India's Prototype Fast Breeder Reactor achieves first criticality, entering stage 2 of nuclear programme

BHAVINI / IGCAR (India DAE)/Prototype Fast Breeder Reactor (PFBR), Kalpakkam

The Prototype Fast Breeder Reactor attained first criticality on 6 April 2026 at 8:25 PM IST, initiating a sustained nuclear chain reaction. This milestone marks India's official entry into stage 2 of its three-stage nuclear fuel cycle programme, which envisions eventual use of the nation's substantial thorium reserves.

• First criticality achieved on 6 April 2026 at 8:25 PM IST after careful fuel loading and control.
• PFBR is a 500 MWe sodium-cooled fast breeder reactor burning mixed uranium-plutonium oxide fuel.
• Fast breeder technology enables plutonium-239 to be bred from uranium-238, multiplying usable fuel.
• Stage 2 achievement brings India closer to stage 3, when thorium-based fuel cycles will provide long-term energy security.
• Reactor will now undergo low-power testing and gradual power escalation toward full 500 MWe operation.