Following a massive multi-year refurbishment, the world’s oldest operational nuclear reactors have officially returned to India’s energy grid. On June 19, 2026, the Nuclear Power Corporation of India Limited (NPCIL) announced that Units 1 and 2 at the Tarapur Atomic Power Station (TAPS) in Maharashtra are once again generating and supplying electricity.

Built by GE under a turnkey contract, the two boiling water reactor (BWR) units became India’s first commercial nuclear power plant when they were commissioned in 1969. While originally designed with a capacity of 200 MWe, the units were later downrated to a gross output of 160 MWe. After a previous six-month upgrade period between 2005 and 2006, both reactors had been taken offline in 2020 to undergo comprehensive modernization.

Last month, the Atomic Energy Regulatory Board (AERB) reported that it had authorized the restart and continued operation of TAPS Unit 2 on May 7, following the completion of NPCIL’s extensive overhaul. The agency noted that the project involved entirely replacing the reactor coolant recirculation piping using forged fittings and piping manufactured from advanced corrosion-resistant stainless steel. Additional safety enhancements included the implementation of an alternate cooling water system alongside a new reactor containment filtered venting system.

During the prolonged shutdown, technicians thoroughly inspected critical aging components, such as the welds on the reactor pressure vessel, to evaluate the remaining operational lifespan of the facility. Approving Unit 2 for another 10 years of operation, the AERB stated, “The evaluations have shown that the reactor can continue safe operation with the normal maintenance and surveillance programme,”

Meanwhile, TAPS Unit 1 received its own restart permit following refurbishment last December and is currently functioning at its maximum rated capacity of 160 MWe.

Celebrating the achievement on the social media platform X, NPCIL called the reactors’ grid reconnection “a major milestone in India’s nuclear power programme … this achievement reaffirms the enduring legacy of India’s first nuclear power station and reflects the dedication, technical expertise and unwavering commitment of Team NPCIL. For over five decades, TAPS-1 & 2 have contributed to the nation’s energy security and development while providing clean, reliable and low-carbon electricity. The successful operation of both units marks another significant milestone in India’s nuclear energy journey and demonstrates the strength of indigenous capabilities, engineering excellence and a robust safety culture. As India advances towards a cleaner and more secure energy future, Tarapur continues to stand as a symbol of innovation, resilience and technological excellence”.

Beyond the historic BWR units, the Maharashtra site currently operates Tarapur 3 and 4, which are indigenous Indian-designed pressurised heavy water reactors connected to the grid in 2005 and 2006. The Tarapur location has also been proposed to host the first units of two upcoming Indian-designed small modular reactors: the 55 MWe SMR-55 and the BSMR-200, a 200 MWe facility utilizing pressurised water reactor technology.