Bulk modulus and electron density distribution of high-pressure polymorphs of Fe-Ti-O minerals

Yamanaka, Takamitsu*; Hattori, Takanori

Physics and Chemistry of Minerals, 53(3), p.21_1 - 21_11, 2026/09

https://doi.org/10.1007/s00269-026-01350-2

Bulk modulus and electron density distribution of high-pressure polymorphs of Fe-Ti-O minerals (FeO magnetite, FeTiO ulvspinel, FeTiO ilmenite, FeTiO pseudobrokite) are investigated by X-ray and neutron diffraction. The vacant sites in the unit cell have much larger volumes than cation sites in the all structures. Cation site partly occupied by Ti atom shows a smaller than that of only Fe atom and the compressibility of unit cell increases with increasing Ti content. The compressibility of the vacant sites is close to that of unit cells, but are much smaller than that of the cation site. The structure changes such as high-low electron spin transition, Jahn-Teller effect and hybridization in the Fe-O bonds are elucidated by present high-pressure experiments. The hybridization in the octahedral cation site was observed by molecular orbital calculation and it brings the deformation of the octahedral cation site, which triggers structure changes in the high-pressure polymorphs.

Ultrasonic visualization technique for spatial recognition in highly radiated environments with poor visibility(Contract research); FY2024 Nuclear Energy Science & Technology and Human Resource Development Project

Collaborative Laboratories for Advanced Decommissioning Science; The University of Osaka*

JAEA-Review 2026-010, 87 Pages, 2026/07

JAEA-Review-2026-010.pdf:4.87MB

The Collaborative Laboratories for Advanced Decommissioning Science (CLADS), Japan Atomic Energy Agency (JAEA), has been conducting the Nuclear Energy Science & Technology and Human Resource Development Project (hereafter referred to "the Project") from FY2019. The Project aims to contribute to solving problems in the nuclear energy field represented by the decommissioning of the Fukushima Daiichi Nuclear Power Station (1F), Tokyo Electric Power Company Holdings, Inc. (TEPCO). For this purpose, intelligence was collected from all over the world, and basic research and human resource development were promoted by closely integrating/collaborating knowledge and experiences in various fields beyond the barrier of conventional organizations and research fields. The sponsor of the Project was moved from the Ministry of Education, Culture, Sports, Science and Technology to JAEA since the newly adopted proposals in FY2018. On this occasion, JAEA constructed a new research system where JAEA-academia collaboration is reinforced and medium-to-long term research/development and human resource development contributing to the decommissioning are stably and consecutively implemented. Among the adopted proposals in FY2024, this report summarizes the research results of the "Ultrasonic visualization technique for spatial recognition in highly radiated environments with poor visibility" conducted in FY2024. The objective of this research project is to establish a visualization technique using ultrasonic phased array (hereinafter referred to as PA) as a technique that enables spatial recognition in poor visibility and highly radiated environments that are expected during the removal of fuel debris in the decommissioning of 1F. The project aims to develop a visualization technique for object shapes both in the air and in the water, and each research group will conduct the following projects: (1) Visualization of object shapes in the air and in the water by ultrasonic PA measurement (The University of Osaka), (2) Development of airborne ultrasonic PA device (Nihon University), (3) Visualization in particle suspended environment by high frame rate PA (Tohoku University), and (4) Development of ultrasonic measurement methods for high intensity gamma-ray environments (The University of Osaka).

None

Harjo, S.

Kinzoku, 96(5), p.354 - 360, 2026/05

no abstracts in English

Ultrasonic analysis of columnar crystal propagation echo in acoustically anisotropic weld metals; Targeting intergranular cracking of stainless-steel piping in pressurized water reactor primary system "FY2024 Nuclear Regulation Research Technology Infrastructure Construction Project Subsidy 'The Grant to Establish Technology Bases for Enhancement of Nuclear Regulation Research'"

Matsui, Tetsuya; Shimodaira, Masaki; Yamaguchi, Yoshihito; Toyama, Takeshi; Katsuyama, Jinya

JAEA-Research 2025-017, 41 Pages, 2026/03

JAEA-Research-2025-017.pdf:4.52MB

The JAEA Safety Research Center has been conducting fundamental research on advanced inspection and structural integrity assessment technologies since FY2024, including the development of a machine-learning-based ultrasonic flaw detection method using an ultrasonic simulator. To assess the simulator's applicability, phased array ultrasonic testing (PAUT) results produced by the simulator were compared with actual measurement data. Due to limited publicly available datasets, an intergranular crack in the pressurizer spray line piping of Kansai Electric Power Co. Inc.'s Ohi Nuclear Power Station Unit 3 was selected as the reference case. PAUT linear scanning analysis at a 45 incident angle detected the crack's corner and edge echoes. Strong columnar-crystal propagation echoes were also observed within the weld metal, with their intensity showing dependence on the symmetric axis angle. Analysis at a 31 incident angle similarly identified strong columnar-crystal propagation echoes, which connected to the crack's corner echoes and propagated into the weld region. These results align with actual measurements, indicating that the observed weld-metal echoes are likely attributable to columnar-crystal propagation.

