Kudankulam's Two 1,000 MW Russian-Designed Reactors in Tamil Nadu Have Fed the Southern Grid Since 2013 and 2016, and Four More Units Are Under Construction

The Kudankulam Nuclear Power Plant in Tirunelveli district, Tamil Nadu, has two Russian-designed VVER-1000 reactors in commercial operation: Unit 1 since 31 December 2014 and Unit 2 since 31 March 2017, according to the Nuclear Power Corporation of India Limited (NPCIL), which owns and runs the plant. Each is rated at 1,000 MW, so the site accounts for 2,000 MW of the 8,780 MW that NPCIL lists for India’s 24 operating nuclear units, about 23 percent.

Rosatom, the Russian state nuclear corporation, reported that the first two units had generated more than 127 billion kilowatt-hours by April 2026, and World Nuclear News (WNN) gave NPCIL’s own rounded figure as nearly 130 billion units. Four more units of the same type are under construction, and six units of 1,000 MW each would add up to 6,000 MW.

What a VVER-1000 is and who runs it

A VVER is a Russian pressurised water reactor: ordinary water kept under high pressure carries heat from the core to steam generators, which drive the turbines. WNN describes the Kudankulam units as India’s first pressurised water reactors and its largest reactors. Atomstroyexport, part of Rosatom’s engineering arm, supplied them under a Russian-financed contract.

NPCIL built, commissioned and operates both units under the safeguards of the International Atomic Energy Agency, with Russian specialists supervising, WNN reported in 2016. The same report says Russia supplies the enriched uranium fuel for the plant’s whole life. Tamil Nadu, the host state, is profiled in tuput’s Tamil Nadu at a glance.

The agreements from 1988 to 2017

WNN records that the cooperation began with a 1988 intergovernmental agreement signed by Prime Minister Rajiv Gandhi and the Soviet leader Mikhail Gorbachev. The Minister of State for Atomic Energy told the Rajya Sabha on 12 February 2026 that the project was conceived in 1988 and that construction began in 2002. WNN’s report of 31 December 2014 puts first concrete for Unit 1 in March 2002 and for Unit 2 about four months later, with commercial operation first targeted for December 2007 and December 2008. Its 2008 report says Russia was building the two units under a June 1998 agreement, so the sources give both 1988 and 1998 as the founding paper.

More units needed a new agreement. WNN reported that an intergovernmental agreement for four additional Kudankulam reactors was initialled on 11 February 2008. NucNet reported that a civil nuclear cooperation agreement covering additional Kudankulam units and Russian-designed plants at new Indian sites was signed in New Delhi on 5 December 2008, by Anil Kakodkar, then head of the Atomic Energy Commission, and Sergei Kiriyenko, then head of Rosatom, during a summit between President Dmitry Medvedev and Prime Minister Manmohan Singh. A general framework agreement with Rosatom for Units 3 and 4 followed in 2014, Nuclear Engineering International reports. On 1 June 2017 the two sides signed a framework agreement and an intergovernmental credit protocol for Units 5 and 6, WNN reported the next day.

The India and Russia partnership article places these agreements within the wider relationship.

From first criticality to the grid, unit by unit

For Unit 1, WNN reports that the reactor building work was finished in March 2011. Commissioning was then delayed by more than two years by protests and legal action after the Fukushima Daiichi accident, and pump problems in the passive core cooling system, found in April 2013, were fixed by replacing the pumps. First criticality, the start of a self-sustaining chain reaction, came in July 2013. NPCIL synchronised the unit with the grid at 2:45 am on 22 October 2013, and WNN reported it initially generating 160 MWe, with power to rise in steps to 500, 750 and 1,000 MWe and the regulator approving each step.

Unit 1 first reached full power in June 2014, WNN’s report of 31 December 2014 records. It was taken offline in October 2014 for a turbine inspection, restarted on 7 December, ran at 1,000 MWe from 10 December and was declared in commercial operation on 31 December 2014.

Unit 2 followed a similar path. Construction was finished in July 2015 and fuel was loaded in May 2016. WNN reports that the approach to criticality began on 8 July 2016 and that NPCIL announced first criticality at 8:56 pm on 10 July. The unit was test synchronised with the southern grid at 11:17 am on 29 August 2016, and the plant’s site director, R S Sundar, told the Press Trust of India that it was supplying 245 MW and that the Atomic Energy Regulatory Board (AERB) had cleared the first synchronisation. NPCIL lists commercial operation from 31 March 2017, and WNN’s 2017 report says the unit was provisionally accepted in April 2017.

Where the electricity goes

The Minister of State described the rule for sharing nuclear power in the Rajya Sabha on 12 February 2026: under the long-standing Gadgil formula, the host state keeps 50 percent, neighbouring states receive 35 percent and 15 percent goes to the central grid. For Unit 1 at the end of 2014, WNN listed the southern grid shares as Tamil Nadu 56 percent, Karnataka 22 percent, Kerala 13 percent, Andhra Pradesh 5 percent and Puducherry 3 percent.

