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Cs leaching from a forest litterSakuma, Kazuyuki; Yoshimura, Kazuya; Nakanishi, Takahiro
no journal, ,
We investigated characteristic of dissolved Cs leaching from litters collected at a coniferous needle and a deciduous broadleaf forests using litterbags at upstream area of Ota River in Fukushima. Each leaf type of litters was collected into 36 litterbags, respectively, and installed each forest floor in June and December, 2017. Triplicate samples were collected at each forest floor and readily transported to laboratory in August and December, 2017 and March, May, August and December, 2018. Samples were put in buckets and soaked in purified water immediately after back to laboratory. We took leaching water samples from the buckets at 20 min., 2 hours, 24 hours after soaking litter samples in the water. These samples were analysed about Cs activity. The main results are that the deciduous broadleaf litter showed much higher leaching ratio of dissolved Cs (0.81-7.3%, mean: 3.2%) than that of the coniferous needle litter (0.15-2.1%, mean: 0.80%).
Okumura, Taiga*; Kogure, Toshihiro*; Yamaguchi, Noriko*; Dohi, Terumi; Fujiwara, Kenso; Iijima, Kazuki
no journal, ,
Most of the radiocesium released by the Fukushima nuclear accident was sorbed to clay minerals such as weathered biotite (WB), whereas radiocesium-bearing microparticles (CsMPs) were also emitted from the damaged reactors. In this study, we report CsMPs with smaller size and lower radioactivity and suggest the way to distinguish CsMPs from other radioactive particles. Radioactive particles were collected from non-woven fabric cloth and contaminated soil and identified by SEM-EDS, and their radioactivity was measured by IP autoradiography. As a result, five CsMPs of less than 0.05 Bq and two WB particles of more than 0.05 Bq were identified, indicating the presence of CsMPs with lower radioactivity than WB. Next, the contaminated soil was uniformly scattered on the substrate to which a heat-resistant adhesive was applied, and IP autoradiography was performed before and after heating at 800 
C. It was suggested that CsMPs could be distinguished by the heating treatment.
Baba, Yuji*; Shimoyama, Iwao
no journal, ,
no abstracts in English
Shimoyama, Iwao
no journal, ,
Cs-free mineralization is a decontamination method to remove radiocesium from soil by converting clay minerals to different minerals through chemical reaction with additives, and its efficiency considerably depends on reagents. In this work, nitrate reagents were used to decrease processing temperatures. Weathered biotite (WB) which sorbed non-radioactive Cs was used as model soil. WB was heated with an additive for two hours and analyzed using X-ray fluorescence and X-ray diffraction after rinsing with water and drying. When calcium nitrate was added, Cs removal ratio reached to 100%at 450C in Ar atmosphere, and this achieves significant decrease of processing temperature as compared with the cases of chloride reagents. In the case of NaCl or KCl addition, ion exchange was the major Cs removal process at 700C, whereas in the case of NaNO
or KNO addition, phase transformations were induced at 634C under vacuum, which suggests that Cs removal process depends on the anion in the reagent. In the case of calcium nitrate, the phase transformation temperature decreased to approximately 500C, however, ion it is presumed that ion exchange was the major Cs removal process at 450C because WB was preserved at this temperature.
Sugita, Tsuyoshi; Shimoyama, Iwao
no journal, ,
The treatment of a large amount of contaminated soil caused by the Fukushima nuclear accident is a significant issue for the restoration of the Fukushima. This studies aim is the development of a new recycling way about Cs contaminated soil, and we investigated the giving of photocatalytic activity to substances after decontamination by cesium-free mineralization. As a result, we succeeded in converting Cs sorption biotite to photocatalytic material and revealed that the product after Cs removal could be used for photocatalytic reduction of Cr (VI).
Maruyama, Ippei*; Yamada, Kazuo*; Ida, Masaya*; Shibuya, Kazutoshi*; Igarashi, Go*; Koma, Yoshikazu
no journal, ,
no abstracts in English
