Nuclear Reactors


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Nuclear Reactors

  1. 1. Nuclear Reactors Tu Anh Tran CHEM 312 UNLV Fall 2013
  2. 2. Background • Fission: spontaneous radioactive decays of atoms and releases energy • Energy is converted into heat to produce steam and generate electricity • Original nuclear reactors were designed for submarines and navy ships
  3. 3. Components of a nuclear reactor • • • • Fuel Control rods Coolant Containment
  4. 4. Components: Fuel • Fissionable: isotopes that undergo induced fission when struck by a free neutron • Fissile: isotopes that can sustain a fission chain reactions when struck by a thermal neutron  U-233  U-235  P-239 • Alpha/Beta decays • Neutron capture • Critical mass
  5. 5. Components: Fuel • Enriched uranium hexafluoride (UF6) is converted into uranium oxide (UO2) powder • The power is processed into pellets via heat • Stacked pellets are placed into tubes of corrosion-resistant metal alloy
  6. 6. Components: Control Rods • Neutron-absorbing materials – Elements with varying capture cross sections for neutrons of varying energies. – Boron, silver, indium, cadmium • Can be inserted or withdrawn from the core • Control the rate of reaction • Rods are attached to the lifting machinery by electromagnets
  7. 7. Components: Coolant • Circulating fluid through the core to control heat transfer • Water is a primary coolant • In fast reactors, liquid metals such as sodium and lead are used • Molten salts • Gas – helium • Hydrocarbons
  8. 8. Components: Containment • Protective structure around the reactor • Protection against intrusion and radiation leakage • Steel or reinforced concrete
  9. 9. Types of reactors • Boiling water reactor • Pressurized water reactors • Liquid-metal fast-breeder reactor
  10. 10. Pressurized Water Reactors • Operate with thermal neutrons • Steam is generated outside the reactor in a secondary heat transfer loop
  11. 11. Boiling Water Reactor • water is converted to steam, and then recycled back into water by a part called the condenser, to be used again in the heat process. • steam generated inside the reactor goes directly to the turbine
  12. 12. Liquid-Metal Fast-Breeder Reactors • breeder reactors are designed to produce more fissile material than they consume • the fission reaction produces heat to run the turbine while at the same time breeding plutonium fuel for the reactor.
  13. 13. Nuclear power plants in commercial production Sources: Nuclear Engineering Handbook 2011
  14. 14. The Nuclear Reactor Debate • Environmentally less harmful than fossile fuels • Potential radiation contamination in the event of a meltdown • Nuclear proliferation and terrorism concerns • Health effect concerns of those living near nuclear power plants • Political implications preventing new development of nuclear reactors
  15. 15. References • • •