The CM said the development marks a key step in the second stage of India's nuclear programme and strengthens the country's long-term energy roadmap.
"A proud moment for every Indian and a boost to India's civil nuclear journey. India's indigenously built (Prototype Fast Breeder Reactor) PFBR at Kalpakkam has attained criticality, marking a key step in the second stage of India's nuclear programme," said Naidu in a post on X.
The chief minister said the milestone brings India closer to harnessing its vast thorium reserves in the third stage of the programme.
He further said the achievement strengthens the path towards long-term energy security under the leadership of Prime Minister Narendra Modi.
Naidu congratulated the scientists and engineers for the remarkable achievement, acknowledging their contribution to the country's nuclear advancement.
YSRCP supremo YS Jagan Mohan Reddy congratulated the scientists, engineers and the entire Department of Atomic Energy for the milestone.
"This 500 MW reactor marks a proud step towards clean, secure energy for generations and brings us closer to harnessing our vast thorium reserves for true energy self-reliance," said Reddy in a post on X.
Calling the milestone a "giant leap" in India's nuclear energy, Reddy said it is a proud moment for every Indian.