In a landmark achievement for India’s nuclear energy programme, the 500 MWe Prototype Fast Breeder Reactor (PFBR) at Kalpakkam has successfully attained first criticality, the start of a controlled fission chain reaction, on April 6, 2026, at 08:25 PM, marking a historic step towards long-term energy security and advancement of indigenous nuclear technology capabilities.
Indigenous design and execution
The technology development and design of the PFBR were carried out indigenously by the Indira Gandhi Centre for Atomic Research (IGCAR), an R&D centre of the Department of Atomic Energy. The reactor was built and commissioned by Bharatiya Nabhikiya Vidyut Nigam Ltd (BHAVINI), a PSU under the Department of Atomic Energy.
Cornerstone of India’s three-stage nuclear programme
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 reactor core is surrounded by a blanket of Uranium-238, where fast neutrons convert fertile Uranium-238 into fissile Plutonium-239, enabling the reactor to produce more fuel than it consumes.
The reactor is also designed to eventually utilise 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.
Enhanced fuel efficiency and resource utilisation
This unique capability significantly enhances the utilisation of nuclear fuel resources, enabling India to extract far greater energy from its limited uranium reserves while preparing for large-scale use of thorium in the future.
Bridging present and future reactor technologies
With the achievement of first criticality, India moves closer to realising the full potential of its three-stage nuclear power programme. Fast breeder technology serves as a 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.
Advanced safety and sustainable technology
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, improving sustainability and reducing waste.
Collective scientific and industrial effort
The project reflects the dedication of a significant number of scientists, engineers, technicians, and industry partners who contributed to the design, fabrication, and construction of the reactor using predominantly indigenous technologies and components. Their efforts highlight the nation’s growing capability in advanced nuclear engineering and reinforce India’s commitment to technological self-reliance in line with Atmanirbhar Bharat.
Strengthening strategic and technological capabilities
Beyond energy generation, the fast breeder programme strengthens India’s strategic capabilities in nuclear fuel cycle technologies, advanced materials, reactor physics, and large-scale engineering. The knowledge and infrastructure developed through this programme will support future reactor designs and next-generation nuclear technologies.