Occurrence of radioactive cesium-rich micro-particles (CsMPs) in a school building located 2.8 km south-west of the Fukushima Daiichi Nuclear Power Plant

Fueda, Kazuki*; Komiya, Tatsuki*; Minomo, Kenta*; Horie, Kenji*; Takehara, Mami*; Yamasaki, Shinya*; Shiotsu, Hiroyuki; Onuki, Toshihiko*; Grambow, B.*; Law, G. T. W.*; et al.

Chemosphere, 328, p.138566_1 - 138566_12, 2023/07

https://doi.org/10.1016/j.chemosphere.2023.138566

Preface to the special issue on the Fukushima Daiichi Nuclear Power Plant accident and geochemistry; 10 years after the Fukushima accident

Tanaka, Kazuya; Yamasaki, Shinya*

Chikyu Kagaku, 55(4), p.93 - 95, 2021/12

https://doi.org/10.14934/chikyukagaku.55.93

Ten years have passed since the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident. In this special issue, we compiled review papers on the environmental behavior of the FDNPP-derived radionuclides from various research fields. This special issue shows that various research fields contributed to better understandings on the environmental behavior of the FDNPP-derived radionuclides.

investigation of radioactive Cs mobility around litter zone in contaminated forest using spent mushroom substrata

Onuki, Toshihiko*; Sakamoto, Fuminori; Kozai, Naofumi; Yamasaki, Shinya*; Sasaki, Yoshito; Niizato, Tadafumi

Journal of Nuclear Science and Technology, 56(9-10), p.814 - 821, 2019/09

https://doi.org/10.1080/00223131.2019.1588799

We used the spent mushroom substrata (SMSs) which are a kind of by-product after growing edible mushrooms for the investigation of radioactive Cs mobility in litter zone in a forest of Fukushima prefecture, Japan. The powder SMS was filled in a plastic net bag of 0.350.55 m, then was placed in a forest for 6 months under three kinds of different conditions without treatment (No treatment), covered with wooden box (With box), and with zeolite placed on upper position of ground surface (With zeolite). We determined the ratio of radioactivity (TF) in the SMS to that of the soil and litter beneath the SMS bags. TFs of "No treatment" and of "With zeolite" were determined between 0.01 and 0.05 for 6 months. On the other hand, TFs of "With box" were lower by one order at 2 and 4 months than those of "No treatment" and of "With zeolite", and nearly the same values as TFs of "No treatment" and "With zeolite" at 6 months. These results clearly indicate that radioactive Cs accumulates in SMS mainly by throughfall. In addition, for a period of several months, fungi contribute to the accumulation of radioactive Cs in the litter zone, even though radioactive Cs was tightly associated with the soil.

High spectral resolution of diode laser absorption spectroscopy for isotope analysis using a supersonic plasma jet

Kuwahara, Akira; Aiba, Yasuaki*; Yamasaki, Shinya*; Nankawa, Takuya; Matsui, Makoto*

Journal of Analytical Atomic Spectrometry, 33(7), p.1150 - 1153, 2018/07

https://doi.org/10.1039/C8JA00120K

Although high-temperature plasma sources have been used for direct isotope analysis of solid samples, the spectral resolution of diode laser absorption spectroscopy in high-temperature plasma is limited by the Doppler broadening of atomic absorption lines. Thus, a decrease in translational temperature is necessary to enhance the spectral resolution and distinguish isotope shifts due to mass number. In this study, a supersonic plasma wind tunnel, also called an arc-jet plasma wind tunnel, was used to enhance spectral resolution drastically, and a demonstration was carried out using natural stable xenon isotopes. As a result, the temperature was found to be about 180 K and the spectral resolution was about one order of magnitude higher than that of the conventional high-temperature source. Additionally, the method proposed herein was verified by using two xenon isotopes.

