Three-stage Nuclear Program of India

Context: Recently, the “Core Loading” at India’s first indigenous Fast Breeder Reactor (500 MWe) was commenced at Kalpakkam, Tamil Nadu. 

Core loading is the process of placing nuclear fuel assemblies inside the core of a nuclear reactor.

Upon completion of the core loading, the first approach to criticality will be achieved, i.e., the initiation of a self-sustaining nuclear fission reaction that will eventually lead to the generation of power by the 500 megawatt electric (MWe) FBR.

Nuclear Fuel: Fissile and Fertile

• Fissile Material: Ready Fuel for Fission
  • Fissile isotopes readily undergo fission when hit by neutrons, releasing a tremendous amount of energy. Examples include Uranium-235 (U-235), Uranium- 233 (U-233) and Plutonium-239 (Pu-239). 
  • However, fissile materials like U-235 make up a small portion of Natural Uranium (less than 1%).
    • ​​Naturally occurring Uranium is composed of three major isotopes:
      • Uranium-238 (99.284% natural abundance)
      • Uranium-235 (0.711%)
      • Uranium-234 (0.005%) 
  • U-235 atoms is the only nuclide existing in nature (in appreciable amount) that is fissile with thermal neutrons. Since naturally occurring Uranium does not have a high enough concentration of U-235, Uranium enrichment is necessary to create an effective nuclear fuel out of mined Uranium. 

• Fertile Material: Breeding Potential 
  • Though not directly fissile by slow neutrons, fertile isotopes can absorb neutrons and transmute into fissile materials through radioactive decay.
    • In the context of nuclear reactors, nuclear transmutation often refers to the conversion of one nuclide into another within the fuel or target material. This process can involve the absorption of a neutron, the emission of a neutron, or the capture and subsequent decay of a particle.
  • Common fertile materials include Uranium-238 (U-238) and Thorium-232 (Th-232).
    • Uranium U-238, the dominant isotope of Uranium, is a fertile material that cannot by itself make the reactor achieve criticality, so it has to be converted to fissile plutonium (Pu-239) in a nuclear reactor. The spent fuel from thermal reactors contains Pu-239, which is most efficiently burnt in a fast reactor. 
    • Thorium Th-232 is a fertile material that has to be converted to fissile material U233.  

India’s three stage Nuclear program:

• The Department of Atomic Energy’s (DAE’s) three-stage power programme envisages a pathway to utilising India’s abundant thorium reserves — found in coastal and inland placer sands on the beaches of Kerala, Tamil Nadu, Odisha, Andhra Pradesh, Maharashtra, and Gujarat, and in the inland riverine sands of Jharkhand and West Bengal — to generate electricity.
• India owes the vision of the three-phase programme of nuclear power to ensure energy security to Dr Homi J Bhabha, the father of India’s nuclear programme, and Dr Vikram Sarabhai, who recognised the need for developing FBRs as these reactors generate more nuclear fuel than they consume due to the gainful conversion of fertile isotopes into fissile material.

1st Stage: Pressurised Heavy Water Reactor 

• The first stage includes the setting up of Pressurised Heavy Water Reactors (PHWRs) and associated fuel cycle. 
• PHWRs use natural uranium (U-238) as fuel and heavy water (deuterium oxide) as coolant and moderator. 
• The Nuclear Power Corporation of India Limited (NPCIL) presently operates 22 commercial nuclear power reactors with an installed capacity of 6,780 MWe.

2nd Stage: Fast Breeder Reactors: 

• The Fast Breeder Reactor (FBR) will initially use the Uranium-Plutonium Mixed Oxide (MOX) fuel.
  • The Uranium-238 surrounding the fuel core will undergo nuclear transmutation to produce fuel (Plutonium, Pu-239), thus earning the name ‘Breeder’. 
  • Also, by transmutation, Thorium-232 will create fissile Uranium-233 which will be used as fuel in the third stage. 
• In 2003, the Government had approved the creation of Bharatiya Nabhikiya Vidyut Nigam Ltd (BHAVINI) to construct and operate India’s most advanced nuclear reactor-Prototype Fast Breeder Reactor (PFBR). Once the FBR attains criticality, India will only be the second country after Russia to have a commercial operating Fast Breeder Reactor.

Benefits of FBR

• FBR is thus a stepping stone for the third stage of the program paving the way for the eventual full utilisation of India’s abundant thorium reserves. 
• Electricity generated by FBR would be a source of green energy as the waste (Plutonium) from the first stage nuclear programme is reprocessed and used as fuel in FBR. Hence, it offers significant reduction in nuclear waste generated, thereby avoiding the need for large geological disposal facilities.
• In terms of safety, the PFBR is an advanced reactor with inherent passive safety features ensuring a prompt and safe shut down of the plant in the event of an emergency. 
• Despite the advanced technology involved, both the capital cost and the per unit electricity cost is comparable to other nuclear and conventional power plants.
• Hence, the second-stage of the Indian nuclear power program is imperative to meet the twin goals of energy security and sustainable development.

3rd Stage: Thorium-based Reactors 

• The third stage will utilise India’s vast Thorium reserves. For it an Advanced Heavy Water Reactor (AHWR) is proposed that will use Uranium-233. 
  • By transmutation, Thorium will create fissile Uranium-233 which will be used as fuel in the third stage.