November 01, 2014
This figure is lower than the 130 billion to 260 billion becquerels estimated by the plant's operator, Tokyo Electric Power Co., in August.
Radiation readings rose significantly during debris removal that day, with radioactive substances found to have contaminated plant workers about 500 meters from the reactor building.
However, NRA Commissioner Toyoshi Fuketa emphasized, "The affected area of the fallout was within the nuclear plant compound."
"While it is difficult to simulate the spread of radioactive substances (outside the plant), it is unlikely that the debris cleanup caused the contamination (of the rice paddies)," Fuketa said.
The nuclear facility was ravaged by the March 2011 Great East Japan Earthquake and ensuing tsunami, triggering a triple meltdown.
The NRA arrived at the figure of 110 billion becquerels by analyzing radiation levels recorded at monitoring posts north-northwest of the plant on the day in question.
Radioactive fallout on this scale constitutes a Level 0 incident on the International Atomic Energy Agency's International Nuclear and Radiological Event Scale.
Earlier, the farm ministry pointed to the possibility that radiation from the plant had spread to rice paddies in Minami-Soma more than 20 kilometers away, and called on TEPCO to take preventive measures in its debris removal work.
During the NRA meeting, some experts noted that despite the NRA's estimate, it is unlikely that factors other than debris cleanup at the plant could have caused such high levels of radioactive fallout at the rice farms.
“From a broader perspective, the Fukushima No. 1 plant is responsible for the contamination," one participant said.
Source: Asahi Shimbun