A Novel kinetic model for dissolution and precipitation of oxide on stainless-steel surface in stagnant liquid sodium

Kawaguchi, Munemichi*; Ikeda, Asuka; Saito, Junichi

Annals of Nuclear Energy, 226, p.111880_1 - 111880_9, 2026/02

https://doi.org/10.1016/j.anucene.2025.111880

Numerical investigation of systematic measurement errors in conductance-type wire-mesh sensors for rod-bundle flows

Uesawa, Shinichiro; Yoshida, Hiroyuki

Journal of Nuclear Science and Technology, 24 Pages, 2026/00

https://doi.org/10.1080/00223131.2026.2714322

In void-fraction measurements using conductance-type wire-mesh sensors (WMSs) in rod-bundle flows, the measurement accuracy is governed by the non-uniform electric current density formed near the electrodes. This non-uniformity causes the instantaneous WMS signal to be strongly affected by the bubble position and shape, thereby introducing systematic errors specific to rod-bundle geometries. However, these errors have not been sufficiently evaluated. In this study, three-dimensional electrostatic simulations were performed to clarify the mechanisms and magnitudes of these errors. The current density distributions and WMS signal responses were analyzed for the subchannel, inter-subchannel, and corner-subchannel regions while varying the bubble position, bubble shape, and transmitter-receiver layer distance. The results demonstrated that the spatial characteristics of the current-density distribution differ among the three channel types. Consequently, the correlation between the WMS signal and void fraction was not unique, and the channel-dependent variations in the correlation were confirmed to arise from differences in bubble position, bubble shape, and layer distance. By consolidating these correlations, representative void-fraction conversion formulas incorporating quantitative systematic errors were developed. The findings of this study provide a quantitative basis for improving the reliability of WMS measurements and for evaluating experimental uncertainties in the validation of two-phase flow CFD simulation codes.

Mechanistic insights into deformation, load redistribution, and stress partitioning in high-strength dual-phase medium-entropy alloys

Gu, G. H.*; Ha, H.*; Harjo, S.; Gong, W.; Louzguine-Luzgin, D. V.*; Kim, H. S.*

Materials Science & Engineering A, 943, p.148818_1 - 148818_10, 2025/10

https://doi.org/10.1016/j.msea.2025.148818

Experimental study of two-phase flow in a four-by-four unheated rod bundle for validation of thermal-hydraulics simulation codes

Muhammad, I.; Nagatake, Taku; Uesawa, Shinichiro; Ono, Ayako

Proceedings of 21st International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-21) (Internet), 12 Pages, 2025/08

This research aims to validate ACE-3D using data from a two-phase flow experiment. For this purpose, a two-phase flow experiment was conducted in a four-by-four unheated fuel assembly. In the experiment, the time-averaged void fraction distribution was measured using a wire mesh sensor system under high temperatures and high-pressure conditions. The experimental results were analyzed, and the data were visualized to understand better the behavior and characteristics of the two-phase flow in the fuel assembly. A two-phase flow data set is being developed, covering a wide range of experimental conditions, including higher-pressure regions, which can be used for validating thermal-hydraulic codes. Finally, the ACE-3D code was applied to the two-phase flow experiment. The calculation results were then compared to the experimental ones, and the issues were identified for improving ACE-3D in future simulations.

Development of HCl-free solid-phase extraction combined with ICP-MS/MS for rapid assessment of difficult-to-measure radionuclides, 3; Measurement of Se concentration in concrete rubble

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

Journal of Radioanalytical and Nuclear Chemistry, 334(7), p.4997 - 5006, 2025/05

https://doi.org/10.1007/s10967-025-10143-w

Reduction and phase transformation of Ce-doped zirconolites

Hayashizaki, Kohei; Hirooka, Shun; Yamada, Tadahisa*; Sunaoshi, Takeo*; Murakami, Tatsutoshi; Saito, Kosuke

Ceramics (Internet), 8(1), p.24_1 - 24_12, 2025/03

https://doi.org/10.3390/ceramics8010024