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Weighted delayed neutron fraction?

  1. Jan 18, 2007 #1
    I am plotting the in-hour equation. For the delayed neutron fraction, I was thinking of using a weighted dnf for the particular U fuel enrichment of interest, ie combination of U235 & U238 dnfs, as I cannot look one up for this particular enrichment. Any comment on the “validity” or otherwise of this approach?

    Btw, this is just for playing around with data & equations, not any kind of serious or real application. I am using dnf values from an old textbook which is adequate for my purposes but if you are aware of a reputable web resource for this kind of data I’d be grateful for a link.

    Thanks for any input.
  2. jcsd
  3. Jan 18, 2007 #2


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    Science Advisor


    You can use a weighted average of the delayed fraction.

    Additionally, you have two isotopes of Uranium with similar delayed fractions.

    The place where this would really come into play is when you have a mixture of
    Uranium and Plutonium because the the delayed fraction for Plutonium is about a
    1/3 of what it is for Uranium; 0.2% vs 0.7% if I recall.

    Dr. Gregory Greenman
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