On 7 April 2026 the Indian government announced that the Prototype Fast Breeder Reactor (PFBR) reached criticality. The 500 MWe reactor is located at Kalpakkam.

Reactor construction began over 20 years ago, in 2004, with a plan to begin operation in 2010 but it has experienced recurring delays. In March 2024 the operator began loading fuel in the reactor. In August 2025 the Department of Atomic Energy announced that the criticality would be achieved in March 2026.

In 2026, India's Parliamentary Standing Committee on Science and Technology, Environment, Forests and Climate Change noted that the cost of the breeder reactor project was now estimated to be over twice the initial planned cost: ₹8,181 crore, compared with an original cost of estimate of ₹3,492 crore. (In purchasing power parity terms, the costs are $3.9 billion and $1.7 billion.)

The Committee also noted that 'fast reactor fuel cycle facility' (FRFCF) to reprocess the breeder's spent fuel was originally to be ready to operate in 2014 but it was now expected to be commissioned in December 2029.

The lengthy delays and cost escalations of the PFBR are illustrative of challenges faced by fast breeder reactors elsewhere. For background on the troubled history and operating experiences worldwide of breeder reactors, see the IPFM report Fast Breeder Reactor Programs: History and Status.