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I know this question may seem a bit simple, but I would like to know about how fission products of an element are formed. There seems to be no way for krypton-92 and barium-141, the immediate fission products of U235, to decay into a fission product like caesium-137 or technetium-99. Instead, I found they quickly decay to the stable nuclides zirconium-91, zirconium-92, and praseodymium-141, and the intermediate radioactive nuclides all have half-lives of within a few months.

So, my question is, how are these other fission products formed?

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  • $\begingroup$ @Poutnik Then how are they formed? $\endgroup$ Apr 16, 2022 at 13:21
  • $\begingroup$ @Poutnik But the fission of uranium-235 seems to only produce krypton-92 and barium-141. $\endgroup$ Apr 16, 2022 at 13:50
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    $\begingroup$ It is false premise I have tried to negate since the beginning. See also Fission product yield $\endgroup$
    – Poutnik
    Apr 16, 2022 at 13:57
  • $\begingroup$ Comments moved to the answer. $\endgroup$
    – Poutnik
    Apr 16, 2022 at 14:23
  • $\begingroup$ i wonder why the popular texts as well as a lot of textbooks are concentrated exactly on the Ba / Kr example $\endgroup$
    – fraxinus
    Apr 17, 2022 at 17:46

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There are many immediate primary fission products, with 2 probability peaks near 2/5 and 3/5 of original uranium-235 nucleon number. By other words, there are multiple ways how the nucleus can be broken, some more probable than others.

But the fission of uranium-235 seems to only produce krypton-92 and barium-141.

This is false premise. These are just the products of a single fission mode from many. In a classical analogy, there is multiple ways how to break a stone.

See also Nuclear fission products and Fission product yield

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