India has entered the second stage of its nuclear power programme as the Prototype Fast Breeder Reactor (PFBR) at Kalpakkam achieves first criticality. Fully indigenous and powered by plutonium-based fuel, the reactor is designed to generate more fuel than it consumes — a key step toward long-term energy security and sustainability. With this milestone, India joins a select group of nations that have mastered fast breeder reactor technology. NDTV’s Science Editor Pallava Bagla had earlier gained rare access to this high-security facility. Here’s his exclusive ground report from Kalpakkam.