CHENNAI, Apr 7 : How a reactor battered by nature and delays finally came alive. On December 26, 2004, the sea came rushing in.
At Kalpakkam, on India’s southeastern coast, waves from the Indian Ocean tsunami surged into a construction site that was meant to house one of the country’s most ambitious scientific projects, the Prototype Fast Breeder Reactor (PFBR). The huge foundation pit flooded. Structures were damaged. Work came to a sudden halt.
For a project that had only just begun, it was a brutal start. More than two decades later, that same site witnessed a very different moment.
At 8:26 pm on Monday, the PFBR achieved criticality, the point at which a controlled, self-sustaining nuclear chain reaction begins.
What was once a flooded construction zone had become the centre of one of India’s most significant nuclear milestones.
The tsunami was only the first of many tests.
Rebuilding required not just repairing damage but rethinking safety. Designs were revisited. Additional safeguards were incorporated. Timelines stretched.
Then came another global shock. The Fukushima nuclear disaster in Japan in 2011 triggered fresh safety reviews across nuclear programmes worldwide, including India’s. The PFBR was no exception.
Each review added layers of complexity,and delay.
Even as construction progressed, technical challenges surfaced. Equipment had to be reworked. Systems recalibrated. Costs climbed steadily.
What was conceived in the early 2000s as a pioneering project was fast becoming a lesson in persistence.
By 2025, the reactor was ready for its final steps-fuel loading and commissioning. But even at this stage, the project resisted closure.
During trial operations, a critical fuel transfer mechanism failed to function as intended. Inside the reactor, liquid sodium-used as a coolant-made direct inspection impossible.
The solution required ingenuity. Engineers devised an alternative fuel handling method and built a new system in-house within months. It was tested, validated, and cleared by regulators.
Fuel loading resumed. The final clearances came from the Atomic Energy Regulatory Board, allowing fuel loading, low-power physics experiments, and the first approach to criticality.
Then came the moment itself. At 8:26 p.m., the reactor crossed the threshold. The chain reaction began-and sustained itself.
For many associated with the project, the news brought a mix of relief and exhilaration.
Their phones lit up. News was exchanged with excitement. Many mused. And sleep was forgotten.
“It is a great feeling. It really took me a long time to sleep after hearing the news,” said Prabhat Kumar, former Chairman and Managing Director of Bharatiya Nabhikiya Vidyut Nigam Ltd (BHAVINI), who had earlier served as the project director.
Prime Minister Narendra Modi described the achievement as a “defining step” in India’s nuclear journey, marking progress in the second stage of the country’s three-phase programme.
The PFBR is not just another nuclear plant-it is central to India’s long-term energy strategy.
Unlike conventional reactors, it is designed to produce more fuel than it consumes. Using uranium-plutonium mixed oxide fuel, it converts Uranium-238 into Plutonium-239.
In the future, it is expected to incorporate thorium, producing Uranium-233-the fuel for the third stage of India’s nuclear programme.
This capability enables a closed fuel cycle and allows India to maximise its limited uranium resources while preparing to tap its vast thorium reserves.
The PFBR is a “Hanuman Jump”-a leap from India’s earlier 13.6 MW Fast Breeder Test Reactor to a full-scale 500 MW system.
The phrase captures both ambition and scale.
Designing and building such a reactor required new approaches in materials, engineering, and safety-many developed indigenously by scientists at the Indira Gandhi Centre for Atomic Research.
Criticality is only the beginning.
The reactor will now undergo a phased increase in power, a process expected to take several months before it reaches full capacity. Each stage will be closely monitored.
Meanwhile, Kalpakkam is set to expand its role. Plans are already underway for two more fast breeder reactors, incorporating lessons from the PFBR.
From a site flooded by a tsunami to a reactor sustaining nuclear fission, the PFBR’s journey has been anything but ordinary.
It has withstood natural disasters, global nuclear crises, technical setbacks, and years of delay.
Yet, it has endured.
Today, as the reactor comes alive, it represents more than an engineering achievement. It stands as a symbol of persistence-and of a nation’s determination to shape its energy future on its own terms.
In that sense, the real story of the PFBR is not just about the moment it went critical.
It is about everything it took to get there.
(UNI)
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