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 said.
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 said.
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 persons working in the area were analysed and based on those results, a few were sent for medical consultation.
All the persons 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 of the 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 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. 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.
Kakodkar said, "No harm is expected as the regulatory limits are very stringent.
"There is plenty of margin between the permissible exposure level and exposure level when it causes same harm," he said.
Few years ago, a similar malevolent act was observed in Tarapur atomic power sub-station and the culprits were dismissed after investigations by the department of atomic energy.
Uttara Kannada district Superintendent of Police Raman Gupta said the police had offered their assistance in the investigation at the Kaiga plant.
"We are taking it seriously as public interest is involved. We are waiting for the nod of Kaiga authorities for investigation", Gupta said.
Authorities of Kaiga plant, a high security area, have told the police that an internal investigation is on. The contents of the water in the cooler are being investigated.
Uttara Kannada district Commissioner Channappa Gouda said the affected employees are recovering.
He said there was no radiation leakage in the plant. The experts' team is investigating on how the water in the cooler contained nuclear radiation, he said.
KAPS-1 has been shut down since October 20 for annual maintenance. Kaiga has three atomic power units of 220 MW each. A fourth unit is ready for commissioning.
Kaiga Station Director Gupta told PTI on telephone from Kaiga that the incident has also been reported to the intelligence department.
"We are investigating the mischief. A committee has been formed," he said.
Nuclear scientists are among those on the committee and state government agencies have also been sounded, he said.
Asked if he suspected "conspiracy" or "sabotage" behind the episode, Gupta said he did not wish to comment, saying, "It's being investigated."
Sources said the incident has baffled the authorities in Kaiga, a high-security plant owned by NPCIL.
Gupta said some 50 employees were subjected to treatment to quickly reduce tritium dosage in their bodies, after they drank water from the cooler kept in "operation island", a highly restricted zone.
He said the water cooler was isolated and the employees became "normal" within hours of the treatment.
"Tritium is not poisonous," he clarified.
"It's a form of water". The employees were treated to bring down the dosage in their bodies quickly, he said, adding even otherwise, it would have come down on its own in normal course.
Former AEC Chairman M R Srinivasan said such incidents were probed by the Atomic Regulatory Board, which is the independent inspecting authority for nuclear safety.
He also said steps needed to be taken to tighten internal procedures to prevent such incidents.
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