Thursday 09 / April / 2026
New Delhi: In a landmark achievement for India's nuclear energy programme, the 500 MWe Prototype Fast Breeder Reactor (PFBR) has successfully attained first criticality (start of controlled fission chain reaction) on 6th April 2026 at 08:25 PM marking a historic step in providing long-term energy security and advancing indigenous nuclear technology capabilities, according to the Department of Atomic Energy.
The criticality was achieved in the presence of Dr Ajit Kumar Mohanty, Secretary, DAE & Chairman, AEC, Sreekumar G Pillai, Director, IGCAR, Allu Ananth, CMD-In-Charge, BHAVINI and KV Suresh Kumar, Former CMD, BHAVINI & Homi Sethna Chair after meeting all the stipulations of the Atomic Energy Regulatory Board (AERB), which had issued clearance after a rigorous review of safety of the plant systems.
The technology development & design of PFBR was indigenously done by Indira Gandhi Centre for Atomic Research (IGCAR), an R&D Centre of the Department of Atomic Energy, and was built & commissioned by Bharatiya Nabhikiya Vidyut Nigam Ltd (BHAVINI), a PSU under the Department of Atomic Energy.
Fast Breeder Reactors are a cornerstone of India's long-term nuclear strategy. Unlike conventional thermal reactors, the PFBR uses Uranium-Plutonium Mixed Oxide (MOX) fuel.
The core of PFBR is surrounded by a blanket of Uranium-238. Fast neutrons convert fertile Uranium-238 into fissile Plutonium-239, enabling the reactor to produce more fuel than it consumes.
The reactor is designed to eventually use Thorium-232 in the blanket. Through transmutation, Thorium-232 will be converted into Uranium-233, which will fuel the third stage of India's nuclear power programme.
This unique capability significantly enhances the utilization of nuclear fuel resources and enables the country to extract far greater energy from its limited uranium reserves while also preparing for large-scale use of thorium in the future.
With the achievement of first criticality, India moves closer to realizing the full potential of its three-stage nuclear power programme.
Fast breeder technology forms the vital bridge between the current fleet of pressurized heavy water reactors and the future deployment of thorium-based reactors, leveraging the country's abundant thorium resources for long-term clean energy generation.
Achieving this milestone demonstrates the strength of India's indigenous design, engineering and manufacturing ecosystem.
The reactor incorporates advanced safety systems, high-temperature liquid sodium coolant technology and a closed fuel cycle approach that enables recycling of nuclear materials, thereby improving sustainability and reducing waste.
The project also reflects the dedication of significant number of scientists, engineers, technicians and industry partners who have contributed to the design, fabrication and construction of the reactor using predominantly indigenous technologies and components.
Their efforts highlight the nation's growing capability in advanced nuclear engineering and reinforce India's commitment to technological self-reliance complying with Atmanirbhar Bharat.
Beyond energy generation, the fast breeder programme strengthens strategic capabilities in nuclear fuel cycle technologies, advanced materials, reactor physics and large-scale engineering. The knowledge and infrastructure developed through this programme 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 crucial role in delivering reliable, low-carbon, base-load power with higher thermal efficiency.
Fast breeder reactors use both plutonium and uranium. The uranium is converted further into plutonium, too.
“One bonus of this type of system is that it can increase nuclear fuel reserves enormously, by in theory making use of ‘all of the uranium’ [via plutonium conversion] rather than just a small part of it,” he said.
“The technology can also be tweaked towards thorium systems, and there is meant to be more thorium out there in the earth than uranium, providing a further huge boost in the amount of nuclear fuel,” he explained.
Globally, thorium reserves are four times larger than uranium reserves.
And in India, this equation is even more loaded: The country is home to about 1-2 percent of the world’s uranium, but has more than 25 percent of the world’s thorium.
How do the vast thorium reserves help India?
The construction of the PFBR officially began in 2004 after multiple delays. But its importance was highlighted by the country’s scientists much earlier.
An October 1996 report written by Indian scientists Shivram Baburao Bhoje and Perumal Chellapandi for the International Atomic Energy Agency said that the fast reactor programme was important in India because of the country’s growing and continuous demand for electricity.
India is the world’s third-largest energy guzzler, after China and the United States. With the world’s largest population and a fast-growing economy, India’s energy consumption is only expected to grow further.
As the US-Israel war on Iran and its impact on global energy prices have demonstrated, a continuing overwhelming dependence on fossil fuels poses a risk to economies like India’s.
At the moment, nuclear energy represents only 3 percent of the country’s energy mix, but India wants to raise that dramatically, from 8,180MW in 2024 to 100GW by 2047.
That’s where the three-stage nuclear programme and thorium fit in.
In the second stage, the fast breeder reactors use uranium and the plutonium waste from heavy water reactors to generate electricity. They also produce more plutonium and a lighter isotope of uranium called uranium-233, which is ready, fissile material that can be used as fuel in third-stage reactors.
Those third-stage reactors, once designed, would be thorium-based. They would be fed with thorium – which India has in abundance – and uranium-233. The waste those reactors would produce, also uranium-233, would be fed back as fuel for the reactors.
Once India accomplishes its three-stage process, it would, in effect, be able to reduce its need for naturally found uranium significantly, and instead use thorium for much of its nuclear energy needs.
Why does this matter to the rest of the world?
Other countries – including the US, France, United Kingdom, Japan, China and Russia – have worked on fast breeder reactor technology.
But until now, only Russia has a commercial fast breeder reactor.
If India is able to turn the success of its prototype reactor into a commercial nuclear-energy-generating model, it could inspire other countries to follow suit.
Yet Koroush Shirvan, a professor in the Department of Nuclear Science and Engineering at the Massachusetts Institute of Technology (MIT), cautioned against overemphasising India’s achievement.
He pointed out that it took India more than 20 years since the start of the construction of the reactor to achieve this milestone.
“China recently also built a slightly larger plutonium fast breeder reactor in only six years,” he said. “India needs to scale its nuclear energy programme much faster if it wants it to make meaningful impact in their energy sector.”
Ramana said that globally, nuclear energy is declining in importance and the share of electricity from nuclear reactors has come down from 17.5 percent in 1996 to only 9 percent in 2024. He noted that in contrast, modern renewables, not including power from large hydroelectric dams, produced 17.3 percent of the world’s electricity, up from around one percent in the mid 1990s.
“If anything, the high cost and the lengthy delay in bringing the PFBR to criticality, should serve as a lesson to the rest of the world not to waste their time and resources on fast breeder reactors,” he said.
