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Radiation Basics Candace C. Davison, M.Engr. Research & Education Specialist Pennsylvania State University Radiation Science and Engineering Center Mary Lou Dunzik-Gougar, Ph.D. Assistant Prof of Nuclear Engineering Idaho State University / Idaho National Laboratory
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Medicine/Health
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Voyager
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Soda Can
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Bugs
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Questions we’ll answer... What is Radiation? Where does it come from? What is Radioactivity? What’s the difference between Contamination and Irradiation? How does radiation interact?
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Remember atomic structure? 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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n Neutrons have large mass, approximately equal to proton mass, but no charge. p+p+ Protons have a large mass and a positive charge. Electrons have a very small mass and a negative charge. Electrons travel outside the nucleus. e-e- More on this helium isotope... 4242 He ELEMENT SYMBOL MASS NUMBER is total number of protons and neutrons ATOMIC NUMBER is number of protons & identifies the element
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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 (rays) 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
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Electromagnetic Spectrum http://www.lbl.gov/MicroWorlds/ALSTool/EMSpec/EMSpec2.html
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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 science/medicine/reactors.
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If radiation comes from atoms and everything is made of atoms, is there radiation around us right now? You Betcha! It’s called background radiation.
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Sources of average radiation dose in the US Source: National Council on Radiation Protection and Measurement Report 160 (2006) Nuclear Power (<0.1%) Human Body (5%) Cosmic (5%) Consumer Products (2%)
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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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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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PENETRATING ABILITY + + -
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Paper alpha beta gamma Wood Lead Concrete SHIELDING
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What’s radioactivity?
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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 Different atom formed Energy and radiation released
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Radioactive atoms emit radiation.
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Half Life
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If I’m exposed to radiation, do I become (more) radioactive?
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No! You’ve been irradiated, exposed to radiation. Which is not to be confused with...
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Radioactive Contamination is radioactive material in an unwanted place. Radioactive Contamination
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Question... How were radioactive atoms formed?
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Answer... Supernova Explosion
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Question... How do we make a stable atom radioactive?
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Answer... How do we make a stable atom radioactive? – By adding energy to the nucleus – This is done by adding a particle such as a neutron from a reactor or a high energy charged particle from an accelerator such as an electron or proton
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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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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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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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