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Horie, Hiroki*; Akiyama, Yoko*; Mishima, Fumihito*; Nishijima, Shigehiro*; Mitsui, Seiichiro; Umezawa, Katsuhiro; Kato, Mitsugu; Okada, Takashi; Sekiyama, Tomio*
no journal, ,
A technique for volume reduction and recycle of cesium contaminated soil in combination with wet classification and high gradient magnetic separation was investigated. The magnetic separation can fractionate the fine soil particles (silt and clay) into high-dose and low-dose soil. This method utilizes the phenomenon that paramagnetic 2:1 clay strongly adsorbs cesium whereas diamagnetic 1:1 clay has low adsorption ability of cesium. One of the main issues in this technique is that the soil components are aggregated by organic matters, which prevents 2:1 type clay minerals from selective separation. In this study, pretreatment of the soil by K
CO
solution was conducted, prior to the magnetic separation, in order to disperse aggregates. As a result, further selective separation for 2:1 type clay minerals by the pretreatment was confirmed.
Shimoyama, Iwao; Honda, Mitsunori; Kogure, Toshihiro*; Baba, Yuji; Yaita, Tsuyoshi; Okamoto, Yoshihiro
no journal, ,
We study radioactivity concentration of contaminated soil in Fukushima to examine the effectiveness of cesium free mineralization (CFM) and analyze structural change of the soil using X-ray diffraction (XRD). CaCl or KCl was added to the soil and heated in air or under low-pressure conditions. In the case of CaCl, decontamination ratio Rd showed similar tendency for both air and low-pressure heating, and we found that Rd reached to 97% after heating at 790
C. XRD analysis showed that basal reflection peaks of clay minerals in the soil disappeared and quite different XRD patterns were observed between air and low-pressure heating treatments. These results indicate that CFM is effective for decontamination of actual Fukushima soil, and product by CFM largely depends on pressure condition during heating. On the other hand, Rd was higher for low-pressure heating than for air heating with KCl, and XRD showed that clay minerals remained after the heating treatment. This means different mechanisms of Cs removal from contaminated soil exist for heating treatments with KCl and CaCl.
-ray directional radiation dose detector with good efficiency for field surveyYamamori, Ryo*; Kobayashi, Hikaru*; Honta, Shohei*; Yoshino, Hiroshi*; Nozaki, Atsuo*; Ichijo, Yusuke*; Hijikata, Yoshio*; Yoshida, Hiroko*; Furuta, Takuya
no journal, ,
Understanding radiation field is important to predict radiation dose rate in newly constructing buildings in an area widely contaminated by radioactive nuclei. Directional spectra of the radiations are important to consider the shielding effect of the building. We adopts a method to measure the directional spectra by adopting a plate of lead collimator in front of the scintillator and subtract the values from the spectra measured without lead collimator. We investigated a possible weight saving detection system having sufficient detection efficiency. The investigation was carried out for the condition of the collimator radius (
= 10, 15, 20 cm) and the distance between collimator and detector (
= 1, 3, 5 cm). We found that three combinations satisfied the 90 field view and the detection efficiency became better with larger collimator radius. On the other hand, larger collimator radius indicate heavier detection system. Therefore, we developed an optimum detection system for field survey with the 15 cm diameter plate (10kg), the scintillator (3.4kg), and the folder (1.0kg).
Uchida, Shinichi; Haginoya, Masashi*; Yamada, Koji*; Nishino, Katsumi*; Kawase, Keiichi; Okada, Takashi
no journal, ,
no abstracts in English
Sakuma, Kazuyuki; Kim, M.; Malins, A.; Machida, Masahiko; Kitamura, Akihiro
no journal, ,
We developed evaluation tools for air dose rates in forested area including the depth profile of radiocesium in the environment, the effects of topography and land use, litter layer, and geometric tree model. We report results of air dose rate in forested area in Fukushima prefecture using radiation transport code (PHITS) with the developed tools.