India’s largest nuclear park has faced the second incident of radioactivity leakage within a month, though the plant operator claimed it to be a minor incident.
The leakage happened on July 16 at the 220 MWe unit-4 of Rajasthan Atomic Power Station at Rawatbhatta. The unit was shutdown for maintenance when one of the seals in a moderator pump gave away spilling radioactive heavy water outside and exposing four workers.
Heavy water is used as moderator and coolant in all the six RAPS reactors, which are pressurised heavy water reactors.
The heavy water used in RAPS-4 contained tritium, an isotope of hydrogen, which emits radioactivity. When the seal broke, four workers in the unit inhaled higher dose of tritium, which was confirmed by their urine tests, a RAPS-4 engineer told Deccan Herald.
All the four workers were put off duty, he said. The exposure was much less than what had been specified by the Atomic Energy Regulatory Board. Moreover, tritium does not stay in the body as it is quickly degraded and flushed out from the body within a week.
Radiation doses of four departmental people were in the range of only 10-25 per cent of the yearly AERB dose limit. These four people were continuing to carry out their assigned work as usual, said an official from the Nuclear Power Corporation of India Ltd.
This is the second incidence of tritium contamination in RAPS within a month as two contract workers were exposed to high level of radioactivity on June 23 due to accidental release of tritium vapour from a pipe. However, both are safe and resumed work within days.
Incidentally, the Kaiga nuclear power station, too, had problems with tritium in 2009 when somebody dropped a tritium vial in a water cooler contaminating drinking water. Medical treatment was provided close to 50 people and all of them resumed work within days.
