NEW DELHI: The Atomic Energy Regulatory Board AERB ) has given its nod for commencing work on Kudankulam Nuclear Power Plant units 3 and 4."The permission was granted last week," said KKNP site Director R S Sunder.KKNPP units 3 and 4, with a production capacity of 1,000 MW each, are being built with the help of Russians. Atomenergoproekt JSC, a subsidiary of Russian state nuclear corporation Rosatom, is the general designer of the Kudankulam plant.The project cost of the new units is estimated at around Rs 39,000 crore as of now, against Rs 17,000 crore for Unit 1 and 2. It would take around 69 months for the projects to get completed from the time construction starts.The official said the unit 1 has again reached the stage of criticality and it is likely to be connected to the power grid this week. The Unit 2 is expected to start between March and April this year. Unit 1 started generating electricity in October 2013.On January 21, the first unit of Kudankulam plant was restarted after maintenance. In 2015, with Russian technical support, the first scheduled maintenance work was successfully completed on the unit 1. In December 2015, the plant's first unit was again loaded with nuclear fuel.