Radioactive substance detected in incinerator ashes in Tokyo

TOKYO (Kyodo) - A highly radioactive substance was detected in incinerator ashes at a sewage plant in eastern Tokyo in late March, shortly after the start of the nuclear crisis at the Fukushima Daiichi nuclear power station, metropolitan government sources said Friday.
The radioactive density of the substance reached 170,000 becquerels per kilogram, the sources said.
The ashes, which have already been recycled as construction materials, including cement, were collected from a sludge plant in Koto Ward.
Almost at the same time in late March, a radioactive substance of 100,000-140,000 becquerels per kg was also detected in ashes at two other sewage plants in Ota and Itabashi wards, the sources said.
The radiation levels went down to 15,000-24,000 becquerels per kg at the three sewage plants a month later, they added.
The substance has yet to be identified and researchers are currently looking into whether it is radioactive cesium, the sources said.
Meanwhile, the municipal government of Maebashi, Gunma Prefecture, said Friday it has detected radioactive cesium of 41,000 becquerels per kg from incinerator ashes collected Monday at a water sanitation facility.
It also said it has detected cesium with a density of 1,844 becquerels per kg from sludge and 17,090 becquerels per kg from molten slag that was processed at a high temperature.
It is keeping the radioactivity-contaminated materials at the water sanitation facility and plans to dispose of them under instruction from the central government, city officials said.