India Achieves Historic Milestone in Nuclear Programme as Prototype Fast Breeder Reactor at Kalpakkam Attains Criticality

In a landmark development for India’s energy security and self-reliance, Prime Minister Narendra Modi announced on Monday that the indigenously designed and built Prototype Fast Breeder Reactor (PFBR) at Kalpakkam in Tamil Nadu has attained criticality, marking a defining step forward in the country’s three-stage civil nuclear programme.

“Today, India takes a defining step in its civil nuclear journey, advancing the second stage of its nuclear programme,” PM Modi posted on X (formerly Twitter). “The indigenously designed and built Prototype Fast Breeder Reactor at Kalpakkam has attained criticality. This advanced reactor, capable of producing more fuel than it consumes, reflects the depth of our scientific capability and the strength of our engineering enterprise. It is a decisive step towards harnessing our vast thorium reserves in the third stage of the programme. A proud moment for India. Congratulations to our scientists and engineers.”

The attainment of criticality — the point at which a nuclear reactor achieves a self-sustaining chain reaction — represents a major technological breakthrough. The 500 MWe PFBR, developed by the Indira Gandhi Centre for Atomic Research (IGCAR) and implemented by BHAVINI (Bharatiya Nabhikiya Vidyut Nigam Ltd), is India’s first indigenous fast breeder reactor. Unlike conventional reactors that consume more fuel than they produce, fast breeder reactors “breed” additional fissile material, making them far more efficient in fuel utilisation.

This milestone advances India into the second stage of its unique three-stage nuclear power programme, originally envisioned by Dr. Homi Bhabha. The first stage, which relies on Pressurised Heavy Water Reactors (PHWRs) using natural uranium, has already reached a level of maturity with multiple operational plants across the country. The second stage employs fast breeder reactors that use plutonium-239 recovered from reprocessed spent fuel of the first stage, combined with natural uranium. The surrounding “blanket” of uranium-238 captures neutrons to produce more plutonium, effectively generating more fuel than consumed.

Crucially, the PFBR paves the way for the third stage, which aims to harness India’s abundant thorium reserves — among the largest in the world — by converting thorium-232 into fissile uranium-233. This stage is expected to provide the country with energy security for centuries, significantly reducing dependence on imported uranium and supporting long-term goals of energy self-reliance and net-zero emissions.

The PFBR project has been years in the making. Construction began in 2004, with core loading witnessed by Prime Minister Modi in March 2024. The Atomic Energy Regulatory Board (AERB) granted permission for the first approach to criticality in 2024, following extensive safety reviews and low-power physics experiments. After overcoming technical challenges typical of first-of-a-kind reactors, the reactor has now achieved this critical operational state.

Experts view the development as a testament to India’s robust nuclear ecosystem. Scientists and engineers at IGCAR and BHAVINI have demonstrated world-class capabilities in handling complex sodium-cooled fast reactor technology, which requires sophisticated engineering to manage liquid sodium coolant and ensure safety.

“India’s three-stage programme is a strategic response to our resource profile — modest uranium but vast thorium deposits,” said a senior Department of Atomic Energy official. “The successful criticality of the PFBR not only validates our indigenous technology but also opens the door for scaling up fast breeder reactors, which will multiply our nuclear power capacity while minimising waste.”

The achievement comes at a time when India is aggressively expanding its clean energy mix to meet growing electricity demand and climate commitments. Nuclear power, being a reliable baseload source with near-zero carbon emissions, forms a vital pillar of this strategy. Once fully operational, the PFBR is expected to generate 500 megawatts of electricity while demonstrating the closed fuel cycle that will be central to future reactors.

The government has hailed the moment as a source of national pride. PM Modi’s message underscores the human element behind the technical success — decades of dedicated work by thousands of scientists, engineers, and technicians who have persevered through delays and challenges to deliver this indigenous marvel.

As India moves closer to commercial deployment of fast breeder technology, plans are already underway for additional FBRs. The success of the PFBR is likely to boost confidence in the programme and attract greater investment in nuclear infrastructure.

This development not only strengthens India’s position in the global nuclear community but also reinforces its commitment to peaceful, self-reliant atomic energy for national development. With the third stage on the horizon, the country edges closer to realising Dr. Bhabha’s vision of a thorium-based nuclear future.

The nation joins Prime Minister Modi in congratulating the scientific community on this proud achievement, which promises cleaner, more abundant energy for generations to come.