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values calculated from radiocesium interception potentialUno, Koichiro*; Nakao, Atsushi*; Okumura, Masahiko; Yamaguchi, Akiko; Kogure, Toshihiro*; Yanai, Junta*
Nihon Dojo Hiryo Gaku Zasshi, 94(5), p.376 - 384, 2023/10
Radiocesium interception potential (RIP) has been widely used as a quantitative indicator of cesium (Cs) adsorption capacity of soil, but it has been found that RIP does not always correlate with the distribution coefficient () of Cs in the actual environment. In order to clarify the cause of this discrepancy, we measured Kd using more realistic solutions, compared it with RIP, and evaluated the mineral structure. As a result, it was found that the concentration of competing cations, such as potassium and ammonium ions, and the structural change of the mineral itself are important.
Igarashi, Yasuhito*; Kogure, Toshihiro*; Kuribara, Yuichi; Miura, Hikaru*; Okumura, Taiga*; Satou, Yukihiko; Takahashi, Yoshio*; Yamaguchi, Noriko*
Journal of Environmental Radioactivity, 205-206, p.101 - 118, 2019/09
Times Cited Count：74 Percentile：69.22(Environmental Sciences)Scientists face challenge in identifying the radioactive materials which are found as dotted images on various imaging plate (IP) autoradiographic photos of radioactively contaminated materials by the Fukushima Dai-ichi Nuclear Power Plant (F1NPP, or FDNPP) accident, such as air filter, fugitive dust, surface soil, agricultural materials, and water-shed samples. It has been revealed that they are minute particles with distinct morphology and elemental composition with high specific radioactivity, and different from those of the so-called Chernobyl hot particles. Basically, they are glassy particles once molten, composed of Si, O, Fe, Zn etc. with highly concentrated radiocaesium, which can be called as radiocaesium-bearing microparticles (CsMP). At present, CsMP can be classified into two types, Types-A and -B, which are characterized by different specific radioactivity, 
Cs/
Cs ratio, size and morphology, and geographic distribution around F1NPP. Such studies on the CsMP from various aspects have provided valuable information about what happened in the nuclear reactors during the F1NPP accident and fates of the CsMP in the environment. This review first provides a retrospective view on the research history of the CsMP, which is helpful to understand the unique character of the CsMP. Subsequently, more details about the current understanding of the natures of these hot particles, such as origin, morphology, chemical compositions, thermal properties, water-solubility, and secondary migration of CsMP in river and ocean systems are described with future prospects.
Okumura, Taiga*; Yamaguchi, Noriko*; Dohi, Terumi; Iijima, Kazuki; Kogure, Toshihiro*
Microscopy, 68(3), p.234 - 242, 2019/06
Times Cited Count：11 Percentile：66.61(Microscopy)Radiocesium-bearing microparticles (CsMPs), consisting substantially of silicate glass, were released to the environment during the Fukushima nuclear accident in March 2011. We investigated a total of nine CsMPs using transmission electron microscopy (TEM) and inferred the atmosphere in the reactors during the accident. From elemental mapping using energy-dispersive X-ray spectrometry, Fe and Zn showing radial inhomogeneities were found in the CsMPs, in addition to the Cs that had been previously reported. Four of the CsMPs included submicron crystals, which were identified as chromite, franklinite, acanthite, molybdenite, and hessite. The chromium-containing spinels, chromite and franklinite, indicated the presence of ferrous iron (Fe
), suggesting that the inside of the reactors was reductive to some extent. Electron energy-loss spectroscopy also confirmed that the CsMPs did not contain boron, and therefore the atmosphere in which they were formed might be boron-free.
