Chennai, Apr 1 (IANS): India's atomic power plant operator Nuclear Power Corporation of India Ltd. (NPCIL) said Monday that only steam was being let out of the first unit of the Kudankulam Nuclear Power Project (KNPP) as part of tests.

"As a part of commissioning tests of Kudankulam Nuclear Power Project, the steam relief valves on the steam lines are being tested. These tests are conducted only during the day and only steam, or water vapour, is released as part of the tests," said R.S. Sundar, KNPP site director.

Disputing NPCIL's stand, M. Pushparayan of the People's Movement Against Nuclear Energy (PMANE) told IANS: "For the past three days we heard loud noises from the plant. Thick black and white smoke emanated from the plant and there was a strong stench."

He said that in 2011, KNPP had carried out similar tests, but this time the noise and the stench was much more.

The PMANE will lay siege to the NPCIL employee's residential colony near Kudankulam April 3, protesting the indifferent attitude of the government towards the people and their demands, Pushparayan added.

NPCIL, India's atomic power plant operator, is setting up the project in Kudankulam in Tirunelveli district in Tamil Nadu, around 650 km from here, with two Russian-made VVER 1,000-MW each reactors.

KNPP is an outcome of the inter-governmental agreement between India and erstwhile Soviet Union in 1988. However, construction only began in 2001.

Pushparayan said there were contradictions about the plant and its commissioning date.

"Prime Minister Manmohan Singh says the plant will be operational in April while NPCIL's website mentions the date as May 2013," he said.