What happened: PFBR attained first criticality
The Prototype Fast Breeder Reactor (PFBR), designed and built in India at Kalpakkam in Tamil Nadu by the Department of Atomic Energy ecosystem, attained its first criticality on 6 April 2026. The government also stated that PFBR moved from first criticality to power operations, supporting progress toward scaling the next stage of India’s three-stage nuclear power programme. PFBR is described as the forerunner of the second stage of the programme.
Background: India’s three-stage nuclear power programme (closed fuel cycle)
India’s three-stage nuclear power programme is presented as a route to long-term energy sovereignty using a closed fuel cycle (reprocessing and recycling of nuclear material rather than one-time use). The programme is described in stages as follows:
First stage: Natural uranium is used as fuel in Pressurised Heavy Water Reactors (PHWRs).Fuel transition step: Spent fuel from PHWRs is reprocessed to recover plutonium.Second stage: Fast Breeder Reactors (FBRs) use U-238 breeding to convert plutonium into more fissile plutonium for continued fuel supply.Third stage: After adequate FBR capacity exists, large-scale use of thorium-232 begins by breeding it into uranium-233, with the government-stated plan to use plutonium-239 as an initial driver fuel in breeder reactors.