Uranium 238 is not fissile. When bombarded with thermal neutrons it becomes Plutonium 239 which is fissile. However, I have read that U238 nucleus can split apart if bombarded with energetic fast moving neutrons. My question is, when bombarded with fast neutrons what exactly would be the fission products when U 238 splits apart, as U235 may split into barium and krypton?


It's surprisingly hard to find this information. Presumably it's because U238 fission is of no commercial importance. Anyhow, the data can be found on the International Atomic Energy Agency web site.

The fast neutron fission can go via many different paths and there are many daughter products. For convenience I have sorted the data on the linked web page in descending order of fission product abundance:

Isotope     % of fission products
53-I-135     1.12
52-Te-132    0.34
2-He-4       0.149
35-Br-85     0.046
53-I-133     0.017
56-Ba-140    0.0142
54-Xe-135m   0.0106
1-H-3        0.0103

This shows only the most abundant fission products as there are dozens of products with tiny abundances.

In general when you use fast neutrons you're going to get a messy fission process as there is lots of spare energy around to be randomly distributed around the nucleons.


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