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Nuclear Power: Basics An Alternative to Coal? Statistics • Over 16% of the worlds energy is produced from nuclear reactors • There are 439 nuclear power stations in the world, 104 of which are in the USA Fun Facts • Nuclear energy is the energy from the nucleus of a Uranium atom. • Uranium is made into small pellets, about the size of your fingertip. • Each pellet produces the same amount of energy as 150 gallons of oil. Atoms and Radioactivity Section 16.1 What is an Atom? • Atoms: protons, neutrons, electrons • Nucleus: cluster of protons and neutrons in the center of an atom Atoms and Isotopes • Atomic number: number of protons in an atom • Mass number: number of protons plus the number of neutrons • Isotopes: atoms of the same element that have different numbers of neutrons Isotopes What is the difference between U-238 and U-235? Examples: Page 429 Element 1. Silver 2. Ca 3. Hydrogen 4. Iron 5. Cu Atomic Number / Mass Number Radioactivity • Radioactive atoms: unstable atoms that decay and emit particles and energy from their nuclei – Not all elements are radioactive • Most cases it is only certain isotopes that are radioactive – Example: »H – 1 = »H – 2 = »H – 3 = 3 Types of Particles • Alpha particles: made up of two protons and two neutrons – Emitted by uranium – byproduct of Nuclear Energy • Beta particles: high speed electron – used to treat health conditions such as eye and bone cancer • Gamma particles: form of electromagnetic radiation – often used to kill living organisms, in a process called irradiation • sterilizing medical equipment Radiation • Radiation: the alpha particles, beta particles, and gamma rays given off in the decaying of unstable nuclei HALF-LIFE • Emitting alpha particles = – Losing protons and neutrons • Emitting beta particles = – Converting neutrons to protons • ULTIMATELY – Change alters the atomic number and the mass number of the atom – Atomic number = determines identity • CHANGES ONE ELEMENT INTO ANOTHER HALF-LIFE • The amount of time it takes for half of the atoms in a sample of radioactive element to decay – Amount of time it takes for half of atom to decay • Vary from few seconds to billions of years • U-238 = 4.5 billion years & U-235 = 700 million years Section 16.2 Reactions and Reactors Nuclear Energy • Nuclear energy: energy within the nucleus of an atom • Advantages: – Very concentrated – Doesn’t produce air polluting gases – Release less radioactivity than coal fired power plants • Disadvantages: – Very expensive – Difficult to find a safe place to store waste – High safety concerns Nuclear Fission Nuclear fission is the process of splitting a nucleus into two nuclei with smaller masses. • Energy can be released from an atom by splitting the nucleus of the atom apart • Nuclear Fission: a reaction in which the nucleus of a large atom is split into smaller nuclei – Large Energy = Electricity Nuclear Fission • Fissionable: an atom splits when its nucleus is struck by a neutron – Only large nuclei with atomic numbers above 90 can undergo fission. • CONTINUOUS REACTION CREATES – Chain reaction: continuous action of neutrons splitting atomic nuclei • Mass of atomic nucleus is converted to energy Nuclear Reactors • Heat is produced through the fission of nuclear material • Nuclear reactor vessel: where the fission of U-235 takes place • Control rods: absorbs neutrons 1. Raising and lowering rods regulates the amount of heat produced – 2. Sot water moves inside pipes to a heat exchanger where it heats water for steam 3. Steam is then used to turn turbines connected to electric generators Nuclear Reactor vs. Breeder Reactor • Nuclear Reactor – Uses Uranium – 235 (U-235) • Breeder Reactor – 99% of natural occurring Uranium = U-238 • Not Fissionable • BUT • Absorbs neutron = Highly fissionable Plutonium-239 – Process forms energy. Breeder Reactors • Breeder reactor: process used to produce new fuel while generating usable energy • NOT used in the U.S. because of concerns about nuclear terrorism – the plutonium produced by breeder reactors can be used to make atomic bombs Section 16.3 Radioactive Waste Nuclear Power Plants • Produce Radioactive Waste • Radiation –Changes in DNA = Cancer & Genetic Mutations –Large Doses = Burns, Anemia, & Death –Amount of Exposure = Extent of Damage Radiation Exposure • Measured in “rems” –Normally = 0.2-0.5 rems per year • 88% Natural occurring substances • TWO TYPES –High-Level Wastes –Medium-Level & Low-Level Wastes High-Level Waste • Emits large amounts of radiation • Types – Used Uranium fuel rods – Control Rods – Water used to cool and control chain reaction – Vessel surrounding the fuel rods Medium-Level & Low Level Waste • Slightly less radioactive, BUT generated in much larger volume. • Types of Medium-Level – Mine waste around uranium mine – Containment protective clothing • Low-Level – Hospitals and laboratories Waste: Storage Pools The spent fuel rod pool inside the Clinton Nuclear Power Plant in Clinton, Ill., is shown on Tuesday, Nov. 19, 1996. The water in the pool acts as a shield against radiation from the used uranium rods. The reactor was shut down due to an equipment malfunction Sept. 5, 1996. (AP Photo/Mark Cowan) Waste: Dry Cask Storage In this photo released by Holtec International, dry cask storage units are seen at the James A. Fitzpatrick nuclear power plant in Scriba, N.Y., in this undated photo. The Vermont Public Service Board approved "dry cask storage," of spent nuclear fuel at Vermont Yankee, lifting the threat that running out of room in its existing spent fuel storage pool would cause the plant to close by 2008.(AP Photo/Holtec International) Waste: Long-Term Storage NRC Nuclear Waste & Nuclear Accidents Three Mile Island nuclear power plant is pictured in Jan. 21, 1996. This is the site of the 1979 partial core melt. (AP Photo/Tim Shaffer, files) Accidents: Chernobyl http://blogs.newamericamedia.org/kitchensink/78/nuclear-nightmares-twenty-yearssince-chernobyl Nuclear Future?