India's fast breeder reactor attains criticality: Here's why it matters

India's Prototype Fast Breeder Reactor at Kalpakkam has attained criticality, moving closer to full power generation and advancing the second stage of the country's long-term nuclear energy strategy

India on Monday achieved a key milestone in its civil nuclear programme as the Prototype Fast Breeder Reactor (PFBR) at Kalpakkam in Tamil Nadu attained criticality.

 

Criticality marks the point at which a nuclear reactor sustains a controlled chain reaction, generating energy continuously. The PFBR is now a step away from full-power operations and commercial electricity generation.

 

The 500-megawatt reactor, developed by the Indira Gandhi Centre for Atomic Research (IGCAR), is India’s most advanced nuclear project to date and a crucial element of its long-term atomic energy strategy.

 

What is a fast breeder reactor and how does it work?

 

A fast breeder reactor (FBR) is a type of nuclear reactor that produces more fissile fuel than it consumes. Unlike conventional reactors, which primarily use uranium-235, FBRs use fast neutrons and are typically fuelled by plutonium-239 mixed with uranium.

 

 

The key feature of breeder reactors is their ability to convert non-fissile material, such as uranium-238, into fissile fuel like plutonium-239. This process, known as breeding, allows the reactor to generate additional fuel during operation. 

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In India’s case, the PFBR uses plutonium-based mixed oxide fuel and liquid sodium as a coolant, enabling efficient heat transfer without slowing down neutrons.

 

In 2003, the government approved the creation of Bharatiya Nabhikiya Vidyut Nigam Ltd (BHAVINI) to construct and operate India’s most advanced nuclear reactor, the PFBR.

 

How does a fast breeder reactor differ from conventional reactors?

 

Conventional nuclear reactors, such as pressurised heavy water reactors (PHWRs), use thermal (slow) neutrons and consume more fissile material than they produce. Their fuel cycle is largely linear, requiring a steady supply of enriched uranium.

 

In contrast, fast breeder reactors operate with fast neutrons and have a closed fuel cycle. They can reuse spent fuel and significantly extend the energy extracted from uranium resources.

 

FBRs also reduce nuclear waste by burning long-lived actinides, though they involve greater technological complexity, including the handling of liquid sodium coolant.

 

Which countries currently operate fast breeder reactors?

 

Fast breeder reactor technology has been pursued by several countries, but only a few have achieved sustained operations.

 

Russia is currently the global leader in operational FBRs, with reactors such as BN-600 and BN-800 in commercial use. China has also made progress with its CFR-600 fast reactor.

 

France, Japan and the United States have experimented with breeder reactors in the past, but many programmes were scaled down due to cost, safety concerns or policy shifts. 

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India remains among a small group of countries pursuing a full-scale breeder reactor programme as part of its long-term nuclear strategy.

 

Why does PFBR criticality matter for India’s energy sector?

 

The PFBR is central to India’s three-stage nuclear power programme, which aims to maximise the use of the country’s limited uranium reserves and vast thorium resources.

 

In the second stage of this programme, breeder reactors generate plutonium, which can be used to fuel more advanced reactors. This eventually supports the third stage, focused on thorium-based reactors, where India holds a significant resource advantage.

 

By enabling fuel recycling and improving resource efficiency, breeder reactors can reduce India’s dependence on imported uranium and fossil fuels.

 

They also offer a pathway to stable, low-carbon baseload power, supporting the country’s climate commitments and growing electricity demand.

 

What happens next after PFBR attains criticality?

 

Following criticality, the PFBR will undergo a series of tests before reaching full power generation. Once operational, it is expected to pave the way for additional breeder reactors in India.

 

Prime Minister Narendra Modi described the development as a defining moment in India’s nuclear journey. “Today, India takes a defining step in its civil nuclear journey, advancing the second stage of its nuclear programme,” he said. “The indigenously designed and built Prototype Fast Breeder Reactor at Kalpakkam has attained criticality.”