"Thorium is a great fuel in light water reactors, but it really excels in molten salt reactors," says David LeBlanc, a nuclear physicist at Carleton University in Ottawa, Canada. The fuel rods used in light water reactors tend to succumb to radiation damage within a few years.
In proposed molten salt reactors, by contrast, thorium is dissolved in a mixture of damage-resistant liquid salts, allowing for more plant uptime.
Radioactive fission products generated in a thorium-fueled molten salt reactor can also be re-added to the reactor for many successive rounds of power generation, enabling utilities to extract more power from small amounts of fuel.
Japanese company IThEMS, which is working on a thorium-fueled molten salt reactor, estimates power generated by such a reactor would cost at least 30 percent less than power from today's light water reactors.
In addition, molten salt reactors could potentially burn through hazardous waste stockpiles produced by previous generations of nuclear reactors.
I think India is most advanced in building a thorium reactor but I don't know if it's a light water type. Every government has visions of thorium plums dancing in their heads.