In a case of sabotage, Atomic Energy Commission chief Anil Kakodkar on Sunday said somebody "deliberately" put radioactive tritium in a water cooler at the Kaiga Nuclear Power Plant that exposed about 50 workers to increased level of radiation.
People involved will be punished under the Atomic Energy and other acts after investigation, he said.
"Somebody deliberately put the tritiated water vials into a drinking water cooler. Therefore, we are investigating who is behind the malevolent act," he told PTI in Mumbai.
About 45 to 50 employees working in the first maintenance unit of the Kaiga plant in Uttara Kannada district were treated at the plant hospital in Mallapur for increased level of tritium after they drank water from a cooler in the operating area on November 24, official sources told PTI.
Tritium, a radioactive isotope of hydrogen, is used in research, fusion reactors and neutron generators.
The plant's Station Director J P Gupta said from Kaiga that investigations have revealed that one of the water coolers was found to be contaminated, and as a precautionary measure body samples of all the people working in the area were analysed and based on those results a few were sent for medical consultation.
All the people are on their normal duty now, he said.
Kakodkar said, "The investigations are being carried out from two angles. First to ascertain as to who contaminated the water cooler with tritiated heavy water, and the second from radiation protection angle."
B Bhattacharjee, Member, National Disaster Management Authority, said, "The cooler is supposed to be sealed and it was found to be sealed.
"But later on, the investigators found that through the drainage, the overflow line of the cooler, that it seems some mischief monger inserted some tritiated water and contaminated the whole cooler. And people have consumed that (water)," he said, noting that "everything is normal. There is nothing serious."
Bhattacharjee said, "As soon as it was detected, they did a routine sampling. They gave some diuretics to all. Out of 55, 53 have been cleared."
Kakodkar said normally, it is a practice to test small amounts of tritiated heavy water for chemical parameters from different locations of the reactors.
The AEC chairman said the heavy water in all the pressurised heavy water reactors (PHWR) routinely goes for assessment of chemical parameters and during that process small samples are taken from different locations of the reactor to carry out analysis.
"It is a regular practice and while doing that the tritiated heavy water is carried in small vials to chemical labs within the premises to carry out analysis, and all these vials are sent back to the reactor when the analysis is over", he said.
Kakodkar also said, "We also check all the radiation workers with termoluminiscent dosimetry (TMD). So, we know the inventory and in the process of monitoring the dosimetry we found that some workers had tritiated water content in their body.
"They are being treated and are normal now," he said. "Surely it is an overdose for some people and investigations are on currently," he said.