India, April 7 -- Prime Minister Narendra Modi on Monday hailed a major milestone in India's nuclear energy journey, as the country's first indigenous Prototype Fast Breeder Reactor (PFBR) at Kalpakkam attained criticality.

Describing it as a "defining step," Modi said the achievement reflects India's growing strength in advanced nuclear technology and its commitment to energy self-reliance.

He congratulated the scientists, engineers, and all those involved in the project, calling it a proud moment for the nation's scientific community.

What 'criticality' means

The attainment of "criticality" marks a crucial stage in a nuclear reactor's lifecycle-when a self-sustaining nuclear fission chain reaction begins under controlled conditions....