A Preliminary result on time-reversal invariance violation in polarized neutron transmission through polarized La

Nakabe, Rintaro; Endo, Shunsuke; Kambara, Wataru*; Kimura, Atsushi; Kobayashi, Ryuju; Oku, Takayuki; Sakai, Kenji; Shinohara, Takenao; Takahashi, Ryuta*; Tsuchikawa, Yusuke; et al.

JPS Conference Proceedings (Internet), 45, p.011066_1 - 011066_5, 2026/06

https://doi.org/10.7566/JPSCP.45.011066

We evaluate the time-reversal invariance violation using previous neutron transmission data with polarized neutrons propagating through a transversely polarized La. By incorporating precise spin observables and the scattering amplitudes into our analysis, we preliminarily constrained the time-reversal invariance violating cross section.

Study of the distribution of partial radiative widths for the Ta(n,)Ta reaction

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

JPS Conference Proceedings (Internet), 45, p.011069_1 - 011069_7, 2026/06

https://doi.org/10.7566/JPSCP.45.011069

Measurements of neutron capture cross-sections for nuclides of interest in decommissioning (V); Zr(n, )Zr and Zr(n, )Zr reactions at JRR-3

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

Journal of Nuclear Science and Technology, 63(6), p.653 - 666, 2026/06

https://doi.org/10.1080/00223131.2025.2586632

First constraint on the P-odd/T-odd cross section in polarized neutron transmission through transversely polarized La

Nakabe, Rintaro; Endo, Shunsuke; Kambara, Wataru*; Kawamura, Shihori; Kimura, Atsushi; Kobayashi, Ryuju; Oku, Takayuki; Okudaira, Takuya*; Sakai, Kenji; Shinohara, Takenao; et al.

Progress of Theoretical and Experimental Physics (Internet), 2026(6), p.063D01_1 - 063D01_15, 2026/06

https://doi.org/10.1093/ptep/ptag088

We report the first constraint on time-reversal invariance violating (TRIV) effects in polarized neutron transmission through a transversely polarized La target. We formulate the transmission asymmetry within the density matrix formalism, explicitly incorporating the forward scattering amplitude of La including tensor polarization terms up to third-rank. The formalism is applied to existing transmission data originally obtained to measure the spin-dependent cross section near the ~eV -wave resonance. Since these data were not optimized for P-odd/T-odd observables, the attainable sensitivity is intrinsically limited; nevertheless, they provide a useful test of the formalism on real experimental data. No statistically significant TRIV signal is observed. By analyzing the global structure in the parameter space, we obtain an upper limit of at the 90% confidence level. This corresponds to an upper limit on the resonance-averaged TRIV cross section of . These results validate the present theoretical framework and provide guidance for future dedicated TRIV searches in polarized neutron transmission experiments.

Construction and deployment of an on-premises generative AI infrastructure using supercomputers

Takaku, Yuhi; Sakazume, Shun; Kimura, Hideo

JAEA-Technology 2025-017, 33 Pages, 2026/03

JAEA-Technology-2025-017.pdf:2.73MB

At the Japan Atomic Energy Agency (JAEA), expectations and demand for generative AI had been increasing, particularly to improve operational efficiency and foster ideas in research and development. However, cloud-based external generative AI services such as ChatGPT typically use input data for learning, which raised security concerns and prevented handling a considerable amount of information. In addition, the required procedures and applications before use were cumbersome, making it hard to say that generative AI was widely adopted or effectively used within JAEA. To address these issues, we built a generative AI infrastructure using JAEA's existing computing resources, including its supercomputers, and open-source software. This approach kept implementation costs low while ensuring safety and ease of use. After deployment across the organization, we observed notable improvements in daily operational efficiency and a surge in interest in generative AI, leading to expanded initiatives for its utilization.

Neutron total and capture cross-section measurement and resolved resonance analysis of Er

Rovira Leveroni, G.; Kimura, Atsushi; Nakamura, Shoji; Endo, Shunsuke; Iwamoto, Osamu; Iwamoto, Nobuyuki; Katabuchi, Tatsuya*

Annals of Nuclear Energy, 225, p.111688_1 - 111688_18, 2026/01

https://doi.org/10.1016/j.anucene.2025.111688

Horonobe Underground Research Laboratory Project Investigation report for the 2024 fiscal year

Nakayama, Masashi; Ishii, Eiichi; Aoyagi, Kazuhei; Hayano, Akira; Murakami, Hiroaki; Ono, Hirokazu; Takeda, Masaki; Fukatsu, Yuta; Mochizuki, Akihito; Ozaki, Yusuke; et al.

