Kalpakkam Prototype Fast Breeder Reactor Attains Criticality
India's Prototype Fast Breeder Reactor (PFBR) at Kalpakkam, Tamil Nadu achieved criticality on April 6, 2026 — the point at which a sustained nuclear chain reaction is first initiated.
Prime Minister Narendra Modi announced and congratulated scientists, calling it a "defining step" in India's civil nuclear journey.
The achievement formally marks India's entry into the second stage of its three-stage nuclear power programme conceived by physicist Homi Bhabha.
Once fully operational, India will become only the second country in the world after Russia to have a commercially operating Fast Breeder Reactor.
The PFBR is a 500 MWe sodium-cooled pool-type reactor, designed and developed indigenously by the Indira Gandhi Centre for Atomic Research (IGCAR) at Kalpakkam.
India's Three-Stage Nuclear Power Programme
India's three-stage nuclear programme was conceived by physicist Homi Jehangir Bhabha in the 1950s to achieve long-term energy independence by leveraging India's abundant thorium reserves. India holds approximately 25% of global thorium reserves but only 1–2% of global uranium reserves — this asymmetry drove the programme's design.
The PFBR achieving criticality operationalises Stage 2 for the first time, transitioning India from being purely a uranium-dependent nuclear state to one that can breed its own fissile fuel — a critical step toward thorium-based energy self-reliance.
Fast Breeder Reactor Technology
A Fast Breeder Reactor (FBR) uses fast neutrons (unlike conventional reactors that use moderated/slow neutrons) to both sustain fission and transmute fertile material (uranium-238, thorium-232) into fissile fuel (plutonium-239, uranium-233). The term "breeder" denotes that it produces more fissile material than it consumes, with a breeding ratio greater than 1.
Achieving criticality confirms all reactor systems — fuel, coolant circulation, control rods, instrumentation — are functioning as designed, enabling controlled self-sustaining fission for the first time.
Nuclear Energy and India's Energy Security
India's installed electricity generation capacity has grown substantially, but the country remains heavily dependent on coal (~70% of generation). Nuclear power (~3% share) is seen as a low-carbon baseload alternative aligned with India's climate commitments (Net Zero by 2070). The Atomic Energy Act, 1962 governs all nuclear activities in India, and the Atomic Energy Regulatory Board (AERB) provides safety oversight.
The PFBR's criticality is a prerequisite for India to eventually close its nuclear fuel cycle with thorium, reducing dependence on imported uranium and significantly expanding domestic nuclear capacity at scale.
- Reactor name: Prototype Fast Breeder Reactor (PFBR)
- Location: Kalpakkam, Tamil Nadu (co-located with Madras Atomic Power Station)
- Capacity: 500 MWe electrical; 1,250 MWt thermal
- Coolant: Liquid sodium (pool-type LMFBR)
- Fuel: Mixed Oxide (MOX) — uranium dioxide + plutonium dioxide
- Designer: IGCAR (Indira Gandhi Centre for Atomic Research), Kalpakkam
- Operator: BHAVINI (Bharatiya Nabhikiya Vidyut Nigam Ltd.), under DAE
- Fuel fabrication: AFFF, Tarapur (under BARC)
- Project cost: ~₹7,700 crore (escalated from original ₹3,500 crore)
- Fuel loading start: October 18, 2025
- Criticality achieved: April 6, 2026
- Commercial operations target: September 2026
- Global status: India to become 2nd country (after Russia) with a commercially operating FBR
- India's thorium reserves: ~25% of global known reserves
- Three-stage programme conceived by: Homi Jehangir Bhabha, 1950s
- BHAVINI established: October 2003