The three stage nuclear power programme of DAE is rather unique to India and is based on the Uranium and Thorium resources available in country. It has been planned based on a closed fuel cycle concept, requiring reprocessing of spent fuel from every reactor, to judiciously reutilize all available fissile material for peaceful purposes. The first stage comprises the commercial deployment of Pressurized heavy water Reactors (PHWRs) based on natural Uranium and Heavy water. While the less abundant U-235 undergoes fission generating energy, the most abundant U-238 gets converted to fissile Pu-239. The Pu can be extracted by reprocessing the spent fuel from the first stage. In the second stage, the fast breeder reactors (FBR) which use fuels based on Pu-239 will be built. These reactors in addition to enhancing the nuclear power, will also be used to convert the fertile Thorium to fissile U-233, thereby multiplying the inventory of fissile material.s Reprocessing of the spent fuel is vital for the efficient utilization of Pu and U. The third stage of the programme will be based on the fissile U-233 produced in the second stage and the vast resources of fertile Th-232 and the Th-233 U cycle. An advanced Heavy Water Reactor (AHWR) is being planned to gain useful experience in using thorium based fuels and to expedite the transition to thorium based systems for long term energy security. In addition, for large scale utilization of Thorium, the DAE also has plans to develop Accelerator Driven sub-critical Reactor system (ADS) in future.