Neutron diffraction study of the crystal and magnetic structures of antiferromagnetic manganese deuteride at high temperatures and high pressures

Machida, Akihiko*; Saito, Hiroyuki*; Aoki, Katsutoshi*; Komatsu, Kazuki*; Hattori, Takanori; Sano, Asami; Funakoshi, Kenichi*; Machida, Shinichi*; Sato, Toyoto*; Orimo, Shinichi*

Physical Review B, 111(22), p.224413_1 - 224413_6, 2025/06

https://doi.org/10.1103/yf8k-cy61

The crystal and magnetic structures of antiferromagnetic Mn deuterides formed by hydrogenating Mn metal at high temperature and high pressure, fcc -MnDx and hcp -MnDx, were investigated by in-situ neutron powder diffraction. Deuterium atoms partially occupied the octahedral interstitial positions of the fcc and hcp metal lattices. The site occupancies increased rapidly with decreasing temperature from 700 to 450 K and remained down to 300 K. Nel temperature of 543(10) K was determined for -MnD. For -MnD, saturation magnetic moment and Nel temperature were determined to be 0.82(1) and 347(3) K, respectively. The Nel temperatures determined for -MnD and -MnD are consistent with those predicted by the respective Slater-Pauling curves proposed in previous studies. The updated Nel temperatures provide insights into the development of more accurate Slater-Pauling curves based on electronic band structure calculations.

Competition between mass-symmetric and asymmetric fission modes in Md produced in the He + Es reaction

Nishio, Katsuhisa; Hirose, Kentaro; Makii, Hiroyuki; Orlandi, R.; Kean, K. R.*; Tsukada, Kazuaki; Toyoshima, Atsushi*; Asai, Masato; Sato, Tetsuya; Chiera, N. M.*; et al.

Physical Review C, 111(4), p.044609_1 - 044609_12, 2025/04

https://doi.org/10.1103/PhysRevC.111.044609

Development of a bio-based adhesive by polymerization of Boc-protected vinyl catechol derived from caffeic acid

Tanizaki, Shiho*; Kubo, Tomohiro*; Bito, Yosuke*; Mori, Shigeki*; Aoki, Hiroyuki; Sato, Kotaro*

RSC Sustainability (Internet), 3(4), p.1714 - 1720, 2025/04

https://doi.org/10.1039/D4SU00629A

Separating urban heat island circulation and convective cells through dynamic mode decomposition

Sato, Takuto; Hino, Hideitsu*; Kusaka, Hiroyuki*

Atmospheric Science Letters, 25(12), p.e1279_1 - e1279_10, 2024/12

https://doi.org/10.1002/asl.1279

This study applies dynamic mode decomposition (DMD) to three-dimensional simulation results of urban heat island circulation (UHIC, which is horizontal circulation) and thermals (vertical convections). The aim of this study is to revisit how these phenomena coexist based on the characteristics of temporal changes in the flow field. We used DMD to obtain the dominant spatial patterns and information on temporal changes. One of the modes of horizontal wind, which does not change temporally (no oscillation or amplification), exhibits a spatial UHIC pattern. The unique feature of this UHIC mode is that there are small-scale striated structures (150-200 m) and large-scale convergence. The other modes are time-varying (oscillating and decaying) and represent smaller spatial-scale phenomena (150-250 m), such as thermals. The frequency of each mode takes various values, some of which are lower than the lifetime of thermals in accordance with the Deardorff convective scale (10 min). These low-frequency modes showed striated structures similar to that observed in the UHIC modes. These results suggest that UHIC and thermals deform each other through components that vary in long temporal scales.

Experimental studies of in-medium modification of meson mass through decays

Sako, Hiroyuki; Ichikawa, Masaya; Naruki, Megumi; Sakaguchi, Takao; Sato, Susumu; 12 of others*

Journal of Subatomic Particles and Cosmology (Internet), 1-2, p.100012_1 - 100012_7, 2024/11

https://doi.org/10.1016/j.jspc.2024.100012

Development of a multi-scale meteorological Large-eddy simulation model for urban thermal environmental studies; The "City-LES" Model Version 2.0

Kusaka, Hiroyuki*; Ikeda, Ryosaku*; Sato, Takuto; Iizuka, Satoru*; Boku, Taisuke*

Journal of Advances in Modeling Earth Systems (Internet), 16(10), p.e2024MS004367_1 - e2024MS004367_38, 2024/10

