Three stage Nuclear Program [ India ]

In the first stage, Heavy water reactors using enriched uranium derived from India’s limited uranium reserve, would be constructed and begin operating. The use of heavy water reactors meant that India did not need to to develop expensive and power demanding uranium enrichment facilities.

During the second stage, India was to construct Fast Breeder Reactors, which burned plutonium reprocessed from the spent fuel of the heavy water reactors as well as their depleted uranium. India needed to develop breeder technology quickly, because it had limited uranium resources. Breeders allowed India’s uranium supply to be used much more efficiently.

During the third stage thorium was to be bred, and U-233 would fuel Indian power reactors.

 Natural Uranium contains two isotopes, U-235 (0.7%) and U-238 (99.3%). Out of these two isotopes, only U-235 is useful for nuclear reactors, as it is fissile. U-238 is not fissile, similar to Th-232. However, this U-238 gets converted into Plutonium (Pu-239) during its stay inside the Uranium reactors by absorbing one neutron. This Pu-239 can then be extracted and used as fuel in Fast Breeder reactors. Therefore to sustain the Fast Breeder Reactors, enough Plutonium from Uranium based reactors is necessary. The only way it can be done is to have enough operational Uranium based reactors. This is why India is importing Uranium to sustain Uranium based reactors.

As mentioned above, Pu-239 will be used in Fast Breeder Reactors as fuel, but a blanket, or coating of Th-232 will be placed over Pu-239 (the fuel). This Th-232, during its stay inside the Fast Breeder Reactor, will get converted into Uranium-233 by absorbing one neutron. Uranium-233 is fissile but is not naturally occurring.

This Uranium-233  can then be extracted from the spent-fuel, and used as fuel in another type of reactors. Now, if you place a blanket of Th-232 over this Uranium-233 fuel, that blanket will again get converted into Uranium-233 during its stay inside the reactor by absorbing one neutron, and we will have a process where fuel can be re-generated inside the reactor! Though Uranium-233 is the fuel in these reactors, they are also termed as Thorium based reactors.

Thus in order to reach the Thorium based energy generation, building enough Plutonium stock for fast breeder reactors is necessary, which can only be done by having enough Uranium based electricity generation.