KNPP Unit 1 turbine generator has operated for 4,701 hours so far and generated 282.5 crore units of power, which was supplied to the Southern grid since October 2013, KNPP site director R S Sundar said in a statement.
"The unit has been shutdown to inspect the turbine and its associated components before putting it for commercial operation," he said.
"Maintenance activities are in progress and we wanted some more time to put it back in service. That is why we have taken time," he said.
Sundar said Unit 1 was expected to be back in service in six to eight weeks.
The Nuclear Power Corporation of India had undertaken construction of two 1,000 MW units at KNPP jointly with Russia at Kudankulam in Tiruneveli district in Tamil Nadu.
Unit-1 attained criticality on July 13 last year after much delay following protests against KNPP by anti-nuclear activists in areas around the complex, citing safety reasons.