NAGOYA -- Chubu Electric Power Co. announced on Jan. 18 that granular deposits containing radioactive materials have been found on the second floor of a building at its Hamaoka Nuclear Power Station in Shizuoka Prefecture.

After radioactivity exceeding the standard level was detected, Chubu Electric banned entry to the waste volume reduction process building at the plant in the city of Omaezaki. There have been no reports of radiation leaking outside the building.

According to the utility, a worker from a subcontractor discovered deposits near a floor drain at around 11 a.m. during an inspection. The deposit material looked like round resin beads measuring roughly 0.5 millimeters in diameter. Radioactivity detected in an area of 1 square centimeter measured up to 105 becquerels, more than twice as much as the standard level of 40 becquerels.

The utility is investigating causes and possible links to a similar incident in May last year, when radioactive granular deposits were discovered on the second basement floor of the same building.