India's Kalpakkam Prototype Fast Breeder Reactor Achieves Criticality

India has achieved a major milestone in its civil nuclear program with the successful attainment of 'criticality' by the indigenously developed 500 MWe Prototype Fast Breeder Reactor (PFBR) at Kalpakkam, Tamil Nadu, on April 6, 2026. This event, announced by Prime Minister Narendra Modi, signifies the start of a controlled, self-sustaining nuclear chain reaction and marks a defining step in the second stage of India's three-stage nuclear power program, originally envisioned by Homi J. Bhabha. The PFBR, designed by the India===Indira Gandhi Centre for Atomic Research and built by Department of Atomic Energy===BHAVINI, is a 'breeder' reactor capable of producing more nuclear fuel than it consumes, initially using uranium-plutonium mixed oxide fuel and later transitioning to thorium. This capability is crucial for India's long-term energy security, as it possesses limited uranium but abundant thorium reserves. The achievement places India among a select group of nations, alongside Russia, capable of operating advanced breeder reactors, enhancing its indigenous nuclear technology capabilities and moving towards self-reliance in energy.