India’s Nuclear Leap: Kalpakkam’s Fast Breeder Reactor Attains First Criticality
New Delhi, April 7, 2026 — Marking a monumental achievement in India’s quest for long-term energy security, the 500 MWe Prototype Fast Breeder Reactor (PFBR) at Kalpakkam, Tamil Nadu, has successfully attained its first criticality. This historic event—the start of a controlled fission chain reaction—occurred on the evening of April 6, 2026, at 8:25 PM.
The breakthrough signifies a massive step forward in advancing India’s indigenous nuclear technology capabilities and operationalizing the crucial second stage of the nation’s ambitious three-stage nuclear power programme.
A Masterpiece of Indigenous Engineering
The criticality was achieved following rigorous safety reviews and clearance from the Atomic Energy Regulatory Board (AERB). The event was witnessed by top officials, including Dr. Ajit Kumar Mohanty, Secretary, DAE & Chairman, AEC, and senior leadership from the Indira Gandhi Centre for Atomic Research (IGCAR) and Bharatiya Nabhikiya Vidyut Nigam Ltd (BHAVINI).
The technology, development, and design of the PFBR were indigenously executed by IGCAR, an R&D arm of the Department of Atomic Energy (DAE). The reactor was subsequently built and commissioned by BHAVINI.
Producing More Fuel Than It Consumes
Fast Breeder Reactors (FBRs) form the cornerstone of India’s long-term nuclear strategy. Unlike conventional thermal reactors, the PFBR uniquely utilizes Uranium-Plutonium Mixed Oxide (MOX) fuel.
The core of the reactor is surrounded by a “blanket” of Uranium-238. Through the interaction with fast neutrons, the fertile Uranium-238 is converted into fissile Plutonium-239. This specific mechanism enables the reactor to effectively produce (or “breed”) more fuel than it actually consumes during operation.
The Bridge to Thorium
Furthermore, the Kalpakkam reactor is designed to eventually incorporate Thorium-232 into its blanket. Through the process of transmutation, this Thorium-232 will be converted into Uranium-233. This Uranium-233 is the vital fuel required for the third and final stage of India’s nuclear power programme.
By successfully bridging the gap between the current fleet of pressurized heavy water reactors and future thorium-based models, the PFBR maximizes the extraction of energy from India’s limited uranium reserves while simultaneously laying the groundwork for the large-scale exploitation of the country’s vast, naturally occurring thorium deposits.
The successful first criticality of the PFBR is a testament to the “Atmanirbhar Bharat” vision, proving the strength of India’s indigenous design, engineering, and manufacturing ecosystem in delivering reliable, low-carbon, baseload power.