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Nuclear energy

Nuclear energy. Summary of period 1. Parts of the atom. Add/subtract a proton: creates a different atom Add/subtract a neutron: creates a different isotope Add/subtract an electron: changes oxidation state / creates ion. Isotopes. Mass number (protons + neutrons).

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Nuclear energy

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  1. Nuclear energy Summary of period 1

  2. Parts of the atom • Add/subtract a proton: creates a different atom • Add/subtract a neutron: creates a different isotope • Add/subtract an electron: changes oxidation state • / creates ion

  3. Isotopes Mass number (protons + neutrons) Element symbol Atomic number (number of protons) • The isotope of uranium above has 92 protons • It has 143 neutrons • U-238 has 92p and 146n

  4. Isotopes of hydrogen • 3 forms of hydrogen: • Protium, deuterium, tritium • Differ only in the number of neutrons they have Diagram from Microsoft Encarta

  5. Fission and Fusion • Typical output of chemical reaction ~ 10 eV per atom • Output of nuclear fission reaction ~ 3.2 MeV per atom • Output of nuclear fusion reaction ~ 200 MeV per atom • The energy outputs of nuclear rxns are massive compared to the output of a chemical reaction, like burning HC fuels Possible advantages: • Lower mass of fuel needed • Less atmospheric emissions

  6. Fusion & Fission • Fusion: collision of two nuclei to make a new nucleus, e.g. two deuterium atoms fuse to make a helium-3 nucleus, emission of a neutron and released energy • Fission: neutron collides with large, unstable nucleus causing it to break into smaller fragments. In ex. Shown, two neutrons emitted which may collide with two more U-235 nuclei – chain reaction Illustration from Microsoft Encarta

  7. Fusion & Fission • Fusion reactions – usu. Small stable nuclei • Fission reactions – usu. Large, unstable nuclei • Natural abundance of U-235 is very low (~ 0.7%) • Not enough to ensure stray neutrons collide with them and give a sustained nuclear reaction (critical mass) • Fuel enrichment is required (next period – the nuclear fuel cycle)

  8. The pressurized water reactor • Make sure you can label this or a similar diagram • Be able to describe the operation of the reactor • Why are PWR’s generally located by a lake, river or the sea?

  9. Location, location , location… The nuclear pwr station need not damage local ecology

  10. The San Onofre reactor

  11. Cooling • Volumes of steam are released after work has been done on the turbines. • Is this efficient use of all that energy?

  12. The reactor core • The long object is a boron control rod that is being removed for maintenance

  13. The turbine floor • These are the turbines that turn the generator to make electricity

  14. Next Period • The Nuclear Debate • Arguments for • Arguments against

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