FUKUSHIMA—Two parking lots in the city of Fukushima were declared off-limits to the public on May 7 after high concentrations of radioactive cesium were detected in the exposed soil there.
Local authorities shut down the parking lots for emergency decontamination operations after a nonprofit organization found a maximum of 430,000 becquerels per kilogram of radioactive cesium during a survey conducted between April 29-May 2 at the behest of local residents.
The Citizen’s Radioactivity Measuring Station also detected a maximum level of airborne radiation at 3.8 microsieverts per hour, above the benchmark for evacuation, at the two sites.
“It's the first time that soil with cesium levels exceeding 100,000 becquerels was found on the grounds of an urban area, not in sludge accumulated in ditches," said a city official in charge of decontamination work.
The CRMS measured exposed soil radiation levels at three locations in a parking lot for a municipal library and public hall in Matsuki, and at four locations in a parking lot for a prefectural library and museum in Moriai.
The exposed soil had accumulated to a height of 1 to 3 centimeters around the edges of the parking lots or in sunken parts of the surface, mixed with fragments of dead leaves and other material.
The survey at the Matsuki parking lot found radioactive cesium concentrations of 220,000 or more becquerels per kilogram of soil, with the highest level at 433,772 becquerels.
The survey at the Moriai parking lot detected concentrations of 120,000 or more becquerels per kilogram, with the maximum level of 289,144 becquerels.
Airborne radiation levels at a height of 1 meter ranged between 0.6 and 3.8 microsieverts per hour at the two sites.
The CRMS was established in July 2011 after complaints were raised that the central and local governments were not offering sufficient monitoring systems.
According to the Environment Ministry, the central government plans to dispose of sludge, incinerator ash and other substances with radioactive levels of more than 8,000 becquerels caused by the accident at the Fukushima No. 1 nuclear power plant. It plans to keep those containing radioactive levels of more than 100,000 becquerels at a temporary storage facility.
After the nuclear disaster, decontamination operations were conducted in gutters and other areas at the Matsuki site and on grass at the Moriai site. But the parking lots themselves at the two sites were not decontaminated.
In addition to visitors to the facilities, local residents, including students, usually enter the sites for walking and extracurricular activities.
Ikuro Anzai, professor emeritus at Ritsumeikan University versed in radiation protection, has been involved in decontamination operations at nursery schools and other facilities in Fukushima city.
Anzai warned that radiation hotspots still remain that were overlooked after decontamination work was conducted.
“The public and private sectors must cooperate to keep people's exposure to radiation to a minimum by frequently measuring radiation levels and removing radioactive materials,” he said.
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