International benchmark on radionuclide solubility and speciation for the Long-term In-situ Test (LIT) at Grimsel Test Site (GTS, Switzerland)

Noseck, U.*; Schfer, T.*; Alonso, U.*; Hamamoto, Takafumi*; Havlova, V.*; Hibberd, R.*; Ishidera, Takamitsu; Kitamura, Akira; Klajmon, M.*; Missana, T.*; et al.

Applied Geochemistry, 201, p.106762_1 - 106762_23, 2026/04

https://doi.org/10.1016/j.apgeochem.2026.106762

Thermodynamic benchmark calculations have been performed to better understand the behavior of Se(VI), Tc(VII), U(VI), Np(V), Am(III), Th(IV) and Pu(IV)) in the evolving geochemical conditions of the Long-term In-situ Test (LIT) at the Grimsel Test Site (GTS) and corresponding mock-up experiment. It also aims to identify the status of the geochemical speciation models and databases for these elements. The experiments are simulating the near-field conditions in some radioactive waste repository concept including a bentonite engineered barrier emplaced in crystalline rock and the findings are contributing to the long-term safety assessment of these facilities.

In situ study of growth mechanism of germanene segregated through Ag(111) thin films by Raman and X-ray photoelectron spectroscopy

Terasawa, Tomoo; Katsube, Daiki*; Yano, Masahiro; Ozawa, Takahiro*; Tsuda, Yasutaka; Yoshigoe, Akitaka; Asaoka, Hidehito; Suzuki, Seiya

Chemistry of Materials, 38(6), p.2933 - 2945, 2026/03

AA2025-0822.pdf:1.33MB

https://doi.org/10.1021/acs.chemmater.5c03462

Microbial survivability during repeated extreme dry-wet cycles determines CO emissions after rewetting of dried soils in humid temperate forests

Nakayama, Masataka*; Suzuki, Yuri; Abe, Yukiko; Taniguchi, Takeshi*; Atarashi-Andoh, Mariko; Koarashi, Jun; Nagano, Hirohiko*

Biogeochemistry, 169(2), p.15_1 - 15_15, 2026/02

https://doi.org/10.1007/s10533-026-01310-6

Development of HCl-free solid-phase extraction combined with ICP-MS/MS for rapid assessment of difficult-to-measure radionuclides, 4; Rapid determination of ^$Pd in concrete rubble

Ota, Yuki; Do, V.-K.; Banjarnahor, I. M.; Iwahashi, Hiroyuki; Furuse, Takahiro; Tanaka, Kosuke

Journal of Radioanalytical and Nuclear Chemistry, 335(1), p.939 - 948, 2026/02

https://doi.org/10.1007/s10967-026-10735-0

Enhancement of deuterium enrichment efficiency in PEM water electrolysis via isotope exchange equilibrium shift

Yano, Masahiro; Kubo, Shinji; Yasuda, Satoshi

Chemical Engineering Journal, 528, p.172423_1 - 172423_9, 2026/01

https://doi.org/10.1016/j.cej.2025.172423

Negligible hydrogen solubility in FeS under high-pressure and high-temperature conditions; Implications for hydrogen storage in planetary cores

Takano, Masahiro*; Kagi, Hiroyuki*; Mori, Yuichiro*; Kobayashi, Hiroki*; Aoki, Katsutoshi*; Takahashi, Yoshio*; Ijichi, Yuta*; Kakizawa, Sho*; Tsujino, Noriyoshi*; Higo, Yuji*; et al.

ACS Earth and Space Chemistry (Internet), 15 Pages, 2026/00

https://doi.org/10.1021/acsearthspacechem.5c00326

Iron monosulfide (FeS) is an important sulfide phase in planetary materials and has been proposed as a potential host of hydrogen in planetary interiors. However, hydrogen solubility in FeS at high pressure and temperature remains debated. In this study, hydrogen incorporation in the NiAs-type FeS phase (FeS V) was reexamined using synchrotron X-ray absorption spectroscopy, in situ X-ray and neutron diffraction, and first-principles calculations. The experimental results indicate that the volume expansion observed under hydrogen-saturated conditions is explained by the reduction of Fe to Fe and a decrease in the value of Fe-deficient FeS, rather than hydrogen incorporation into the lattice. These results suggest that hydrogen incorporation in FeS is extremely limited, with an upper bound of approximately 200 ppm up to 30 GPa.

