31.1 Nuclear Reactions and Transmutation - PowerPoint PPT Presentation

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31.1 Nuclear Reactions and Transmutation

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31.1 Nuclear Reactions and Transmutation When a particle collides with a nucleus Charge, energy and momentum are conserved Does the reaction have excess KE after the ... – PowerPoint PPT presentation

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Title: 31.1 Nuclear Reactions and Transmutation


1
  • 31.1 Nuclear Reactions and Transmutation
  • When a particle collides with a nucleus
  • Charge, energy and momentum are conserved
  • Does the reaction have excess KE after the
    reaction?
  • Q gt 0 or exothermic
  • Q lt 0 or endothermic (requires KE input)
  • Enrico Fermi determines that neutrons are the
    most effective projectiles for nuclear reactions.

2
  • 31.2 Nuclear Fission
  • 200 MeV / fission

3
  • 31.2 Nuclear Fission
  • Starter neutrons for nuclear reactors
  • Slow vs. fast neutron capture
  • Not 100 guaranteed
  • 235U has about 40 decay modes with all fragments
    being radioactive

4
  • 31.2 Nuclear Fission
  • Slow neutrons absorbed easier by 235U
  • Moderator heavy water, graphite
  • Criticality
  • Some neutrons are absorbed without fission or
    escape
  • Depends on geometry and the distribution and type
    of material
  • Decrease number of escaping neutrons
  • Control rods B, Cd

5
  • 31.2 Nuclear Fission
  • Nature 99.3 238U and 0.7 235U
  • Reactors 96 238U and 4 235U
  • Weapons 10 238U and 90 235U
  • Critical mass (a few kg)

6
  • 31.2 Nuclear Fission
  • Safety - Structure, leaks, transport/storage of
    waste

7
  • 31.3 Nuclear Fusion
  • Most stars are in hydrostatic equilibrium
  • For fusion T gt 107 K and ? gt 100 g/cm3
  • Net result (26.7 MeV)

8
  • 31.3 Nuclear Fusion
  • Reactors fuel, temperature, density, containment
  • Waste products 3H, n (structural damage)
  • Small amounts and short half-lives

9
  • 31.3 Nuclear Fusion

10
  • 31.3 Nuclear Fusion
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