The South Asian country's most advanced atomic reactor has attained criticality, putting it one step away from full operation

India has achieved a significant milestone in the development of its civil nuclear energy program, Prime Minister Narendra Modi announced on Tuesday.

In a post on X, Modi said the indigenously designed and built Prototype Fast Breeder Reactor (PFBR) in Kalpakkam has attained criticality, describing it as a "defining step" and marking advancement to the second stage of the country's nuclear program. 

The PBFR is expected to generate electricity in the next stage, when it becomes fully operational.

"This will pave the way for utilization of the abundant thorium reserves in the third stage of the nuclear power program, comprising of thorium-based reactors," Ajit Kumar Mohanty, chairman of the Atomic Energy Commission, said.

India has the world's largest thorium reserves, and experts have said its thorium program should be fast-tracked with Russian collaboration.

Russia is currently the only country to have a functional commercial fast breeder reactor.

New Delhi plans to boost nuclear power capacity to 100 gigawatts by 2047, as part of its push towards clean energy.

The country's current nuclear installed capacity is just 8.18 GW. India is aiming to achieve the net zero emission target by 2070, Mohanty added.

India's nuclear energy architects believe it can generate 500 GW of electricity for the next four centuries using its economically extractable thorium reserves, according to reports.

New Delhi's three-stage nuclear power program was envisaged by physicist Homi Bhabha in the 1950s to secure the South Asian nation's long-term energy independence.