He stated this while participating in the Indo-Russian cultural and friendship society conference in the district today, but did not specify reasons for the delay.
Sundar said maintenance of turbines was over and work on the reactors was being done now.
"This will be completed by the end of November and power generation will begin by November end or December this year," he said.
The Director said preliminary work on Units 3 and 4 were going on in full swing.
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Referring to the fifth and sixth units, he said talks were going on.
The first unit of the Indo-Russian Joint Venture has been operational commercially since December 2014.
It had attained criticality in July 2013 after much delay, largely due to protests against the project by anti-nuclear activists, spearheaded by People's Movement Against Nuclear Energy, in areas around the complex, citing safety reasons.
He also paid rich tributes to the Russian engineers "who have been working in the site with dedication."
Sergey L Kotov, Consul General of the Russian Federation in Chennai, presided.