MUMBAI/NEW DELHI: Even as the Atomic Energy Commission confirmed that the contamination of drinking water at the Kaiga atomic plant in Karnataka was an ``inside job'', the heavy water that was introduced into a water cooler has been traced to vials kept in labs within the complex. ( Watch Video )

The heavy water, used as a coolant in the nuclear plant, is collected for lab tests before being released for use.

It is suspected that some vials of heavy water were diverted to ``spike'' the water cooler instead of being released into specified areas. The heavy water was pushed into the cooler through an outflow pipe as the machine itself is sealed and authorities do not rule out the act of sabotage being carried out by a disgruntled nuclear scientist.

``The staff who had access to vials and the various points in the chain where the vials could have been diverted are being examined,'' said MoS in PMO, Prithviraj Chavan.

He said all safety related procedures would be thoroughly reviewed and those responsible for the act would be traced. The government is examining whether there was an intent to sabotage the functioning of the plant or whether a disgruntled individual had played a ``vicious prank''.

The water cooler is located outside the reactor area and was found contaminated by radioactivity on the night of November 24.

While not ruling out sabotage, senior nuclear scientists emphasized there was no radiation leak in the plant itself as reported in a section of the media.

Outgoing chairman of the Atomic Energy Commission, Anil Kakodkar , who is laying down office on Monday, was quoted as saying that it ``clearly is a malevolent act''. Sabotage has not been ruled out, he said, adding that somebody had ``deliberately'' put radioactive vials in a water cooler.

The heavy water samples need to be accounted for more carefully in future, sources admitted. Tritium is a radioactive isotope of hydrogen, which is used for research, and in fusion reactors and neutron generators.

The alleged act of sabotage took place a fortnight after intelligence agencies warned of a terrorist attack on the country's atomic plants. After the alert, security at all the units had been stepped up. Years ago, a similar incident took place at the Tarapur atomic power station. An inquiry was held, leading to the dismissal of an employee.

According to the AEC chief, investigations are now focusing on two angles. The authorities are working to identify the worker who contaminated the water cooler with tritiated (or super heavy) water. They will also review security aspects related to radiation hazard.

Kakodkar said normally small quantities of tritiated heavy water are tested for chemical parameters.

Speaking to TOI on Sunday, chairman and managing director of Nuclear Power Corporation (NPC), S K Jain, said the water cooler had been padlocked and the person in charge of maintenance on the night of November 24 was being examined. ``The whole area has computer-accessed control. So in course of time we will be able to narrow down on the person who did the mischief,'' he said.

``I will certainly describe this as a very serious incident because it has taken place even after we initiated special security checks following the advice of the Intelligence Bureau recently,'' he said.

Asked why any staffer should resort to sabotage, Jain, said he could not rule out a ``small percentage of employees being disgruntled for one reason or the other''. ``In a place with a manpower strength of nearly 700, discontent among a small section of workers is inevitable,'' he said.

He said that credentials of workers at the plant are cleared by intelligence agencies prior to their appointment.

In an earlier statement, Jain said there were a number of measures for routine monitoring of radiation exposure of workers at a nuclear power plant. One of them is urine sampling, in which some samples had indicated contamination.

NPC chief engineer N Nagaich said the water cooler served both Kaiga 1 and 2 units, which are 220 megawatt pressurized heavy water reactors. Kaiga 1 has been shut for maintenance. ``Not a single person was hospitalized because their condition was not serious,'' he said. Kaiga 2 was operating normally.

Preliminary investigations were being conducted by the Atomic Energy Regulatory Board and NPC.

Former chairman of AEC, P K Iyengar, told TOI that prima facie it appeared that the primary motive of the employee who contaminated the water cooler was ``merely to create a scare''. Another former AEC chief, M

R Srinivasan, has called for strengthening of nuclear security.

The reported act of sabotage at Kaiga has triggered speculation among a section of nuclear scientists as to whether it could possibly be a ``dry run'' by a disgruntled staffer.

``By resorting to such mischief he perhaps wanted to gauge the reaction of other employees and the department as a whole,'' a scientist said on condition of anonymity.