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Nishiuchi, Masashi*; Suzuki, Satoshi*; Kawase, Keiichi; Watanabe, Masanori; Yamashita, Takuya
no journal, ,
By monitoring air dose rate etc. for public facilities where decontamination work was completed, we confirmed the status of maintaining decontamination effect, and predicted future air dose rate change by "The Restoration Support System for Environment (RESET)" and "prediction model of ambient dose equivalent rate" developed by JAEA. As a result, it became clear that the decontamination effect was maintained, and the future air dose rate was predicted to be reduced by about 30% after 10 years. This survey was conducted in response to concerns of municipalities. The research results were reported to the relevant municipalities and was used as the basic data residents correspondence etc. in the municipalities.
Cs discharge from a forested catchmentSakuma, Kazuyuki; Yoshimura, Kazuya
no journal, ,
Dissolved radiocesium source and migration behavior in river system are still unknown. In this study, we showed spatial distribution and temporal change of dissolved radiocesium and various ions concentrations in upstream Ota River in Fukushima to evaluate dissolved radiocesium source and migration behavior in a forested catchment. Dissolved Cs concentration in river water were 0.1-0.4 Bq/L at almost sampling points, correlated with a catchment's inventory, and showed seasonal variability. Also dissolved Cs concentration in spring water were not detected (the detection limit was estimated as 0.07 Bq/L), however dissolved Cs concentrations in stream water at a few meter from the spring point were 0.13-0.32 Bq/L. This indicated that dissolved Cs could be leaching from the surface soil and/or forest litter. Furthermore standardized dissolved Cs concentration in river water by the catchment's inventory showed a good correlation with dissolved organic carbon concentrations, indicating that dissolved Cs could be leaching from the surface soil and/or forest litter.
Shimoyama, Iwao; Kogure, Toshihiro*; Okumura, Taiga*; Baba, Yuji
no journal, ,
Cs removal processes from soil largely depend on reagents and pressure in cesium free mineralization. We have proposed a hypothesis that monovalent cations remove Cs from clay minerals through ion exchange and divalent cations remove Cs through phase transformation of clay minerals based on results using CaCl
and KCl reagents. In this work, we used MgCl and NaCl reagents to verify this hypothesis and studied decontamination ratio and structural change of mineral phase in soil. We found that the examination with these reagents supports our hypothesis, but both phase transformation and ion exchange were enhanced under low-pressure conditions. Because sea water includes NaCl and MgCl as major components, we attempted to use sea water salt as a reagent and demonstrated that soil can be decontaminated by about 99% after heat treatment at 790 
C under low pressure conditions. This result indicates the processing cost of heat treatment can be decreased using cheap sea water.
Okumura, Taiga*; Kogure, Toshihiro*; Yamaguchi, Noriko*; Dohi, Terumi; Iijima, Kazuki
no journal, ,
no abstracts in English