P4 - Fission and Fusion

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  • Created by: Naomi
  • Created on: 22-01-13 16:46
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  • Nuclear fission and fusion
    • Nuclear power stations
      • Natural uranium consists of two isotopes, uranium-235 and uranium-238
      • Fission occurs when a large unstable nucleus is split up and energy is released as heat
        • The heat is used to boil water to produce steam
        • The pressure of the steam acting on the turbine blades makes it turn
        • The rotating turbine turns the generator, producing electricity
      • In a power station atoms of uranium-235 are bombarded with neutrons
        • This makes the atom even more unstable, and the nucleus splits, releasing energy
          • The uranium splits into a krypton atom and a barium atom and releases 3 extra neutons as well as some gamma rays
            • The extra neutons emitted cause furthur uranium nuclei to split
              • This is described as a chain reaction
    • Controlling nuclear fission
      • The output of a nuclear reactor can be controlled
        • A graphite moderator between the fuel rods slows down the fast moving neutrons during fission
          • Slow moving neutrons are more ikely to be captured by other uranium nuclei
        • Boron control rods can be raised or lowered
          • Boron absorbs neutrons, so fewer neutrons are able to split more uranium nuclei
            • This controls the rate of fission
    • Fusion
      • Nuclear fusion happens when two light nuclei fuse (join) together releasing large amount of heat energy
      • Fusion requires extremely high temperatures
      • In stars, fusion takes place under extremely high temperatures and pressures
      • Fusion bombs are started with a fission reaction which creates exceptionally high temperatures and pressures

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Miss KHP

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This is a good resource for all GCSE Science students as it covers (and links) nuclear power stations to fission and fusion. I have recommended this to students as it helps to break it down and focuses on key terms such as 'chain reactions' and 'uranium nuclei' etc- things that some students forget to mention.

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