Small amounts of radioactive cesium were detected on a glove of a worker at an nuclear facility in Aomori Prefecture last month, Japan Nuclear Fuel Ltd. said Thursday.
However, as the worker was not himself exposed to any radiation and none was recorded outside the building, it is believed the cesium was the result of a previous leak.
The company suspects the cesium leaked from a container of high-level radioactive liquid waste in July 2010 at the spent nuclear fuel reprocessing plant, which has yet to start operations. In the previous incident, a facility worker was exposed to radiation.
According to a report submitted to the Nuclear Regulation Authority, a trace of cesium was detected on Oct. 27 on the glove of the worker, who was working on the second floor of the building.
Japan Nuclear Fuel said it found radioactive contamination at three spots on the same floor, adding the spots had since been cleaned up.
The authority instructed the company to conduct a probe into the latest incident, saying it is obvious that it failed to conduct sufficient decontamination work when the 2010 incident occurred.
Japan Nuclear Fuel said it is highly possible that remnants of radioactive materials from the previous incident were floating in the air and became attached to the glove.
Nuclear power facility operators in the country have come under criticism in recent years for lacking safety awareness and improper management of radioactive materials.
In June, five workers suffered internal radiation exposure after a plastic bag exploded and scattered radioactive materials during an inspection of a container of fuel materials at Japan Atomic Energy Agency's research facility in Ibaraki Prefecture.