I didn't say to buy thorium. It seems very abundant compared to the energy it contains. The bigger reserves are in australia, us, india and then china if I remember it well. You should buy rare earth miners in those countries if you want to get the thorium.

EDIT: By the way, thorium is far more clean than uranium and its by-products (unlike plutonium) aren't suitable for war. That's why the plutonium way was researched first.