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Radiation Basics Candace Davison, M.Engr. Pennsylvania State University Mary Lou Dunzik-Gougar, PhD Idaho State University/Idaho National Laboratory ANS Teachers’ Workshop August 2006
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Doctor
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Voyager
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Soda Can
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Bugs
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What we’ll cover... Atomic Basics What is Radiation? –Types –Characteristics Sources of Ionizing Radiation Concepts –Radioactivity –Half-Life –Contamination vs. Exposure –Protection and Biological Effects
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100 Years of Radiation Discovery
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Atomic Structure of Helium THE HELIUM’S subATOMIC HELIUM ATOM COMPOSITION 2 Protons 2 Neutrons 2 Electrons e-e- n e-e- p+p+ n p+p+
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MASS NUMBER is the total number of protons and neutrons 4242 He ATOMIC NUMBER is the number of protons ELEMENT SYMBOL n Neutrons have a large mass approximately equal to a proton’s mass. Neutrons have no charge. p+p+ Protons have a large mass and a positive charge. The number of protons identifies an element. Electrons have a very small mass and a negative charge. Electrons travel outside the nucleus. e-e- More on helium...
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What is Radiation? Transmission of energy via... Particles or Waves
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Types of radiation Ionizing Alpha Beta Gamma X-Rays Neutrons Non-Ionizing Radiowaves Microwaves Infrared Ultraviolet Visible Light
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Why is it called ionizing? Because it creates ions -- atoms with a charge. Ionizing Radiation Ejected Electron Neutrons and Protons
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Electromagnetic Spectrum
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Where does radiation come from? Atoms... from radioactive or unstable atoms
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What part of atoms? The Nucleus Hence, we have terms such as nuclear medicine.
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What is radioactivity? The spontaneous emission of “fragments” or “bundles” of energy from energetic nuclei creating more stable nuclei. Radioactive atom More stable atom formed Energy and radiation released
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If radiation comes from atoms and everything is made of atoms, is there radiation around us right now? Absolutely! It’s called background radiation
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Sources of radiation The average American receives about 360 millirems or radiation per year from all sources 63% 8% 11% 15% 3% Source: National Council on Radiation Protection & measurements.1%
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Terms Roentgen (R) - unit of exposure - ionization of air by x or gamma rays RAD (Radiation Absorbed Dose) - energy deposited in material rem - (Roengten Equivalent Man) –unit of dose equivalent
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Radiation Types Alpha ( ) 2 protons, 2 neutrons positively charged particle n p+ n Beta ( ) like an electron negatively charged particle - Gamma ( ) Wave energy (not a particle)
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PENETRATING ABILITY + + -
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Paper alpha beta gamma Wood Lead Concrete SHIELDING
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RADIOACTIVE DECAY REACTIONS ALPHA DECAY BETA DECAY GAMMA DECAY 238 92 U 234 90 Th + 4242 Th Pa + m 56 Ba Ba + +
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Units of “Activity” Activity - a rate; the number of emissions (of radiation) per unit time. dps - disintegrations per second Bequerel = 1 dps Curie = 37,000,000,000 dps Picocurie = 0.037 dps or 2.2 dpm
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Radioactive Contamination - is radioactive material in an unwanted place. Radioactive Contamination
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Half Life
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Why are we concerned about Radiation? Ionizing Radiation Human Cells Atoms in Cells Form Ions Change in CellCell Dies No/Neutral Change in Cell Not Replaced ReplacedReproducesMalignant GrowthBenign Growth
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Time How do we protect ourselves? Distance Shielding
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The End...
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