《辐射安全常识》PPT课件.ppt

,Principles of Radiation,Industrial Studies 4020 Topics in Industrial Studies Environmental Safety Management,Atomic number Atomic mass Number 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 + two neutrons. Its a radioactive isotope of hydrogen also known as tritium,Isotopes,Same number of protons; different number of neutrons Same chemical properties Different nuclear properties,Hydrogen 1 Proton,Deuterium 1 Proton, 1 Neutron,* Tritium 1 Proton, 2 Neutrons,H,1,1,* Note: Tritium is Radioactive,H,H,2,1,3,1,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,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 Radiation,mrem/yr Cosmic 27 Terrestrial 28 Inhaled 200 Internal 39 Man-made 63 Total: 357,Radiation,Microwave light bulb cell phone UV lamp radio / TV laser heat lamp x-rays,Emission / propagation of energy through space or material medium as waves or particles,Ionizing Radiation,Alpha Particles,2 Protons + 2 Neutrons Short Range in Air Not an External Hazard Internal Hazard,Beta Particles,Negligible Mass Long Range in Air Internal/External Hazard Charged,Gamma Rays/Photons,Gamma photons & X-Ray both electromagnetic differ only by place of origin No mass or charge Highly-penetrating,Neutrons,Very Long Range Very Penetrating Difficult to detect,Other modes of Decay,Positron emission Electron capture Fission Electron,Activity,Decay is a statistical process. 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) 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 & Units,Beta and gamma radiation about equally damaging: 1 R = 1 rad = 1 rem Alpha radiation causes greater cellular damage 1 rad of a = 20 rem,Decay Rate,Half-life, A= A0 e 0.693t/T A = A0 ()# of half-lives,Non-Ionizing Radiation,Questions?,Radiation Safety,Industrial Studies 4020 Topics in Industrial Studies Environmental Safety Management,Radiation 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 treated 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 Effects,Whole body, external acute exposure effects 25 rad some chromosome aberrations 50 rad minor blood changes 100 rad 2% radiation sickness 400 rad 50% die in 60 days (LD50/60) 700 rad lethal single exposure 6000 rad cancer therapy (local),Low Dose Biological Effects,ALARA As Low As Reasonably Achievable,Benefits outweigh risks? Lower Dose = Lower Risk,Whole body badge (TLD) Collar or Ring TLD Bioassay - thyroid (iodine) urinalysis (tritium),Monitoring Workers,Occupational Exposure Limits,Not to Exceed mrem/yr rem/yr mSv/yr 5,000 5 50 15,000 15 150 50,000 50 500 50,000 50 500,Accumulated Dose Equivalent to: Whole Body Lens of the Eye Skin of Whole Body Extremities of Whole Body - Hands, Feet, etc,General Safety Measures,TIME Exposure increases with time SHIELDING Plastic for beta Lead for gamma,DISTANCE Exposure decreases with distance v,Time vs Exposure,Increased exposure (risk) over time Linear 3 mR/hr * 4 hr = ?,Distance vs Exposure,I1d12 = I2d22,Exposure & Shielding,Thick, dense (i.e., lead) for gamma / x-rays Plastic beta Hydrogeneous (or boron + cadmium) for neutrons,No shielding needed for alpha or low-energy beta,Detectors/ Monitors,Detectors/ Monitors,1) Capable of Detecting 2) Efficiency 3) Calibration,Industrial Uses of Radiation,/rpdweb00/source-reduction-management/applications.html,Industrial Uses of Radiation,Lasers X-rays Gauges Wireless exit signs X-ray Fluorescence (XRF),Industrial Uses of Radiation,/rpdweb00/source-reduction-management/applications.html,Moisture/density gauges Radiography Static control Smoke detectors,Emergency Response,Lifesaving and serious injury take precedence over radiation exposure and contamination Control Access to Area Call for Help,Radioactive Waste,Industrial Studies 4020 Topics in Industrial Studies Environmental Safety Management,Types of Radioactive Waste,Spent Fuel - Withdrawn from a nuclear reactor following irradiation High-level waste - Highly radioactive material from reprocessing spent nuclear fuel Transuranic - Man-made elements above atomic number 92,Types of Radioactive Waste,NORM Naturally-occurring radioactive material (primarily uranium & thorium Special Nuclear - Pu, U-233, or uranium enriched in the Material isotopes U-233 or U-235 Low-level waste - not high-level radioactive waste, spent nuclear fue