[Jimmy The Snake]

I searched Wikipedia on U236. It does support fission and won’t go boom, but it appears as a trace isotope in minimal quantiles, but comes from enriching U238 (natural) into U235 becoming a waste product.

You take U238 turn it into a gas at like 7000 degrees F then by spinning it in centrifuges the force from spinning separates the atoms and U238 is denser than U235.

[103198]

U236 is not naturally occurring. It is created by U235 absorbing a neutron. This means the uranium being enriched had to been exposed to a neutron flux of some type - and most likely a reactor. The IAEA table for U236 neutron cross section is 5 barns for radiative capture which is more than 100 times less than the fission cross section for U235. See http://www.nuclear-power.net/nuclear-power-plant/nuclear-fuel/uranium/uranium-236/.

I'm actually very familiar with centrifuge and other types of Uranium enrichment.