Hydrogen in the Earth core inferred from neutron imaging and diffraction

Takahashi, Naoki*; Sakamaki, Tatsuya*; Hattori, Takanori; Funakoshi, Kenichi*; Arima-Osonoi, Hiroshi*; Sano, Asami; Abe, Jun*; Suzuki, Akio*

Scientific Reports (Internet), 16, p.14162_1 - 14162_13, 2026/05

https://doi.org/10.1038/s41598-026-49969-z

We performed high-pressure and high-temperature neutron diffraction and imaging experiments in situ to determine the hydrogen content in liquid iron. We observed that liquid iron contains 0.17(3) wt.% H at 3.4 GPa and 1400 K, indicating that liquid iron is hydrogenated in the magma ocean during core formation. For the hydrogen content in the liquid iron at the base of the magma ocean, we estimated that the outer and inner cores contain 0.60-0.72 and 0.30-0.44 wt.% H, corresponding to 70-85 and 1.9-2.7 times the mass of hydrogen in the ocean, respectively. This suggests that hydrogen can contribute more than half of the density deficit in the outer core. For the magma ocean equilibrating with the hydrogen-rich primary atmosphere, the study findings show that liquid iron plays a crucial role in transporting a large amount of hydrogen into the core.

Cesium sorption onto alkaline activated materials

Hagiwara, Hiroki; Takaku, Atsushi*; Sagawa, Hiroshi*; Kanno, Futoshi*; Ito, Azusa; Ando, Taichi*; Ichihara, Masatsugu*; Watanabe, Yusuke; Koarai, Kazuma; Kato, Jun; et al.

Proceedings of Waste Management Symposia 2026 (WM2026) (Internet), 7 Pages, 2026/03

Frustrated random-singlet state with ice-type structural fluctuation in spinel titanates

Hanasaki, Noriaki*; Hattori, Takayuki*; Komoda, Takumi*; Minamoto, Kakuei*; Torigoe, Shuhei*; Yamashita, Satoshi*; Nakazawa, Yasuhiro*; Nakano, Takehito*; Yoshimi, Kohei*; Yashima, Mitsuharu*; et al.

Proceedings of the National Academy of Sciences of the United States of America, 123(1), p.e2517926123_1 - e2517926123_6, 2026/01

https://doi.org/10.1073/pnas.2517926123

Sampling of radioactive materials remaining in JMTR Reactor Facility

Ouchi, Takuya; Nagata, Hiroshi; Shinoda, Yuya; Yoshida, Hayato; Inoue, Shuichi; Chinone, Marina; Abe, Kazuyuki; Ide, Hiroshi; Watahiki, Shunsuke

JAEA-Technology 2025-006, 25 Pages, 2025/10

JAEA-Technology-2025-006.pdf:1.59MB

In the future, radioactive waste which generated from nuclear research facilities in Japan Atomic Energy Agency are planning to be buried for the near surface disposal. It is necessary to establish the method to evaluate the radioactivity concentrations of the radioactive wastes. Therefore, at the Oarai Nuclear Engineering Institute, in order to contribute to the study of methods for evaluating radioactivity concentrations of the radioactive wastes from nuclear research facilities, samples were taken from radioactive waste that are expected to be buried in the future and radiochemical analysis is used to obtain data on the radioactivity concentration of each nuclide contained in the radioactive waste. This report presents the concept of selecting sample collection targets and summarizes the sampling of radioactive materials conducted at the JMTR reactor facility in fiscal years 2023 and 2024 to obtain data on radioactivity concentrations.

Particle arrangements and optical changes induced by the water swelling of melanin-like polydopamine layers

Watanabe, Taku*; Maejima, Yui*; Ueda, Yuki; Motokawa, Ryuhei; Takabatake, Ai*; Takeda, Shinichi*; Fudoji, Hiroshi*; Kishikawa, Keiki*; Koori, Michinari*

Langmuir, 41(34), p.22762 - 22773, 2025/09

https://doi.org/10.1021/acs.langmuir.5c01855

The assembled structures of melanin particles, i.e., colloidal particles coated with a melanin-like polydopamine (PDA) layer, create vivid structural colors. While the thickness of the PDA layer influences the particle arrangement and optical properties, the underlying mechanism has remained controversial. We demonstrate that the water swelling characteristics of PDA are crucial factors governing the dispersion and aggregation of these particles in solution. Detailed comparisons between dry and wet conditions revealed that the PDA layer readily absorbs water molecules, which leads to significant swelling in the thicker layers. The swelling of the PDA layers determined whether the particles remained dispersed or partially aggregated in the water, ultimately controlling the particle arrangement in the dry state once the water evaporated. These findings provide insights into the self-assembly of colloidal particles and offer a strategy for tuning the periodic particle order. This feature is pivotal for various applications in optical and sensing technologies.