https://doi.org/10.1029/2024MS004367

To bridge the gaps between meteorological large-eddy simulation (LES) models and computational fluid dynamics (CFD) models for microscale urban climate simulations, the present study has developed a meteorological LES model for urban areas. This model simulates urban climates across both mesoscale (city scale) and microscale (city-block scale). The paper offers an overview of this LES model, which distinguishes itself from standard numerical weather prediction models by resolving buildings and trees at the microscale simulations. It also differs from standard CFD models by accounting for atmospheric stratification and physical processes. Noteworthy features of this model include: (a) the calculation of long- and short-wave radiations in three dimensions, incorporating multiple reflections within urban canopy layers using the radiosity method, and accounting for building and tree shadows in the simulations; (b) the provision of various heat stress indices (Universal Thermal Climate Index, Wet Bulb Globe Temperature, MRT, THI); (c) the assessment of the efficacy of heat stress mitigation measures such as dry-mist spraying, roadside trees, cool pavements, and green/cool roofs strategies; (d) the capability to run on supercomputers, with the code parallelized in a three-dimensional manner, and the model can also run on a graphics processing unit cluster. Following the introduction of this model, the study confirms its basic performance through various numerical experiments, including simulations of thermals in the convective boundary layer, coherent structure of turbulence over urban canopy, and thermal environment and heat stress indices in urban districts. The model developed in this study is intended to serve as a community tool for addressing both fundamental and applied studies in urban climatology.

Project plan of HTTR heat application test facility; Safety design and Safety analysis

Aoki, Takeshi; Hasegawa, Takeshi; Kurahayashi, Kaoru; Nomoto, Yasunobu; Shimizu, Atsushi; Sato, Hiroyuki; Sakaba, Nariaki

Proceedings of 11th International Topical Meeting on High Temperature Reactor Technology (HTR 2024), 6 Pages, 2024/10

Japan Atomic Energy Agency (JAEA) is planning to perform a test named HTTR heat application test coupling HTTR (High temperature engineering test reactor) and a hydrogen production plant. The present study reports results of the safety design and safety analysis for HTTR heat application test facility. As a safety design, safety classification of structures, systems, and components was defined in the test facility based on their safety functions. As a preliminary safety analysis, a thermal-hydraulic analysis was performed with RELAP5 code. The safety analysis revealed that newly identified events for HTTR heat application test facility except for the rupture of heat transfer tube of steam generator was enveloped by the licensing basis events in conventional HTTR. The preliminary analysis proved that the safety criteria is satisfied in the candidate of licensing basis event.

Current status of high temperature gas-cooled reactor development in Japan

Nagatsuka, Kentaro; Noguchi, Hiroki; Nagasumi, Satoru; Nomoto, Yasunobu; Shimizu, Atsushi; Sato, Hiroyuki; Nishihara, Tetsuo; Sakaba, Nariaki

Nuclear Engineering and Design, 425, p.113338_1 - 113338_11, 2024/08

https://doi.org/10.1016/j.nucengdes.2024.113338

HTGR has a potential to contribute to decarbonization of hard-to-abate industries by supplying a large amount of hydrogen and high temperature heat or steam without carbon dioxide emission. JAEA has been conducting R&Ds for HTGR technologies with High Temperature Engineering Test Reactor (HTTR). This paper shows that HTTR's tests including the loss of core cooing test as a joint the OECD/NEA international research project and a HTTR heat application test plan which demonstrate hydrogen production by coupling the HTTR with a hydrogen production test facility. Additionally, aiming for operation start from the latter half of 2030s, the basic design of the HTGR demonstration reactor has been shown. The Japan's HTGR technology capabilities established by the HTTR project will be fully utilized for the construction of HTGR demonstration reactor.

Development of a radioactive substance detection system integrating a Compton camera and a LiDAR camera with a hexapod robot

Sato, Yuki; Kakuto, Takeshi*; Tanaka, Takayuki*; Shimano, Hiroyuki*; Morohashi, Yuko; Hatakeyama, Tomoyoshi*; Nakajima, Junsaku; Ishiyama, Masahiro

Nuclear Instruments and Methods in Physics Research A, 1063, p.169300_1 - 169300_7, 2024/06

https://doi.org/10.1016/j.nima.2024.169300

Production rates of long-lived radionuclides Be and Al under direct muon-induced spallation in granite quartz and its implications for past high-energy cosmic ray fluxes

Sakurai, Hirohisa*; Kurebayashi, Yutaka*; Suzuki, Soichiro*; Horiuchi, Kazuho*; Takahashi, Yui*; Doshita, Norihiro*; Kikuchi, Satoshi*; Tokanai, Fuyuki*; Iwata, Naoyoshi*; Tajima, Yasushi*; et al.

Physical Review D, 109(10), p.102005_1 - 102005_18, 2024/05

https://doi.org/10.1103/PhysRevD.109.102005

Secular variations of galactic cosmic rays (GCRs) are inseparably associated with the galactic activities and should reflect the environments of the local galactic magnetic field, interstellar clouds, and nearby supernova remnants. The high-energy muons produced in the atmosphere by high-energy GCRs can penetrate deep underground and generate radioisotopes in the rock. As long lived radionuclides such as Be and Al have been accumulating in these rocks, concentrations of Be and Al can be used to estimate the long-term variations in high-energy muon yields, corresponding to those in the high-energy GCRs over a few million years. This study measured the production cross sections for muon induced Be and Al by irradiating positive muons with the momentum of 160 GeV/c on the synthetic silica plates and the granite core at the COMPASS experiment line in CERN SPS. In addition, it the contributions of the direct muon spallation reaction and the nuclear reactions by muon-induced particles on the production of long lived radionuclides in the rocks were clarified.