India’s 500-MWe Prototype Fast Breeder Reactor (PFBR) at Kalpakkam, Tamil Nadu, achieved first criticality on April 6, Prime Minister Narendra Modi announced on X that day. This places India among a small handful of nations operating fast breeder technology at commercial scale, and formally moving the country into the second stage of the three-stage nuclear program first charted by Homi Bhabha in the 1950s. Modi called the milestone “a decisive step towards harnessing our vast thorium reserves” in the third stage of the program, and praised the indigenous design, engineering, and construction effort behind the reactor.
The sodium-cooled reactor was developed by the Indira Gandhi Centre for Atomic Research (IGCAR). It runs on uranium-plutonium mixed-oxide (MOX) fuel reprocessed from the spent fuel of India’s existing pressurized heavy water reactors. A blanket of U-238 surrounds the core, where fast neutrons transmute the fertile isotope into fissile Pu-239—producing more fuel than the reactor consumes.
