X-ray inverse fluorescence approach for accurate determination of Fe valence in Fe-rich geological materials

Nakada, Ryoichi*; Okuda, Hanaya*; Suga, Hiroki*; Yamaguchi, Akiko; Takahashi, Yoshio*; Kawazoe, Takaaki*

Geochemical Journal, 60(2), p.18 - 26, 2026/03

https://doi.org/10.2343/geochemj.GJ26003

Iron undergoes redox transitions between ferrous (Fe) and ferric (Fe) states, playing a key role in various geoscientific processes from Earth's interior to surface environments. Partial fluorescence yield X-ray absorption near edge structure analysis (PFY-XANES) is widely used to evaluate iron valence, but it is susceptible to thickness and self-absorption effects in high-concentration samples. In this study, we applied the inverse fluorescence yield method (IPFY) to geological samples and demonstrated that it enables more accurate iron valence determination than PFY. IPFY-XANES suppressed overestimation of the Fe ratio and reduced thickness effects. This method is expected to be a powerful non-destructive tool for analyzing natural samples such as meteorites and high-pressure recovered specimens.

Speciation of cesium in a radiocesium-bearing microparticle emitted from Unit 1 during the Fukushima nuclear accident by XANES spectroscopy using transition edge sensor

Takahashi, Yoshio*; Miura, Hikaru*; Yamada, Shinya*; Sekizawa, Oki*; Nitta, Kiyofumi*; Hashimoto, Tadashi*; Yomogida, Takumi; Yamaguchi, Akiko; Okada, Shinji*; Itai, Takaaki*; et al.

Journal of Hazardous Materials, 495, p.139031_1 - 139031_19, 2025/09

https://doi.org/10.1016/j.jhazmat.2025.139031

In this presentation, we analyzed the chemical state of cesium in radiocesium-bearing microparticles (CsMPs) released during the 2011 Fukushima Daiichi Nuclear Power Plant accident using high-resolution X-ray absorption spectroscopy (XANES) and micro X-ray fluorescence (-XRF). The results identified two forms of cesium: one dissolved in glass and the other enriched on the surfaces of internal voids. The latter is considered to have originally existed as a gas and became concentrated during the cooling and solidification of the molten glass. These findings are crucial for understanding the formation process of CsMPs during the accident, as well as for future decommissioning and safety assessments.

A Systematic understanding of adsorption reaction on clay minerals focusing on radium as a key element

Yamaguchi, Akiko; Okumura, Masahiko; Takahashi, Yoshio*

SPring-8/SACLA Research Frontiers 2024 (Internet), p.86 - 87, 2025/08

Adsorption reactions on clay minerals are important reactions that affect the environmental behavior of various elements, but due to their complexity, there are still many unresolved issues. In this study, we focused on radium, which has the largest ionic radius among alkaline earth metals, and performed the world's first extended X-ray absorption fine structure (EXAFS) measurement of radium adsorbed on clay minerals to clarify the adsorption structure of radium. The results for radium were compared with those for other elements, and the stability of the adsorption structure was evaluated by first-principles calculations to clarify the determinants of the adsorption structure of clay minerals.

Understanding of effect of dispersion length on maximum nuclide release rate as an indicator for safety assessment of geological disposal

Kabasawa, Satsuki; Yamaguchi, Masaaki; Hirano, Fumio; Kato, Tomoko

Genshiryoku Bakkuendo Kenkyu (CD-ROM), 32(1), p.10 - 22, 2025/06

https://doi.org/10.3327/jnuce.32.1_10

In nuclide migration analyses for the safety assessments of geological disposal, when there is not necessarily sufficient confidence knowledge and data required for modeling phenomena, analyses are conducted using sufficiently conservative depending on the reliability of the technical basis, such as selecting data settings and modeling that yield severe results. There is a high level ofuncertainty for setting a parameter value of dispersion length used for the nuclide migration analysis, due to the difficulty in measuring field scale data. However, the effects of fluctuation of dispersion length on maximum nuclide release rate has not yet been fully understood. In this study, the effect of fluctuation of dispersion length on maximum nuclide release rate was investigated. Specifically, a series of the sensitivity analysis focusing on not only the effect of fluctuation of dispersion length but also the effect of parameters related to the retardation effect such as distribution coefficient and half-life of nuclides was performed for fracture medium. As a result, it was suggested the maximum nuclide release rate may increase due to the shortened nuclide transit time as the dispersion length increases. When peak of the nuclide release rate is less than the half-life of the nuclide, the increase of the maximum release rate due to an increase in the dispersion length remains limited to a few times. On the other hand, in case of exceeding half-life, the maximum nuclide release rate increases ten times or more as the maximum release rate occurrence time of the release rate decreases. These findings would contribute to setting the conservative value of dispersion length taking the uncertainty into consideration.

