"The first unit started feeding power on Saturday morning at 7.12 am. The power generation now is 300 Mw," R S Sundar, station director said.

"We will have a brief interruption according to our previous plan as part of a check. Then again we will reconnect," Sundar said.

The unit, under annual maintenance and shut for nearly seven months, restarted fission on January 21.

NPCIL is setting up two 1,000-Mw atomic power plants at Kudankulam in Tirunelveli, district, around 650 km from here, at an outlay of over Rs 17,000 crore.

The first unit attained criticality, which is the beginning of the fission process, in July 2013.

Subsequently, it was connected to the southern grid in October 2013.

However, commercial power generation began only on December 31, 2014.

The unit also experienced breakdowns after commercial production started.

The unit was shut down in June 2015 for 60 days, for refuelling and annual maintenance in June 2015.

Operating at full capacity, the unit supplies power to Tamil Nadu (562.5 Mw), Puducherry (33.5 Mw), Kerala (133 Mw), Karnataka (221 Mw) and Andhra Pradesh (50 Mw).

The NPCIL skipped several deadlines in restarting the first unit and finally on January 21 the reactor restarted the fission process.

According to the official position, the second 1,000-Mw unit at Kudankulam is expected to go critical, or start the fission process, for the first time sometime this year.

However, sources said that the unit may go critical early next year.

The second unit has to get some parts from Russia as some of its components have been used in the first unit so that the latter could start operating fast. The fuel has to be loaded into the second reactor.

A senior official in the Atomic Energy Regulatory Board (AERB) recently said that the results of the second unit's commissioning and inspection reports are being studied.

"After the reports are studied AERB might lay down some conditions which have to be completed before NPCIL applies for the permission to load the fuel," he had said.(IANS)