Chemical species of cesium and iodine in condensed vaporized microparticles formed by melting nuclear fuel components with concrete materials

Onuki, Toshihiko*; Ye, J.*; Kato, Tomoaki; Liu, J.; Takano, Masahide; Kozai, Naofumi; Utsunomiya, Satoshi*

Environmental Science; Processes & Impacts, 25(7), p.1204 - 1212, 2023/07

https://doi.org/10.1039/D3EM00074E

To elucidate chemical forms of Cs and I in microparticles produced via the Fukushima Daiichi Nuclear Power Plant accident and released into the atmosphere, we analyzed Cs and I in condensed vaporized particles (CVP) produced by melting experiments using nuclear fuel components containing CsI with concrete. CVPs consisted of many round particles containing Cs and I of diameters less than several tens of micrometers. Two kinds of particles were present: one containing large amounts of Cs and I, suggesting the presence of CsI, and the other containing small amounts of Cs and I with large Si contents. Most of CsI from both particles were dissolved in water. On the contrary, some fractions of Cs remained from the latter particles. These results suggest that Cs was incorporated in CVPs along with Si to form water low-soluble CVPs

Volatilization of BC control rods in Fukushima Daiichi nuclear reactors during meltdown; B-Li isotopic signatures in cesium-rich microparticles

Fueda, Kazuki*; Takami, Ryu*; Minomo, Kenta*; Morooka, Kazuya*; Horie, Kenji*; Takehara, Mami*; Yamasaki, Shinya*; Saito, Takumi*; Shiotsu, Hiroyuki; Onuki, Toshihiko*; et al.

Journal of Hazardous Materials, 428, p.128214_1 - 128214_10, 2022/04

https://doi.org/10.1016/j.jhazmat.2022.128214

Function of microbes on chemical species transformation of radionuclides

Onuki, Toshihiko*; Ozaki, Takuo*; Kozai, Naofumi; Utsunomiya, Satoshi*

Behavior of Radionuclides in the Environment I; Function of Particles in Aquatic System, p.67 - 92, 2020/00

https//doi.org/10.1007/978-981-15-0679-6

It has been experimentally revealed that microorganisms transform radionuclides. For example, cells of microorganisms such as bacteria and yeast accumulate actinides on the surface. Phosphate ions released from microorganism cells precipitate actinides as phosphates. This chapter discusses the role of environmental microorganisms on migration of actinides in the groundwater around Lake Karachai where a lot of radioactive wastes from nuclear facilities of the Soviet Union.

Removal of soluble strontium via incorporation into biogenic carbonate minerals by halophilic bacterium Bacillus sp. strain TK2d in a highly saline solution

Horiike, Takumi*; Dotsuta, Yuma*; Nakano, Yuriko*; Ochiai, Asumi*; Utsunomiya, Satoshi*; Onuki, Toshihiko; Yamashita, Mitsuo*

Applied and Environmental Microbiology, 83(20), p.e00855-17_1 - e00855-17_11, 2017/10

https://doi.org/10.1128/AEM.00855-17

Radioactive strontium (Sr) leaked into the ocean from the Fukushima Daiichi Nuclear Power Plant after the nuclear accident. Since the removal of Sr using general adsorbents is not efficient at high salinity, this study investigated removal of soluble Sr from a saline solution by biogenic carbonate minerals. An isolate, Bacillus sp. strain TK2d, from marine sediment removed more than 99 % of Sr in a saline solution. Sr adsorbed at the cell surface and then carbonate minerals containing Sr developed outside the cells.

Radioactive Cs in the estuary sediments near Fukushima Daiichi Nuclear Power Plant

Yamasaki, Shinya*; Imoto, Jumpei*; Furuki, Genki*; Ochiai, Asumi*; Onuki, Toshihiko; Sueki, Keisuke*; Namba, Kenji*; Ewing, R. C.*; Utsunomiya, Satoshi*

Science of the Total Environment, 551-552, p.155 - 162, 2016/05

https://doi.org/10.1016/j.scitotenv.2016.01.155

Cesium-137 (Cs) of estuary sediment impacted by the FDNPP was measured. Increasing radioactivity was observed from surface to bottom. 90% of the Cs was strongly bound to clay minerals in the estuary sediments. These results suggest that Cs is being transported from contaminated paddy fields to the estuary.

