The radioactive element thorium is much more abundant in the earth than uranium, and has many advantages over uranium as use as a nuclear fuel. It can be used as a fissible fuel along with recycled plutonium and fissible uranium-233 in many types of nuclear reactors, including molten salt reactors and normal fuel reactors. It is much safer in rectors than uranium, with meltdowns being more remote; the liquid fluoride would expand in such a situation and cause the chain reaction to stop. This overcomes one of he telling objections to the standard uranium reactors. Liquid Floride Thorium Reactors (LFTR), can digest radioactive waste generated from conventional reactors, overcoming another great problem, of what to do with the radioactive waste. And a cricket ball size chunk of thorium has around 13,000 times more energy that a similar size chunk of coal, so it is very energy dense. It would solve humanities electricity generation issues until nuclear fusion is up and running.
So why was thorium not used as a nuclear fuel? The answer is, unsurprisingly enough that uranium can be readily used in reactors to produce weapons grade plutonium for nuclear weapons, and that is what the great nuclear powers wanted, and still do.
