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Nuclear Energy

Nuclear Energy. Types of Nuclear Reactions. Fusion: Smashing atoms together Makes heavier element Not currently cost effective for large scale production Fission: Energy is released when nucleus is split apart. 1 g U @ 3 tons coal. The Fission Chain Reaction

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Nuclear Energy

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  1. Nuclear Energy

  2. Types of Nuclear Reactions Fusion: • Smashing atoms together • Makes heavier element • Not currently cost effective for large scale production Fission: • Energy is released when nucleus is split apart. • 1 g U @ 3 tons coal

  3. The Fission Chain Reaction • A neutron hits U-235 nucleus. • Produces 2 neutrons that hit 2 more atoms of U-235. • And so on, and so on…

  4. Chain Reaction Simulation • Slowed with control rods &/or water • Pros: • No greenhouse gas emissions • Cons: • Thermal pollution of local waterways; can damage local fish & habitats • Mining issues. Most U is U-238; <1% U-235 • Safety concerns

  5. Boiling Water Reactor (BWR)

  6. Pressurized Water Reactor (PWR) PWR sim clip

  7. Radioactive Decay • Spontaneous disintegration of nucleus to lighter and more stable particles • Emit one of 3 possible classes of decay…

  8. 1. Alpha decay • Alpha Particle He nucleus (2p+, 2n0) • External effect—minimum. Easily stopped. • Internal effect—carcinogenic • Common Source: natural radon, americium-241

  9. 2. Beta Decay • Electron emitted. • Tritium, Carbon-14, medical uses • Carcinogenic, can burn skin. Usually chronic exposure, not acute

  10. 3. Gamma Radiation • Radium-226, cesuim-137 • Can travel through body, hit all organs • Acute Radiation Sickness: vomiting, burns, kills blood cells, hair loss, death

  11. Other Effects of Gamma Radiation

  12. Decay and Half-Life Half-Life: Time needed for ½ of atoms to decay • Co-60 10.47 minutes • P-32 14.28 days • C-14 5715 years • U-238 4.46 x 109 years

  13. Nuclear Waste Disposal • Byproducts U-234, U-237, Np-237, Pu-238 and Am-241, all radioactive • Wet Storage: on site water tanks • Dry Storage: onsite lead & steel casks • Underground Storage: Centralized. Yucca Mt, NV proposal out of the 2010-11 US budget

  14. Breeder Reactors • Convert U-238 into Pu-239, also fissile • Use liquid Na as coolant instead of water • Pu used as weapons material

  15. Infamous Accidents • Three Mile Island, Pa 1979 • Pump malfunctioned in 2o system • Caused Pressure in reactor to rise & vent. • Vent got stuck open • core temps rose, • partial meltdown occurred • No significant release of radiation

  16. Unit 1

  17. Chernobyl, Ukraine 1986 • Power surge during a test. • Emergency shutdown attempt caused spike in power output. • Reactor vessel ruptured and a series of steam explosions • Graphite moderator caught fire when exposed to air. • Plumes of smoke sent over region • Officially 2 plant workers, 29 emergency workers died as a result, most from acute radiation sickness • Detected in Sweden a few days after explosion

  18. Fukushima, Japan 2011 • Reactors automatically shut down following earthquake & tsunami • Emergency generators came on to keep coolant flowing, but were flooded by seawater • Coolant levels dropped, reactor cores overheated & melted down • H2 buildup in reactors caused explosions into containment buildings • No reported radiation deaths; risks of cancer uncertain

  19. Salem I & II (PWR) & Hope Creek (BWR)

  20. Oyster Creek (BWR)

  21. How is Electricity Consumed in US homes

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