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.

Development of a temperature-dependent chemical simulation code based on PHITS for water radiolysis from 0 to 350C

Matsuya, Yusuke; Yoshii, Yuji*; Kusumoto, Tamon*; Wang, Y.*; Ogawa, Tatsuhiko; Sato, Tatsuhiko; Kai, Takeshi

Scientific Reports (Internet), 24 Pages, 2026/00

https://doi.org/10.1038/s41598-026-52128-z

Water radiolysis plays an important role in radiation effects on materials, such as DNA damage in the human body and corrosion processes in nuclear reactors. Conventional chemical simulation codes are generally limited to around room temperature, which differs significantly from the temperature conditions encountered in reactor environments. In this study, we developed a chemical simulation code (PHITS-Chem) based on the general-purpose Monte Carlo code, the Particle and Heavy Ion Transport code System (PHITS), applicable over a temperature range 0 to 350C. The code explicitly considers the temperature dependence of diffusion coefficients and reaction rate constants, and its performance was validated by comparing the calculated G-values with previously reported experimental and theoretical data for low-LET (0.2 keV/m), medium-LET (11.9 keV/m), and high-LET (63.4 keV/m) radiation. The developed code enables high-precision evaluation of the reaction kinetics of radiolytic species over a wide temperature range and is expected to be useful for assessing in-core material degradation and for studies related to severe accident mitigation in nuclear reactors.

A New perspective into molten corium concrete interaction for interpreting Fukushima Dai-Ichi terrace-shaped debris

Pshenichnikov, A.

Scientific Reports (Internet), 15, p.23513_1 - 23513_11, 2025/07

https://doi.org/10.1038/s41598-025-09107-7

Neutron resonance absorption imaging fully utilizing neutron energies from 1 eV to 100 keV

Tsuchikawa, Yusuke; Kai, Tetsuya; Parker, J.*; Matsumoto, Yoshihiro*; Shinohara, Takenao

Scientific Reports (Internet), 15, p.7687_1 - 7687_8, 2025/03

https://doi.org/10.1038/s41598-025-92174-7

A neutron resonance absorption imaging technique to visualize two-dimensional distributions with element discrimination has been developed at the Materials and Life Science Experimental Facility of the Japan Proton Accelerator Research Complex. We measured neutron transmission spectra from 1 eV to 100 keV while rotating a sample containing iron, zirconium, nickel, molybdenum, and aluminum rods. The distributions of hafnium (impurity of zirconium) and molybdenum were clearly obtained by a straightforward analysis using the most prominent resonances. Then an analysis using multiple resonances of each element simultaneously was performed finding that the accuracy of elemental identification was improved, and iron and nickel distributions became clearer. However, these analysis methods sometimes have difficulties in the case of overlapping materials since a resonance shape can be deteriorated by those of other materials. Such an example was demonstrated with the case of iron and nickel. To overcome the issue and aiming for further improvement, we proposed a method to fit the transmission spectrum in a wide range assuming the existence of possible elements, successfully visualizing both the distributions of the sample metals and those of hafnium and manganese (impurities of zirconium and iron). The newly introduced analysis technique will contribute to the establishment of a standard analytical procedure for general users of the facility.

Improved extraction efficiency of radioactive copper produced via accelerator neutrons method through phosphate buffer-enhanced column pre-treatment

Mikhail, M. A. G.*; Kin, Tadahiro*; Eto, Taisei*; Tsukada, Kazuaki

Scientific Reports (Internet), 14, p.27132_1 - 27132_10, 2024/11

https://doi.org/10.1038/s41598-024-76660-y

We have studied a straightforward and robust single-step cation exchange separation method to isolate medical copper radioisotopes Cu and Cu produced in the Zn(n, x) reaction with an accelerator neutrons technique. This study revealed the key role of a phosphate buffer pre-treatment of the cation exchange column in the separation process. It was found that incorporating the phosphate buffer into the column pre-treatment markedly enhances the retention of copper isotopes within the column throughout the separation procedure. This approach yields a high-purity radioactive copper sample with a high extraction efficiency of 94.4% of the initially produced copper, all within a relatively short experimental time frame of approximately 5 h for 100 g of starting material.

