Perhaps Thorium should be called the only viable nuclear fuel.
After speaking of its use on the moon, Kirk Sorernson told an audience, "It could be used to power the entire world."
He added that thorium is not rare and explains in the linked video how it is easier and safer to use than uranium.
Me dino picked up on thorium in nickursis's post, "Thunderstorm Turns Into Nuclear Reactor and Blasts Radiation Everywhere"
where Gulcher jim jamesjames made quick mention of it. So I looked it up.