How the regulator and the courts shaped the safety framework

The Atomic Energy Regulatory Board licenses and inspects the plant. On 5 December 2024 the Minister of State told the Rajya Sabha that plants are inspected quarterly during construction and twice a year in operation and that licences are renewed every five years, under a rule he put as “safety first, production next”. The same reply gave Kudankulam’s emission figure as 0.002 microsieverts, against 0.081 a decade earlier, and set it beside the benchmark of 1,000 microsieverts that he cited. The AERB’s statutory footing changed with the SHANTI Act of December 2025, which tuput covers separately.

The AERB’s chairman at the time, S S Bajaj, described the design and the review to The Hindu in September 2012. He cited a passive heat removal system, more than 150 hydrogen recombiners that absorb leaked hydrogen before it can reach an explosive mixture, and provisions for a station blackout, meaning the loss of all outside power. He said the AERB, the Bhabha Atomic Research Centre and academic specialists had spent more than 7,000 man-days on the review.

After the Fukushima accident of March 2011 an AERB committee made 17 recommendations for Indian plants. The chairman called them precautionary and said they would take about six months or about two years to carry out. Petitioners in the Supreme Court argued that the measures should be in place before commissioning, Business Today reported.

On 6 May 2013 the Supreme Court, with a bench of Justices K S Radhakrishnan and Dipak Misra, allowed commissioning and said a balance had to be struck between the right to life and sustainable development. LiveLaw’s text of the judgment lists 15 directions. They include final clearance from the AERB, NPCIL and the Department of Atomic Energy on the quality of components before the plant operates, inspections at least once every three months, radioactive discharges kept inside the regulator’s limits, completion of the remaining 17 recommendations within the time given in NPCIL’s affidavit of 3 December 2012, and periodic emergency exercises on site and off site under the National Disaster Management Guidelines of 2009. The directions also ask the authorities to withdraw criminal cases against the agitators. On 8 May 2014 a bench of Justice Radhakrishnan and Justice Vikramajit Singh dismissed a plea against commissioning, and the court noticed no laxity in the carrying out of its directions, LiveLaw reported.

Where the spent fuel goes

The Minister of State’s Lok Sabha reply of 8 February 2023 describes a two-stage scheme. Spent fuel first sits in a pool inside each reactor building. When that pool fills, it moves to an Away From Reactor (AFR) storage facility inside the plant premises, where it stays until it is sent for reprocessing. The reply said the Units 1 and 2 pools had enough room until an AFR was ready, and that the environmental impact assessment, which covered storage in the reactor building, found no adverse environmental impact.

The same reply says the AFR for Units 1 and 2 was due by April 2022 and was delayed because the state authorities had yet to hold the public hearing that forms part of the statutory environmental clearance. It estimated that the AFR for Units 3 and 4 would be operating by 2026. The Supreme Court’s 2013 directions had asked the AERB to review the AFR’s design safety periodically and the government to set up a permanent deep geological repository early. The minister said on 12 February 2026 that claims of centralised storage of spent fuel at Kudankulam were scientifically unfounded because each reactor manages its own fuel cycle. The 2023 reply is the most recent official timetable for the facility that tuput could find.

Units 3 to 6 and the 6,000 MW target

WNN reported on 30 June 2017 that first structural concrete for Units 3 and 4 was poured about a week after the AERB’s approval. The units are a repeat of the first pair with improvements drawn from commissioning and operating experience, and Atomstroyexport is the general contractor. Work on Units 5 and 6 started in 2021, WNN reports.

The Rajya Sabha reply of 5 February 2026 gave physical progress of 80.51 percent for Units 3 and 4 and 41.56 percent for Units 5 and 6. On 12 February 2026 the minister said Units 3 and 4 were targeted for 2026-27 and Units 5 and 6 for 2030. Units 3 to 6 sit among the 17 reactors that the Department of Atomic Energy lists as under implementation, and the minister projected national nuclear capacity of 22,380 MW by 2031-32, up from 8,780 MW. The prototype fast breeder reactor at Kalpakkam is covered in a separate article.

For Unit 3, Nuclear Engineering International reported on 1 May 2026 that NPCIL and Rosatom had begun flushing the safety systems. Russia delivered the unit’s first fuel in December 2025. NPCIL’s chairman and managing director said the next steps were a hydrotest of the primary circuit and then a hot run, with fuel loading after the cold and hot tests. For Unit 5, WNN reported on 16 June 2026 that the 320-tonne reactor pressure vessel, made at Atommash in Volgodonsk, had been lifted into place. The steam generators, main circulation pumps and emergency core cooling tanks are the next items to be installed.