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1 Nuclear Energy Chapter 16
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Atoms and Radioactivity All common forms of matter are composed of atoms. All atoms are composed of: 1) Protons (found in the nucleus) 2) Neutrons (found in the nucleus) 3) Electrons (found orbiting the nucleus) 2
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Isotopes Elements that have the same number of protons and electrons but Different numbers of neutrons 3 1 proton and 1 electron 1 proton and 1 electron and 1 neutron 1 proton and 1 electron and 2 neutrons
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4 16.1 Atoms and Radioactivity Radioactive - Nuclei of certain atoms are unstable and spontaneously decompose and release particles and energy. Radioactive Half-Life - Time it takes for half the radioactive material to spontaneously decompose.
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What is released by radiation? 3 Things: Alpha Particles Beta Particles Gamma Rays 5
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16.2 Reactions and Reactors Nuclear Fission – A reactions in which the nucleus of a large atom is split into smaller nuclei 6
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7 – Nuclear Chain Reaction - Splitting nuclei release neutrons, which themselves strike more nuclei, in turn releasing even more neutrons.
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8 The Nature of Nuclear Energy Only certain kinds of atoms are suitable for development of a nuclear chain reaction. – The two most common are uranium-235 and Plutonium-239. Requires certain quantity of nuclear fuel (critical mass).
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9 Nuclear Fission Reactors Nuclear Reactor - Device that permits a controlled fission chain reaction. – Nucleus of U-235 atom struck by slowly moving neutron from another atom. Nucleus split into smaller particles. More neutrons released. Strike more atoms.
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10 Nuclear Fission Reactors Control Rods - Made of a non-fissionable material (boron, graphite) that are lowered into reactor to absorb neutrons. – Withdrawn to increase rate of fission.
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11 Workings of A Nuclear Reactor Nuclear reactor serves same function as fossil-fuel boiler: produces heat - converts water to steam - turns a turbine - generating electricity. Breeder Reactors - Nuclear fission reactor that forms a new supply of radioactive isotopes during operation. (i.e., U 238 turns into Pu 239 )
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12 Boiling Water Reactor
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13 Nuclear Power Plants in North America
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14 16.3 Radioactive Waste High Level Radioactive Waste: – At this time, no country has a permanent storage solution for the disposal of high- level radioactive waste. Politics of disposal are as crucial as disposal method. Most experts feel the best solution is to bury waste in a stable geologic formation.
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16 Low-Level Radioactive Waste Includes cooling water from nuclear reactors, material from decommissioned reactors, protective clothing, and like materials. – Prior to 1970, U.S. alone placed 90,000 barrels of low-level radioactive waste on the ocean floor. Moratorium in 1970, banned in 1983.
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17 Low - Level Waste Currently, U.S. produces about 800,000 cubic meters of low-level radioactive waste annually. – Presently buried in various scattered disposal sites. Political limbo.
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18 Low-Level Radioactive Waste Sites
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19 Reactor Safety Three Mile Island - Pennsylvania – March 28, 1979 - Partial Core Melt-Down. Pump and valve malfunction. Operator error compounded problem. Crippled reactor was de-fueled in 1990 at a cost of about $1 billion. Placed in monitored storage until its companion reactor reaches the end of its useful life.
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20 Reactor Safety Chernobyl - Ukraine – April 26, 1986 – Experiments being conducted on reactor. Multiple serious safety violations. – Reactor Explodes. 31 deaths. 116,000 people evacuated. 24,000 evacuees received high doses of radiation. Increased thyroid cancer in children.
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