Chennai: The second unit of Kudankulam atomic power project in Tamil Nadu that went critical or started nuclear fission on Sunday is expected to touch its rated capacity in three months time, said a senior official on Monday. "In the next three months, the second unit will reach to 100 per cent power and will operate at 1,000 MW," H.N. Sahu, Station Director of first and second units, told IANS. He said in the next one month the second unit is expected to generate 430 MW and the unit will be connected to the grid. The unit started the fission process for the first time on Sunday night at 8.56 p.m. As per procedure, the power generation will be gradually increased to 50 per cent, then to 75 per cent, 90 per cent and finally to 100 per cent. However till commercial generation begins, the unit will not be earning much on the power it feeds into the Tamil Nadu power grid as it is "infirm power" or unpredictable power. Meanwhile, the components for the third and fourth units have started arriving at Kudankulam, Sahu said. The Nuclear Power Corporation of India (NPCIL) has built two 1,000 MW nuclear power stations at Kudankulam in Tirunelvelli district around 650 km from here with the equipments supplied by the Russian Federation. Construction activities for two more 1,000 MW units have started involving an outlay of around Rs 40,000 crore. "The third and fourth units will be built on the terms like the first two units. The equipments will be supplied by Russia while construction and commissioning will be NPCIL's responsibility," S.K. Sharma, Chairman and Managing Director, NPCIL had told IANS earlier. He added that the local content in the third and fourth units will be there with Indian manufacturers making some of the components. Queried about the third and fourth units at Kudankulam, Sharma said orders for the equipments have been placed. According to Sahu, the excavation works have started and the first pour of concrete is expected to take place between March-June 2017. "Sixty-nine months after the first pour of concrete the third unit is expected to go critical and six month later the fourth unit will go critical," Sahu added.