New Delhi [India], April 26 : Prime Minister Narendra Modi on Sunday congratulated the scientists for achieving 'first criticality' at the Prototype Fast Breeder Nuclear Reactor at Kalpakkam in Tamil Nadu, terming the accomplishment as a "historic milestone"
In the 133rd episode of his radio show Mann Ki Baat, PM Modi, celebrating this feat, noted that the nuclear reactor is built with entirely indigenous technology, stating that this will give new energy to our resolve of Viksit Bharat.
"A few days back, our Nuclear Scientists brought glory to India through a major achievement. In Tamil Nadu's Kalpakkam, the Fast Breeder Reactor has achieved Criticality. This is a stage in which the reactor achieves success in a self-sustaining nuclear reaction for the first time. The stage means the beginning of the reactor's operation phase," PM Modi said.

The criticality was achieved in the presence of Dr Ajit Kumar Mohanty, Secretary, DAE & Chairman, AEC, Shri Sreekumar G Pillai, Director, IGCAR, Shri Allu Ananth, CMD-In-Charge, BHAVINI, and K.V. Suresh Kumar, Former CMD, BHAVINI & Homi Sethna Chair, after meeting all the stipulations of the Atomic Energy Regulatory Board (AERB), which had issued clearance after a rigorous review of safety of the plant systems.
"This is a historic milestone in India's nuclear energy journey. And the big thing is that this nuclear reactor is built with entirely indigenous technology. I congratulate all those who have made invaluable contributions to India's nuclear program. Their efforts to make the lives of countrymen better and easier are really commendable. This will give new energy to our resolve of Viksit Bharat," he added.
In a landmark achievement for India's nuclear energy programme, the 500 MWe Prototype Fast Breeder Reactor (PFBR) has successfully attained first criticality (start of controlled fission chain reaction) on 6th April 2026 at 08:25 PM marking a historic step in providing long-term energy security and advancing indigenous nuclear technology capabilities, according to the Department of Atomic Energy.
The criticality was achieved in the presence of Dr Ajit Kumar Mohanty, Secretary, DAE & Chairman, AEC, Sreekumar G Pillai, Director, IGCAR, Allu Ananth, CMD-In-Charge, BHAVINI and KV Suresh Kumar, Former CMD, BHAVINI & Homi Sethna Chair after meeting all the stipulations of the Atomic Energy Regulatory Board (AERB), which had issued clearance after a rigorous review of safety of the plant systems.
The technology development & design of PFBR was indigenously done by Indira Gandhi Centre for Atomic Research (IGCAR), an R&D Centre of the Department of Atomic Energy, and was built & commissioned by Bharatiya Nabhikiya Vidyut Nigam Ltd (BHAVINI), a PSU under the Department of Atomic Energy.
Fast Breeder Reactors are a cornerstone of India's long-term nuclear strategy. Unlike conventional thermal reactors, the PFBR uses Uranium-Plutonium Mixed Oxide (MOX) fuel.
The core of PFBR is surrounded by a blanket of Uranium-238. Fast neutrons convert fertile Uranium-238 into fissile Plutonium-239, enabling the reactor to produce more fuel than it consumes.
The reactor is designed to eventually use Thorium-232 in the blanket. Through transmutation, Thorium-232 will be converted into Uranium-233, which will fuel the third stage of India's nuclear power programme.
This unique capability significantly enhances the utilisation of nuclear fuel resources and enables the country to extract far greater energy from its limited uranium reserves while also preparing for large-scale use of thorium in the future.
Fast breeder technology forms the vital bridge between the current fleet of pressurised heavy water reactors and the future deployment of thorium-based reactors, leveraging the country's abundant thorium resources for long-term clean energy generation.

Achieving this milestone demonstrates the strength of India's indigenous design, engineering and manufacturing ecosystem. The reactor incorporates advanced safety systems, high-temperature liquid sodium coolant technology and a closed fuel cycle approach that enables recycling of nuclear materials, thereby improving sustainability and reducing waste.