Effect of flavin compounds on uranium(VI) reduction- kinetic study using electrochemical methods with UV-vis spectroscopy

Yamasaki, Shinya*; Tanaka, Kazuya; Kozai, Naofumi; Onuki, Toshihiko

Applied Geochemistry, 78, p.279 - 286, 2017/03

https://doi.org/10.1016/j.apgeochem.2017.01.014

This study examined the rate constant for the U(VI) reduction process by three flavin analogues, which are redox-active biomolecules secreted from anaerobic bacteria, to elucidate their substituent group effect on the U(VI) reduction rate by electrochemical methods. The formation of the U(IV) was monitored by UV-vis spectrometry in the presence of the flavins. The rate constant for the U(VI) reduction by the flavins was determined. The apparent reduction potential of U(VI) increased about 0.2 V in the presence of the mediators, which strongly suggests that the biological electron mediator makes the U(VI) reduction possible even under more oxidative conditions.

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.

Utilization status of the electron accelerator and the -ray irradiation facilities

Agematsu, Takashi; Uno, Sadanori; Hanaya, Hiroaki; Yamagata, Ryohei; Seito, Hajime; Nagao, Yuto; Yamasaki, Shota; Kawashima, Ikuo*; Yagi, Norihiko*; Takagi, Masahide*; et al.

JAEA-Review 2015-022, JAEA Takasaki Annual Report 2014, P. 173, 2016/02

https://doi.org/10.11484/jaea-review-2015-022

The electron accelerator and the three -ray irradiation facilities of Takasaki Advanced Radiation Research Institute were operated for various research subjects according to the operation plan in FY 2014. The number of research subjects in FY 2014 decreased at the electron accelerator with operation stop by accelerator trouble, and increased slightly at the -ray irradiation facilities as compared with FY 2013, and research subjects were 205 and 857, respectively. Among these research subjects, 35 and 172 related to recovery from the Fukushima Daiichi Nuclear disaster, respectively, were performed at the electron accelerator and the -ray irradiation facilities, respectively.

Current status of the electron accelerator at TARRI, JAEA

Uno, Sadanori; Hanaya, Hiroaki; Yamasaki, Shota; Yamagata, Ryohei; Seito, Hajime; Nagao, Yuto; Agematsu, Takashi; Kawashima, Ikuo*; Yagi, Norihiko*; Takagi, Masahide*; et al.

Dai-28-Kai Tandemu Kasokuki Oyobi Sono Shuhen Gijutsu No Kenkyukai Hokokushu, p.121 - 123, 2015/12

no abstracts in English

Sorption of trivalent cerium by a mixture of microbial cells and manganese oxides; Effect of microbial cells on the oxidation of trivalent cerium

Onuki, Toshihiko; Jiang, M.*; Sakamoto, Fuminori; Kozai, Naofumi; Yamasaki, Shinya*; Yu, Q.; Tanaka, Kazuya; Utsunomiya, Satoshi*; Xia, X.*; Yange, K.*; et al.

Geochimica et Cosmochimica Acta, 163, p.1 - 13, 2015/08

https://doi.org/10.1016/j.gca.2015.04.043

The association of Ce(III) with the microbial cell surface and the formation of Ce phosphate nano-particles are responsible for suppressing the oxidation of Ce(III) to Ce(IV) in the mixtures.

Application of simplified desorption method to study on sorption of americium(III) on bentonite

Kozai, Naofumi; Yamasaki, Shinya; Onuki, Toshihiko

Journal of Radioanalytical and Nuclear Chemistry, 299(3), p.1571 - 1579, 2014/03

https://doi.org/10.1007/s10967-013-2799-x

To elucidate the sorption behavior of americium(III) on bentonite simplified desorption experiments were applied to the solid phases collected after the sorption experiments. The sorption-desorption behavior was examined in the final pH range from 2 to 8. The desorption experiments revealed that most of the Am was sorbed on the montmorillonite moiety of the bentonite. The sorption of Am on montmorillonite was divided into two types: one was the "exchangeable" sorption, in which the sorbed Am was desorbed with a 1M KCl aqueous solution, and the rest was the "unexchangeable" sorption. The exchangeable sorption was ion exchange of mostly Am. The unexchangeable sorption was the strong sorption of Am hydroxides. An accessory iron mineral, pyrite, might be involved in the Am sorption on bentonite at neutral pH.