A worker dismantling tanks at the wrecked Fukushima No. 1 nuclear plant was found to have been exposed to a small amount of radiation during a routine safety check on Friday, plant operator Tokyo Electric said.

Radiation was detected in the nasal cavities of the worker, an unidentified man in his 30s, a spokesman for Tokyo Electric Power Company Holdings Inc. said on Friday.

The company estimated the amount of radiation at up to 0.010 millisieverts — less than a typical 0.05-millisievert chest X-ray — and said it did not pose an immediate health risk.

Reported radiation exposure incidents have been rare during work to clean up the plant, which was devastated by a magnitude-9 earthquake and tsunami on March 11, 2011, that left nearly 16,000 people confirmed dead and more than 2,000 officially unaccounted for.

The Tepco spokesman said the last Fukushima No. 1 radiation exposure incident in official records was for a worker who was exposed to at least 2 millisieverts in January 2012.