Radioactive Cs in the severely contaminated soils near the Fukushima Daiichi Nuclear Power Plant

Kaneko, Makoto*; Iwata, Hajime; Shiotsu, Hiroyuki; Masaki, Shota*; Kawamoto, Yuji*; Yamasaki, Shinya*; Nakamatsu, Yuki*; Imoto, Jumpei*; Furuki, Genki*; Ochiai, Asumi*; et al.

Frontiers in Energy Research (Internet), 3, p.37_1 - 37_10, 2015/09

https://doi.org/10.3389/fenrg.2015.00037

The mobility of the aggregates of submicron-sized sheet aluminosilicate in the surface environment is a key factor controlling the current Cs migration in Fukushima.

Effect of minerals on accumulation of Cs by fungus

Onuki, Toshihiko; Sakamoto, Fuminori; Yamasaki, Shinya*; Kozai, Naofumi; Shiotsu, Hiroyuki; Utsunomiya, Satoshi*; Watanabe, Naoko*; Kozaki, Tamotsu*

Journal of Environmental Radioactivity, 144, p.127 - 133, 2015/06

https://doi.org/10.1016/j.jenvrad.2015.02.018

The accumulation of Cs by unicellular fungus of in the presence of minerals has been studied to elucidate the role of microorganisms in the migration of radioactive Cs in the environment. In the presence of minerals in the agar medium, the radioactivity in the yeast cells was in the order of mica smectite, illite vermiculite, phlogopite, zeolite. This order is inversely correlated to the ratio of the concentration of radioactive Cs between the minerals and the medium solution. These results strongly suggest that the yeast accumulates radioactive Cs competitively with minerals.

Adsorption of ytterbium onto fungal cells; A pH-dependent contribution of phosphoryl functional group

Jiang, M. Y.*; Onuki, Toshihiko; Yamasaki, Shinya; Tanaka, Kazuya*; Utsunomiya, Satoshi*

Journal of Radioanalytical and Nuclear Chemistry, 295(3), p.2283 - 2287, 2013/03

https://doi.org/10.1007/s10967-012-2285-x

The adsorption of Ytterbium on the cells of yeast has been studied by batch type experiment by changing solution pH. The Yb adsorption species on the yeast cell wall of the was determined by extended X-ray absorption fine structure (EXAFS) spectroscopy combined with a linear combination analysis at various pHs. The results indicated that the contribution of Yb-phosphoryl species was constant between pH 3 and 5, strongly suggesting that most of the Yb was associated with undeprotonated phosphoryl functional groups.

Biological nano-mineralization of Ce phosphate by

Jiang, M.; Onuki, Toshihiko; Kozai, Naofumi; Tanaka, Kazuya; Suzuki, Yoshinori*; Sakamoto, Fuminori; Kamiishi, Eigo*; Utsunomiya, Satoshi*

Chemical Geology, 277(1-2), p.61 - 69, 2010/10

https://doi.org/10.1016/j.chemgeo.2010.07.010

We have investigated the mechanism underlying Ce sequestration by yeast after exposure to Ce(III) solution at pH 3, 4, or 5. We found that needle-shaped Ce(III) phosphate nanocrystallites with a monazite structure formed on the yeast cells by exposure to Ce(III) for 42 h, even though the initial solutions did not contain any P species. These results suggest that the sorbed Ce on the cell surfaces reacted with P released from inside the yeast cell, resulting in the formation of Ce(III) phosphate nanocrystallites.

Biomineralization of REE phosphate nano-minerals by Saccharomyces cerevisiae

Jiang, M.; Onuki, Toshihiko; Kozai, Naofumi; Tanaka, Kazuya; Suzuki, Yoshinori; Utsunomiya, Satoshi*

no journal, , 

We investigated association of Ce with yeast S. cerevisiae at pH of 3, 4, and 5. SEM analysis showed that nano-sized Ce bearing minerals were developed on the cell surface. TEM and SAED analyses showed that the Ce- bearing mineral is monazite.