The Kudankulam NPP site director R S Sundar was quoted by Press Trust India as saying that the incident has occurred when the workers were carrying out maintenance on a valve at turbine building of Unit 1 on 14 May 2014.
After being given first aid, the injured were shifted to near by hospital, Sundar said.
NPCIL has dismissed reports about blast or steam pipe leak at the plant.
Sundar said that the maintenance activities in turbine building systems had been taken up as scheduled following the shutdown of Unit 1 on 12 May 2014.
The unit had attained criticality on 14 May 2014 and was scheduled for steam supply to turbine, which runs to produce electricity.
