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Nuclear Reactors and Nuclear Energy

Conversion of mass-energy to electrical energy mass-energy  thermal  kinetic  electric Produces large amounts of electrical energy for large-scale use (city, province, country) small-scale: submarines, large ships Energy released by Fission of Uranium-235

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Nuclear Reactors and Nuclear Energy

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  1. Conversion of mass-energy to electrical energy • mass-energy  thermal  kinetic  electric • Produces large amounts of electrical energy for large-scale • use (city, province, country) • small-scale: submarines, large ships • Energy released by Fission of Uranium-235 • Reactions occur in Nuclear Reactor • Electricity produced by spinning electric generator Nuclear Reactors and Nuclear Energy

  2. Nuclear Reactor www.ems.psu.edu/~pisupati/ Pickering Nuclear Power plant cbc.ca

  3. Fuel • Natural uranium: 99% uranium-238 , 1% uranium-235 • Energy produced by chain reaction (nuclear decay produces • neutrons that can initiate other reactions) • U-238 cannot produce chain reaction, U-235 can • Nuclear fuel = 3 – 5 % U-235 (enriched uranium) • Uranium formed into fuel pellets • Fuel pellets inserted in fuel rods, fuel bundles www.nti.org www.virginmedia.com/digital/science/pictures/

  4. Moderator • neutrons produced by fission may be too fast to initiate decay • slowed down by a moderator • ordinary water can slow down neutrons (but can absorb many) • heavy water (D2O) slows down neutrons without absorbing • Control Rods • rate of reactions controlled • by material that absorbs • neutrons (cadmium, boron) • rods inserted into fuel • bundle to slow or allow • reactions (prevents • overheating) reference.findtarget.com/ commons.wikimedia.org

  5. The Core • core = fuel bundles, control rods, immersed in coolant • coolant (water) pumped into core, absorbs heat from reactions • coolant pumped to steam generator • heat from coolant boils water • Steam • steam used to turn turbine • steam condensed back to water using • cool water (lake or river) • 3 separate water circuits • core • turbine • cooling www.hk-phy.org/energy/power/

  6. CANDU • Canada Deuterium Uranium • Designed in 1950’s • Uses natural uranium • U-238 can produce plutonium-239, • which also produces chain reactions • Uses heavy water as moderator www.nucleartourist.com/type/candu2.htm • Energy Output • Large scale: CANDU reactor – 800 MW per reactor • Power plant = several reactors • Bruce Power (Lake Huron): 8 reactors (enough for 20% of • Ontario’s hospitals, homes, schools) • More than 50% of Ontario’s electricity produced by nuclear • Submarines, ships about 100 MW

  7. Safety • Reactors buildings heavily shielded by concrete and steel • Interior at low air pressure so material won’t leak • Uncontrolled reactions could lead to • meltdown (Three Mile Island 1979) • explosion (Chernobyl 1986) • – releases radioactive material to atmosphere • Reactions can be stopped quickly by • dumping moderator • dropping control rods into core www.wired.com/wiredscience/2009/05/threemile/ toxipedia.org/display/toxipedia/Chernobyl+Accident

  8. Environmental Concerns • rods removed when useful reactions too low (“spent” fuel) • still radioactive, with some long half-life isotopes • stored in large pools of water • later removed to dry storage • sometimes stored in glass (vitrification) • could eventually be stored deep underground • possibly contaminate environment if leaked • heat from cooling process could alter marine ecosystems www.world-nuclear.org/info/inf04.html www.biopxenor.com/tag/nuclear-waste-storage

  9. http://en.wikipedia.org/wiki/Nuclear_power_by_country

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