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1、Principles Principles of Radiationof RadiationIndustrial Studies 4020 Topics in Industrial Studies Environmental Safety Management Atomic number Atomic mass Number of Protons ONLY Number of Protons different number of neutrons Same chemical properties Different nuclear propertiesHydrogen 1 ProtonDeu
2、terium 1 Proton, 1 Neutron* Tritium 1 Proton, 2 NeutronsH1 1* Note: Tritium is RadioactiveHH2 13 1Radioactivity Atoms with too many neutrons or protons are unstable and emit energy to become more stable. Energy is carried away by a- / b-particleor x- / g-ray. These atoms are called radioactive and t
3、he process is called radioactive decayRadioactivity Natural Uranium Thorium Potassium-40 Carbon-14 (C-14) Hydrogen-3 (H-3) (tritium)Man made Phosphorus-32 (P-32) Sulfur-35 (S-35) Calcium-45 (Ca-45) Chromium-51 (Cr-51) Zinc-65 (Zn-65) Rubidium-86 (Rb-86) Iodine-125 (I-125)Background RadiationBackgrou
4、nd Radiationmrem/yrmrem/yr Cosmic Cosmic 2727 Terrestrial Terrestrial 2828 Inhaled Inhaled 200200 Internal Internal 3939 Man-madeMan-made6 63 3Total:Total: 357357RadiationMicrowave light bulb cell phone UV lamp radio / TV laser heat lamp x-raysEmission / propagation of energy through space or materi
5、al medium as waves or particlesIonizing RadiationAlpha Particles2 Protons + 2 NeutronsShort Range in AirNot an External Hazard Internal HazardBeta ParticlesNegligible MassLong Range in AirInternal/External HazardChargedGamma Rays/PhotonsGamma photons & X-Ray both electromagneticdiffer only by place
6、of origin No mass or chargeHighly-penetratingNeutronsVery Long RangeVery PenetratingDifficult to detectOther modes of DecayPositron emissionElectron captureFissionElectronActivityActivity Decay is a statistical process. Cannot predict when a particular atom will decay. Can predict when certain amoun
7、t (%) will have decayed.Units of ActivityCurie (Ci) 1 Ci = 37,000,000,000 dps (3.7 x 1010 dps) or 1 Ci = 2.22 x 1012 dpm Becquerel (Bq) 1 Bq = 1 dps 1 Ci = 37,000,000,000 Bq = 37 GBq (Giga Becquerel)Quantities & UnitsQuantities & Units Beta and gamma radiation about equally damaging:1 R = 1 rad = 1
8、rem Alpha radiation causes greater cellular damage1 rad of a = 20 remDecay RateDecay RateHalf-life, A= A0 e 0.693t/TA = A0 ()# of half-livesNon-Ionizing RadiationQuestions?RadiationRadiation SafetySafetyIndustrial Studies 4020 Topics in Industrial Studies Environmental Safety ManagementRadiation Haz
9、ardsRadiation Hazards External Hazard (exposure from outside the body) High-energy beta (i.e., energy 300 keV or 0.3 MeV) Gamma and X-rays Neutrons Internal Hazard Radioactive material enters body by eating/drinking in radiation area, by breathing vapors/aerosols, or skin absorption In body, it is t
10、reated like non-radioactive elements If not incorporated into organ, rapidly excreted and may pose only slight hazard If stored in organ, slowly excreted (effective half-life)Acute Biological EffectsAcute Biological EffectsWhole body, external acute exposure effects25 rad some chromosome aberrations
11、50 rad minor blood changes100 rad 2% radiation sickness400 rad 50% die in 60 days (LD50/60)700 rad lethal single exposure6000 rad cancer therapy (local)Low Dose Biological EffectsLow Dose Biological EffectsALARAALARA As Low As Reasonably AchievableBenefits outweigh risks? Lower Dose = Lower Risk Who
12、le body badge (TLD) Collar or Ring TLD Bioassay - thyroid (iodine) urinalysis (tritium)Monitoring WorkersMonitoring WorkersOccupational Exposure LimitsNot to Exceed mrem/yr rem/yr mSv/yr 5,000 5 5015,000 15 15050,000 50 50050,000 50 500Accumulated Dose Equivalent to: Whole BodyLens of the EyeSkin of
13、 Whole BodyExtremities of Whole Body - Hands, Feet, etcGeneral Safety MeasuresGeneral Safety Measures TIMEExposure increases with time SHIELDINGPlastic for beta Lead for gamma DISTANCEExposure decreases with distance vTime vs ExposureTime vs ExposureIncreased exposure (risk) over time Linear3 mR/hr
14、* 4 hr = ?Distance vs ExposureDistance vs ExposureI1d12 = I2d22 Exposure & ShieldingExposure & ShieldingThick, dense (i.e., lead) for gamma / x-raysPlastic betaHydrogeneous (or boron + cadmium) for neutronsNo shielding needed for alpha or low-energy betaDetectors/ MonitorsDetectors/ MonitorsDetector
15、s/ MonitorsDetectors/ Monitors1)Capable of Detecting 2)Efficiency3)Calibration Industrial Uses of Radiationhttp:/www.epa.gov/rpdweb00/source-reduction-management/applications.htmlIndustrial Uses of Radiation Lasers X-rays Gauges Wireless exit signsX-ray Fluorescence (XRF) Industrial Uses of Radiationhttp:/www.epa.gov/rpdweb00/source-reduction-management/applications.htmlMoisture/density gaugesRadiographyStatic controlSmoke detectorsEmergency Response Lifesaving and serious injury take precedence over radiation exposure and contamination Control Access to Area Ca
