India's first Prototype Fast Breeder Reactor (PFBR), located in Kalpakkam, Tamil Nadu, achieved criticality at 8:25 PM on April 6, marking a pivotal moment in the country's nuclear energy journey. This event signifies the transition to the second stage of India's three-stage nuclear program, which aims to create a self-sustaining nuclear cycle. The PFBR is designed to produce more fuel than it consumes, utilizing plutonium-239 extracted from spent fuel of existing reactors. Prime Minister Narendra Modi hailed this as a defining step towards harnessing India's vast thorium reserves, which are the third largest globally. The reactor is expected to begin commercial operations by late 2026 to early 2027, following a series of low-power physics experiments to ensure stability. India's nuclear program, initiated shortly after independence, aims to achieve energy independence, with the third stage focusing on utilizing thorium to produce U-233, thereby reducing reliance on imported fuel.