Clustering in nuclei and hadrons

Hosaka, Atsushi; Kanada-Eno, Yoshiko*; Yamaguchi, Yasuhiro*

European Physical Journal A, 61(5), p.103_1 - 103_17, 2025/05

https://doi.org/10.1140/epja/s10050-025-01530-8

no abstracts in English

Effect of the ratio of water to rice on the molecular dynamics of cooked rice starch during retrogradation; Implications for amorphous structure in gelatinized state

Hirata, Yoshinobu*; Nakagawa, Hiroshi; Yamauchi, Hiroki; Kaneko, Koji; Hagihara, Masato; Yamaguchi, Hideyuki*; Imaizumi, Teppei*; Nishizu, Takahisa*

International Journal of Biological Macromolecules, 306, p.141668_1 - 141668_7, 2025/03

https://doi.org/10.1016/j.ijbiomac.2025.141668

We used quasi-elastic neutron scattering (QENS) to investigate the effect of the ratio of water to rice on the molecular dynamics of cooked rice starch during retrogradation. X-ray diffraction and differential scanning calorimetric measurements revealed that the degree of recrystallization and change in enthalpy were smaller with an increase in the amount of water added for cooking rice, whereas little difference in the crystallinity of the gelatinized rice starch was detected. The QENS measurements determined that the elastic incoherent structure factor (EISF) values of gelatinized samples were smaller with an increase in the amount of water added for cooking rice, indicating that the molecular dynamics of gelatinized rice starch with higher added water content were spatially more extended.

Adsorption structures and bonding states of cesium and barium adsorbed on various sites of vermiculite

Yamaguchi, Akiko; Okumura, Masahiko; Kawamura, Naomi*; Takahashi, Yoshio*

Science of the Total Environment, 964, p.178585_1 - 178585_13, 2025/02

https://doi.org/10.1016/j.scitotenv.2025.178585

There are many unresolved issues in the adsorption reactions of clay minerals. One of the reasons is the existence of multiple adsorption sites. It is known that the contribution of each adsorption site depends on the concentration of adsorbed ions, and there is a challenge in comprehensively correlate the results of atomic-level simulations that employ limited number of atoms and inevitably deal high-concentration samples with actual environmental samples where concentrations are orders of magnitude lower. In this study, we combined experiments using synchrotron radiation and first-principles calculations to comprehensively elucidate the systematic changes in the local structure of adsorption sites and adsorbed ions based on the adsorption concentration at the atomic level, and demonstrated that the interaction between adsorbed ions and clay minerals involves ionic bonding.

Interpretation of vertical migration and enrichment processes of rare earth elements (REEs) in ion-adsorption-type mineralization in Japan based on REE speciation analyses

Nagasawa, Makoto*; Shimizu, Yusuke*; Yamaguchi, Akiko; Tokunaga, Kohei; Mukai, Hiroki*; Aoyagi, Noboru; Mei, H.; Takahashi, Yoshio*

Chemical Geology, 670, p.122431_1 - 122431_25, 2024/12

https://doi.org/10.1016/j.chemgeo.2024.122431

Meeting report on the EPRBioDose2024, Hirosaki

Fujishima, Yohei*; Anderson, D.*; Abe, Yu*; Alkebsi, L.*; Oka, Toshitaka; Tani, Atsushi*; Kranrod, C.*; Toyoda, Shin*; Hamasaki, Kanya*; Hirota, Seiko*; et al.

Nihon Hoshasen Jiko, Saigai Igakkai Zasshi, 7(1), p.21 - 26, 2024/12

no abstracts in English

Characterization of mineral composition using PIXE and EXAFS analyses to elucidate the Barium adsorption mechanism

Oguri, Kaori; Hagura, Naoto*; Yamaguchi, Akiko; Okumura, Masahiko; Matsuura, Haruaki*; Tsunashima, Yasumichi; Aoki, Katsumi; Arai, Yoichi; Watanabe, So

Nuclear Instruments and Methods in Physics Research B, 556, p.165516_1 - 165516_8, 2024/11

https://doi.org/10.1016/j.nimb.2024.165516

Ningyo-toge is the uranium mine that has been operated in Japan. Various radioactive elements such as Uranium (U), and Radium (Ra) are still present in the mine ground water with very small amount, and behavior of those elements is not fully understood. In this study, we investigated the composition of metal oxides and clay minerals in a soil of slag deposit at the mine, and systematics of adsorption structure of various ions were examined. Identifying the composition and chemical forms of minerals present in the soil of slag can provide useful information for the safety assessment and evaluation of influence on the surrounding environment.