Over 1,500 metric tons of radioactive sludge requiring controlled handling has been found in five prefectures across Japan amid the ongoing Fukushima nuclear crisis, the government announced on July 28.
The Ministry of Health, Labor and Welfare said that an examination of 49,250 tons of sludge produced during decontamination work at water-treatment facilities in Tokyo and 13 other prefectures by July 12 detected 1,557 tons of sludge in five prefectures with a level of radioactivity of over 8,000 becquerels per kilogram. It has judged that sludge with radioactivity of over 8,000 becquerels per kilograms should be placed temporarily at controlled disposal facilities.
The five prefectures are Fukushima, Miyagi, Niigata, Tochigi and Gunma.
The survey also found that 36,333 tons of sludge is being stored on the grounds of water treatment facilities without any decision made on what to do with it.
The survey did not find any cesium-contaminated sludge with radioactivity exceeding 100,000 becquerels per kilogram, a level at which storage in a sealed facility is recommended. However, 33,950 tons of sludge with radioactivity exceeding 100 becquerels per kilogram but below 8,000 becquerels per kilogram, which cannot be buried in places where homes will be built, was found in 11 prefectures, including Tokyo and Saitama.
The most radioactive sludge was found in Koriyama, Fukushima Prefecture, where a level of 89,697 becquerels was detected.
A total of 54,613 tons of untested sludge remains in the 14 prefectures. Problems have emerged over how to treat the sludge and where to keep it.
Health ministry officials say that final disposal sites have often been reluctant to accept sludge contaminated with radioactive materials, and many sewage facility operators have stored the sludge on their premises. Tokyo has already buried all 6,912 tons in landfill areas, but many local bodies are struggling to find storage sites.
The health ministry will cooperate with the Ministry of Land, Infrastructure, Transport and Tourism and consider reprocessing the sludge as soil for gardening.