The uranium 238 and the Plutonium can be used in fast neutron reactors and new molten salt nuclear reactors and they can generate energy. The Uranium 238 in a fast reactor has about the same energy as Uranium 235 in most of the current reactors. The Russians have operated fast reactors commercially for decades. The French ran a fast reactor for a  while as well. China is building some.
There are several companies making molten salt nuclear reactors. There was a 10 megawatt thermal molten salt reactor operated in the 1960s. These reactors are not as useful for generating nuclear bombs. Molten salt reactors can use up almost all of the uranium and plutonium.
If you use the neutrons in the right way or use advanced chemistry the uranium and plutonium in what is called nuclear waste can be used as nuclear fuel.