Most people are totally unaware the the element Thorium (number 90 on the periodic table) is around 4X more abundant than uranium, and that it is a fertile element. That means that every atom of Thorium will convert to U233 when exposed to neutrons in a reactor. The U233 will then fission releasing 1 million times more energy than a carbon atom does when it is burnt. Furthermore, Thorium, being lower on the table of elements, does not produce Plutonium 239, which is the favorite of weapons builders. It does produce useful amounts of Plutonium 238, which is great for powering deep space probes.
Thorium fueled reactors are also excellent sources of heat for distillation of water, which is why we like them at Aquacraft.
Thanks to Kirk Sorensen, FLIBE Energy for this diagram.