Radiation What makes something radioactive?


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Radiation What makes something radioactive?

  1. 1. Radiation
  2. 2. What makes something radioactive? <ul><li>The nucleus of an atom contains protons and neutrons </li></ul><ul><li>They are packed together with a lot of repulsive charge </li></ul><ul><ul><li>Opposites attract, same charges repel </li></ul></ul><ul><li>If atom has too many neutrons, beta emission occurs </li></ul><ul><li>235 92 U  0 -1 e + 235 93 Np </li></ul><ul><li>If atom has too few neutrons, positron emission occurs </li></ul>
  3. 3. Band of Stability <ul><li>Picture </li></ul><ul><li>Notice most elements are stable & elements possess a driving force to try to become stable </li></ul>
  4. 4. Radioactivity & Safety <ul><li>Depends upon half life, amount of material involved, the nature of the released radiation, & total exposure to the radioactivity released. </li></ul><ul><li>Larger amount of material is obviously more dangerous </li></ul>
  5. 5. Radiation & Safety Continued <ul><li>Type of radiation also important </li></ul><ul><li> particles can be stopped by skin </li></ul><ul><li> particles can be stopped by Al foil </li></ul><ul><li> rays are ultimately most dangerous, dominant problem in nuclear waste storage </li></ul><ul><li>Half life  Shorter half life will emit more of its radiation over a given period of time </li></ul><ul><li>131 I half life of 8 days </li></ul><ul><li>238 U half life of 4.5 billion years </li></ul>
  6. 6. Nuclear Applications <ul><li>Far more lives have been saved from nuclear chemistry than have been lost, even including Nagasaki and Hiroshima </li></ul><ul><li>Nuclear Medicine is used in diagnosis of cancers and other diseases also used in treatment of diseases </li></ul>
  7. 7. Food irradiation <ul><li>E. coli bacteria has killed numerous people and sickened thousands of times more </li></ul><ul><li>Food spoilage can sometimes account for 50% food loss </li></ul><ul><li>Food irradiation can prevent or lessen both things </li></ul>
  8. 8. What is food irradiation? <ul><li>Uses gamma rays from 60 Co or 137 Cs </li></ul><ul><li>Irradiates the food, effectively killing bacteria such as Trichinella and Salmonella </li></ul><ul><li>Does not cause the food to become radioactive! </li></ul>
  9. 9. Radioisotopic Dating <ul><li>Each radioisotope decays at a specified rate, the amount of radioisotope in an object will give a measure of age </li></ul><ul><li>Living organisms contain a constant amount of 14 C, dead tissue less b/c it is converted to 14 N </li></ul>
  10. 10. Nuclear Power <ul><li>Nuclear power is a clean source of energy </li></ul><ul><li>Power plants use 235 U, 233 U or 239 Pu to participate in a controlled nuclear fission reaction </li></ul><ul><li>Excess heat from fission is used to create steam, drives turbines to generate electricity </li></ul>
  11. 11. Nuclear Power continued <ul><li>Moderators such as water or graphite slow the speed of the reaction </li></ul><ul><li>Nuclear power is a significant source of power in many countries </li></ul><ul><li>Waste disposal continues to be problematic </li></ul>12.7 Canada 21 14.4 Russia 20 19.9 U.S.A. 19 46.8 Sweden 6 47.0 Slovakia 5 47.1 Bulgaria 4 57.7 Belgium 3 73.1 Lithuania 2 75.0 France 1 % Power from Nuclear Country Rank
  12. 12. Nuclear Disasters <ul><li>3 Mile Island: 1979 Pump failure resulted in partial core meltdown, no deaths, 10 years later no elevated cancer risk </li></ul><ul><li>Chernobyl: 1986 Core meltdown, explosion, & fire </li></ul><ul><li>Graphite was used as a moderator (most designs use water or water and graphite) </li></ul><ul><li>3 Mile Island: 1979 pump fail </li></ul>
  13. 13. Chernobyl <ul><li>100 million curies of radioactivity were released affecting Ukraine, Belarus, Poland, Great Britain, and Norway </li></ul><ul><li>170,000 forced to permanently evacuate </li></ul><ul><li>At least 4300 deaths </li></ul>
  14. 14. Nuclear Waste <ul><li>Biggest problem with nuclear energy is not nuclear disasters but waste disposal </li></ul><ul><li>Waste is ubiquitous to many processes but nuclear waste has additional complications of danger & time </li></ul><ul><li>20 half-lives considered safe  isotopes used in power plants are exceptionally long lived </li></ul>
  15. 15. Nuclear Waste <ul><li>Prairie Island is used as a storage facility in MN </li></ul><ul><li>Yucca Mountain in NV is slated to be long term storage facility for U.S.A. </li></ul><ul><li>Video </li></ul>
  16. 16. What should we do about nuclear waste? <ul><li>What benefits/ disadvantages are there to the Yucca Mountain site for nuclear storage? </li></ul><ul><li>Should we continue to pursue this site? Why or why not? </li></ul><ul><li>What challenges exist in storing something for 10,000+ years? </li></ul><ul><li>What other alternatives exist for the safe storage of spent nuclear fuel? Advantages/ disadvantages of these? </li></ul><ul><li>Should we continue to use nuclear power given these concerns about storage? Why or why not? </li></ul>