Fast Breeder Reactor and Criticality – Kalpakkam Nuclear Milestone

Fast Breeder Reactor Latest News

• India’s Prototype Fast Breeder Reactor (PFBR) at Kalpakkam has achieved criticality, marking a key milestone in the nuclear programme. 

About Fast Breeder Reactor

• A Fast Breeder Reactor (FBR) is a type of nuclear reactor that generates more fissile material than it consumes.
• Unlike conventional reactors, which use thermal (slow) neutrons, FBRs use fast neutrons to sustain nuclear fission. This allows efficient utilisation of fuel and enhances energy output.
• FBRs typically use plutonium-based fuel, often in the form of Mixed Oxide (MOX), along with fertile materials such as uranium-238. These fertile materials are converted into fissile material (like plutonium-239) during reactor operation.
• A key feature of FBRs is the “breeding” process. In this process, non-fissile material is transformed into fissile material through neutron absorption, thereby creating additional fuel.
• FBRs are crucial for countries like India that have limited uranium reserves but abundant thorium resources. 
• They form the second stage of India’s three-stage nuclear programme, enabling the transition toward thorium-based energy systems.

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Significance of Fast Breeder Reactors

• Fast breeder reactors play a critical role in ensuring long-term energy security.
• They significantly improve fuel efficiency by extracting more energy from available uranium resources.
• They also reduce nuclear waste by utilising materials that would otherwise remain unused.
• In India’s context, FBRs are essential for converting thorium into uranium-233, which is vital for the third stage of the nuclear programme. 

Criticality in Nuclear Reactors

• Criticality refers to the state in which a nuclear reactor achieves a self-sustaining chain reaction.
• At this stage, each fission event produces enough neutrons to sustain further fission reactions without external intervention.
• Criticality is a crucial milestone in reactor commissioning. It indicates that the reactor core is functioning as designed and is ready to move toward power generation. 
• There are three states associated with criticality:
  • Subcritical state, where the reaction dies out over time. 
  • Critical state, where the reaction is stable and self-sustaining. 
  • Supercritical state, where the reaction increases rapidly. 
• Achieving controlled criticality is essential for the safe and efficient operation of nuclear reactors.

News Summary

• India’s 500 MWe Prototype Fast Breeder Reactor (PFBR) at Kalpakkam in Tamil Nadu has attained criticality, marking a defining step in the country’s nuclear energy programme. 
• The reactor is located at the Indira Gandhi Centre for Atomic Research and is operated by Bharatiya Nabhikiya Vidyut Nigam Limited (BHAVINI), a public sector enterprise under the Department of Atomic Energy. 
• The PFBR is a sodium-cooled, pool-type fast breeder reactor that uses mixed oxide (MOX) fuel consisting of uranium-238 and plutonium-239. It is designed to generate more fissile material than it consumes, thereby enhancing fuel sustainability. 
• Achieving criticality means that the reactor has initiated a self-sustaining nuclear fission chain reaction, indicating readiness for eventual power generation. 
• The project is a key component of India’s three-stage nuclear programme. 
  • In the first stage, Pressurised Heavy Water Reactors (PHWRs) produce plutonium. 
  • In the second stage, fast breeder reactors like PFBR use this plutonium to generate additional fissile material. 
  • The third stage aims to use thorium to produce uranium-233 for long-term energy security. 
• India is now among a select group of countries possessing advanced fast breeder reactor technology, with Russia being the only other nation operating commercial-scale FBRs. 
• The reactor also incorporates important safety features such as a negative void coefficient, which reduces reaction rates in case of overheating, enhancing operational safety. 
• Overall, the achievement of criticality at Kalpakkam marks a significant step toward India’s goal of developing a closed nuclear fuel cycle and reducing dependence on imported uranium.

Source: TH | IE