Okumura, Taiga*; Yamaguchi, Noriko*; Dohi, Terumi; Iijima, Kazuki; Kogure, Toshihiro*
Scientific Reports (Internet), 9(1), p.3520_1 - 3520_9, 2019/03
Times Cited Count：39 Percentile：87.76(Multidisciplinary Sciences)Radiocesium-bearing microparticles (CsMPs) were released by the FDNPP accident. We conducted dissolution experiments of CsMPs by reaction with pure water absorbing CO 
from the atmosphere and seawater. The activation energy for the dissolution of CsMPs was estimated to be 67 and 89 kJ/mol, and the dissolution rate at 13
C was 0.011 and 0.130 
m/y for pure water and seawater, respectively. Probably the faster dissolution rate in seawater than in pure water is mainly owing to the difference in pH. The shapes of CsMPs dissolved in pure water were considerably altered. Tin oxide and iron oxide nanoparticulates were formed on their surfaces. Such features were similar to those observed in a CsMP collected recently in Fukushima Prefecture, indicating that dissolution of CsMPs is also occurring in the environment. In the case of CsMPs dissolved in seawater, a crust of secondary minerals rich in Mg and Fe was formed and the glass matrix became smaller inside the crust.
Nihei, Naoto*; Yoshimura, Kazuya; Okumura, Taiga*; Tanoi, Keitaro*; Iijima, Kazuki; Kogure, Toshihiro*; Nakanishi, Tomoko*
Journal of Radioanalytical and Nuclear Chemistry, 318(1), p.341 - 346, 2018/10
Times Cited Count：4 Percentile：34.86(Chemistry, Analytical)Okumura, Taiga*; Yamaguchi, Noriko*; Dohi, Terumi; Iijima, Kazuki; Kogure, Toshihiro*
Scientific Reports (Internet), 8, p.9707_1 - 9707_8, 2018/06
Times Cited Count：11 Percentile：33.85(Multidisciplinary Sciences)Radiocesium-bearing microparticles (CsP) substantially made of silicate glass are a novel form of radiocesium (RCs) emitted from the Fukushima Dai-ichi NPP. CsPs have a potential risk of internal radiation exposure caused by inhalation. Radiation-contaminated waste (Rcw) including CsPs is being burned in incinerators; therefore, this study has investigated the responses of CsPs to heating in air. The radioactivity of CsPs gradually decreased from 600 C and was almost lost when the temperature reached 1000 C. The size and spherical morphology of CsPs were almost unchanged after heating, but Cs including RCs, K and Cl were lost, probably diffused away from the CsPs. When the CsPs were heated together with weathered granitic soil that is common in Fukushima, the RCs released from CsPs was sorbed by the surrounding soil. From these results, it is expected that the radioactivity of CsPs will be lost when Rcw including CsPs is burned in incinerators.
Yoshigoe, Akitaka; Shiwaku, Hideaki; Kobayashi, Toru; Shimoyama, Iwao; Matsumura, Daiju; Tsuji, Takuya; Nishihata, Yasuo; Kogure, Toshihiro*; Okochi, Takuo*; Yasui, Akira*; et al.
Applied Physics Letters, 112(2), p.021603_1 - 021603_5, 2018/01
Times Cited Count：6 Percentile：27.37(Physics, Applied)A synchrotron radiation photoemission electron microscope (SR-PEEM) was applied to demonstrate pinpoint analysis of micrometer-sized weathered biotite clay particles with artificially adsorbed cesium (Cs) atoms. Despite the insulating properties of the clay, we observed the spatial distributions of constituent elements (Si, Al, Cs, Mg, Fe) without charging issues. We found that Cs atoms were likely to be adsorbed evenly over the entire particle. Spatially-resolved X-ray absorption spectra (XAS) of the Cs M
-edge region showed Cs to be present in a monocation state (Cs
). Further pinpoint XAS measurements were also performed at the Fe L
-edge to determine the chemical valence of the Fe atoms. Our results demonstrate the utility of SR-PEEM as a tool for spatially-resolved chemical analyses of various environmental substances, which is not limited by the poor conductivity of samples.
