India's plans for thorium cycle

With huge resources of easily-accessible thorium and relatively little uranium, India has made utilization of thorium for large-scale energy production a major goal in its nuclear power programme, utilising a three-stage concept.

1. Pressurised heavy water reactors (PHWRs) and light water reactors fuelled by natural uranium producing plutonium that is separated for use in fuels in its fast reactors and indigenous advanced heavy water reactors.
2. Fast breeder reactors (FBRs) will use plutonium-based fuel to extend their plutonium inventory. The blanket around the core will have uranium as well as thorium, so that further plutonium (particularly Pu-239) is produced as well as U-233.
3. Advanced heavy water reactors (AHWRs) will burn thorium-plutonium fuels in such a manner that breeds U-233 which can eventually be used as a self-sustaining fissile driver for a fleet of breeding AHWRs. 

In all of these stages, used fuel needs to be reprocessed to recover fissile materials for recycling.

India is focusing and prioritizing the construction and commissioning of its fleet of 500 MWe sodium-cooled fast reactors in which it will breed the required plutonium which is the key to unlocking the energy potential of thorium in its advanced heavy water reactors. This will take another 15-20 years, and so it will still be some time before India is using thorium energy to any extent. The 500 MWe prototype FBR under construction in Kalpakkam was expected to start up in 2014, but 2018 is now the target date.