India has reached a major milestone in its civilian nuclear programme: the Prototype Fast Breeder Reactor (PFBR) at Kalpakkam has attained criticality, the point at which a reactor sustains a controlled nuclear chain reaction. The PFBR is a 500-megawatt electric, indigenously designed facility located near Chennai in Tamil Nadu.
Prime Minister Narendra Modi announced the development on X, calling it a defining and proud moment for the country. He said the advanced reactor, which can produce more fuel than it consumes, demonstrates India’s scientific and engineering capabilities and represents a decisive step toward exploiting the country’s large thorium reserves in the third stage of its three-step nuclear strategy.
The PFBR’s successful attainment of criticality is an essential step toward full commissioning and commercial power generation. Modi visited the site in 2024 to observe the start of core loading, and the latest announcement moves the project closer to delivering electricity to the grid.
Fast breeder reactors are important for long-term nuclear sustainability because they generate more fissile material than they use, extending fuel resources and supporting a closed fuel cycle. Once the PFBR is fully operational, India would become only the second country, after Russia, to have a commercial fast breeder reactor in operation.
The milestone also supports India’s broader energy goals. The country currently has about eight gigawatts of nuclear capacity and aims to expand that to 100 GW by 2047 as part of its efforts to diversify the power mix and reduce greenhouse gas emissions.
Reaching criticality does not yet mean commercial operation; further testing, fuel management and regulatory approvals are required before the reactor begins sustained power production. Still, the achievement marks a significant technical and strategic advance for India’s nuclear programme.