedinawaythatcauseseffects,suchascancer,toappearlaterinlife. Nationalandinternationaldoselimitsforoccupationally-exposedworkersandmembersofthepublicaremanytimeslowerthanthesehighlevels.Inaddition,thegoalofradiationprotectionistokeeplong-termenvironmentalexposure,abovenormalbackgroundradiation,toaminimum. HowmuchdoesANSTO’soperationscontributetotheradiationdosesofnearbyresidents? ThedosethatamemberofthecommunitylivingnearANSTOwouldreceivefromouroperationsisnegligible.ThosepeoplelivingclosetothebushlandperimeteratLucasHeights(whichextends1.6kmoutfromtheOPALmultipurposereactor)receivelessthan10μSvperyear.Thisisonly0.7percentoftheaveragenaturalbackgroundradiationinAustralia.Peoplelivingfurtherawayreceiveproportionatelyless. This10μSvmaximumdosefromANSTO'soperationsisaboutthesameasthedosereceivedfromcosmicraysduringareturnflightbetweenSydneyandMelbourne,orthedosereceivedfromeatingtwobananasperweekforayear. Howareradiationdosesmeasured? Whentryingtomeasureradiationtherearetwoseparateaspectstoconsider:radiationactivity,andradiationexposure.Activityreferstohowmuchradiation(intheformofparticlesorphotons)isbeingemittedbyasource,whileexposuremeasurestheeffectsofthatradiationonanythingthatabsorbsit. RadiationactivityismeasuredinaninternationalunitcalledaBecquerel(Bq),where1Bqcorrespondstooneparticleorphotonofradiationemittedpersecond. Radiationexposurecanbemeasuredinthreeways: Absorbeddose,whichistheenergythataradiationsourcewoulddeposit inonekilogramofasubstance.AbsorbeddoseismeasuredinaninternationalunitcalledtheGray(Gy),where1Gycorrespondstoonejouleofenergyperkilogram. Equivalentdose,whichrelatestheabsorbeddoseinhumantissuetotheeffectivebiologicaldamagetheradiationcauses.Equivalentdosetakesintoaccountthefactthatdifferentformsofradiationhavedifferentbiologicaleffects,evenwhentheamountofabsorbeddoseisthesame—someformsofradiationaremoredamagingthanothers.Equivalentdoseisobtainedbymultiplyingabsorbeddosebyaradiationweightingfactorthatcorrespondstothetypeofradiationabsorbed.ItismeasuredinaunitcalledtheSievert(Sv). Effectivedose,whichtakesintoaccountthatdifferentpartsofthebodyreact differentlytoradiationexposure—someorgansaremoresensitivetoradiationthanothers.Effectivedoseisobtainedbymultiplyingequivalentdosebyatissueweightingfactorthatcorrespondstothetypeoftissueexposedtoradiation.Ifmorethanoneorganisexposedtoradiation,thenalleffectivedosestoallexposedorgansareaddedtogethertoobtainanoveralleffectivedose.Effectivedoseisalsomeasuredusingthe Sievert (Sv). TheSievertisquitealargeunitformeasuringradiation-adoseof1Svinashorttimewillcauseacuteradiationsickness.Fordescribingnormalradiationexposureandprotectionlevelsitiscommontouse smallerunitssuchas microSieverts(μSv),ormillionthsofaSievert,where1,000,000 μSv=1Sv. Radiationisoftenmeasuredasadoseoveraspecificperiodoftime,knownasthedoserate.Forexample,thetypicaldoseratefromnaturalbackgroundradiationinAustraliais1,500to2,000μSvperyear,orequivalently,4to5μSvperday.Theactualexposurereceiveddependsonboththedoserateandtheexposuretime. Whatarethesafelimitsforradiationdose? Radiographers,workersinthenuclearindustry,andradiationworkersingeneralwearapersonaldosimetertorecordtheirradiationdoses.TheNationalStandardforlimitingoccupationaldosesrequiresthatallradiationdosesshould‘bekeptaslowasreasonablyachievable’(ALARA),andthatdosesreceivedbyradiationworkersshouldnotexceed20,000μSv(about14timestheaverageannualnaturalbackgroundlevelinAustralia)tothewholebodyperyear,averagedoverfiveyears—andnotmorethan50,000μSv inanyoneyear. Thesedoseratesareselectedtobewellbelowharmfullevelsandcanbeconsideredsafelimitsforradiationdose. TheAustralianRadiationProtectionandNuclearSafetyAgency(ARPANSA)prescribesanannualdoselimitformembersofthepublicof1,000μSv.Thisisadosethatmayresultfromtheuseofionisingradiationbutdoesnotincludebackgroundradiationdoses,ordosagesyoumayreceivefrommedicalprocedures.