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A 2017 image of a building in the Fukushima Daiichi Nuclear Power Plant.
Novembre 19, 2019
Japanese media has reported that soil with relatively high concentrations of radioactive contaminants spilled over from forested regions in Japan’s Fukushima Prefecture onto neighboring roads, rivers, and residential areas amid the destruction of Typhoon Hagibis last month. The report is prompting fears of spreading contamination.
Reporting on a study conducted jointly with Shinzo Kimura, an associate professor of radiation hygiene at Dokkyo Medical University, in which soil samples were gathered on Oct. 24-29 from 15 sites in the cities of Minamisoma, Iwaki, Nihonmatsu, and Motomiya in Fukushima Prefecture, the Tokyo Shimbun newspaper said on Nov. 18 that radioactive cesium was detected at levels as high as 5,063 becquerels (Bq, representing the quantity of radioactive material undergoing one disintegration per second) per kilogram. Radioactively contaminated soil in forested regions of Fukushima appeared to have spread to residential areas and roads when Typhoon Hagibis swept through Japan.
The highest concentrations of contaminated soil were found on the roads of Minamisoma’s Odaka District, with testing of soil from the nearby hills showing a reading of 5,063 Bq. The amount is lower than the 8,000 Bq threshold designated by the Japanese government as permissible for radioactive waste. But with a permissible threshold of 100 Bq having been in place before the 2011 nuclear power plant disaster, it may be considered a relatively high concentration in view of the criticisms the Japanese government has faced for “unreasonably” increasing the threshold by 80 times in the wake of the incident in order to encourage residents to return to their homes. Indeed, Odaka District was previously subject to an evacuation order due to damage from the leakage of radioactivity from Fukushima Daiichi Nuclear Power Plant in 2011. In 2016, the classification “uninhabitable region” was lifted for all but a few areas.
The Japanese government has undertaken decontamination through the removal of soil and fallen leaves in contaminated parts of Fukushima Prefecture, with a policy approach of encouraging residents to return home once the efforts are completed. But the decontamination has been focused chiefly on areas with a large human presence, including stations, residential areas, and farmland — while many locations within the hills have yet to undergo decontamination efforts. It’s this situation that appears to account for the highest concentrations of contaminated soil being detected in Odaka. Commenting on the contamination levels they had measured, an Odaka resident surnamed Shirahige told the newspaper, “I wouldn’t be surprised if it were 10,000 Bq, given how serious the contamination in the hills has been. What worries me is the possibility of contamination spreading as large volumes of contaminated soil travel into the living zone.”
The Fukushima Preference radioactivity monitoring office told the newspaper, “Decontamination has not been carried out deep in the mountains. Spillage of highly concentrated [radioactive] soil is a concern.”
Levels of 1,470 Bq and 753 Bq were respectively detected in soil from a garden in a Nihonmatsu residential district and in dust in a parking facility. In a downstream area of Haramachi District in Minamisoma, a level of 819 Bq was detected.
Meanwhile, Kyodo News reported the publication of a report by the Japanese Ministry of Economy, Trade and Industry (METI) on Nov. 18 stating that few effects would result from the full dumping of “treated water” stored at Fukushima Dai-ichi into the ocean and atmosphere over a period of one year. The Japanese government uses the term “treated water” to refer to contaminated water from which all radioactive material apart from tritium has been eliminated with multi-nuclide removal equipment.
Speaking at a Japanese government subcommittee meeting that day to discuss the disposal of treated water from Fukushima Daiichi, METI estimated the additional annual radioactivity emissions from the full release of treated water into the ocean and atmosphere over a one-year period at between 1/1600 and 1/40,000 the daily radiation exposure of 2,100 microsieverts for an average person. This suggests that Tokyo continues moving ever closer to releasing contaminated water from the disabled Fukushima Daiichi Nuclear Power Plant into the ocean.
By Cho Ki-weon, Tokyo correspondent