India’s nuclear leap: Indigenous fast breeder reactor goes critical
An incident that happened on Monday night (6th April 2026) was totally ignored by the mainstream media in India. And it is surprising. Around 8 PM. India’s 500 MWe prototype fast breeder reactor, coming up at Kalpakkam, 70 km north of Chennai, went critical, and this was announced to the outside world by none other than Prime Minister Narendra Modi via his social media page.
Today, India takes a defining step in its civil nuclear journey, advancing the second stage of its nuclear programme.
The indigenously designed and built Prototype Fast Breeder Reactor at Kalpakkam has attained criticality.
This advanced reactor, capable of producing more fuel…
— Narendra Modi (@narendramodi) April 6, 2026
With the fast breeder reactor becoming operational, India became the second country in the world to possess this technology developed fully indigenously by the desi engineers and scientists.
For those who are not familiar with terms like “critical” and “breeder reactor”, this development could be explained as follows. “Nuclear reactors operate on the basis of a self-sustaining chain reaction. To attain this state, the neutron population in the reactor core must remain steady; that is, the rate of neutron production through the fission process must equal the rate of neutron absorption. When this equilibrium is attained, the reactor is said to have attained criticality. Going “critical” also means that a steady rate of power output has been achieved. (The Upside Down Book of Nuclear Power by Saurav Jha, Page 120).
The reactor, the groundwork of which was commenced in 2004, saw many ups and downs during the construction phase. What makes this reactor unique is that it is fully built indigenously without any outside help. The special steel with which the reactor vault/ vessel has been built was designed and fabricated by the late Baldev Raj, noted metallurgist and nuclear engineer.
Another specialty of the fast breeder reactor is that it breeds more fuel than it consumes. With the FBR going critical, India has entered the second stage of the three-phase nuclear program devised and developed by Dr Homi Bhabha, described as the founding father of the nation’s atomic energy program.
Reactors across the world operate with uranium as fuel. But the uranium available in India is of very low quality, and the nation was at the mercy of the USA, France, and Russia for fissile quality uranium with which reactors operate. It was to surmount this handicap that Bhabha developed the three-stage program. He visualized reactors fuelled by thorium, which are available in plenty along the seashore of South India. But thorium could not be used straight away as reactor fuel. Hence, Bhabha built a reactor that could be fueled by naturally available uranium. This uranium, once used as fuel, gets converted into plutonium, which could be recovered from the spent fuel. The second-generation reactors could be fueled by plutonium. The core of the reactor, where the uranium rods are inserted, is covered by thorium. Once this blanket of uranium is bombarded with neutrons, plutonium is generated inside the reactor itself, and this is used as fuel for the fast breeder reactor.
The plutonium generated inside the reactor when used as fuel generates power and more plutonium than what it consumes, and this is known as a breeder reactor. The best way to explain how the FBR works is to borrow the words of Dr Baldev Raj (who is unfortunately not with us anymore). “It is like filling a car with petrol and driving from Chennai to Kochi. You need not fill the tank again because as you drive, more petrol would be generated in the tank”.
Once the FBR starts commercial power generation, India need not worry about fuel to fire the reactor because it would generate more fuel than what it consumes. Hitherto, India was at the mercy of nuclear powers for its quota of fissile uranium and had to pay an exorbitant price for the same. Not anymore. The country is on the verge of becoming self-reliant in its nuclear fuel requirement. And there is yet another icing on the cake. India is the second country in the world, after Russia, to develop its own fast breeder reactor.
There is a big saga behind India’s evolution as a nuclear power, and that too from scratch. When the Madras Atomic Power Station at Kalpakkam was being built, scientists from France were taken aback by the sight of head-load workers walking to the site carrying baskets filled with concrete mix on their heads. “They told us that it would take more than 100 years for us to build the reactor because there were no concrete mixing machines or JCBs to speed up the work. Still, we succeeded in executing the work as scheduled by the planners,” S C Chetal, former director, Indira Gandhi Centre for Atomic Research (IGCAR) at Kalpakkam, had told this writer.
Engineers of BHAVINI (Bharatiya Nabhikya Vaidyut Nigam Limited), the company under the Department of Atomic Energy tasked with building and operating fast breeder reactors, are confident of constructing the new Gen reactors in less than ten years.
Prof Anand Ranganathan, scientist and author, is of the view that the Prime Minister’s statement on nuclear dreams is the most heartening announcement in recent times. “India’s goal of 500 GW clean power cannot be realized without nuclear energy. A single nuclear plant powers 700,000 homes while emitting less CO₂ than a hybrid car. Climate change is real. But activism must be rescued from the talons of the loony Left,” said Prof Ranganathan in a social media message. He also pointed out that there are 58 nuclear power plants in France and nuclear energy constitutes 71.7 percent of that country’s total power production. India has just 22 reactors, and nuclear power constitutes less than 3 percent of its total power output. “A push for developed India is incomplete without a push for nuclear. India has set a target of 500 GW clean and green energy by 2030, and we should raise the share of nuclear power to 15 percent,” said Prof Ranganathan.
Perhaps one of the most heartening announcements to have come out in recent times is @narendramodi‘s push for nuclear. India’s goal of 500 GW clean power cannot be realised without it.
A single nuclear plant powers 700,000 homes while emitting less CO₂ than a hybrid car.… pic.twitter.com/lwf5z6VjRh
— Anand Ranganathan (@ARanganathan72) April 7, 2026
Last but not least, the 3rd stage of India’s nuclear program will see the reactors using thorium, which will generate energy as well as uranium, the process of generating more fuel than what is consumed by the mother reactors.
Watch out world, India is coming… Full-scale research is on at Bhabha Atomic Research Centre, Trombay, to develop Advanced High Temperature Reactor Technology.
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2. The views expressed here are those of the author and do not necessarily represent or reflect the views of PGurus.
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