Magnetization process of the layered diluted ferromagnetic semiconductor (Ba,K)(Zn,Mn)As studied by X-ray magnetic circular dichroism

Wan, Y.*; Shibata, Goro; Takeda, Yukiharu*; Okane, Tetsuo; Saito, Yuji; Yamagami, Hiroshi; Fujimori, Atsushi*; 10 of others*

Physical Review Materials (Internet), 10(5), p.054402_1 - 054402_8, 2026/05

https://doi.org/10.1103/69sm-fz7z

Effect of grain refinement on cracks occurring in SUS304L stainless steel under nuclear reactor operating conditions

Hirota, Noriaki; Takeda, Ryoma; Ide, Hiroshi; Tsuchiya, Kunihiko; Kobayashi, Yoshinao*

Nuclear Materials and Energy (Internet), 45, p.102009_1 - 402009_10, 2025/12

https://doi.org/10.1016/j.nme.2025.102009

Using SUS304L stainless steel, which is employed in reactor structural components, the effects of grain refinement on stress corrosion cracking occurring under nuclear reactor operating conditions were investigated. As a result, after conducting slow strain rate testing (SSRT) in air and nuclear reactor operating environments, a comparison of the tensile properties of SUS304L with the same grain size revealed that elongation significantly decreased with increasing grain size under nuclear reactor operating conditions. In SSRT conducted in air, the -value obtained from the Hall-Petch relationship was lower than the conventional values. Observations showed the absence of cracks on SUS304L with 0.59 and 1.52 m grains; however, SUS304L with larger grains exhibited rougher fracture surfaces and side cracks. Thin oxide films were formed on SUS304L with 0.59 m and 1.52 m grains, while SUS304L with coarse grains of 28.4 m or larger enabled the formation of oxide films with over 2 m thickness. CrO films were formed on SUS304L with 0.59 m, 1.52 m, and 28.4 m, while CrO and Fe based oxides were formed on SUS304L with 39.5 m and 68.6 m. Crystal orientation analysis revealed linear surface layers without cracks in the -phase for SUS304L with 0.59 m and 1.52 m. In materials with Larger grain sizes, surface irregularities and cracks were observed in the -phase. In fine-grained SUS304L, lattice diffusion caused uniform O diffusion in the -phase, resulting in the formation of a thin CrO layer that suppressed cracks. In coarse-grained SUS304L, grain boundary diffusion caused Fe oxide formation at the grain boundaries, weakening them, and supersaturated O led to the formation of thick films comprising CrO and Fe-based oxides, resulting in peeling and cracking.

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.

Effect of grain refinement on transgranular stress corrosion cracking in SUS304L under boiling water reactor conditions

Hirota, Noriaki; Nakano, Hiroko; Takeda, Ryoma; Ide, Hiroshi; Tsuchiya, Kunihiko; Kobayashi, Yoshinao*

Material Science and Technology of Japan, 61(6), p.248 - 252, 2024/12

A comparative analysis of the 0.2 % yield stress in SUS304L stainless steel revealed that lower strain rates and higher temperatures significantly reduce yield stress. Grain refinement from 68.6 m to 0.59 m minimally impacted the rate of yield stress reduction at slower strain rates. However, finer grains showed a decrease in yield stress at reactor operating temperature compared to room temperature. In slow strain rate tests under conditions promoting intragranular stress corrosion cracking (SCC), SUS304L with grain sizes of 28.4 m or smaller exhibited similar fracture strains comparable to those at reactor operating temperatures, whereas coarse-grained SUS304L showed reduced fracture strain. Microstructural analysis showed that in smaller grains, over 87 % of the fracture surface was ductile. In particular, SUS304L with 0.59 m grains exhibited a higher presence of {111} / 3 boundaries, which decreased with grain growth. These results indicate that grain refinement will suppress intragranular SCC by slowing corrosion progression through increased {111} / 3 boundaries.

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

A Systematic approach for the adequacy analysis of a set of experimental databases; Application in the framework of the ATRIUM activity

Baccou, J.*; Glantz, T.*; Ghione, A.*; Sargentini, L.*; Fillion, P.*; Damblin, G.*; Sueur, R.*; Iooss, B.*; Fang, J.*; Liu, J.*; et al.

