[ko_kyi]

So if I am reading you correctly a nuclear reactor can have a mix of U-235, which fissions and keeps the reaction going, and U-238 which bit by bit becomes plutonium which can be isolated later and made into a bomb.

I had always thought the U-238 fissioned as well.

[William McKinley]

I wouldn't say you would have a mixture. More accurate is that you would have targets made of U-238.

U-238 doesn't fission. Depleted uranium is mainly U-238.