Honda, Mitsunori; Shimoyama, Iwao; Kogure, Toshihiro*; Baba, Yuji; Suzuki, Shinichi; Yaita, Tsuyoshi
ACS Omega (Internet), 2(12), p.8678 - 8681, 2017/12
Times Cited Count：8 Percentile：27.60(Chemistry, Multidisciplinary)Shimoyama, Iwao; Honda, Mitsunori; Kogure, Toshihiro*; Baba, Yuji; Hirao, Norie*; Okamoto, Yoshihiro; Yaita, Tsuyoshi; Suzuki, Shinichi
Photon Factory News, 35(1), p.17 - 22, 2017/05
We introduce Cs-free mineralization (CFM) for Cs removal and reuse of radioactive-contaminated soil in Fukushima and report recent work conducted in the BL27A beamline in Photon Factory. In this work, we investigated compositional and structural changes of Cs-sorbed weathered biotite (WB) before and after heating treatment with addition of NaCl-CaCl salts under low-pressure condition, to study Cs desorption mechanism from clay minerals. X-ray fluorescence spectroscopy clarified that almost all Cs and K were removed with the salts at 700 C. On the other hand, Ca increased with heating temperature. X-ray diffraction and transmission electron microscopy analysis clarified that phase transitions from WB to some Ca-rich silicate minerals, e.g., augite, were caused by the heating treatment with the salt. Based on these results, CFM is proposed for Cs removal utilizing the mechanism in which large monovalent cations are discharged with accompanying the phase transition. We also discuss the role of Cl in this reaction showing chemical bonding change of Cl observed using X-ray absorption spectroscopy in the early stage of the chemical reaction.
-XRD with synchrotron radiationMotai, Satoko*; Mukai, Hiroki*; Watanuki, Tetsu; Owada, Kenji; Fukuda, Tatsuo; Machida, Akihiko; Kuramata, Chisaki*; Kikuchi, Ryosuke*; Yaita, Tsuyoshi; Kogure, Toshihiro*
Journal of Mineralogical and Petrological Sciences, 111(5), p.305 - 312, 2016/10
Times Cited Count：17 Percentile：50.39(Mineralogy)no abstracts in English
Kogure, Toshihiro*; Yamaguchi, Noriko*; Segawa, Hiroyo*; Mukai, Hiroki*; Motai, Satoko*; Akiyama, Kotone*; Mitome, Masanori*; Hara, Toru*; Yaita, Tsuyoshi
Microscopy, 65(5), p.451 - 459, 2016/10
Times Cited Count：56 Percentile：96.81(Microscopy)Mukai, Hiroki*; Hirose, Atsushi*; Motai, Satoko*; Kikuchi, Ryosuke*; Tanoi, Keitaro*; Nakanishi, Tomoko*; Yaita, Tsuyoshi; Kogure, Toshihiro*
Scientific Reports (Internet), 6, p.21543_1 - 21543_7, 2016/02
Times Cited Count：137 Percentile：96.36(Multidisciplinary Sciences)Mukai, Hiroki*; Hatta, Tamao*; Kitazawa, Hideaki*; Yamada, Hirohisa*; Yaita, Tsuyoshi; Kogure, Toshihiro*
Environmental Science & Technology, 48(22), p.13053 - 13059, 2014/12
Times Cited Count：116 Percentile：94.23(Engineering, Environmental)no abstracts in English
Murakami, Takashi*; Kogure, Toshihiro*; ; Onuki, Toshihiko
American Mineralogist, 83, p.1209 - 1219, 1998/00
no abstracts in English
; Murakami, Takashi*; Kogure, Toshihiro*; Isobe, Hiroshi; Sato, Tsutomu
Mat. Res. Soc. Symp. Proc., 506, p.839 - 846, 1998/00
no abstracts in English
Shimoyama, Iwao; Honda, Mitsunori; Kogure, Toshihiro*; Hirao, Norie*; Baba, Yuji; Okamoto, Yoshihiro; Yaita, Tsuyoshi; Suzuki, Shinichi
no journal, ,
We adopted low pressure heating treatments for Cs saturated and sorbed weathered biotite (WB) with some alkaline salts, e.g., CaCl, KCl, NaCl to develop decontamination method for radioactive Cs contaminated soil in Fukushima, and analyzed the samples before and after the treatments using X-ray fluorescence analysis, X-ray diffraction, transmission electron microscopy, and thermal desorption spectroscopy. When we heated WB at 700 C with CaCl, the structure of WB completely decomposed, and almost 100% of Cs and K sorbed in WB were removed from the sample. We observed that the Ca content in the product increased with temperature, which induced phase change from WB to augite and wadalite. These results indicate that Cs and K that are large monovalent cations were discharged by formation of these products. Meanwhile, the addition of KCl removed only 55% of Cs at 700 C through ion exchange reaction keeping the layered structure of WB. Based on these phenomena, we propose the idea of Cs free mineralization that enables us to decontaminate soil using phase change from clay minerals to other minerals by reactions with alkaline salts.
