Nuclear Fission Yields

  • #1

Main Question or Discussion Point

I'm looking for the most common thermal fission products for U-233, U-235, Pu-239 and Pu-241. As far as I understand it there are two quantities of interest, the cumulative fission yield and the independent fission yield. The latter being "number of atoms of a specific nuclide produced directly by a fission event (not via radioactive decay of the precursors)," whilst the former does include the precursors. This is defined http://www-nds.iaea.org/sgnucdat/safeg2008.pdf" [Broken].

I have found some values http://www-nds.iaea.org/sgnucdat/c3.htm" [Broken]. Unless I've misunderstood both the cumulative fission yield and the independent fission yield columns should add up to 100% yet the cumulative fission yield sums to considerably more than that and the independent fission yield less than that.

Wikipedia gives a list of products in order of yield for U-235 http://en.wikipedia.org/wiki/Fission_product_yield" [Broken]. This is apparently based on the link above but the two don't seem to correspond and I don't know where the numbers have come from.
 
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Answers and Replies

  • #2
arivero
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I think the independent yields should add to 200%. No idea about the cumulative, and in fact I am rescuing this thread to ask what is exactly the definition of cummulative... Should not be only the final stable nuclei?
 
  • #3
Astronuc
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Cumulative yield for a given nuclide includes it's yield from fission, from decay and from transmutation, since fission products absorbs neutrons, e.g., Te-134 > I-134 > Xe-134 > Cs-134 > Ba-134 . . . and e.g., I-133 + n => I-134, Xe-133 + n => Xe-134, . . . .
 
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  • #4
arivero
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Ok, to fix it:

independent yields are the immediate yields
cumulative yields are all the possible nuclei during the reaction process
chain yields are the final stable nuclei, or very long term.

I guess cumulative is for radatiation in the reactor and chain for the nuclear waste.
 
  • #5
Astronuc
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Cumulative is what we have to deal with in the reactor, and later on in either reprocessing or spent fuel. Certainly the cumulative yields provide the isotopic vector at shutdown. The reinsert fuel will go back in and the fission products will again change. Depletion codes have to track production, transmutation and decay. The discharge fuel will define the waste, with it's from recycling or from direct burial of spent/used fuel.
 

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