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information about Fukushima published in English in Japanese media info publiée en anglais dans la presse japonaise

Aerial radiation lower than standard for decontamination

March 12, 2015


FOUR YEARS AFTER: Radiation levels clear decontamination standard in 88% of areas



By YU KOTSUBO/ Staff Writer

Aerial radiation levels are lower than the standard requiring decontamination work in 88 percent of about 3,600 areas monitored in Fukushima Prefecture, an Asahi Shimbun survey found.

The positive trend was evident at the 78 spots that have measured radiation levels since immediately after the accident started at the Fukushima No. 1 nuclear power plant. In March 2011, the highest monthly aerial radiation levels cleared the standard at only four of these 78 spots.

But the number increased to 62 in February this year following the natural decay of radiation and the effects of decontamination work.

The Asahi Shimbun’s survey results, which showed that more residential areas are becoming safer, provided much-needed relief to residents of the prefecture.

“When I hear that radiation levels are lower than the standard in nearly 90 percent of the spots, I feel relieved because the areas where we can be at ease are expanding,” said Riken Komatsu, a 35-year-old member of citizens group Umilabo (Sea laboratory), which voluntarily measures radiation levels in the seabed and fish off the coast of Fukushima Prefecture.

“But we must not forget that the serious situation is continuing in 10 percent of the spots,” he added.

In Fukushima Prefecture’s coastal Soso region, where the nuclear plant is located, 58 percent of the monitored spots showed radiation levels below the standard. In seven of the municipalities in the region, only 22 percent of 302 spots cleared the standard.

The municipalities include the towns of Okuma and Futaba, the two co-hosts of the nuclear plant that have remained evacuated since the disaster unfolded. The highest radiation level recorded was 18.30 microsieverts per hour in a spot in Okuma.

The central government’s Nuclear Regulation Authority and the Fukushima prefectural government have set up monitoring posts in 3,661 spots in residential areas, including schools, parks and municipal government offices. The devices, which automatically measure aerial radiation levels around the clock, have also been placed at certain intervals from the nuclear plant.

Local governments view a reading of 0.23 microsievert per hour as the level that requires decontamination work in the area.

The Asahi Shimbun checked radiation levels measured at noon on March 11 and found that 88 percent of the 3,574 spots where accurate measurements were taken fell below 0.23 microsievert per hour.

In the Aizu region, which is more than 73 kilometers west of the nuclear plant, and the Minami-Aizu region, which is further distant from the plant, the radiation levels were lower than the standard in all spots monitored.

In the Iwaki region, which is more than 21 km southwest of the nuclear plant, the radiation levels cleared the standard in 99 percent of the spots.

The rates were 98 percent in the Kennan region in the southern part of the prefecture and 96 percent in the central Kenchu region, according to the survey.

In the northern Kenhoku region, including the prefectural capital of Fukushima, where many radioactive substances flew immediately after the accident, the corresponding figure was 89 percent.

Outside the prefecture, the radiation level at noon on March 11 was 0.06 microsievert per hour in Tokyo’s Shinjuku Ward and 0.08 microsievert per hour in Osaka.

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