If you have uranium and the proper equipment, you can seperate out U235 from U238. It's a relatively simple process, but I won't detail it here.

If you have U235 you can use that for a fission weapon, or you can further work on it to make Plutonium 239. Pu239 can also be used in fission weapons.

U235 and Pu239 can also be used in electricity-producing reactors.

Just as with sinning, it's often a matter of intent.