From an interesting summary of Thorium research and use in the Encyclopedia of Earth.
eoearth.org
India
In India, both Kakrapar-1 and -2 units are loaded with 500 kg of thorium fuel in order to improve their operation when newly-started. Kakrapar-1 was the first nuclear reactor in the world to use thorium, rather than depleted uranium, to achieve power flattening across the reactor core. In 1995, Kakrapar-1 achieved about 300 days of full power operation and Kakrapar-2 about 100 days utilizing thorium fuel. The use of thorium-based fuel is planned in Kaiga-1 and -2 and Rajasthan-3 and -4 reactors, which are currently under construction.
With about six times more thorium than uranium, India has made utilization of thorium for large-scale energy production a major goal in its nuclear power program, utilizing a three-stage concept:
Pressurized Heavy Water Reactors (PHWRs), elsewhere known as CANDUs fuelled by natural uranium, plus light water reactors, produce plutonium;
Fast Breeder Reactors (FBRs) use this plutonium-based fuel to breed 233U from thorium. The blanket around the core will have uranium as well as thorium, so that further plutonium (ideally high-fissile Pu) is produced as well as the 233U; and then
Advanced Heavy Water Reactors (AHWRs) burn the 233U and this plutonium with thorium, getting about 75% of their power from the thorium.
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