PM Modi threw in a few words of Russian as he thanked President Putin for joining him in formally launching the first phase of the nuclear plant and also said: "I look forward to meeting you at the G-20 summit."

Speaking before him, President Putin had said: "We have huge plans with India in areas of Nuclear energy. We expect that by the end of this year the third part of this project is signed."

Both units of the Kudankulam plant have been made at a cost of over Rs 22,000 crore and are 10 years behind schedule. The first unit started generating electricity in 2013. It produces around 1,000 mw of power, half of which feeds Tamil Nadu.

The reactors, which are India's largest, are being built jointly by the Nuclear Power Corporation of India and a subsidiary of Russia's nuclear regulatory body Rosatom.

The project was signed by former Prime Minister Rajiv Gandhi and then Soviet Union President Mikhail Gorbachev in 1988 but construction started nearly a decade later due to the turmoil after the collapse of the Soviet Union.

Anti-nuclear activists in Tamil Nadu call the facility unsafe but plant engineers suggest it is one of the safest in the world.

Villagers in coastal areas allege that the Russian technology is flawed and untested and the plant is like a live bomb in their backyard which would destroy fishing.

SP Udhayakumar, the face of the anti-nuclear protests, alleges: "The first plant tripped 32 times in the last two years and is still limping along its way to credible power generation. Video conference seems to be the best hi-tech solution for the Russians and the Indian government to duck and dodge all kinds of disturbing questions."

The atomic reactor will provide electricity to Tamil Nadu, Puducherry, Kerala and Karnataka. Four more similar atomic reactors are expected to come up at Kudankulam in future.