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Spontaneous fission

  1. Oct 28, 2015 #1

    Garlic

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    Are there isotopes that decay only through spontaneous fission, or in other words can normally stable nuclei decay through spontaneous fission?
     
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  3. Oct 28, 2015 #2

    mfb

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    There are a few nuclides where spontaneous fission is the only possible decay mode (apart from proton decay maybe), but it has never been observed and the expected lifetime is so long that it is unlikely that we will ever see such a decay.
    As usual, Wikipedia has a list.
     
  4. Oct 28, 2015 #3

    Garlic

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    Thank you. This is really interesting.
     
  5. Nov 2, 2015 #4
    I thought there were a few places in Africa where there were streams trickling over uranium deposits. The water acted like a moderator to enable fission until it became so hot the water boiled away. The fission reaction shut down due to lack of slow energy neutrons. The water comes back and the fission restarts.
     
  6. Nov 2, 2015 #5

    mfb

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    Oklo is the most prominent place. It happened in the past, when the fraction of fissile uranium was higher. Today it is too low.
     
  7. Nov 2, 2015 #6

    SteamKing

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    The natural reactors at Oklo were active about 1.7 billion years ago. At that time, the percentage of U-235 in uranium deposits was several times the current fraction of 0.7% found in natural uranium. Since that time, the percentage of U-235 has declined, because its half-life is roughly 700 million years or so.

    https://en.wikipedia.org/wiki/Natural_nuclear_fission_reactor
     
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