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Nuclear Fission & Fusion

Nuclear Fission & Fusion. Nuclear Fusion. - Energy released when two light nuclei combine or fuse. However, a large amount of energy is required to start a fusion reaction:. Need this energy to overcome ________ forces of protons. Extremely high temperatures can provide start-up energy.

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Nuclear Fission & Fusion

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  1. Nuclear Fission & Fusion

  2. Nuclear Fusion - Energy released when two light nuclei combine or fuse • However, a large amount of energy is required to start a fusion reaction: • Need this energy to overcome ________ forces of protons. • Extremely high temperatures can provide start-up energy. repulsion More energy in fusing hydrogen that fission of uranium

  3. Nuclear Fusion

  4. Stars energy is produced through fusion reactionsFusion occurs until Fe is produced because less energy is released than required to fuse Fe nuclei = _____ ____ ____ Star burns out http://www.telegraph.co.uk/science/science-news/3981697/Scientists-plan-to-ignite-tiny-man-made-star.html

  5. Nuclear Fission +15 + energy + + – splitting of heavier nuclei into lighter nuclei.

  6. Nuclear Chain Reactions: • Nuclear fission releases more neutrons which trigger more fission reactions • The number of ________ released determines the success of a chain reaction neutrons

  7. Applications of Controlling Chain Reactions • Atomic Bomb (fission bomb) – Triggering an uncontrolled chain reaction inU-235 or Pu-239 ·Must have a minimum amount of radioactive isotope to sustain a chain reaction =_________ _______ CRITICAL MASS • Nuclear Power Plants – Convert heat energy from fission chain reaction into __________. electricity control rods Control chain reaction with ________ _____ that absorb ________ emitted after fission reaction. neutrons

  8. So how does a Nuclear power plant work?

  9. Inside reactor core, the fission of U-235 is occurring. Control rods (Ag, Cd, Ir) are rasied and lowered into the core to absorb neutrons and control the reaction. (prevent a meltdown) Water is under high pressure and absorbs the energy (heat) around the core w/o boiling (>600 °F) This extremely hot water is used to heat separate water in a secondary system that turns to steam.

  10. The steam is used to turn the turbine creating electricity. The water hot water is then piped to the top of the cooling tower which noramlly have fans on the top pulling air out. The water is allowed to trickle down the sides to aid in cooling. Once its cooled down, it is recirculated to the lake, river, pool where it came from.

  11. What is a meltdown? Failure to remove the heat being generated by the reaction causes the internal temperature to climb. If the temperature gets high enough, the material the core is made of can start melting (hence the term). If the core fails, radioactive uranium can be spilled into the water or into the air if it mixes with the steam.

  12. Three Mile Isle

  13. March 28, 1979, 4:00 am • Secondary cooling loop stops pumping. • Rising temperatures caused emergency valve to open to release pressure, but indicator light malfunctioned • Due to loss of steam, water level drops, water overheats and burns out pump • Reactor core overheats and begins to melt (a “meltdown”)

  14. March 28, 1979, 6:30 am • Overheated water contains 350 times normal level of melted down radioactive matter • A worker sees the open valve and closes it • To prevent an explosion, he reopens it, releasing radioactive steam into the atmosphere

  15. March 28, 1979, 8:00 am • Nuclear Regulatory commission is notified • White House is notified • TMI is evacuated • All small children and pregnant women within a five mile radius are evacuated • A fifteen-year clean up project awaits

  16. Chernobyl 1986 • Human stupidity turned off cooling system • Poor steam cooling reactor design allowed unstable steam pocket to explode • Graphite caught fire • Design not used in other countries • Fukushima 2011 • Had 3 cooling towers to remove heat from core. • Tsunami flooded the low levels which is where the controls for the cooling towers were housed. • Reactor started to overheat, steam valves were released and this hydrogen exploded. • Multiple explosions released radioactive cloud causing radiation in children

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