title: Behavior of radioactive materials and safety stock of contaminated sludge.
abstract: The radioactive fallout from the Fukushima Dai-ichi nuclear power plant disaster in 2011 has flowed into and accumulated in many wastewater treatment plants (WWTPs) via sewer systems; this has had a negative impact on WWTPs in eastern Japan. The behavior of radioactive materials was analyzed at four WWTPs in the Tohoku and Kanto regions to elucidate the mechanism by which radioactive materials are concentrated during the sludge treatment process from July 2011 to March 2013. Furthermore, numerical simulations were conducted to study the safe handling of contaminated sewage sludge stocked temporally in WWTPs. Finally, a dissolution test was conducted by using contaminated incinerated ash and melted slag derived from sewage sludge to better understand the disposal of contaminated sewage sludge in landfills. Measurements indicate that a large amount of radioactive material accumulates in aeration tanks and is becoming trapped in the concentrated sludge during the sludge condensation process. The numerical simulation indicates that a worker's exposure around contaminated sludge is less than 1 µSv/h when maintaining an isolation distance of more than 10 m, or when shielding with more than 20-cm-thick concrete. The radioactivity level of the eluate was undetectable in 9 out of 12 samples; in the remaining three samples, the dissolution rates were 0.5-2.7%.
authors: a Water Quality Team, Water Environment Research Group, Public Works Research Institute , Ibaraki , Japan.
authors: Ikuo
authors: I
authors: Tsushima
mesh_terms: D002588:Cesium Radioisotopes / Q000737:chemistry*; D062406:Fukushima Nuclear Accident; D006801:Humans; D007457:Iodine Radioisotopes / Q000737:chemistry*; D007564:Japan; D011847:Radioactive Fallout; D012722:Sewage; D064091:Waste Disposal Facilities; D014875:Water Pollutants, Radioactive / Q000737:chemistry*
chemical_list: D002588:Cesium Radioisotopes; D007457:Iodine Radioisotopes; D011847:Radioactive Fallout; D012722:Sewage; D014875:Water Pollutants, Radioactive
keywords: Behavior research; Great East Japan Earthquake; dissolution test; numerical simulation; radioactive material; wastewater treatment plant