Tritium incidents at Rajasthan

25 July 2012

Two minor contamination incidents have taken place at India's Rajasthan nuclear power plant, both due to tritium exposure during maintenance. All the personnel involved continue to work at the plant, although two have had to change their duties.

During normal operation, mildly radioactive tritium builds up in the heavy-water moderator of pressurized heavy-water reactors, of which six are present at Rajasthan. This represents a routine radiological concern for managers, who therefore plan maintenance in order to minimise exposure for workers. However, two recent incidents have triggered investigations by plant owner Nuclear Power Corporation of India Ltd (NPCIL) and the safety regulator.

The first came on 23 June during work to alter the moderator system of Rajasthan 5. Workers were preparing to conduct some welding when the opening of a moderator gas cover line caused a local increase in the concentration of tritium. NPCIL said two people were likely to have received radiation doses that would take them above annual regulatory limits. Those workers have been assigned roles in other parts of the plant, while the remainder of people in the area at the time continue to work as normal.

A second tritium exposure incident took place on 16 July during work on Rajasthan 4 when a leak of heavy-water moderator was observed from a pump seal. The pump was immediately shut down and isolated. NPCIL said that radiation doses to the four workers involved were in the range of between 10% and 25% of the regulated annual limit. The company said that the individuals continue to work as normal.

The single exposure of an individual exceeding 10% of the annual limit is a trigger point for NPCIL and the Atomic Energy Regulatory Board beyond which they are each required to compile an investigation.

Resarched and written
by World Nuclear News