Estimating the origin of reprocessed Pu for nuclear forensics, 2; Identification of key signature nuclides

Sato, Kaede*; Sagara, Hiroshi*; Han, C. Y.*; Kimura, Yoshiki; Tanabe, Kosuke*

Dai-45-Kai Nihon Kaku Busshitsu Kanri Gakkai Nenji Taikai Kaigi Rombunshu (Internet), 3 Pages, 2024/11

no abstracts in English

Start-up of a test equipment for corrosion evaluation using copper thin film

Suganuma, Kazuaki; Sekiyama, Yoshio*; Honda, Tomoyuki*; Dei, Tatsumi; Suzuki, Katsuo; Fujirai, Kosuke; Suzuki, Hiroshi*; Nakata, Morihiro*; Hosokawa, Hideaki*; Watanabe, Yasuhiro; et al.

Proceedings of 21st Annual Meeting of Particle Accelerator Society of Japan (Internet), p.738 - 740, 2024/10

https://www.pasj.jp/web_publish/pasj2024/proceedings/PDF/THP0/THP061.pdf

In the J-PARC accelerator, the inner surface of the copper tubes that make up most of the coolant pipes is corroded. Generally, additives are added to the coolant to prevent corrosion, but the accelerator is in a radiation environment and additives cannot be used in the coolant to avoid impurities in the coolant become polluted by radiation. For example, in materials research in the nuclear field, there is a lot of research on strong acidic or strong alkaline solutions and corrosion resistant materials, but there is little literature on corrosion protection studies of purified water and copper materials. In general, we believe this is because the use of purified water and copper together in a radiation environment is limited. Corrosion testing of purified water and copper materials is unique to accelerators. The use of a thin copper film was considered as a possible method. In this case, we report on the current status of a new initiative, testing with copper thin films.

Effect of water activity on the mechanical glass transition and dynamical transition of bacteria-solute systems

Kawai, Kiyoshi*; Sogabe, Tomochika*; Nakagawa, Hiroshi; Yamada, Takeshi*; Koseki, Shigenobu*

Journal of Food Engineering, 375, p.112066_1 - 112066_9, 2024/08

https://doi.org/10.1016/j.jfoodeng.2024.112066

The purpose of this study was to clarify effect of glycerol and glucose on the mechanical glass transition and dynamical transition of freeze-dried bacteria at various water activity (aw)-conditions. From the water sorption isotherm, it was noted that the water content at each aw and monolayer water content were higher in the order of glycerol, glucose, non-added samples. Effect of temperature on the mean square displacement (MSD) of atoms in the samples was investigated by incoherent elastic neutron scattering. The MSD increased gradually with an increase in temperature depending on the aw and added solute. From the linear fitting, three dynamical transition temperatures (low-, middle- and high-Tds) were determined. The Couchman-Karasz model suggested that the added solute and bacteria were not completely miscible.

Compact and transportable system for detecting lead-shielded highly enriched uranium using Cf rotation method with a water Cherenkov neutron detector

Tanabe, Kosuke*; Komeda, Masao; Toh, Yosuke; Kitamura, Yasunori*; Misawa, Tsuyoshi*; Tsuchiya, Kenichi*; Sagara, Hiroshi*

Scientific Reports (Internet), 14, p.18828_1 - 18828_10, 2024/08

https://doi.org/10.1038/s41598-024-69526-w

Current numbers of qubits and their uses

Ichikawa, Tsubasa*; Hakoshima, Hideaki*; Inui, Koji*; Ito, Kosuke*; Matsuda, Ryo*; Mitarai, Kosuke*; Miyamoto, Koichi*; Mizukami, Wataru*; Mizuta, Kaoru*; Mori, Toshio*; et al.

Nature Reviews Physics (Internet), 6(6), p.345 - 347, 2024/06

https://doi.org/10.1038/s42254-024-00725-0