Nuclear Power Plants

• Nuclear fission: splitting atoms
  • giving off extraordinary amounts of (steam producing) heat
  • huge unstable atoms are hit with neutrons (usually of radioactive uranium 235)
• Process releases energy & more neutrons
• Neutrons hit other uranium atoms
  • chain reaction

Nuclear fuel rods inside a power station

• Control rods (neutron absorbing material) can be raised or lowered between the fuel rods to control the reaction
• Reactors are cooled by the same water used to moderate the fuel cycle
• Fuel rods are inserted into water to make superheated, high pressure steam (300 C)
  • Steam is radioactive
  • a closed loop heat exchanger is used to transfer heat to non radioactive water

Nuclear meltdown & melt-through

• meltdown
  • fuel rods overheat
  • leaves a molten mass of fuel and fission products at the bottom of the reactor vessel (in the casting)
• melt through
  • molten fuel and fission products leak through the casing into the environment

Nuclear power generation summary

• Uranium fuel rods, bombarded with neutrons which break apart U 235 atoms (fission)
  • Reaction releases large amounts of heat
  • Water directed through heat to make steam
  • Steam turns turbine connected to generator