Development and validation of a fluence boundary method for efficient indoor dose assessment from ground-deposited Cs

Kobayashi, Hikaru*; Ma, X.*; Suto, Masahito*; Yamamori, Ryo*; Furuta, Takuya

Radiation Measurements, 197, p.107743_1 - 107743_13, 2026/09

https://doi.org/10.1016/j.radmeas.2026.107743

Monte Carlo photon transport simulations are widely used to predict indoor dose distributions from Cs-137 ground deposition, but their computational cost can be high. To improve efficiency, we propose the fluence boundary method (FBM), which accounts for contributions from distant sources by applying analyzed photon fluence profiles at near-site boundaries surrounding a building. These profiles are defined according to the land-cover type adjacent to each boundary. The method was validated by comparing FBM results with full simulations, demonstrating that FBM achieved a maximum absolute percentage error below 5% across indoor dose distributions. The feasibility of representing fluence boundaries using land-cover types was further examined by evaluating the impact of uncertainties in relaxation mass depth () for paved and soil surfaces. The normalized indoor dose distributions showed weak dependence on within a reasonable range, indicating that indoor dose distributions can be reliably predicted using representative values when doses are normalized to measurements.

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.

Local and electronic structures of BaTiO/KNbO nanocomposite particles

Yoneda, Yasuhiro; Kobayashi, Toru; Tsuji, Takuya; Shibata, Goro; Takeda, Yukiharu*; Saito, Yuji; Khanal, G. P.*; Fujii, Ichiro*; Ueno, Shintaro*; Sato, Yukio*; et al.

Japanese Journal of Applied Physics, 64(8), p.08SP07_1 - 08SP07_8, 2025/08

https://doi.org/10.35848/1347-4065/adf4f1

It has become possible to synthesize high-quality composite nanoparticles in which a different material is grown on the surface of nanoparticle crystals. To evaluate such nanostructures, it is effective to combine different evaluation methods at various scales. We performed various structural and electronic state evaluations of BaTiO/KNbO nanocomposite particles using synchrotron radiation. From the structural evaluation, it was confirmed that the nanocomposite particles have a core of 100 nm of BaTiO covered with 20 nm of KNbO. The O-K absorption edge spectrum of the outermost surface KNbO was different from that of the bulk and nanoparticles, and it was found that the chemical bonding state changes when KNbO is made into composite particles.

Development of a compact He neutron spin filter at J-PARC

Takahashi, Shingo; Kiyanagi, Ryoji; Okudaira, Takuya*; Takada, Shusuke*; Kobayashi, Ryuju; Okuizumi, Mao; Ino, Takashi*; Asai, Kanta*; Tsuchikawa, Yusuke; Oikawa, Kenichi; et al.

Nuclear Instruments and Methods in Physics Research A, 1075, p.170410_1 - 170410_8, 2025/06

https://doi.org/10.1016/j.nima.2025.170410

The Development of a hypothetical facility aimed at high-quality physical protection training

Nakamura, Yo; Mizuedani, Miku; Kobayashi, Takuya; Sekine, Megumi; Kato, Akane; Ashima, Junko*; Noro, Naoko

Dai-45-Kai Nihon Kaku Busshitsu Kanri Gakkai Nenji Taikai Kaigi Rombunshu (Internet), 3 Pages, 2024/11

Since 2012, the ISCN has been conducting a "Physical Protection Training Course for Nuclear Materials and Facilities" for domestic power companies, government agencies, and other relevant organizations as part of its human resource development support programs related to nuclear security. From the beginning, the training course utilized a hypothetical research institute as training material in line with the IAEA training course on physical protection systems. However, in response to the needs of domestic stakeholders, a new training tool featuring a hypothetical nuclear power plant was newly developed to deliver higher-quality courses. This paper outlines the content of the newly developed training tool and discusses its potential future applications.

Analysis on sorption structure of cesium in clay minerals under dry/wet condition

Tsuji, Takuya; Matsumura, Daiju; Kobayashi, Toru

SPring-8/SACLA Riyo Kenkyu Seikashu (Internet), 12(5), p.259 - 262, 2024/10

https://doi.org/10.18957/rr.12.5.259

no abstracts in English

Continuous structural phase transition and antiferromagnetic order in ilmenite-type NiVO

Yamamoto, Hajime*; Ikeda, Osamu*; Honda, Takashi*; Kimura, Kenta*; Aoyama, Takuya*; Ogushi, Kenya*; Suzuki, Akio*; Ishii, Kenji*; Matsumura, Daiju; Tsuji, Takuya; et al.

Physical Review Materials (Internet), 8(9), p.094402_1 - 094402_6, 2024/09

https://doi.org/10.1103/PhysRevMaterials.8.094402

Enhancement of modelling approaches for the assessment of radionuclide transfer in the marine environment

Periez, R.*; Bezhenar, R.*; Maderych, V.*; Brovchenko, I.*; Liptak, L.*; Kobayashi, Takuya; Min, B.-I.*; Suh, K. S.*; Little, A.*; Iosjpe, M.*; et al.

IAEA-TECDOC-2060, 55 Pages, 2024/07

https://doi.org/10.61092/iaea.pjuc-aha9

This publication describes the work undertaken by Working Group 7, Assessment of Fate and Transport of Radionuclides Released in the Marine Environment of the IAEA's Modelling and Data for Radiological Impact Assessments (MODARIA II) programme (2016-2019). In MODARIA II, the degree of complexity of the models used was increased in order to effectively consider additional processes, specifically uptake by biota, and the spatiotemporal scales of the simulations were also expanded.

Spin dependence in the -wave resonance of +

Okudaira, Takuya*; Nakabe, Rintaro*; Auton, C. J.*; Endo, Shunsuke; Fujioka, Hiroyuki*; Gudkov, V.*; Ide, Ikuo*; Ino, Takashi*; Ishikado, Motoyuki*; Kambara, Wataru*; et al.

Physical Review C, 109(4), p.044606_1 - 044606_9, 2024/04

https://doi.org/10.1103/PhysRevC.109.044606

Estimation of temporal variation of discharged inventory of radioactive strontium Sr (Sr) from port of Fukushima Daiichi Nuclear Power Plant; Analysis of the temporal variation from the accident to March 2022 and evaluation of its impact on Fukushima coast and offshore areas

Machida, Masahiko; Iwata, Ayako; Yamada, Susumu; Otosaka, Shigeyoshi*; Kobayashi, Takuya; Funasaka, Hideyuki*; Morita, Takami*

Nihon Genshiryoku Gakkai Wabun Rombunshi (Internet), 22(4), p.119 - 139, 2023/11

https://doi.org/10.3327/taesj.J22.016

We estimate monthly discharged inventory of Sr from port of Fukushima Daiichi Nuclear Power Plant (1F) from Jun. 2013 to Mar. 2022 by using the Voronoi tessellation method inside the port, following the monitoring of Sr sea water radioactivity concentration inside the port. The results suggest that the closure of sea side impermeable wall is the most effective for the reduction of discharged one. In addition, the results roughly reveal the monthly discharged inventory required to observe visible enhancement of the sea radioactivity concentration from the background level in each area. Such outcome is significant for considering environmental impacts on the planned future releasing of the treated water accumulated in 1F site.