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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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Presentation Transcript
nuclear power
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.
nuclear fission
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.

nuclear fission4
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
slide5

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
slide8

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
slide9

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 )
nuclear fission power
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.
fusion
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
slide21

FUSION

411H 42He + 2 ? + + energy

slide22

The most destructive force on the planet

H-bombs 1000s of times more powerful than A-bombs

practice 4 2 he 8 4 be energy 4 2 he 16 8 o energy 4 2 he 16 8 o energy 4 2 he 20 10 ne energy
Practice42He + 84Be  ? + energy42He + ? 168O + energy42He + 168O  ? + energy42He + 2010Ne  ? + energy
slide26

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