Nuclear Engineering and Design, 421, p.113035_1 - 113035_16, 2024/05

https://doi.org/10.1016/j.nucengdes.2024.113035

Accident consequence analysis for JMTR as a decommission facilities

Nagata, Hiroshi; Omori, Takazumi; Maeda, Eita; Otsuka, Kaoru; Nakano, Hiroko; Hanakawa, Hiroki; Ide, Hiroshi

JAEA-Review 2023-033, 40 Pages, 2024/01

JAEA-Review-2023-033.pdf:1.39MB

Japan Materials Testing Reactor (JMTR) was decided as a one of decommission facilities in April 2017. In order to submit the decommissioning plan to the Nuclear Regulation Authority, the type of accident assumed in the first stage of the decommissioning plan was selected, and the public exposure dose was evaluated. A fuel handling accident and a fire accident during storage of waste were selected as assumed accidents in the first stage of the decommissioning plan. An evaluation of the public exposure dose from the radioactive materials released into the atmosphere due to these accidents was estimated to be a maximum of 0.019 mSv (due to a fire accident during storage of waste). This estimated value was found to be sufficiently smaller than the judging criteria (5 mSv), and not to pose a significant risk of radiation exposure to the general public.

Upgrade of the small-angle neutron scattering diffractometer SANS-J at JRR-3

Kumada, Takayuki; Motokawa, Ryuhei; Oba, Yojiro; Nakagawa, Hiroshi; Sekine, Yurina; Micheau, C.; Ueda, Yuki; Sugita, Tsuyoshi; Birumachi, Atsushi; Sasaki, Miki; et al.

Journal of Applied Crystallography, 56(6), p.1776 - 1783, 2023/12

https://doi.org/10.1107/S1600576723009731

The combination of the existing position-sensitive photomultiplier and the He main detector with focusing devices, and the newly installed front detectors in SANS-J at JRR-3 covers small-angle neutron scattering signals in the range of the magnitude of the scattering vector Q from 0.002 to 6 nm-1 gaplessly with three standard device layouts. The installation of the front detector and a graphical user interface system largely improved the usability of SANS-J.

Impact of the Ce states in the electronic structure of the intermediate-valence superconductor CeIr

Fujimori, Shinichi; Kawasaki, Ikuto; Takeda, Yukiharu; Yamagami, Hiroshi; Sasabe, Norimasa*; Sato, Yoshiki*; Shimizu, Yusei*; Nakamura, Ai*; Maruya, A.*; Homma, Yoshiya*; et al.

Electronic Structure (Internet), 5(4), p.045009_1 - 045009_7, 2023/11

https://doi.org/10.1088/2516-1075/ad0a3d

Benchmark analyses on control rod worths of TRIGA reactor modeled in the ICSBEP handbook using continuous-energy Monte Carlo code MVP version 3

Yanagisawa, Hiroshi; Umeda, Miki; Motome, Yuiko; Murao, Hiroyuki

Proceedings of 12th International Conference on Nuclear Criticality Safety (ICNC2023) (Internet), 10 Pages, 2023/10

https://doi.org/10.11484/jaea-conf-2024-001

The benchmark analyses on the TRIGA reactor of the IEU-COMP-THERM-013 (ICT-013) in the ICSBEP handbook using the MVP version 3 code were carried out with the Japanese, US and European nuclear data libraries, including JENDL-5. The analyses on effective neutron multiplication factors (k's) were also performed for another TRIGA reactor defined in the ICT-003 as well as the ICT-013. As a result, it is confirmed that the calculated k's vary in the range of 0.8% with the libraries. The results also suggest that there might be unknown bias in the ICT-013 for the calculated k's. For the analyses on the control rod worths of the ICT-013, it is confirmed that differences in the worths among the libraries become smaller than those in k's. Most of the errors involved in k's are considered to be cancelled in the calculation of the worths since the worths are obtained by subtraction of the reciprocals of two sorts of k's. The differences in the worths by between the benchmark and alternative methods defined in the ICT-013 were tried to be examined from the aspect of the differences in horizontal flux distributions by between those methods. It is confirmed that the differences in the worths for two shim control rods, which are fully withdrawn at a delayed critical state, are well understood by that attempt, but on the other hand the differences are not sufficiently explained for a regulating control rod, which is partially inserted to attain delayed criticality.