India’s 500 MWe Prototype Fast Breeder Reactor (PFBR) at Kalpakkam in Tamil Nadu attained first criticality — the start of a controlled nuclear fission chain reaction — on April 6 at 8.25 pm.
The Department of Atomic Energy (DAE) said the development marks a significant step towards strengthening India’s long-term energy security and advancing indigenous nuclear technology capabilities.
The criticality was achieved in the presence of DAE Secretary and Atomic Energy Commission Chairman Ajit Kumar Mohanty, Indira Gandhi Centre for Atomic Research (IGCAR) Director Sreekumar G. Pillai, BHAVINI CMD-in-charge Allu Ananth, and former BHAVINI CMD K.V. Suresh Kumar, who holds the Homi Sethna Chair.
The milestone was reached after meeting all stipulations set by the Atomic Energy Regulatory Board (AERB), which granted clearance following a detailed review of the plant’s safety systems.
The PFBR’s technology development and design were carried out indigenously by the Indira Gandhi Centre for Atomic Research, a research and development centre under the Department of Atomic Energy. The reactor was constructed and commissioned by Bharatiya Nabhikiya Vidyut Nigam Ltd (BHAVINI), a public sector undertaking under the department.
Fast breeder reactors form a key component of India’s long-term nuclear power strategy. Unlike conventional thermal reactors, the PFBR uses uranium-plutonium mixed oxide (MOX) fuel. Its core is surrounded by a blanket of uranium-238, where fast neutrons convert the fertile uranium into fissile plutonium-239, enabling the reactor to generate more fuel than it consumes.
The reactor is also designed to eventually use thorium-232 in the blanket. Through transmutation, thorium-232 can be converted into uranium-233, which will serve as fuel for the third stage of India’s nuclear power programme.
According to the DAE, this capability enhances the utilisation of nuclear fuel resources and allows India to extract significantly more energy from its limited uranium reserves while preparing for the future large-scale use of thorium.
With the reactor achieving first criticality, India moves closer to realising the full potential of its three-stage nuclear power programme. Fast breeder technology is considered a crucial bridge between the existing fleet of pressurised heavy water reactors and the planned deployment of thorium-based reactors.
The PFBR incorporates advanced safety systems, high-temperature liquid sodium coolant technology and a closed fuel cycle approach that allows the recycling of nuclear materials, improving sustainability and reducing waste.
The project involved the contributions of a large number of scientists, engineers, technicians and industry partners in the design, fabrication and construction of the reactor, most of it based on indigenous technologies and components.
The fast breeder programme is also expected to strengthen India’s capabilities in nuclear fuel cycle technologies, advanced materials, reactor physics and large-scale engineering, while supporting future reactor designs and next-generation nuclear technologies.
Officials said fast breeder reactors will play an important role in expanding India’s clean energy capacity by providing reliable, low-carbon base-load power with higher thermal efficiency, marking a significant step towards a sustainable and self-reliant energy future.
