Tetsuji Imanaka, Research Reactor Institute, Kyoto University / via CNIC
Immediately after the occurrence of the Fukushima Daiichi nuclear accident in March 2011, there were many things I found difficult to understand. One of them was that virtually no data on radioactive contamination in the vicinity of the Fukushima Daiichi power plant was publicized. Since Units 1 and 3 exploded due to hydrogen accumulation and residents living within 20 km of the plant had evacuated, it was clear that the accident was developing on a tremendous scale. Nevertheless, the only publicized data on contamination were air dose rates measured by Tokyo Electric Power Company at the boundaries of the plant premises. Contamination in the areas surrounding the plant was totally unknown.
Because no data was available, I thought that I should visit the areas myself to collect measurements. I visited Iitate Village, Fukushima, on March 28 and 29, 2011, and surveyed the radioactive contamination there. The highest dose rate measured during this survey was 30 microsieverts per hour (μSv/h), recorded in the Nagadoro–Magata area located in the southern part of the village. This survey clarified that the contamination in Iitate was not something that could simply be expressed by the term hotspot, but that serious contamination covered the entire village. The further to the south, namely, the closer to the plant, the severer the contamination in the village.