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Homework Help: Fission reaction

  1. Feb 3, 2010 #1
    1. The problem statement, all variables and given/known data
    235U92 + 1n0 --> 148La57 + 85Br35 + neutrons

    How many neutrons are released in this reaction? What is the importance of these neutrons in a nuclear reactor?

    2. Relevant equations

    3. The attempt at a solution
    I want to ask about the importance of these neutrons in a nuclear reactor. My guess why neutrons are used because they are neutral so they can penetrate to the nucleus. And about the neutrons on the RHS, it just to balanced the atomic and mass number..

    I'm completely not sure about my answer...

  2. jcsd
  3. Feb 3, 2010 #2


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    It is critical to realize that a neutron hitting the Uranium nucleus causes the reaction. If the reaction releases at least one neutron that causes another reaction, it will continue as a chain reaction. If several successful neutrons are released, then you get a big bang.
  4. Feb 3, 2010 #3
    Hi delphi

    So the neutrons on the left side is used to cause the reaction and on the left side is used for another reaction?

  5. Feb 3, 2010 #4


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    Yes, the left side is "before" and the right side "after".
    Looks like you have more neutrons after, so it can sustain a fission reaction.
  6. Feb 4, 2010 #5


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    U235 is a radioactive element but it does not split. When it absorbs a neutron, it becomes U236.
    It is in a highly excited state and splits into two fragment almost instantaneously.
  7. Feb 4, 2010 #6
    Hi there,

    Just so you know, the reaction you wrote above is one of the possible fission reaction in a reactor.

    There are many others, which can free one or more neutrons. These neutrons are released with great energy and need to be slowed down, before they can induce another reaction.

  8. Feb 4, 2010 #7
    Ok. Thanks a lot for all of you
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