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

https://doi.org/10.1016/j.jenvrad.2019.04.011

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.

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

https://doi.org/10.1038/s41598-019-40423-x

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 13C 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.

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

https://doi.org/10.1038/s41598-018-28087-5

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.

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

https://doi.org/10.1021/acsomega.7b01304

Mineralogical characterization of radioactive particles from Fukushima soil using -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

https://doi.org/10.2465/jmps.150722

no abstracts in English

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

https://doi.org/10.1038/srep21543

Formation of secondary minerals and its effect on anorthite dissolution

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

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

http://ammin.geoscienceworld.org/content/83/11-12_Part_1/1209.abstract

no abstracts in English

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

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.

Advantages of molten salt processing for volume reduction of Cs-contaminated soil; Structure change of weathered biotite by the reaction with NaCl-CaCl 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 mixed salt. XRF showed that almost all Cs was desorbed from Cs-saturated WB after heating at 700 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.