India’s indigenously developed Prototype Fast Breeder Reactor at Kalpakkam in Tamil Nadu achieved first criticality on Tuesday, marking a major step in the country’s nuclear programme.
First criticality is the stage at which a reactor begins a self-sustaining nuclear chain reaction. It means the reactor is producing enough neutrons to continue operating on its own and can move to the next phase of development.
Prime Minister Narendra Modi called the achievement a “defining step” in India’s civil nuclear journey and congratulated the scientists and engineers involved.
The reactor was developed by the Indira Gandhi Centre for Atomic Research and is located at Kalpakkam.
A fast breeder reactor is designed to produce more fissile fuel than it consumes while generating electricity. The reactor uses uranium-plutonium mixed oxide fuel and liquid sodium as a coolant, allowing it to operate at high temperatures. It also uses a closed fuel cycle in which spent fuel is reprocessed and reused.
The Prototype Fast Breeder Reactor is expected to help India move towards the next stage of its nuclear programme, which involves using the country’s large thorium reserves.
India currently generates 8.78 gigawatts of nuclear power. Indigenous nuclear plants produced 56,681 million units of electricity last year, accounting for 3.1 per cent of the country’s total power generation.
With 700MW and 1,000MW reactors under development, India expects nuclear capacity to rise to 22.38 gigawatts by 2032.
The government has also set a target of 100 gigawatts of nuclear power capacity by 2047. In the 2025-26 Union Budget, it allocated Rs 20,000 crore under the Nuclear Energy Mission to develop small modular reactors, with at least five expected to be operational by 2033.