Phonon spectrum in the spin-Peierls phase of CuGeO

Spitz, L.*; Razpopov, A.*; Biswas, S.*; Lane, H.*; Nikitin, S. E.*; Iida, Kazuki*; Kajimoto, Ryoichi; Fujita, Masaki*; Arai, Masatoshi*; Mourigal, M.*; et al.

Physical Review B, 112(18), p.184302_1 - 184302_18, 2025/11

https://doi.org/10.1103/jz36-8kz9

Development of passive wireless communication systems operatable under inferior-wireless environment with obstacles (Contract research); FY2023 Nuclear Energy Science & Technology and Human Resource Development Project

Collaborative Laboratories for Advanced Decommissioning Science; Yokohama National University*

JAEA-Review 2025-025, 90 Pages, 2025/10

JAEA-Review-2025-025.pdf:5.59MB

The Collaborative Laboratories for Advanced Decommissioning Science (CLADS), Japan Atomic Energy Agency (JAEA), had been conducting the Nuclear Energy Science & Technology and Human Resource Development Project (hereafter referred to "the Project") in FY2023. The Project aims to contribute to solving problems in the nuclear energy field represented by the decommissioning of the Fukushima Daiichi Nuclear Power Station, 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 FY2022, this report summarizes the research results of the "Development of passive wireless communication systems operatable under inferior-wireless environment with obstacles" conducted in FY2023. This study aims to develop a wireless communication system for obstacle-dense environments by designing base stations, sensor nodes (SN), positioning algorithms, and wireless area formation methods for electromagnetic wave-shielded regions. Key outcomes are as follows: For direction-finding with high-performance antennas, triangulation positioning accuracy was evaluated, and a sensor information demodulation system was built. SNs with frequency-scanning analog and frequency-fixed digital methods achieved communication distances of 6-8 meters and wireless charging of 1-2 V in 3-15 minutes at 6 meters. Diode characteristics remained unchanged after 1,000 Gy radiation. Positioning algorithms using multipath tomography were validated with a high-resolution measurement system in the lab. Simulations with reactor building CAD diagrams optimized node numbers and arrangements. Wireless coverage in electromagnetic wave-shielded regions was tested using a composite antenna (patch array and waveguide), achieving a range of approximately 1.5 meters.

Upper limit for the Cm(Ti,xn)Og reaction cross section

Gall, B. J.-P.*; Asai, Masato; Ito, Yuta; Toyoshima, Atsushi*; 30 of others*

Journal of the Physical Society of Japan, 94(9), p.094201_1 - 094201_9, 2025/09

https://doi.org/10.7566/JPSJ.94.094201

An experiment to search for Og isotopes using the Ti beam impinging on Cm target was performed at RIKEN Nishina Center. The optimal beam energy was determined from the quasielastic barrier distribution extracted from the excitation function of quasielastic backscattering. As a result, no Og decay was found, enabling only an estimation of the sensitivity for one event of 0.27 pb, and the 1 cross section upper limit of 0.50 pb.

Development of the continuous monitoring of tritium water by mid-infrared laser spectroscopy (Contract research); FY2023 Nuclear Energy Science & Technology and Human Resource Development Project

Collaborative Laboratories for Advanced Decommissioning Science; National Institutes of Natural Sciences*