Environmentally friendly geopolymers; Synthesis and characterization of pH-Controlled metakaolinite; Phosphate-based hardened bodies

Kozai, Naofumi; Tokunaga, Kohei; Dohi, Terumi; Takahashi, Yoshio*

Journal of Environmental Chemical Engineering, 13(6), p.119612_1 - 119612_9, 2025/12

https://doi.org/10.1016/j.jece.2025.119612

High stabilization of pentavalent uranium on magnetite nanoparticles evidenced by high-energy-resolution X-ray absorption spectroscopy

Yomogida, Takumi; Scaria, J.*; Fablet, L.*; Tokunaga, Kohei; Dei, Shuntaro; Higashi, Kotaro*; Kawamura, Naomi*; Takahashi, Yoshio*; Marsac, R.*

Chemical Communications, 61(91), p.17926 - 17929, 2025/11

https://doi.org/10.1039/D5CC04540A

This paper presents insights into the influence of magnetite stoichiometry (0 R = Fe(II)/Fe(III) 0.5) on the surface reduction of U(VI) to U(V) and U(IV), as a key parameter controlling U redox speciation in natural settings. Although R can readily change due to the oxidation of structural Fe(II) or proton/ligand-promoted dissolution, prior studies have not quantified U(V) when assessing these effects. We employed U L-edge HERFD-XANES spectroscopy to investigate the electronic structure of U on magnetite with varying stoichiometries and observed a peak splitting of U(V) on magnetite. Our results demonstrate the high stability of U(V) species under a wide range of conditions, and after 10 days on magnetite by the combination of MCR-ALS analysis. A key finding is that structural Fe(II), whose abundance depends on pH and redox conditions, plays a critical role for in the stabilization of U(V) on magnetite.

Ion solvation under gigapascal pressure

Jing, Z.*; Yamaguchi, Toshio*; Machida, Shinichi*; Hattori, Takanori; Zhou, Y.*

Journal of Chemical Physics, 163(19), p.194505_1 - 194505_12, 2025/11

https://doi.org/10.1063/5.0304419

Ion solvation in a range of gigapascal pressure is of great significance for high-pressure chemical synthesis and the circulation of matter within the Earth's interior. We perform neutron scattering (NS) experiments and molecular dynamics simulations of deuterated aqueous solutions of MCl (M = Li, Na, K, Rb, and Cs) at 0.1 MPa and 0.7 GPa/298 K. An empirical potential structure refinement method analyzes the NS data. Upon compression to 0.7 GPa, the outer-shell water molecules enter the nearest neighbor of ions, and the solvated ion clusters become denser. The hydration factor and static hydration number based on the orientation distribution of the water dipole in the first solvation shell, show that the compression weakens the hydration ability of the ions. Compression suppresses the diffusion of ions, particularly of the structure-breaking ions. The ionic diffusion coefficient residence time of water molecules and dynamic hydration number indicate that Rb and Cs exhibit characteristics of structure-making ions under compression. The dynamic properties are more pressure-sensitive than the static structure.

Actinide separation by column method using polyvinylpolypyrrolidone

Wada, Kazuma*; Kazama, Hiroyuki*; Abe, Chikage*; Onishi, Takashi; Yamamoto, Masahiko; Taguchi, Shigeo; Kuno, Takehiko; Maeda, Koji; Idemitsu, Kazuya*; Suzuki, Tatsuya*

Journal of Radioanalytical and Nuclear Chemistry, 334(11), p.8961 - 8968, 2025/11

https://doi.org/10.1007/s10967-025-10539-8

The feasibility of using commercially available polyvinylpolypyrrolidone (PVPP) as a pretreatment for mass spectrometry to separate actinides was investigated. Uranium, thorium, and plutonium were used as actinides in the study. Adsorption data for An(IV) and An(VI) were obtained by adsorption experiments in nitric acid. In addition, An(III)/An(IV)/An(VI) mutual separation was successfully performed by a column separation method using PVPP. Furthermore, the elution efficiency of U(VI) was improved by the introduction of carbonate ions. This method may be applicable as a mutual separation for actinide mass spectrometry.