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Nuclear Fission and Nuclear Fusion

Nuclear Fission and Nuclear Fusion. Enormous Energies. Nuclear Fission. Take a large atom and impact the nucleus with a particle. Split the atom releasing high energy, more high energy neutrons, and two daughter nuclides.

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Nuclear Fission and Nuclear Fusion

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  1. Nuclear Fission and Nuclear Fusion Enormous Energies

  2. Nuclear Fission • Take a large atom and impact the nucleus with a particle. • Split the atom releasing high energy, more high energy neutrons, and two daughter nuclides. • Fission occurs only rarely in nature. Alpha decay is much more common.

  3. Uranium-235 • Elements with an atomic number greater than 80 are capable of undergoing fission. • 23592U absorbs a neutron, 10n, temporarily producing unstable23692U. • Almost immediately 23692U splits into two more stable daughter nuclides plus large amounts of energy and two to three fast neutrons depending on the reaction.

  4. Fission and energy • The fast neutrons produced by fission fly off to impact other atoms of 23592U resulting in a chain reaction. • The fission of uranium-235 releases ~200MeV. That equals ~100x energy release by burning a coal molecule.

  5. Concepts • Fissile: atoms (235U or 239Pu)that are capable of undergoing fission when an atom captures a thermal slower neutron. • Fissionable: atoms (238U)able to undergo fission when bombarded with high energy neutrons such as in a thermonuclear weapon, bomb. • Nuclear fuels: elements that can sustain a fission chain reaction such as uranium-235 and plutonium-239. • Spontaneous fission: the slowly occurring process of fission in nuclear fuels unaltered by human intervention. • Critical mass: enough nuclear fuel present and emitting neutrons in quantities to sustain a chain reaction.

  6. Chain Reaction • Once the fission reaction is initiated, the high energy neutrons released keep the reaction going. This is a chain reaction. • The mousetrap model. • http://www.youtube.com/watch?v=0v8i4v1mieU Student project 2:54 minutes • http://www.youtube.com/watch?v=vjqIJW_Qr3cNatSciDemo 2:28 minutes

  7. Power Production • A coal fired plant and a nuclear plant share the same power generation type: conversion of heat to electricity via pressurized steam. • The fission reaction releases energy which is absorbed by water converting some of the water to steam. • Steam is used to drive the turbine connected to a generator.

  8. Schematic of Nuclear Plant

  9. The Bomb http://www.youtube.com/watch?v=CGRx2cPjUXM Navy Film of Bikini Crossroads Test A bomb typically uses a contained explosion or impact to induce a chain reaction. No controls limit the progress of the reaction.

  10. Fusion • Fusion reactions are the combining of two nuclei to form a more massive nucleus. • Many fusion reactions release large amounts of energy. • An example is the combining of two isotopes of hydrogen (tritium and deuterium) to form helium and a neutron plus a large amount of kinetic energy in the reaction products: 3H + 2H 4He + n + 17.6 MeV

  11. http://www.youtube.com/watch?feature=endscreen&v=yTkojROg-t8&NR=1&safety_mode=true&persist_safety_mode=1&safe=active Best of Science, Fission and Fusion 8:38 minutes

  12. Resources • http://www.lbl.gov/abc/wallchart/teachersguide/contents.html DOE Teacher’s Guide

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