• Department of Atomic Energy (DAE) has planned the use of large deposits of Thorium available in the country as a long-term option.
• A three-stage nuclear power programme has been chalked out to use Thorium as a viable and sustainable option, right at the inception of India’s nuclear power programme.
• The three-stage nuclear power programme aims to multiply the domestically available fissile resource through the use of natural Uranium in Pressurised Heavy Water Reactors, followed by use of Plutonium obtained from the spent fuel of Pressurised Heavy Water Reactors in Fast Breeder Reactors.
• Large scale use of Thorium will subsequently follow making use of the Uranium-233 that will be bred in Reactors.
• The utilisation of Thorium, as a practically inexhaustible energy source, has been contemplated during the third stage of the Indian Nuclear Programme.
• As is the case with generation of electricity from Uranium, there will be no emission of greenhouse gases from Thorium also and therefore, it will be a clean source of energy.

Challenges:

• It is not possible to build a nuclear reactor using Thorium (Thorium-232) alone due to its physics characteristics. Thorium has to be converted to Uranium-233 in a reactor before it can be used as fuel.
• Commercial utilisation of Thorium, on a significant scale can begin only when abundant supplies of either Uranium-233 or Plutonium resources are available.
• Accordingly, the large-scale introduction and utilization of Thorium in the programme has been contemplated after an adequate inventory of Plutonium becomes available from our Fast Breeder Reactors (FBRs), comprising the second stage of Indian nuclear power programme. This will be after a few decades of large-scale deployment of FBRs. In preparation for the utilisation of Thorium in Third Stage of India’s Nuclear Power Programme, efforts towards technology development and demonstration are made now so that a mature technology for Thorium utilisation is available in time.

India’s Three Stage Nuclear Programme:

Indian Nuclear Power Generation Envisages Three Stage Programme:

• Pressurized Heavy Water Reactor
• Fast Breeder Reactor
• Breeder Reactor

Pressurized Heavy Water Reactor Uses:

• Natural uranium dioxide as fuel matrix, Heavy water as moderator and coolant
• Natural U isotopic composition is 0.7 % fissile U-235 and the rest is U-238. In the reactor
• India achieved complete self- reliance in this technology

Fast Breeder Reactor:

• India’s second stage of nuclear power generation envisages the use of Pu-239 obtained from the first stage reactor operation, as the fuel core in fast breeder reactors (FBR). The main features of FBTR are:
• Pu-239 serves as the main fissile element in the FBR
• A blanket of U-238 surrounding the fuel core will undergo nuclear transmutation to produce fresh Pu-239 as more and more Pu-239 is consumed during the operation.
• Besides a blanket of Th-232 around the FBR core also undergoes neutron capture reactions leading to the formation of U-233.
• U-233 is the nuclear reactor fuel for the third stage of India’s Nuclear Power Programme.
• It is technically feasible to produce sustained energy output of 420 GWe from FBR.
• Setting up Pu-239 fuelled fast Breeder Reactor of 500 MWe power generation is in advanced stage of completion. Concurrently, it is proposed to use thorium-based fuel, along with a small feed of plutonium-based fuel in Advanced Heavy Water Reactors (AHWRs). The AHWRs are expected to shorten the period of reaching the stage of large-scale thorium utilization

Breeder Reactor:

• The third phase of India’s Nuclear Power Generation programme is, breeder reactors using U-233 fuel. India’s vast thorium deposits permit design and operation of U-233 fuelled breeder reactors.
• U-233 is obtained from the nuclear transmutation of Th-232 used as a blanket in the second phase Pu-239 fuelled FBR.
• Besides, U-233 fuelled breeder reactors will have a Th-232 blanket around the U-233 reactor core which will generate more U-233 as the reactor goes operational thus resulting in the production of more and more U-233 fuel from the Th-232 blanket as more of the U-233 in the fuel core is consumed helping to sustain the long term power generation fuel requirement.
• These U-233/Th-232 based breeder reactors are under development and would serve as the mainstay of the final thorium utilization stage of the Indian nuclear programme. The currently known Indian thorium reserves amount to 358,000 GWe-yr of electrical energy and can easily meet the energy requirements during the next century and beyond.