Radiation Hazards

Radiation Hazards - Radiation Hazards Nuclear Forces At...

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Radiation Hazards
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Nuclear Forces At this scale, gravity is utterly insignificant Protons are repelled by electromagnetic force Two types of nuclear forces bind particles together Very short range
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Nuclear Decay Too many protons (>83, Bi): nuclear forces cannot hold nucleus together Too many neutrons also unstable Unstable nuclei emit particles and energetic radiation (gamma rays) Massive nuclei can sometimes split catastrophically (fission) Natural or Spontaneous Nuclear Reactor Nuclear Weapon
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Isotopes Atoms of element with different number of neutrons Protons = Atomic Number Protons + Neutrons = Atomic Weight Example: Uranium-238 92 protons by definition 238-92 = 146 neutrons Carbon-14 6 protons (by definition), 8 neutrons
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Radioactive Decay: Half-Life
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Radiation and Half-Life Decay Constant: fraction of atoms that decay/time Half-life = 0.693/Decay Constant Example: 10% decay per hour: Half Life = 0.693/(0.1/hour) = 6.9 hours Shorter Half Life = More Radiation Per Unit Time Generally more energetic
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Curie Unit of radioactivity 3.7 x 10 10 decays/second Rn-222 3.8 days .000006 grams Co-60 5.26 yr .0013 grams Sr-90 28 yr .007 grams Ra-222 1600 yr 1 gram Pu-239 24400 yr 16 grams U-238 4.5 b.y. 3,000,000 gm (3 tons)
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Radiation Hazards Three Mile Island: 50 curies About ½ gram Chernobyl (1986) 50,000,000 curies About 500,000 grams (half a ton) Russian Deep Waste Injection Program: 3,000,000,000 curies
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Half-Life and Hazard Very short half-life (days or less) Extremely high radiation hazard Decays very quickly Probably won’t move far during lifetime Extremely long half-life (geological) Radiation hazard negligible Chemical toxicity is worst hazard Daughter products (radon) can be a problem Medium half-lives (years to 1,000’s years) Last long enough to migrate
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This document was uploaded on 12/31/2011.

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Radiation Hazards - Radiation Hazards Nuclear Forces At...

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