JAEA-Review 2025-009, 48 Pages, 2025/07

JAEA-Review-2025-009.pdf:2.19MB

The Collaborative Laboratories for Advanced Decommissioning Science (CLADS), Japan Atomic Energy Agency (JAEA), had been conducting the Nuclear Energy Science & Technology and Human Resource Development Project (hereafter referred to "the Project") in FY2023. The Project aims to contribute to solving problems in the nuclear energy field represented by the decommissioning of the Fukushima Daiichi Nuclear Power Station, 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 FY2021, this report summarizes the research results of the "Development of the continuous monitoring of tritium water by mid-infrared laser spectroscopy" conducted from FY2021 to FY2023. The present study aims to demonstrate the principle for rapid measurement of tritiated water at a concentration level of 60 Bq/cc using a cavity ring-down spectroscopy system with a mid-infrared laser. In fiscal year 2023, research focused on (1) developing the cavity ring-down apparatus and (2) evaluating hydrogen isotope composition and preparing standard samples under environmental conditions (subcontracted to Hirosaki University). For (1), an optical bench was set up at the NIFS to perform laser absorption spectroscopy of various hydrogen isotope concentrations, enabling the evaluation of measurement sensitivity and establishment of guidelines. The light amplification of a quantum cascade laser, was further developed, achieving light amplification of a 4.3 m quantum cascade laser with an iron ion-doped medium, yielding a maximum output of 390 mW with a linewidth of less than 30 MHz. For (2), standard samples were prepared by diluting commercially available heavy water with BG water (tritium-free water) to create samples with approximately 100 Bq/L. Isotope ratio measurements were conducted indoors and outdoors using a high-time-resolution atmospheric water vapor collection system for tritium measurement, and daily measurements of the hydrogen isotope ratio (D) were conducted. The relationship between D and tritium concentration in atmospheric water vapor in Hirosaki City was evaluated. Thus, the principle for the rapid measurement of tritiated water using a mid-infrared laser was successfully demonstrated.

Measurements of neutron capture cross-sections for nuclides of interest in decommissioning (IV); Ho(n,)Ho reactions

Nakamura, Shoji; Shibahara, Yuji*; Endo, Shunsuke; Rovira Leveroni, G.; Kimura, Atsushi

Journal of Nuclear Science and Technology, 14 Pages, 2025/07

https://doi.org/10.1080/00223131.2025.2525327

Investigation of the excited states of Sn using the GRIFFIN spectrometer at TRIUMF

Syeda, N. K.*; Smallcombe, J.; 44 of others*

Nuclear Physics A, 1059, p.123090_1 - 123090_5, 2025/07

https://doi.org/10.1016/j.nuclphysa.2025.123090

Study of the spin-memory effect with low-energy gamma-rays in Hf(n,)Hf reaction measurement

Kawamura, Shiori*; Endo, Shunsuke; Iwamoto, Osamu; Iwamoto, Nobuyuki; Kimura, Atsushi; Kitaguchi, Masaaki*; Nakamura, Shoji; Okudaira, Takuya*; Rovira Leveroni, G.; Shimizu, Hirohiko*; et al.

EPJ Web of Conferences, 329, p.05002_1 - 05002_3, 2025/06

https://doi.org/10.1051/epjconf/202532905002

no abstracts in English

Neutron capture cross-section measurement at TC-Pn in KUR for holmium among nuclides in decommissioning

Nakamura, Shoji; Endo, Shunsuke; Rovira Leveroni, G.; Kimura, Atsushi; Shibahara, Yuji*

KURNS Progress Report 2024, P. 31, 2025/06

no abstracts in English

Application study of adaptive mesh refinement method on unsteady wake vortex analysis

Alzahrani, H.*; Matsushita, Kentaro; Sakai, Takaaki*; Ezure, Toshiki; Tanaka, Masaaki

Nuclear Technology, 13 Pages, 2025/06

https://doi.org/10.1080/00295450.2025.2472582

Development of evaluation method for cover gas entrainment by vortices generated at free surface in upper plenum of sodium-cooled fast reactor is required, and an evaluation method by predicting vortices from flow velocity distribution obtained by CFD analysis is developed. In this study, Adaptive Mesh Refinement (AMR) method is examined to improve efficiency of CFD analysis. Initial mesh was refined with two indexes: the first index (Index-1) is when the second invariant of velocity gradient tensor, Q, is negative and the second one (Index-2) is pressure gradient index added to Index-1. As a result of applying AMR method to unsteady vortices system with a flat plate and performing transient analyses with refined meshes, the result of pressure distribution and velocity around the flat plate in mesh using Index-2 was similar to the result of all refined mesh. It was also confirmed that vortices generation and growth was better simulated by refining meshes around separation area.

Nacre-like MXene/polyacrylic acid layer-by-layer multilayers as hydrogen gas barriers

Auh, Y. H.*; Neal, N. N.*; Arole, K.*; Regis, N. A.*; Nguyen, T.*; Ogawa, Shuichi*; Tsuda, Yasutaka; Yoshigoe, Akitaka; Radovic, M.*; Green, M. J.*; et al.

ACS Applied Materials & Interfaces, 17(21), p.31392 - 31402, 2025/05

https://doi.org/10.1021/acsami.5c03632