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Homework Help: Binding Energy per Nucleon (Fission)

  1. Oct 19, 2009 #1
    1. The problem statement, all variables and given/known data

    By analyzing the Binding Energy per Nucleon Curve, and using the equivalence factor 1amu=931.4 MeV, show that a U fission frees energy equivalent to 0.2 AMU.

    2. Relevant equations


    A fission I picked: U-235 + slow neutron ---> 141/56 Ba + 93/36 Kr + 2n

    3. The attempt at a solution

    I am understanding that the binding energy per nucleon shown in this chart is essentially the mass defect, or in other words, the difference between the sum of the rest masses of the constituent nucleons VS the actual experimental mass of that nucleus.

    I would imagine, that if we had a Fission, we break this U-235 nucleus into other nucleus types, like the fission into Ba and Kr and 2n shown above.

    Then if we take the sum of:

    [the mass defect or binding energy of resultant Ba] +
    [the mass of resultant Ba nucleus in amu] +
    [the mass defect or binding energy of resultant Kr]
    [the mass of resultant Kr nucleus in amu]
    [the mass of 2n in amu]

    and Subtract

    The Actual experimental measured mass of these by products

    You are left with:

    The energy released from the binding energy, as now kinetic energy of the fast neutrons.

    I'm sure I'm making it more complicated.
    What I don't understand is, if in the graph of Binding Energies per Nucleon, if the ones in the middle have Higher binding energies per nucleon, than wouldn't it make sense that the energy release would be in a process that resulted in nucleus's with less binding energies per nucleon?

  2. jcsd
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