Distinguish between a Fast Breeder Reactor (FBR) and a thermal nuclear reactor. In the context of first indigenously developed prototype FBR at Kalpakkam, explain the term ‘criticality’. What are its implications for clean energy future of our country ? (Answer in 150 words)

- Distinguish between a Fast Breeder Reactor (FBR) and a thermal nuclear reactor. In the context of first indigenously developed prototype FBR at Kalpakkam, explain the term ‘criticality’. What are its implications for clean energy future of our country ? (Answer in 150 words)
Introduction
A nuclear reactor sustains controlled fission, but Fast Breeder Reactors (FBRs) and thermal reactors differ mainly in neutron energy, fuel cycle and breeding capability.
Body
FBR vs Thermal Reactor:
1. Neutrons: FBRs use fast neutrons, whereas thermal reactors slow neutrons using moderators such as water or heavy water.
2. Fuel: FBRs generally use plutonium-rich fuel with U-238, while thermal reactors mainly use uranium-based fuel.
3. Breeding: FBRs can produce more fissile material than they consume by converting U-238 into Pu-239; conventional thermal reactors generally do not.
4. Coolant: India’s 500 MWe PFBR at Kalpakkam uses liquid sodium, which does not significantly slow neutrons.
Criticality means the reactor reaches a state where each fission generation produces enough neutrons to sustain the next, i.e. a self-sustaining controlled chain reaction.
Clean-energy Implications:
FBRs improve fuel utilisation, exploit India’s abundant U-238 resources, reduce dependence on imported uranium and form a crucial bridge towards the thorium-based third stage of India’s nuclear programme.
Conclusion
Thus, successful FBR deployment can strengthen India’s low-carbon energy security, resource efficiency and long-term nuclear self-reliance.