Comparison between carrier transport property and crystal quality of TlBr semiconductors

Watanabe, Kenichi*; Sugai, Yusuke*; Hasegawa, Sota*; Tanaka, Seishiro*; Hitomi, Keitaro*; Nogami, Mitsuhiro*; Shinohara, Takenao; Su, Y. H.; Parker, J. D.*; Kockelmann, W.*

Scientific Reports (Internet), 14, p.25224_1 - 25224_13, 2024/10

https://doi.org/10.1038/s41598-024-76005-9

Demonstration of shape analysis of neutron resonance transmission spectrum measured with a laser-driven neutron source

Koizumi, Mitsuo; Ito, Fumiaki*; Lee, J.; Hironaka, Kota; Takahashi, Tone; Suzuki, Satoshi*; Arikawa, Yasunobu*; Abe, Yuki*; Lan, Z.*; Wei, T.*; et al.

Scientific Reports (Internet), 14, p.21916_1 - 21916_9, 2024/09

https://doi.org/10.1038/s41598-024-72836-8

Cell-cycle dependence on the biological effects of boron neutron capture therapy and its modification by polyvinyl alcohol

Matsuya, Yusuke; Sato, Tatsuhiko; Kusumoto, Tamon*; Yachi, Yoshie*; Seino, Ryosuke*; Miwa, Misako*; Ishikawa, Masayori*; Matsuyama, Shigeo*; Fukunaga, Hisanori*

Scientific Reports (Internet), 14, p.16696_1 - 16696_14, 2024/07

https://doi.org/10.1038/s41598-024-67041-6

Boron neutron capture therapy (BNCT) is a unique radiotherapy to selectively eradicate tumor cells using boron compounds (e.g., 4-borono-L-phenylalanine [BPA]) that are heterogeneously taken up at the cellular level. However, the impacts of tempo-spatial heterogenicity on cell killing remain unclear. With the technical combination of radiation track detector, cell cycle analysis, and biophysical simulations, we demonstrated the cell cycle-dependent heterogenicity of BPA uptake and following biological impacts of B(n, )Li reactions in HeLa cells expressing Fluorescent Ubiquitination-based Cell Cycle Indicators (FUCCI), as well as its modification effects of polyvinyl alcohol (PVA). As a result, we revealed that the intracellular BPA concentration in the S/G2/M phase was higher than that in the G1/S phase and that PVA modified the cell cycle dependence. Further, these findings lead to the development of the first BPA-PVA-based model for predicting BNCT treatment effects. These outcomes may contribute to more precision of therapeutic efficacy, when BNCT is combined with PVA and/or cell cycle-specific anticancer agents.

The Impact of dose rate on responses of human lens epithelial cells to ionizing irradiation

Matsuya, Yusuke; Sato, Tatsuhiko; Yachi, Yoshie*; Date, Hiroyuki*; Hamada, Nobuyuki*

Scientific Reports (Internet), 14, p.12160_1 - 12160_14, 2024/05

https://doi.org/10.1038/s41598-024-62679-8

Understand mechanisms of radiation cataracts that are of concern in the field of radiation protection and radiation therapy. However, biological effects in HLEC following protracted exposure have not yet fully been explored. Here, we investigated the temporal kinetics of DNA double-strand breaks (DSBs) and cell survival of HLEC after exposure to photon beams at various dose rates, compared to those of human lung fibroblasts (WI-38). In parallel, we quantified the recovery for DSB and cell survival using a biophysical model. The study revealed that HLEC cells have a lower repair rate than WI-38 cells. There is no significant impact of dose rate on cell survival in both cell lines in the dose-rate range of 0.033-1.82 Gy/min. On the other hand, the experimental residual DSBs showed inverse dose rate effects (IDREs) compared to the model prediction, highlighting the importance of the IDREs in evaluating radiation effects on the ocular lens.

Laser-based angle-resolved photoemission spectroscopy with micrometer spatial resolution and detection of three-dimensional spin vector

Iwata, Takuma*; Kosa, Towa*; Nishioka, Yukimi*; Owada, Kiyotaka*; Sumida, Kazuki; Annese, E.*; Kakoki, Masaaki*; Kuroda, Kenta*; Iwasawa, Hideaki*; Arita, Masashi*; et al.

Scientific Reports (Internet), 14, p.127_1 - 127_8, 2024/01

https://doi.org/10.1038/s41598-023-47719-z