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Journal Articles

A Review of Cs-bearing microparticles in the environment emitted by the Fukushima Dai-ichi Nuclear Power Plant accident

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:29 Percentile:76.47(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, $$^{134}$$Cs/$$^{137}$$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.

Journal Articles

Inner structure and inclusions in radiocesium-bearing microparticles emitted in the Fukushima Daiichi Nuclear Power Plant accident

Okumura, Taiga*; Yamaguchi, Noriko*; Dohi, Terumi; Iijima, Kazuki; Kogure, Toshihiro*

Microscopy, 68(3), p.234 - 242, 2019/06

 Times Cited Count:5 Percentile:70.99(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$$^{2+}$$), 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.

Journal Articles

Dissolution behaviour of radiocaesium-bearing microparticles released from the Fukushima nuclear plant

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:22 Percentile:90.33(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 $$_{2}$$ 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$$^{circ}$$C was 0.011 and 0.130 $$mu$$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.

Journal Articles

Secondary radiocesium contamination of agricultural products by resuspended matter

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:1 Percentile:17.98(Chemistry, Analytical)

Journal Articles

Loss of radioactivity in radiocesium-bearing microparticles emitted from the Fukushima Dai-ichi Nuclear Power Plant by heating

Okumura, Taiga*; Yamaguchi, Noriko*; Dohi, Terumi; Iijima, Kazuki; Kogure, Toshihiro*

Scientific Reports (Internet), 8, p.9707_1 - 9707_8, 2018/06

 Times Cited Count:8 Percentile:47.43(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 $$^{circ}$$C and was almost lost when the temperature reached 1000 $$^{circ}$$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.

Journal Articles

Nanoscale spatial analysis of clay minerals containing cesium by synchrotron radiation photoemission electron microscopy

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:2 Percentile:16.24(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$$_{4,5}$$-edge region showed Cs to be present in a monocation state (Cs$$^{+}$$). Further pinpoint XAS measurements were also performed at the Fe L$$_{2,3}$$-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.

Journal Articles

Proposed cesium-free mineralization method for soil decontamination; Demonstration of cesium removal from weathered biotite

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:4 Percentile:17.92(Chemistry, Multidisciplinary)

Journal Articles

Development of cesium-free mineralization for decontamination and reuse of radioactive contaminated soil in Fukushima

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$$_{2}$$ 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 $$^{circ}$$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.

Journal Articles

Mineralogical characterization of radioactive particles from Fukushima soil using $$mu$$-XRD with synchrotron radiation

Motai, 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:12 Percentile:56.21(Mineralogy)

no abstracts in English

Journal Articles

Constituent elements and their distribution in the radioactive Cs-bearing silicate glass microparticles released from Fukushima Nuclear Plant

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:36 Percentile:97.25(Microscopy)

Journal Articles

Cesium adsorption/desorption behavior of clay minerals considering actual contamination conditions in Fukushima

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:100 Percentile:97.28(Multidisciplinary Sciences)

Journal Articles

Speciation of radioactive soil particles in the Fukushima contaminated area by IP autoradiography and microanalyses

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:94 Percentile:95.71(Engineering, Environmental)

no abstracts in English

Journal Articles

Formation of secondary minerals and its effect on anorthite dissolution

Murakami, Takashi*; Kogure, Toshihiro*; *; Onuki, Toshihiko

American Mineralogist, 83, p.1209 - 1219, 1998/00

no abstracts in English

Journal Articles

Crystal chemistry and microstructures of uranyl phosphates

*; Murakami, Takashi*; Kogure, Toshihiro*; Isobe, Hiroshi; Sato, Tsutomu

Mat. Res. Soc. Symp. Proc., 506, p.839 - 846, 1998/00

no abstracts in English

Oral presentation

A Study of colloids in deep groundwater using spectroscopic analysis

Yamamoto, Yuhei; Aosai, Daisuke; Mizuno, Takashi; Watanabe, Katsuaki*; Kogure, Toshihiro*; Suzuki, Yohei*

no journal, , 

no abstracts in English

Oral presentation

Mineralogical characterization of colloidal materials suspended in the deep groundwater from the Toki Granite, central Japan

Watanabe, Katsuaki*; Yamamoto, Yuhei; Aosai, Daisuke; Mizuno, Takashi; Takeno, Naoto*; Kogure, Toshihiro*; Suzuki, Yohei*

no journal, , 

no abstracts in English

Oral presentation

Synchrotron radiation photoemission electron microscope observation of Cs-containing clay mineral

Yoshigoe, Akitaka; Shiwaku, Hideaki; Kobayashi, Toru; Shimoyama, Iwao; Matsumura, Daiju; Tsuji, Takuya; Nishihata, Yasuo; Yaita, Tsuyoshi; Kogure, Toshihiro*; Motai, Satoko*; et al.

no journal, , 

Fundamental researches on adsorption state of radiaoactive Cs in clay mineral (aluminosilicate) have become important from the virewpoints of development of decontamination or volume-reduction techniques since the accident of Fukushima Daiiichi Nuclear Power Station. Pinpoint surface chemical analysis with nanometer spatial resolutions focusing on a target sample has been needed. In this presentation, I will show our recent work on nanoscale pinpoint surface chemical analysis for Cs-containing clay mineral by means of synchrotron radiation PEEM at BL17SU in SPring-8.

Oral presentation

A Cesium detachment from the clay minerals using molten salt treatment and structure analysis

Honda, Mitsunori; Shimoyama, Iwao; Kogure, Toshihiro*; Okamoto, Yoshihiro; Suzuki, Shinichi; Yaita, Tsuyoshi

no journal, , 

no abstracts in English

Oral presentation

Advantages of molten salt processing for volume reduction of Cs-contaminated soil; Structure change of weathered biotite by the reaction with NaCl-CaCl$$_{2}$$ mixed salt

Shimoyama, Iwao; Honda, Mitsunori; Kogure, Toshihiro*; Okamoto, Yoshihiro; Yaita, Tsuyoshi; Suzuki, Shinichi

no journal, , 

X-ray fluorescence (XRF) and X-ray diffraction (XRD) were employed to study bulk composition and structure changes of weathered biotite (WB) before and after low-pressure sublimation processing with NaCl-CaCl$$_{2}$$ mixed salt. XRF showed that almost all Cs was desorbed from Cs-saturated WB after heating at 700 $$^{circ}$$C under a low-pressure (14 Pa) and XRD showed that WB disappeared and augite appeared as the dominant product. We propose a new idea, Cs-free mineralization method, for reduction of Cs-contaminated soil in Fukushima based on these results.

Oral presentation

Pinpoint Analysis of Cs-contained Vermiculite using Synchrotron Radiation PEEM

Yoshigoe, Akitaka; Shiwaku, Hideaki; Kobayashi, Toru; Shimoyama, Iwao; Matsumura, Daiju; Tsuji, Takuya; Nishihata, Yasuo; Yaita, Tsuyoshi; Kogure, Toshihiro*; Motai, Satoko*; et al.

no journal, , 

Pinpoint chemical analysis for Cs-adsorbed vermiculite was performed by using synchrotron radiation photoelectron emission microscopy (SR-PEEM). It was found that Cs is distributed through the micro-size clay particles and we also succeeded to measure pinpoint X-ray absorption spectra for constituent element simultaneously. Furthermore, we precisely confirmed the existence of Fe in the sample.

39 (Records 1-20 displayed on this page)