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The Prototype Fast Breeder Reactor at Kalpakkam, Tamil Nadu attained first criticality on 6 April 2026.
The PFBR is the forerunner of the second stage of Homi Bhabha's three-stage nuclear power programme.
It uses Uranium-Plutonium Mixed Oxide fuel with a Uranium-238 blanket to breed fissile Plutonium-239, generating more fuel than it consumes.
It is India's first commercial fast reactor, with the Indira Gandhi Centre for Atomic Research as principal architect.
Nearly 90 per cent of the reactor's equipment and systems were manufactured domestically.
Homi Bhabha designed the programme in the 1950s around a resource fact: India holds only about 1-2 per cent of the world's uranium but roughly a quarter of its thorium, concentrated in the monazite sands of the southern coast. Thorium, however, is fertile rather than fissile - it cannot sustain a chain reaction by itself and must first be converted into uranium-233. The three stages are the route to that conversion. Stage 1 uses Pressurised Heavy Water Reactors running on natural uranium, which generate electricity and, as a by-product, plutonium. Stage 2 uses that plutonium in Fast Breeder Reactors, which do something unusual: with a blanket of uranium-238 around the core, they breed more fissile plutonium-239 than they consume, and once enough plutonium inventory exists, thorium can be introduced in the blanket and transmuted to uranium-233. Stage 3 then runs a closed thorium-232 / uranium-233 cycle in advanced reactors. The PFBR is the gateway between Stage 1 and Stage 3, which is why its criticality matters far beyond the 500 MW it will supply - without a working breeder, India's thorium reserves remain geology rather than energy.
Simple Analogy: Stage 1 grows the seed, Stage 2 multiplies it into a much larger stock of seed, and only then can Stage 3 plant the vast thorium field India actually owns.
Principal architect of the PFBR, providing the technical foundation across design, materials and sodium technology, equipment qualification, safety assessment and integrated commissioning. It developed in-house computational codes for radiation shielding, thermal hydraulics and reactor physics.
A remote-controlled robotic vehicle developed to inspect critical welds in the interspace between reactor vessels at high temperature, satisfying regulatory requirements.
An advanced ultrasonic tool that allows operators to visualise internal reactor mechanisms through opaque liquid sodium, enabling safe fuel loading.
The parent department, functioning directly under the Prime Minister, of which IGCAR and BARC are constituent units.
GS Paper 3 > Science and Technology: Nuclear Technology, Indigenisation and Developing New Technology
General Awareness > Science and Technology
General Awareness > Science and Current Affairs
General Knowledge > Nuclear Programme
In India, why are some nuclear reactors kept under "IAEA Safeguards" while others are not?
Answer: Some use imported uranium and others use domestic supplies
The three-stage programme and PFBR are among the most repeated science and technology topics in UPSC Prelims.
The point at which a reactor sustains a controlled self-sustaining chain reaction for the first time; PFBR attained it on 6 April 2026.
A reactor that produces more fissile material than it consumes, using fast neutrons and a fertile blanket.
Uranium-Plutonium Mixed Oxide fuel, used in the PFBR core.
Fissile material (U-235, Pu-239, U-233) can sustain fission directly; fertile material (U-238, Th-232) must first be transmuted into a fissile isotope.
IGCAR's remote-controlled robotic vehicle for high-temperature inspection of welds between PFBR reactor vessels.
The mineral in southern India's coastal sands that holds the country's thorium reserves.