jkp1187
Unindicted Co-Conspirator
It's not mistaken, you can indeed build modern age ships (including Destroyers) with Uranium, however in order to be able to "use" Uranium you need to have researched Fission (in other words.. although you can 'see' Uranium in your city resource box it's not actually there until Fission)
I assume that if you mine uranium prior to Fission, you still get the usual bonuses, no?

. Well, if I recall correctly, it also increases your Power rating so that you can dissuade the aggressive civs a bit more from attacking you.