India achieved a landmark in its nuclear energy programme on 6 April 2026, when its 500 MWe Prototype Fast Breeder Reactor (PFBR) successfully attained first criticality—the initiation of a controlled nuclear fission chain reaction. This milestone marks a historic step toward ensuring long-term energy security and demonstrates India’s advanced indigenous nuclear technology capabilities. The criticality was achieved after receiving clearance from the Atomic Energy Regulatory Board (AERB), following a rigorous safety review and compliance with all stipulated requirements for plant systems.

The PFBR was indigenously designed and developed by the Indira Gandhi Centre for Atomic Research (IGCAR), a premier R&D institution under the Department of Atomic Energy. The reactor was constructed and commissioned by Bharatiya Nabhikiya Vidyut Nigam Limited (BHAVINI), a public sector enterprise under the same department.

The father of India’s nuclear energy programme, Homi Jehangir Bhabha, envisioned a three-stage nuclear power strategy to maximize the country’s limited uranium resources and leverage its abundant thorium reserves:

Stage 1: Pressurized Heavy Water Reactors (PHWRs) use natural uranium (primarily U-238 with a small fraction of U-235) as fuel.

Stage 2: Fast Breeder Reactors (FBRs) utilize plutonium-239, produced as a byproduct of the first stage, along with uranium-238. In this stage, thorium-232 placed in a blanket surrounding the core is converted into uranium-233.

Stage 3: Uranium-233, along with thorium-derived materials, is used as fuel for advanced reactors, enabling long-term sustainability.

India possesses vast thorium reserves, particularly along the coastal regions of Kerala and the eastern coast.

Fast Breeder Reactors form a cornerstone of India’s long-term nuclear strategy. Unlike conventional thermal reactors, FBRs use uranium-plutonium Mixed Oxide (MOX) fuel. The reactor core is surrounded by a blanket of uranium-238, which absorbs fast neutrons and is converted into fissile plutonium-239. This process allows the reactor to generate more fuel than it consumes. The PFBR is also designed for future use of thorium-232 in its blanket. Through nuclear transmutation, thorium will be converted into uranium-233, which will power the third stage of India’s nuclear programme. This capability significantly enhances fuel utilization and enables India to extract far greater energy from its limited uranium resources.

With the attainment of first criticality, India moves closer to realizing the full potential of its three-stage nuclear power programme. Fast breeder technology serves as a crucial bridge between the current fleet of PHWRs and future thorium-based reactors, enabling long-term, sustainable energy generation.

This achievement highlights the strength of India’s indigenous design, engineering, and manufacturing capabilities. The PFBR incorporates advanced safety systems, high-temperature liquid sodium coolant technology, and a closed fuel cycle that allows recycling of nuclear materials—thereby improving sustainability and reducing waste.

The success of this project also reflects India’s growing expertise in advanced nuclear engineering and reinforces its commitment to technological self-reliance under the vision of Atmanirbhar Bharat (self-dependent India).

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 initiative will support future reactor designs and next-generation nuclear technologies.

As India continues to expand its clean energy portfolio, fast breeder reactors will play a vital role in delivering reliable, low-carbon, base-load power with improved efficiency. The attainment of first criticality is not only a technological milestone but also a significant step toward a sustainable, clean, and self-reliant energy future aligned with the vision of Viksit Bharat (developed India).