JAEA-Review 2025-042, 136 Pages, 2025/12

JAEA-Review-2025-042.pdf:12.95MB

The Horonobe Underground Research Laboratory (URL) Project is being pursued by the Japan Atomic Energy Agency (JAEA) to enhance the reliability of relevant technologies for geological disposal of high-level radioactive waste through investigating the deep geological environment within the host sedimentary rocks at Horonobe-cho in Hokkaido, north Japan. In the fiscal year 2024, we continued R&D on "Study on near-field system performance in geological environment", "Demonstration of repository design options", and "Understanding of buffering behaviour of sedimentary rock to natural perturbations". These are identified as key R&D on challenges to be tackled in the Horonobe underground research plan for the fiscal year 2020 onwards. Specifically, "full-scale engineered barrier system (EBS) performance experiment" and "solute transport experiment with model testing" were carried out as part of "Study on near-field system performance in geological environment". "Demonstration of engineering feasibility of repository technology" and "evaluation of EBS behaviour over 100C" were addressed for "Demonstration of repository design options". The validation of a method for assessing permeability using the Ductility Index and a method for estimating the state of in-situ ground pressure from hydraulic perturbation tests were investigated as part of the study "Understanding of buffering behaviour of sedimentary rock to natural perturbations". In FY2024, we continued construction of the East Access Shaft and the Ventilation Shaft, and construction of these shafts were completed to a depth of 500 m. After the completion of the East Access Shaft, excavation of the West Access Shaft and 500 m gallery has began. As of the end of FY2024, excavation progress is as follows, the East Access Shaft and the Ventilation Shaft were 500 m depth, the West Access Shaft was 472 m depth, 500 m gallery was 112.9 m, respectively. In the Horonobe International Project (HIP), Management Board and Joint Task Meeting was held at the Horonobe URL in June 2024 to review the progress of construction of galleries and preparations of experiments. Task Meetings to review the implementation plan for in-situ testing and analysis were also held. HIP will be implemented in two phases: Phase 1 (from FY2022 to FY2024) and Phase 2 (from FY2025 to FY2028), the research results of Phase 1 were compiled in FY2024.

NEA Horonobe International Project - HIP Interim report for Phase 1 (February 2023 - March 2025)

Tachi, Yukio; Aoyagi, Kazuhei; Ozaki, Yusuke; Hayano, Akira; Ono, Hirokazu; Takeda, Masaki; Mochizuki, Akihito; Dei, Shuntaro; Minaka, Jumpei; Murakami, Hiroaki; et al.

NEA/NE(2025)20 (Internet), 118 Pages, 2025/11

https://www.oecd-nea.org/jcms/pl_111824/nea-horonobe-international-project-hip-interim-report-for-phase-1-february-2023-march-2025

An Empirical approach to disposal tunnel design and sealing in Neogene sedimentary rocks

Hayano, Akira; Aoyagi, Kazuhei; Murakami, Hiroaki; Kimura, Shun

Proceedings of 2025 International High Level Radioactive Waste Management Conference (IHLRWM 2025) (Internet), p.8 - 11, 2025/11

Advancing materials studies for high-power proton accelerators in J-PARC

Makimura, Shunsuke*; Matoba, Shiro*; Sunagawa, Hikaru*; Naoe, Takashi; Wakui, Takashi; Ishida, Taku*; Matsubara, Tsurayuki*; Fukao, Yoshinori*; Takahashi, Hitoshi*; Watanabe, Hiroaki*; et al.

Proceedings of 71st ICFA Advanced Beam Dynamics workshop on High-Intensity and High-Brightness Hadron Beams (HB2025) (Internet), p.359 - 363, 2025/10

https://meow.elettra.eu/83/pdf/FRIAA01.pdf

In modern proton accelerators, the survivability of beam-intercepting devices, such as targets, beam windows and beam dumps, under intense beam irradiation is a key factor limiting the achievement of higher beam power. This article introduces the challenges faced by the secondary particle production targets and beam windows at the Japan Proton Accelerator Research Complex (J-PARC), and the developments undertaken to overcome these challenges.