Shimoyama, Iwao; Honda, Mitsunori; Kogure, Toshihiro*
no journal, ,
The decontamination method has not been established for soil contaminated with radioactive Cs. We adopted weathered biotite (WB) which sorbed non-radioactive 
Cs as a model contaminated soil and applied heating treatment to the WB at 700C under a low pressure condition of 14 Pa with NaCl-CaCl mixed salt. X-ray fluorescence analysis showed that almost all Cs and K were removed from the sample at 700C and Ca became dominant with temperature. X-ray diffraction spectra largely changed after the heating treatment indicating some phase transition from WB. Transmission electron microscopy analysis clarified that augite was the dominant product after the heating treatment at 700C. These results suggest a model that Ca derived from the mixed-salt induced the formation of augite, and that K and Cs were eliminated from the product as these large-size cations cannot constitute augite. Based on this model, we propose Cs free mineralization which can achieve decontamination and reuse of soil in Fukushima.
Shimoyama, Iwao; Honda, Mitsunori; Kogure, Toshihiro*; Baba, Yuji; Okamoto, Yoshihiro; Chiba, Noriaki; Yaita, Tsuyoshi; Suzuki, Shinichi
no journal, ,
We have found that Cs can be largely removed from weathered biotite (WB) in Fukushima by low-pressure heating treatment with some alkaline salts, but the detail of the mechanism is still unclear. We analyze compositional and structural change of WB using XRF, XRD, TEM, and NEXAFS. NaCl-CaCl mixed salt and WB were mixed in a weight ratio of 1/1 and heated in a low-pressure condition. Excess salt in the sample was removed by rinsing with distilled water. Cs/Si ratio decreased to 11% and 0 % by the treatment at 600C and 700C, respectively. We found decrease of K with Cs. Meanwhile, Ca and Cl increased with temperature. XRD analysis clarified that new peaks appeared above 500C and peaks of WB disappeared at 700C. TEM analysis clarified that augite and wadalite were dominant products after the heating treatment. NEXAFS analysis clarified that Ca and Cl have different chemical bonding depending on atmospheric and low pressures. Based on these results, we propose Cs free mineralization for decontamination of soil in Fukushima.
Shimoyama, Iwao; Honda, Mitsunori; Kogure, Toshihiro*; Baba, Yuji; Hirao, Norie; Okamoto, Yoshihiro; Yaita, Tsuyoshi; Suzuki, Shinichi
no journal, ,
We have proposed a low-pressure sublimation method for Cs removal from radioactive-contaminated soil in Fukushima. In this work, we investigated compositional and structural changes of Cs-sorbed weathered biotite (WB) before and after low-pressure sublimation with addition of NaCl-CaCl salts, to study Cs desorption mechanism from clay minerals. X-ray fluorescence spectroscopy clarified that 100% of Cs was removed with the salts at 700 C. Moreover, we found that 99% of K in WB was removed as well with the salts. On the other hand, Ca increased with heating temperature. X-ray diffraction analysis clarified that the reflections from WB disappeared and a number of new reflections appeared after the treatment with the salts. These results indicate WB changed to some silicates, and we clarified that the dominant silicate was augite using transmission electron microscopy. Based on these results, we propose a new idea, Cs-free mineralization, for Cs removal from clay minerals utilizing the mechanism in which monovalent large cations are discharged with accompanying phase transition from clay minerals to other minerals.
Honda, Mitsunori; Shimoyama, Iwao; Kogure, Toshihiro*; Okamoto, Yoshihiro; Suzuki, Shinichi; Yaita, Tsuyoshi
no journal, ,
no abstracts in English
