Nuclear reactors that use thorium have been discussed for a long time. Initially (back in the 1950’s) they presented a better option for producing nuclear power. But uranium-based reactors could be used to make weapon-grade material. So thorium designs were rejected. Better, but rejected.
And that is still the story. But now the arguments for not exploring how to make commercial grade thorium reactors is that the cost of renewables will keep falling. Errr … that sounds like a decent argument. But NO ONE in their right mind argues that energy from renewable sources will be enough to meet all of our energy needs for the foreseeable future.
In this article, you get the more complete picture of why thorium is very interesting, and why we are spending so little on it.