In a statement on X, he said: “Heartiest congratulations to our brilliant scientists and engineers at IGCAR, BHAVINI and the entire Department of Atomic Energy! Your dedication has delivered a historic milestone for India. The indigenously built Prototype Fast Breeder Reactor at Kalpakkam has successfully attained first criticality, a giant leap in our nuclear journey. This 500 MW reactor marks a proud step towards clean, secure energy for generations and brings us closer to harnessing our vast thorium reserves for true energy self-reliance. A proud moment for every Indian! Jai Hind!”

The 500 MW reactor was described by Reddy as a major advancement towards clean and secure energy and a crucial development in utilising India's large thorium reserves to achieve energy self-sufficiency.

On April 6, 2026, at 8:25 PM, the 500 MWe Prototype Fast Breeder Reactor (PFBR) attained first criticality, marking the start of a controlled fission chain reaction. This achievement is a landmark for India's nuclear energy programme, contributing to long-term energy security and advancing indigenous nuclear technology, according to the Department of Atomic Energy.

The criticality event took place in the presence of Dr Ajit Kumar Mohanty, Secretary of the Department of Atomic Energy and Chairman of the Atomic Energy Commission; Sreekumar G Pillai, Director of IGCAR; Allu Ananth, CMD-In-Charge of BHAVINI; and KV Suresh Kumar, former CMD of BHAVINI and Homi Sethna Chair. The plant met all requirements set by the Atomic Energy Regulatory Board (AERB), which granted clearance after a thorough safety review of the reactor systems.

The design and technology development of the PFBR were conducted indigenously by IGCAR, a research and development centre of the Department of Atomic Energy. The reactor was constructed and commissioned by BHAVINI, a public sector unit under the same department.

Fast breeder reactors are central to India's long-term nuclear strategy. Unlike conventional thermal reactors, the PFBR uses Uranium-Plutonium Mixed Oxide (MOX) fuel. Its core is surrounded by a Uranium-238 blanket, whereby fast neutrons convert fertile Uranium-238 into fissile Plutonium-239, allowing the reactor to generate more fuel than it consumes.

The PFBR is designed to eventually employ Thorium-232 in the blanket, which will be transmuted into Uranium-233, to fuel the third stage of India's nuclear power programme. This unique feature substantially improves nuclear fuel resource utilisation, enabling greater energy extraction from limited uranium reserves while preparing for the extensive use of thorium in the future.

With the reactor attaining first criticality, India progresses towards fully realising its three-stage nuclear power programme. Fast breeder technology serves as a vital link between current pressurised heavy water reactors and forthcoming thorium-based reactors, leveraging the country's substantial thorium resources for long-term clean energy generation.

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

The project represents the dedication of numerous scientists, engineers, technicians, and industry partners who contributed to the reactor’s design, fabrication, and construction using primarily indigenous technologies and components. Their efforts demonstrate India's advancing expertise in nuclear engineering and reaffirm the nation's commitment to technological self-reliance in line with the Atmanirbhar Bharat initiative.

Beyond energy production, the fast breeder programme bolsters strategic capabilities in nuclear fuel cycle technologies, advanced materials, reactor physics, and large-scale engineering. The knowledge and infrastructure developed through this programme will aid future reactor designs and next-generation nuclear technologies.

As India expands its clean energy portfolio, fast breeder reactors will play a critical role in providing reliable, low-carbon, base-load power with enhanced thermal efficiency. The attainment of first criticality is both a technological accomplishment and a significant advance towards a sustainable and self-reliant energy future for Viksit Bharat.