Aidan Liang Posted January 23, 2021 Share Posted January 23, 2021 Which type neutron is easier to be absorbed by the unstable nuclei. A faster one, or a slower one? Link to comment Share on other sites More sharing options...
Bufofrog Posted January 23, 2021 Share Posted January 23, 2021 (edited) It depends on the nuclei. Uranium 235 will undergo fission from a thermal (slow) neutron but Uranium 238 will undergo fission from a fast neutron. Edited January 23, 2021 by Bufofrog 1 Link to comment Share on other sites More sharing options...
Sensei Posted January 23, 2021 Share Posted January 23, 2021 8 minutes ago, Aidan Liang said: Which type neutron is easier to be absorbed by the unstable nuclei. A faster one, or a slower one? Fast neutrons (with higher kinetic energy) can destroy nuclei i.e. split it to clusters. https://en.m.wikipedia.org/wiki/Cluster_decay Search net for "fast neutrons induced cluster decay" 1 Link to comment Share on other sites More sharing options...
John Cuthber Posted January 23, 2021 Share Posted January 23, 2021 Is there a reason why neither of you said anything about absorbing neutrons (i.e. what the OP asked about)? Anyway, I think the answer is that slow neutrons are generally more likely to be absorbed into the nucleus. e.g https://en.wikipedia.org/wiki/Neutron_capture#/media/File:Neutroncrosssectionboron.png 1 Link to comment Share on other sites More sharing options...
swansont Posted January 23, 2021 Share Posted January 23, 2021 In general, the cross-section for absorption drops with energy. There are some resonances which go against this trend. See, for example fig 1here https://www.researchgate.net/figure/Neutron-absorption-cross-sections-for-several-isotopes-as-a-function-of-incident-neutron_fig5_235915631 (edit: x-post) 1 Link to comment Share on other sites More sharing options...
Aidan Liang Posted January 24, 2021 Author Share Posted January 24, 2021 On 1/23/2021 at 1:08 PM, John Cuthber said: her of you said anything about absorbing Im going to believe in the theory that fast neutrons would: 1. Destroy the nucleus 2. Too fast that the nucleus cannot absorb it Therefore slower neutrons are easier to be absorbed (generally). However, there are exceptions for different elements Link to comment Share on other sites More sharing options...
Bufofrog Posted January 24, 2021 Share Posted January 24, 2021 (edited) 8 minutes ago, Aidan Liang said: Im going to believe in the theory that fast neutrons would: 1. Destroy the nucleus They won't. A neutron will collide elasticity with a nucleus and not destroy or otherwise 'damage' the nucleus. Don't go on belief, you should go on facts. Edit: As Sensi said in rare cases some emissions from the nucleus is possible. That is not typical. Edited January 24, 2021 by Bufofrog 1 Link to comment Share on other sites More sharing options...
Aidan Liang Posted January 24, 2021 Author Share Posted January 24, 2021 4 hours ago, Bufofrog said: They won't. A neutron will collide elasticity with a nucleus and not destroy or otherwise 'damage' the nucleus. Don't go on belief, you should go on facts. Edit: As Sensi said in rare cases some emissions from the nucleus is possible. That is not typical. right thanks! Link to comment Share on other sites More sharing options...
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