Examination of decontamination of various materials at houses in difficult-to-return zone

Mori, Airi; Tanabe, Tsutomu; Wada, Takao; Kato, Mitsugu

Large quantities of radioactive materials were released into the environment as a result of the Fukushima Daiichi Nuclear Power Station accident. Residential areas and forest areas near the power station were contaminated with the radioactive materials. Outside of the houses, schools and the other buildings are being decontaminated by national authority and local government. On the other hand, the materials (such as walls, floors, or windows) which constitute the houses are not decontaminated officially. In order to prepare decontamination methods that can be applied easily, we conducted examinations of decontamination for various materials in houses. Fibrous materials, woods, glasses, concretes, plastics, vinyl chloride materials, metals and synthetic leathers were used in our examinations. These materials were collected from houses in difficult-to-return zone, and were contaminated by radioactive materials released by the accident. Dry methods (suction, wiping, adsorption and peelable coating), wet methods (wiping, brushing, polishing and washing) and physical method (peeling of materials) were used for decontamination. As a result of our examinations, materials with low water permeability, such as glasses, concretes, vinyl chloride materials and metals, were able to be decontaminated efficiently (about 90% reduction) by using wet methods. Materials with high water permeability like woods were relatively well decontaminated by peelable coating (about 60%-70% reduction). In addition to the examination described above, the difference of contamination reduction effect between chemical properties of detergents and the effect of rubbing of peelable coating were also examined. Finally, the most effective method was summarized based on these examinations.