The Prototype Fast Breeder Reactor (PFBR) is a 500 MWe nuclear reactor, a type of advanced nuclear system that generates electricity while producing more fissile fuel than it consumes. Located at Kalpakkam, Tamil Nadu, it was designed by the Indira Gandhi Centre for Atomic Research (IGCAR) and constructed by Bharatiya Nabhikiya Vidyut Nigam Limited (BHAVINI). The PFBR is the crucial second stage of India's three-stage nuclear power programme, a vision conceived by Dr. Homi J. Bhabha to ensure long-term energy security. The reactor solves the problem of India's limited uranium reserves by enabling the eventual utilization of its vast Thorium-232 reserves.
The reactor operates using Uranium-Plutonium Mixed Oxide (MOX) fuel and is cooled by liquid sodium. The "breeding" mechanism involves a blanket of fertile material, initially Uranium-238, surrounding the core. This blanket absorbs fast neutrons to transmute into fissile Plutonium-239, thus generating new fuel. The PFBR connects directly to the first stage, which uses Pressurized Heavy Water Reactors (PHWRs) to produce the plutonium used as its fuel. Most recently, the PFBR achieved first criticality on April 6, 2026, marking India's official entry into the second stage. This milestone paves the way for the third stage, which will use the bred Uranium-233 and Thorium-232 in Advanced Heavy Water Reactors (AHWRs).