Highly radioactive cesium was detected in sewage sludge and molten slag--a sandy substance created by incinerating sewage sludge--at sewage treatment facilities in Koriyama, Fukushima Prefecture, the Fukushima prefectural government said.
Highly radioactive cesium was detected in sewage sludge and molten slag--a sandy substance created by incinerating sewage sludge--at sewage treatment facilities in Koriyama, Fukushima Prefecture, the Fukushima prefectural government said.
Airborne radiation levels around the facilities were also significantly higher than in other areas of the city. The prefectural government said May 1 it is determining if radioactive substances generated by incinerating the sewage sludge could have spread from the facilities.
Results of an inspection conducted April 30 by the prefectural government showed 26,400 becquerels and 334,000 becquerels per kilogram of radioactive cesium (the latter of which is about 1,400 times the level before the Great East Japan Earthquake) were found in sewage sludge and molten slag, respectively, at wastewater treatment facilities in the Hiwada area of Koriyama.
Since there are no guidelines established by the central government for disposing of highly radioactive sewage sludge, the Ministry of Land, Infrastructure, Transport and Tourism was scheduled May 2 to discuss with the Nuclear and Industrial Safety Agency how to handle the radioactive sludge.
Meanwhile, the ministry is expected to ask all municipalities in eastern Japan to measure radiation levels in sewage sludge at sewage treatment facilities.
The Fukushima prefectural government believes that rainfall caused radioactive substances on the ground to flow into sewage systems, leading to a high concentration of radiation at the sewage treatment plant. Eighty tons of sewage sludge are generated per day at the facilities, while 2 tons of molten slag is created by firing 70 tons of the sewage sludge in a furnace at the plant, the prefectural government said. The remaining 10 tons are shipped to cement companies for use as materials.
Since the onset of the Fukushima nuclear power plant accident on March 11, about 500 tons of sewage sludge have been shipped to cement companies. The prefectural government is currently tracking the shipment routes to find out where the sewage sludge is now. All the molten slag, however, has been safely stored at the facilities with plastic-sheet covering.
The prefectural government has decided to suspend shipments to cement companies while instructing staff at the sewage treatment facilities to carry radiation dosimeters at all times. It also plans to implement the same inspections at 22 other sewage treatment facilities in the prefecture.
The radiation levels observed around the facilities on May 1 ranged between 1.8 and 3.4 microsieverts per hour, significantly higher than the level of about 1.6 microsieverts per hour around the Fukushima-Koriyama joint municipal hall, about 10 kilometers from the facilities.
(This article was written by Keiichi Yazaki and Keiichi Kitagawa.)