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Nuclear Fission and Fusion

Nuclear Fission and Fusion. Nuclear power. Power can be obtained two ways. Fission Splitting atoms Get energy if the nucleus is big. The smaller ones are more stable. What we do in nuclear reactors. Fusion Joining atoms Get energy if the nuclei are small.

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Nuclear Fission and Fusion

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  1. Nuclear Fission and Fusion

  2. Nuclear power • Power can be obtained two ways. • Fission Splitting atoms • Get energy if the nucleus is big. • The smaller ones are more stable. • What we do in nuclear reactors. • Fusion Joining atoms • Get energy if the nuclei are small. • The larger one is more stable. • This is how the sun works.

  3. NuclearFission Fission is the splitting of atoms These are usually very large, so that they are not as stable Fission chain has three general steps: 1. Initiation. Reaction of a single atom starts the chain (e.g., 235U + neutron) 2. Propagation. 236U fission releases neutrons that initiate other fissions 3. Termination.

  4. Nuclear Fission • A very heavy nucleus splits into more stable nuclei of intermediate mass. • The mass of the products is less than the mass of the reactants. • Missing mass is converted to energy

  5. Fission • In 1939 Lise Meitner an Austrian chemist in Sweden also working on neutron bombardment experiments proposed that the barium formed as a result of the neutrons splitting the Uranium atoms into two fragments • She proposed the term “fission” to describe this process because of its similarity to the reproductive “fission” of a biological cell

  6. Fission of 238U

  7. Chain Reaction

  8. Uranium Isotopes • Naturally occurring Uranium contains two major isotopes • Uranium-238 (99.3%) • Uranium-235 (0.7%) • As it turns out the only isotope of Uranium that undergoes fission is Uranium-235

  9. 235U Fission • 23592U + 10n 23692U* • and 10-14 seconds later... • 23692U*9236Kr + 14156Ba + 3 10n + ENERGY • 50 possible sets of fission products (sum of atomic numbers = 92) • 3 neutrons released for ONE 23592U • each neutron can split another 23592U • CHAIN REACTION POSSIBLE • If amount of 23592U is sufficient (CRITICAL MASS) then the number of neutrons generated is high enough to result in a nuclear explosion )

  10. Where does all this energy come from?

  11. E = mc2E = Energy (joules)m = mass (kg)c = speed of light = 3 x 108 m/s

  12. Nuclear Fission & POWER • Currently about 103 nuclear power plants in the U.S. and about 435 worldwide. • 17% of the world’s energy comes fromnuclear.

  13. Fusion • Light-mass nuclei combine to form a heavier, more stable nucleus. • More energetic than fission reactions • Source of energy for the H-bomb • Origin of the elements

  14. FUSION 411H 42He + 2 ? + + energy

  15. The most destructive force on the planet H-bombs 1000s of times more powerful than A-bombs

  16. Fusion of Helium atoms42He + 42He  ? + energy

  17. Fusion of Helium atoms 42He + 42He 84Be + energy

  18. Practice42He + 84Be  ? + energy42He + ? 168O + energy42He + 168O  ? + energy42He + 2010Ne  ? + energy

  19. Answers42He + 84Be 126C + energy42He + 126C168O + energy42He + 168O 2010Ne + energy42He + 2010Ne 2412Mg + energy

  20. Binding Energy of Nuclei

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