Unit 3 -Nuclear Power Plant • Principles of nuclear energy • Fission reactions • Nuclear reactor • Nuclear power plants
Nuclear reaction • Chain reaction occurs when a Uranium atom splits
• Different reactions – Atomic Bomb in a split second second – Nuclear Power Reactor more controlled, cannot explode like a bomb
History of nuclear power 1938 – Scientists study Uranium nucleus 1941 – 1941 – Manhattan Project begins 1942 – Controlled nuclear chain reaction 1945 – 1945 – U.S. uses two atomic bombs on Japan 1949 – 1949 – Soviets develop atomic bomb 1952 – 1952 – U.S. tests hydrogen bomb 1955 – 1955 – First U.S. nuclear submarine
“Atoms for Peace”
Program to justify nuclear technology Proposals for power, canal-building, exports First commercial power plant, Illinois
Economic advantages • The energy in one pound of highly enriched Uranium is comparable to that of one million gallons of gasoline.
• One million times as much energy in one pound of Uranium as in one pound of coal.
Emissions Free • Nuclear energy annually prevents – 5.1 million tons of sulfur – 2.4 million tons of nitrogen oxide – 164 metric tons of carbon
• Nuclear often pitted against fossil fuels – Some coal contains radioactivity – Nuclear plants have released low-level radiation
Early knowledge of risks • 1964 Atomic Energy Commission report on possible reactor accident – 45,000 dead – 100,000 injured – $17 billion in damages – Area the size of Pennsylvania contaminated
Nuclear power around the globe • 17% of world’s electricity from nuclear power – U.S. about 20% (2nd largest source)
• 431 nuclear plants in 31 countries – – – –
103 of them in the U.S. Built none since 1970s (Wisconsin as leader). U.S. firms have exported nukes. Push from Bush/Cheney for new nukes.
Nuclear fuel cycle • Uranium mining and milling • Conversion and enrichment • Fuel rod fabrication • POWER REACTOR • Reprocessing, or • Radioactive waste disposal – Low-level in commercial facilities – High level at plants or underground repository
Front end: Uranium mining and milling
Uranium enrichment • U-235 – Fissionable at 3% – Weapons grade at 90%
• U-238 – More stable
• Plutonium-239 – Created from U-238; highly radioactive
Radioactivity of plutonium Life span of least 240,000 years Last Ice Age glaciation was 10,000 years ago Neanderthal Man died out 30,000 years ago
Risks of enrichment and fuel fabrication • Largest industrial users of water, electricity – Paducah, KY, Oak Ridge, TN, Portsmouth, OH
• Cancers and leukemia among workers – Fires and mass exposure. – Karen Silkwood at Oklahoma fabrication plant.
• Risk of theft of bomb material.
Nuclear Reactor Process • 3% enriched Uranium pellets formed into rods, which are formed into bundles • Bundles submerged in water coolant inside pressure vessel, with control rods. • Bundles must be SUPERCRITICAL; will overheat and melt if no control rods. Reaction converts water to steam, which powers steam turbine
Nuclear Reactor Structure • Reactor’s pressure vessel typically housed in 8” of steel
• 36” concrete shielding • 45” steel reinforced concrete
Breeder reactor “Breeds” plutonium as it operates Uses liquid sodium metal instead of water for coolant – Could explode if in contact with air or water
• 1966 Fermi, Michigan – Partial meltdown nearly causes evacuation of Detroit
• 1973 Shevchenko, Russia – Breeder caught fire and exploded
• Controversial proposals in Europe, U.S.
Reprocessing • Separates reusable fuel from waste – Large amounts of radioactivity released
• 1960s West Valley, NY – Radiation leaked into Lake Ontario
• 1970s La Hague, France – Released plutonium plumes into air
Back end: Radioactive wastes • Low-level wastes in commercial facilities • Spent fuel in pools or “dry casks” by plants • Nuclear lab wastes – Hanford wastes leaked radiation into Columbia River
• High-level underground repository – Yucca Mountain in Nevada to 2037 – Yucca – Wolf River Batholith in Wisconsin after 2037? – Risks of cracks in bedrock, water seepage
Radioactive Waste Recycling • Disposal of radioactive waste from nuclear power plants and weapons facilities by recycling it into household products.
• In 1996, 15,000 tons of metal were received by the Association of Radioactive Metal Recyclers . Much was recycled into products without consumer knowledge.
• Depleted Uranium munitions for military.
Nuclear power plant
Summary • Nuclear energy has no typical pollutants or greenhouse gasses
• Nuclear waste contains high levels of radioactive waste, which are active for hundreds of thousands of years.
• The controversy around nuclear energy stems from all parts of the nuclear chain.
