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Neutron fission cross section

  1. May 14, 2017 #1
    Hey all,

    Does anyone happen to know the value of ν∑f for natural uranium? Here ν is the average number of neutron released from fission and ∑f is the macroscopic fission cross section of uranium.

    Kirk
     
  2. jcsd
  3. May 19, 2017 #2
    Thanks for the thread! This is an automated courtesy bump. Sorry you aren't generating responses at the moment. Do you have any further information, come to any new conclusions or is it possible to reword the post? The more details the better.
     
  4. May 19, 2017 #3

    jim hardy

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    I'll wager there's a CANDU reactor engineer aboard who knows.
    .
     
  5. May 24, 2017 #4

    Astronuc

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    Developing a value for ∑f depends on the atomic density, which depends on the form, e.g., elemental, alloy or ceramic. What form is one considering? The value of ν depends on neutron energy, and in a thermal spectrum, it will depend on U-235.
     
  6. May 24, 2017 #5

    jim hardy

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  7. May 25, 2017 #6

    Astronuc

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    Yeah, but that's for fast neutrons. Fast neutrons from fission have a peak distribution around 1 MeV and the energy distribution falls off rapidly up to 10 MeV. With d+t fusion, one gets up to 14.1 MeV neutrons. To go higher, one pretty much needs 20+ MeV protons and spallation reactions.

    The OP did mention whether he flux was thermal, epithermal or fast.
     
  8. May 26, 2017 #7

    jim hardy

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    Fixed it for ya

    old jim
     
  9. May 26, 2017 #8
    Hey guys,

    You were right, I definitely did leave out that vital bit of information. I was simply looking for the macroscopic cross section for thermal neutrons. I was modeling a sub-critical pile with a large amount of graphite moderation. Turns out I was able to find a ν∑f for UO2 to thermal neutrons to be about 0.2274 cm^-1. This was from the good ole D&H tables.

    Kirk
     
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