After more than two decades of arduous scientific research, India has achieved one of the most significant milestones in its civil nuclear program. The Prototype Fast Breeder Reactor (PFBR) in Kalpakkam, Tamil Nadu, has reached initial criticality, which is the establishment of a sustained nuclear fission reaction.
With this, India moves decisively into the second stage of its three-stage nuclear power plan, a concept initially articulated by Dr Homi J Bhabha, the Father of India's Atomic Program, more than half a century ago.
Dr Sreekumar G Pillai, Director of the Indira Gandhi Centre for Atomic Research (IGCAR), Kalpakkam, described the achievement as historic, saying it signifies much more than the commissioning of a reactor.

The large pink-colored building next to the Bay of Bengal houses a major technological accomplishment, which NDTV witnessed during rare access to the facility.
"This attainment of the first criticality of the Prototype Fast Breeder Reactor is a defining milestone in India's nuclear power programme," Dr Pillai said to NDTV. "It represents the realisation of visionary three-stage nuclear programme conceived by Dr Bhabha, aimed at ensuring long-term energy security through optimal utilisation of limited uranium and vast thorium resources."
The PFBR, located in Kalpakkam, is the country's first commercial-scale fast breeder reactor and one of only a handful such reactors running worldwide. With Russia being the only other country operating a commercial fast breeder reactor in Yekaterinburg, India has now joined an incredibly exclusive technological club.

A Project Based on Institutional Memory.
The PFBR is the result of a decades-long institutional effort by scientists, engineers, and politicians. Dr. Pillai attributed the achievement to continuous political and scientific leadership.This feat was made possible by the Government of India's ongoing assistance and direction," he stated. "The leadership of Prime Minister Narendra Modi ji and the proactive role of the Prime Minister's Office have ensured policy continuity, strategic direction and timely decision making."
He also praised Dr. Jitendra Singh, Minister of State for Atomic Energy, for improving programme execution and thanked the contributions of former and present Department of Atomic Energy officials.

"The scientific leadership of Dr Ajit Kumar Mohanty has been instrumental in guiding the Department of Atomic Energy towards advanced reactor deployment and closure of the second-stage fuel cycle," Pillai stated. "The visionary contributions of Dr Anil Kakodkar were fundamental in shaping and advancing the fast breeder reactor programme."
Why Did It Take 20 Years?
The PFBR project has frequently been referred to as delayed. Dr. Pillai disagrees, describing the journey as a necessary learning curve."We've been waiting for this moment for 10 to 15 years," he explained. "There were a number of difficulties which we faced, mainly with respect to handling sodium at high temperature, materials reliability, control systems and sensors which had to be developed for a high-temperature sodium environment."

Fast breeder reactors employ liquid sodium as a coolant. It efficiently transfers heat but reacts strongly with water and air, necessitating high engineering precision.Dr Pillai added that this was the first time such equipment has been designed and operated on this size in the country. "It required elaborate testing and generation of data where no past experience was available."
The commissioning phase took longer than expected. "During testing, we had to generate a lot of data. This data is not available in the international literature and cannot be obtained from any other reactor," he stated.
Far from being a setback, Dr. Pillai described the experience as great learning. "I would call it a learning experience. It has produced information that is unique to India.

Fast and Breeder Explained Simply
The PFBR is a technological advancement from India's first-stage reactors, the Pressurised Heavy Water Reactors (PHWRs), which are the foundation of the country's nuclear fleet."In the first stage, PHWRs use natural uranium," Dr Pillai explained. "During operation, they also produce plutonium-239, which is not available naturally."
The plutonium is reprocessed and utilised as fuel in the fast breeder reactor.Fast reactors use a fast neutron spectrum. "The neutrons are not slowed down," he stated. "The unique advantage is that the reactor produces more fissile material than what is fed into it."
This is why it's called a breeder reactor.

"The breeding ratio is greater than one," Dr Pillai explained. "What you feed into the reactor, you get more Plutonium out of it."
To a layperson, the concept seems almost mystical. "Burning fuel can result in excess fuel."It is real," Dr Pillai stated. "With the current oxide fuel, we anticipate a breeding ratio of 1.03 to 1.05." It may be considerably greater with the development of metallic fuels."
The Closed Fuel Cycle Advantage
India's success with rapid breeders stems from its understanding of the closed fuel cycle."Plutonium does not occur naturally," Dr Pillai stated. "All thermal reactors produce plutonium, but only countries that reprocess spent fuel can use it for fast breeder reactors.""We started reprocessing activities in the early 1960s," Dr. Pillai explained. "From Trombay to Tarapur and Kalpakkam, we have matured the PUREX process and scaled it up."
India now has sufficient reprocessing capability to support the PFBR and future fast reactors."There is no issue with plutonium availability," he stated. "The PFBR itself will generate enough spent fuel to support FBR-1 and FBR-2."
Safety and Regulation
Fast reactors use liquid sodium, which typically raises safety problems. Dr. Pillai provided categorical comfort."IGCAR has decades of experience in handling sodium," he stated. "We have developed sensors, materials and special powders to mitigate risks."
The PFBR adheres to the defense-in-depth doctrine, which is employed globally in nuclear safety. "There are multiple layers of containment to ensure sodium remains within the system," he said.
India's Atomic Energy Regulatory Board played an important role. "There were no international safety codes available for fast reactors at this scale," Pillai added. "AERB was fully involved in developing safety guides and regulatory requirements."

What Comes Next?
With first criticality attained, the reactor will now undergo physics tests and incremental power increases under regulatory supervision. "It may take six to eight months to reach commercial power production," Pillai said.
Preparations for two additional fast breeder reactors, FBR-1 and FBR-2, at Kalpakkam are already underway. "All lessons learned from PFBR will be incorporated," he stated. "This will significantly reduce construction and commissioning time."

Gateway to Thorium and Energy Independence.
Perhaps the most deep relevance of PFBR is in what it permits next. India has minimal uranium but large thorium deposits. "When thorium is used as a blanket material in fast breeder reactors, it produces uranium-233," Dr Pillai said. "That is the fuel for the third stage."
This makes PFBR a critical link to India's long-term energy destiny. "Yes, this milestone will help India attain energy independence in the long run," he replied.
The PFBR is frequently referred to as the 'Akshay Patra of Energy', a mythological vessel of limitless nourishment. Dr. Pillai concurred.In an era of climate change, PFBR provides low-carbon baseload electricity. "This is a stepping stone towards achieving net zero by 2070," Pillai added.
As India commemorates this scientific milestone, the accomplishment honours decades of perseverance, institutional memory, and belief in an indigenous technological path. Dr. Bhabha's dream has moved decisively closer to becoming a reality. Pillai claims that after we perfect the breeder reactor, we will be energy independent for the next several centuries.