The article briefly mentions fast reactors, but I think dismisses them a little too quickly. Waste from fast reactors would be short-lived. Most of our waste i

The article briefly mentions fast reactors, but I think dismisses them a little too quickly. Waste from fast reactors would be short-lived. Most of our waste is uranium, mainly U238 plus a little leftover U235. This is barely radioactive. There's also a fair amount of plutonium and other transuranics, made when uranium and heavier atoms absorb a neutron without fissioning. This is the really long-lived waste that needs to be stored for thousands of years. About one percent of our waste is fission products, the smaller atoms left after breaking apart uranium and plutonium. This is highly radioactive, but only for a couple centuries. Fast reactors can fission the transuranics, and both isotopes of uranium. Their waste is almost entirely fission products. Encase them in glass, bury them, and in three centuries it'll be back to the radioactivity of the original uranium ore.