《辐射安全常识》PPT课件.ppt

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1、,Principles of Radiation,Industrial Studies 4020Topics in Industrial StudiesEnvironmental Safety Management,Atomic number Atomic massNumber of Protons ONLY Number of Protons&Neutrons(weight),C,14,12,Chemical Symbol,Atomic Mass,Atomic Number,Review,So,what is it?,H,3,Hydrogen 3 contains one proton+tw

2、o neutrons.Its a radioactive isotope of hydrogen also known as tritium,Isotopes,Same number of protons;different number of neutrons Same chemical propertiesDifferent nuclear properties,Hydrogen1 Proton,Deuterium1 Proton,1 Neutron,*Tritium1 Proton,2 Neutrons,H,1,1,*Note:Tritium is Radioactive,H,H,2,1

3、,3,1,Radioactivity,Atoms with too many neutrons or protons are unstable and emit energy to become more stable.Energy is carried away by a-/b-particle or x-/g-ray.These atoms are called radioactive and the process is called radioactive decay,Radioactivity,NaturalUraniumThoriumPotassium-40Carbon-14(C-

4、14)Hydrogen-3(H-3)(tritium),Man madePhosphorus-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 Radiation,mrem/yrCosmic 27Terrestrial 28Inhaled 200Internal 39Man-made63Total:357,Radiation,Microwave light bulbcell phone UV lampradi

5、o/TV laserheat lamp x-rays,Emission/propagation of energy through space or material medium as waves or particles,Ionizing Radiation,Alpha Particles,2 Protons+2 NeutronsShort Range in AirNot an External Hazard Internal Hazard,Beta Particles,Negligible MassLong Range in AirInternal/External HazardChar

6、ged,Gamma Rays/Photons,Gamma photons&X-Ray both electromagnetic differ only by place of origin No mass or chargeHighly-penetrating,Neutrons,Very Long RangeVery PenetratingDifficult to detect,Other modes of Decay,Positron emissionElectron captureFissionElectron,Activity,Decay is a statistical process

7、.Cannot predict when a particular atom will decay.Can predict when certain amount(%)will have decayed.,Units of Activity,Curie(Ci)1 Ci=37,000,000,000 dps(3.7 x 1010 dps)or1 Ci=2.22 x 1012 dpm Becquerel(Bq)1 Bq=1 dps1 Ci=37,000,000,000 Bq=37 GBq(Giga Becquerel),Quantities&Units,Beta and gamma radiati

8、on about equally damaging:1 R=1 rad=1 remAlpha radiation causes greater cellular damage 1 rad of a=20 rem,Decay Rate,Half-life,A=A0 e 0.693t/TA=A0()#of half-lives,Non-Ionizing Radiation,Questions?,RadiationSafety,Industrial Studies 4020Topics in Industrial StudiesEnvironmental Safety Management,Radi

9、ation Hazards,External Hazard(exposure from outside the body)High-energy beta(i.e.,energy 300 keV or 0.3 MeV)Gamma and X-raysNeutronsInternal HazardRadioactive material enters body by eating/drinking in radiation area,by breathing vapors/aerosols,or skin absorptionIn body,it is treated like non-radi

10、oactive elementsIf not incorporated into organ,rapidly excreted and maypose only slight hazardIf stored in organ,slowly excreted(effective half-life),Acute Biological Effects,Whole body,external acute exposure effects25 rad some chromosome aberrations50 rad minor blood changes100 rad 2%radiation sic

11、kness400 rad 50%die in 60 days(LD50/60)700 rad lethal single exposure6000 rad cancer therapy(local),Low Dose Biological Effects,ALARAAs Low As Reasonably Achievable,Benefits outweigh risks?Lower Dose=Lower Risk,Whole body badge(TLD)Collar or Ring TLDBioassay-thyroid(iodine)urinalysis(tritium),Monito

12、ring Workers,Occupational Exposure Limits,Not to Exceedmrem/yr rem/yr mSv/yr5,000 5 5015,000 15 15050,000 50 50050,000 50 500,Accumulated DoseEquivalent to:Whole BodyLens of the EyeSkin of Whole BodyExtremities of WholeBody-Hands,Feet,etc,General Safety Measures,TIMEExposure increases with timeSHIEL

13、DINGPlastic for betaLead for gamma,DISTANCEExposure decreases with distancev,Time vs Exposure,Increased exposure(risk)over time Linear3 mR/hr*4 hr=?,Distance vs Exposure,I1d12=I2d22,Exposure&Shielding,Thick,dense(i.e.,lead)for gamma/x-raysPlastic betaHydrogeneous(or boron+cadmium)for neutrons,No shi

14、elding needed for alpha or low-energy beta,Detectors/Monitors,Detectors/Monitors,1)Capable of Detecting 2)Efficiency3)Calibration,Industrial Uses of Radiation,Industrial Uses of Radiation,LasersX-raysGaugesWireless exit signs X-ray Fluorescence(XRF),Industrial Uses of Radiation,Moisture/density gaug

15、esRadiographyStatic controlSmoke detectors,Emergency Response,Lifesaving and serious injury take precedence over radiation exposure and contaminationControl Access to AreaCall for Help,RadioactiveWaste,Industrial Studies 4020Topics in Industrial StudiesEnvironmental Safety Management,Types of Radioa

16、ctive Waste,Spent Fuel-Withdrawn from a nuclear reactor following irradiationHigh-level waste-Highly radioactive material from reprocessing spent nuclear fuelTransuranic-Man-made elements above atomic number 92,Types of Radioactive Waste,NORM Naturally-occurring radioactive material(primarily uraniu

17、m&thoriumSpecial Nuclear-Pu,U-233,or uranium enriched in the Material isotopes U-233 or U-235Low-level waste-not high-level radioactive waste,spent nuclear fuel,transuranic waste,or certain by-product material,Solid Waste,LandfillDecay IncinerateSupercompaction,LSC Vial Waste,Aqueous Waste,Hold for decaySanitary sewerTable IIPOTW,Mixed Waste,RCRA/AEA Dual regulationEPA/State Conditional exemptionDepartment ofEnergy,Questions?,