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Radioactivity

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  1. Radioactivity January 2015

  2. Recall Isotope Notation • Why are some isotopes radioactive? • How do you find the number of neutrons? • What is alpha, beta, gamma decay?

  3. Nuclear Reactions- Fission and Fusion • Why are some nuclei unstable? • In the nucleus, P+ and Nﹾ are held together by the strong nuclear force (SNF) • Protons having the same electrical charge “repel” each other. • SNF must overcome this repulsion for the nucleus to hold together • (Small nucleus: SNF > repulsion …= stable • Large nucleus: SNF and repulsive force are similar strength… =unstable) • All nuclei with 83↑ protons are radioactive.

  4. Fission (Division) • Fission(division): a large nucleus is broken into smaller nuclei. Or a more massive nucleus forming 2 less massive nucli • The nucleus is bombarded by a particle… (nﹾ) • When the nucleus splits, it releases nﹾand Energy • Can lead to a chain reaction. • Uncontrolled = bomb • https://www.youtube.com/watch?v=qT4mSoZsbzM

  5. Fission (Division) • Controlled = nuclear power plant • https://www.youtube.com/watch?v=MGj_aJz7cTs • https://www.youtube.com/watch?v=_AdA5d_8Hm0 • Nuclear power plants use fission of Uranium atoms to generate electricity. • Pros- use small mass to generate a lot of energy • Cons • While it does not produce a lot of waste it produces other pollution such as radioactive material and using lakes and rivers to cool reactors leading to thermal pollution • the half life of Uranium is… Thermal Pollution https://www.youtube.com/watch?v=dLjow_jZjLA (power plants

  6. Critical mass: smallest possible mass that can sustain a nuclear reaction

  7. Fusion • Fusion: Small nuclei combine to form a larger nucleus. • Releases lots of E • Occurs at very high temperatures…10,000,000 ﹾC, this is why it is not yet suitable for energy production • Our sun and most stars are fusion reactors • http://www.youtube.com/watch?v=fSr3V498A3I&feature=related (animation) • http://www.youtube.com/watch?v=sSi-zSeS0_YRates (Torus Facility)

  8. Benefits of Radioactivity • Nuclear power generates electricity • Radioactive tracers used to follow chemicals through living organisms and the environment (groundwater)

  9. Benefits of Radioactivity • Medical imaging: PET scans, autoradiography, etc...

  10. Benefits of Radioactivity • Cancer treatment • Detection …smoke detectors, explosives in luggage, leaks in pipes, location of underground conduit, moisture content of soil, etc…  • Foods are preserved by radiation…spices and dried fruits/vegetables are irradiated to destroy pathogens. Potatoes and onions are irradiated to retard their sprouting. Fruits and vegetables are irradiated to slow down the ripening process. • Used to control the thicknesses of paper, plastics, metal foil • Radiometric dating of ancient objects

  11. Radiation Dangers • Damages/destroys cells….Red blood cells lose ability to carry oxygen, burns the skin, causes cataracts, destroys bone marrow cells, genetic mutations (damages DNA) which can lead to birth defects, etc… • High doses/prolonged exposure = radiation sickness = hair loss, sterility, bone deterioration, cancer, death, etc…

  12. Nuclear Power Plants: Pros and Cons • No pollutants released during the electricity production(compared to coal or natural gas power) • No dams on rivers interrupting natural aquatic ecosystems (compared to hydroelectric power) • Risk of a melt down causing radioactive matter to be released into the environment • Problems storing the nuclear waste (Radioactive Daughter Isotopes) • https://www.youtube.com/watch?v=mFeboB2u3QI -Darlington Pros/Cons • https://www.youtube.com/watch?v=vnjzVNG18jo- Chernobyl • https://www.youtube.com/watch?v=kBmc8SQMBj8-Fukishima

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