How Nuclear Power Works… By Dr. Woodward
How Nuclear Power Works A. The objective of nuclear power technology is to control nuclear reactions so that energy is released gradually as heat.
How Nuclear Power Works B. In nuclear fission, a large atom of one element is split to produce two smaller atoms of different elements.
Recall the Structure of an Atom • Basic Structure of the Atom The atom is comprised of a nucleus, which contains protons and neutrons. Electrons orbit the nucleus held in place by electrostatic forces.
Spit atoms Neutrons Uranium atom Nuclear Energy Comes From Fission
Heat Neutrons Splitting Atoms Releases Neutrons, Creating Heat
How Nuclear Power Works C. As with plants powered by fossil fuels, the heat energy produced by a nuclear plant is used to boil water and produce steam, which then drives conventional turbo generators.
How Nuclear Power Works D. Nuclear power plants are always operating unless they are being refueled.
Thursday (November 17, 2011) Today’s Agenda: Journal Question: What is nuclear fission? • *Lecture III: Nuclear Fuel • Quiz tomorrow on Nuclear Power and Essay Prompt • Class Behavior/Norms • Homework: Get a textbook and bring it to class tomorrow.
Nuclear Power Plant Turbines Spin to Generate Electricity Steam Turbines spin to generate electricity
Steam Generator Steam produced Turbine Electricity Heat Heat Produces Steam, Generating Electricity
Turbines High pressure, intermediate pressure and low pressure turbines required for pressure expansion to vacuum condenser conditions.
Controlling the Chain Reaction Fuel Assemblies Control rods Insert control rods, reaction decreases Withdraw control rods, reaction increases
Types of Nuclear Reactors: A. Light-water reactors (LWRs) produce about 85% of the world’s nuclear-generated electricity. (1) 100% in the United States
From Mass to Energy A. The release of nuclear energy is completely different from the burning of fuels or any other chemical reactions that occur with the use of fossil fuels.
From Mass to Energy • How fossil fuels are used to generate electricity:
From Mass to Energy • Nuclear energy involves changes at the atomic level through one of two basic processes: fission and fusion
From Mass to Energy (Fusion) Basic nuclear fusion reaction: Tritium + Deuterium = Helium + free neutron
Nuclear Fission versus Nuclear Fusion A. In fission, a large atom of one element is split to produce two smaller atoms of different elements.
Nuclear Fission versus Nuclear Fusion • In fusion, two small atoms combine to form a larger atom of a different element. (1) The sun produces helium by fusing hydrogen atoms together.
Nuclear Fission versus Nuclear Fusion C. The amount of energy released in both nuclear fission and fusion is tremendous.
Nuclear Power Plant Fuel A. All current nuclear powerplants employ the fission (splitting) of uranium-235.
Nuclear Power Plant Fuel B. The element uranium, which occurs naturally in various minerals in Earth’s crust, exists in two primary forms, or isotopes: Uranium-238 and Uranium-235.
Nuclear Power Plant Fuel C. Isotopes of a given element contain different numbers of neutrons, but the same number of protons and electrons.
Energy Equivalent of One Fuel Pellet 1,780 Pounds of Coal 149 Gallons of Oil 157 Gallons of Regular Gasoline
Nuclear Fuel and Assemblies • 288 Fuel Pellets per Fuel Rod • 64 Fuel Rods per Assembly (The number will vary depending on the output of the reactor.) • 560 Fuel Assemblies per Reactor Core • 10,321,920 Fuel Pellets
Nuclear Fuel “Enrichment” A. To make nuclear fuel, uranium ore is mined, purified into uranium dioxide and enriched.
Nuclear Fuel “Enrichment” B. Because 99.3% of all uranium found in nature is Uranium-238, enrichment involves separating uranium-235 from uranium-238to produce a material containing a higher concentration of uranium-235.
Nuclear Fuel “Enrichment” C. The technical difficulty of enrichment is the major hurdle that prevents less developed countries from advancing their own nuclear capabilities.
Nuclear Fuel “Enrichment” D. Most of the 495 commercial nuclear power reactors operating or under construction in the world today require uranium “enriched' in the U-235 isotope for their fuel.
Production of Plutonium (Pu) in Nuclear Reactors A. 239Pu is produced in nuclear reactors. B. It also fissions by absorbing a thermal neutron, and on average produces 1/3 of the energy in a fuel cycle. C. 239Pu is relatively stable, with a half life of 24 thousand years. D. It is used in nuclear weapons. E. It can be used for nuclear reactors.
Nuclear Fission A. It takes a neutron hitting the nucleus at just the right speed to cause uranium-235 to undergo fission.
Nuclear Fission B. The fission reaction gives off several more neutrons and releases a great deal of energy.
Nuclear Fission • As these neutrons continue to strike other neutrons, more energy is released, with the potential to repeat the process. -A domino effect, known as a chain reaction, may occur.
Nuclear Bomb When uranium-235 is highly enriched, the spontaneous fission of an atom can trigger a chain reaction. B. In nuclear weapons, small masses of virtually pure uranium-235 or other fissionable materials are forced together so that two or three more atoms undergo fission; each of these in turn triggers two or three more fissions, and so on. C. The whole mass undergoes fission in a fraction of a second, releasing all the energy in one huge explosion.
The Nuclear Reactor A. A nuclear reactor for a power plant is designed to sustain a continuous chain reaction, but not allow it to amplify into a nuclear explosion. B. Control is achieved by enriching the uranium to only 4% uranium-235 and 96% uranium 238 (more stable).
The Nuclear Power Plant A. In a nuclear power plant, heat from the reactor is used to boil water to provide steam for driving conventional turbo generators. B. One way to boil water is to circulate it through the reactor. (Identify parts from diagram and understand their functions for your quiz)
Nuclear Power Plant Components • Reactor Coolant: A coolant, usually water, circulates through the reactor’s core to remove heat (to keep fuels rods and other materials from melting) and to produce steam for generating electricity.