Enrico Fermi’s early patent concerning a “Neutronic reactor” (1955) described how the radioactive fission of natural uranium could be harnessed for useful energy production.
Uranium fuel used in nuclear reactors is enriched with uranium-235: Improvements in and relating to the production of energy through nuclear fission of uranium (1950).
Uranium is also used by the military to power nuclear submarines: Submarine Nuclear Reactor (1974). In a breeder reactor uranium-238 captures neutrons and undergoes negative beta decay to become plutonium-239: Light water breeder reactor using a uranium-plutonium cycle (1990).
Depleted uranium is uranium that has much less uranium-235 than natural uranium; it is considerably less radioactive than natural uranium. It is a dense metal that can be used as ballast for ships: Method of ballasting keel of sailing boat – involves vacuum moulding spent uranium for insertion in keel (1974).