Nuclear: As long as you don’t care about the magic rocks once the magic has decayed to a level where they’re not boiling water anymore
90% of magic rocks that no longer boil wsater is magic rocks that can boil water.
If you’re talking breeder reactors
I was talking about reusing uranium from “spent” fuel, not about using plutonium. Found source that says “spent” fuel is 95-98% mix of uranium isotopes that were there. Sadly, source doesn’t say how much of each isotope, I expect very low amount of U-235. Yes, you can also use plutonium in MOX fuel, but only Russia~~, France~~ and China do that, as far as I know.
do we have any in the US?
Dunno. Do you? If you don’t, you can buy them from mentioned above countries.
EDIT: France no longer has working breeder reactor? How did it happen?