New Delhi | Prime Minister Narendra Modi on Sunday hailed as a "historic milestone" the Kalpakkam fast breeder reactor achieving criticality, and said Indian nuclear scientists have brought glory to the country.

In his monthly radio address 'Mann Ki Baat', he said Indian scientists are advancing the civil nuclear programme and their efforts are making a significant contribution to nation-building.

"Our nuclear scientists have brought glory to India through a major achievement. The fast breeder reactor at Kalpakkam in Tamil Nadu has achieved criticality," he said.

Modi said this is a "historic milestone" in India's nuclear energy journey, and the remarkable thing is that the atomic reactor has been entirely built using indigenous technology.

The prime minister said he had the privilege of witnessing the core loading of the reactor in Kalpakkam in March 2024.

"I congratulate all those who have made invaluable contributions to India's nuclear program," he said.

Modi said the efforts of the scientists to make the lives of fellow citizens better and easier are truly commendable.

In a landmark achievement for India's nuclear energy programme, the 500 MWe Prototype Fast Breeder Reactor (PFBR) has successfully attained first criticality (start of controlled fission chain reaction) on April 6, marking a historic step in providing long-term energy security and advancing indigenous nuclear technology capabilities.

Fast Breeder Reactors are a cornerstone of India's long-term nuclear strategy. Unlike conventional thermal reactors, the PFBR uses Uranium-Plutonium Mixed Oxide (MOX) fuel.

The reactor is designed to eventually use Thorium-232 in the blanket. Through transmutation, Thorium-232 will be converted into Uranium-233, which will fuel the third stage of India's nuclear power programme.