Why does Uranium-238 absorb fast moving neutrons

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Uranium-238 absorbs fast-moving neutrons effectively due to its nuclear properties, despite initial intuition suggesting otherwise. It captures both slow and fast neutrons, but the likelihood of fission in Uranium-235 is significantly higher with slow neutrons. This results in a more favorable ratio for fission in U-235 compared to neutron capture in U-238 when slow neutrons are involved. The discussion highlights the importance of the pairing force in understanding these interactions. Overall, the behavior of U-238 in neutron absorption is complex and influenced by various nuclear dynamics.
Ed Aboud
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Hi all.
Why does Uranium-238 absorb fast moving neutrons very well but not slow moving ones?
My intuition tells me it should be the other way around but its not.
Thanks.
 
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Hmm, I still don't really get it.
 
U-238 captures slow neutrons as well as fast, and even a bit more slow than fast. However, U-235 fissions MUCH MORE easily with slow neutrons than with fast, and hence the ratio for fission in U-235 over capture in U-238 is more favorable for slow neutrons than for fast.
 
Oh ok, I get it now. Thanks very much.
 
it has to with the pairing force, the answer vanesh gave you.
 

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