Last Aug. 19, dirt and dust contaminated by radioactive substances were stirred up and dispersed during work to remove debris at the reactor 3 building, which was severely damaged by the March 2011 meltdown crisis, Tepco said at a review meeting of the Nuclear Regulation Authority.
According to Tepco, up to an estimated 280 billion becquerels per hour of radiation were released into the environment over four hours. The per-hour release amount is 2,800 times the 10 billion becquerels usually discharged from the buildings at the crippled plant.
During the debris removal work, the alarm went off to warn that high levels of radiation had been detected in the air.
The rice found to be tainted with radioactive cesium was produced at paddies located about 20 km north of the nuclear plant. A southeast wind was blowing at the time of the removal work.
Tepco has claimed it was still not known whether the contamination had a causal connection with the work.