Long-term variations in I seawater concentrations off Fukushima and potential of 129I as an oceanographic tracer for ALPS-treated water

Suzuki, Takashi; Otosaka, Shigeyoshi*; Takata, Hyoe*; Kuwabara, Jun; Nakanishi, Takahiro; Ikenoue, Tsubasa

Environmental Science & Technology, 60(17), p.13123 - 13131, 2026/04

https://doi.org/10.1021/acs.est.5c18263

As a results of the 2011 Fukushima Daiichi Nuclear Power Plant accident, long-lived radioactive I has been released into the environment, with additional releases beginning in 2023 through ALPS-treated water. To study its long-term variation and potential as an oceanographic tracer, I concentrations in seawater off Fukushima were measured from 2012 to 2024. The highest concentration, 44510 Bq/L, was observed in 2013 near the plant. Levels have since declined toward the pre-accident value of 1.7610 Bq/L. Spatial and temporal changes in the I/Cs ratio indicate the influence of small water masses and support its use as a tracer in areas with complex ocean circulation.

Conservative ghost fluid method with an interface cell for compressible two-phase fluid simulations

Kamiya, Tomohiro; Yoshida, Hiroyuki

Physics of Fluids, 37(10), p.103359_1 - 103359_23, 2025/10

https://doi.org/10.1063/5.0285810

In this study, we developed a conservative scheme based on a volume of fluid (VOF) and a ghost fluid method for liquid-gas two-phase compressible fluid simulations. We treated several one- and two-dimensional numerical problems to investigate the capability and applicability of the proposed method for compressible two-phase fluid simulations. The results agree well with the exact solutions or the numerical results of previous studies. Furthermore, the results also show that the proposed method can almost completely ensure the conservation property. Consequently, we concluded that the proposed method could simulate compressible two-phase flows and conserve mass, momentum, and total energy.

Prediction of large vapor mass formation under subcooled flow boiling

Ono, Ayako; Okawa, Tomio*

Proceedings of 2025 International Congress on Advances in Nuclear Power Plants (ICAPP 2025) (Internet), 12 Pages, 2025/09

We aim to establish a new prediction method for departure from nucleate boiling (DNB) in fuel assemblies, contributing to the design and safety evaluation of next-generation reactors. Since the formation of a large vapor mass on the heating surface is considered the initial trigger of DNB, we focus on predicting the heat flux required for its formation. To achieve this, we integrate two-phase flow computational fluid dynamics (CFD) with a mechanistic large vapor mass formation model. In this study, we develop a simplified numerical analysis method that simulates bubble generation, growth, motion, and coalescence to predict large vapor mass formation. Additionally, we investigate the vapor volume on the heating surface at the onset of large vapor mass formation and predict their formation conditions.

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

Conceptual study of J-PARC Proton Beam Irradiation Facility

Meigo, Shinichiro; Iwamoto, Hiroki; Sugihara, Kenta*; Hirano, Yukinori*; Tsutsumi, Kazuyoshi*; Saito, Shigeru; Maekawa, Fujio

JAEA-Technology 2024-026, 123 Pages, 2025/03

JAEA-Technology-2024-026.pdf:14.22MB

Based on the design of the ADS Target Test Facility (TEF-T) at the J-PARC Transmutation Experimental Facility, a conceptual study was conducted on the J-PARC proton beam irradiation facility. This research was carried out based on the recommendations of the Nuclear Transmutation Technology Evaluation Task Force of the MEXT. The recommendations state that it is desirable to consider facility specifications that can make the most of the benefits of using the existing J-PARC proton accelerator while also solving the engineering issues of the ADS. We considered facilities that could respond to a variety of needs while reducing the facilities that were not needed in the TEF-T design. In order to clarify these diverse needs, we investigated the usage status of representative accelerator facilities around the world. As a result, it became clear that the main purposes of these facilities were (1) Material irradiation, (2) Soft error testing of semiconductor devices using spallation neutrons, (3) Production of RI for medical use, and (4) Proton beam use, and we investigated the facilities necessary for these purposes. In considering the facility concept, we assumed a user community in 2022 and reflected user opinions in the facility design. This report summarizes the results of the conceptual study of the proton irradiation facility, various needs and responses to them, the roadmap for facility construction, and future issues.

A Decade of neutron diffraction study of iron hydrides

Aoki, Katsutoshi*; Machida, Akihiko*; Saito, Hiroyuki*; Hattori, Takanori

Koatsuryoku No Kagaku To Gijutsu, 35(1), p.4 - 11, 2025/03

https://doi.org/10.4131/jshpreview.35.4

Iron reacts with hydrogen to form solid solutions with body-centered cubic, face-centered cubic, hexagonal close packed, and double hexagonal close packed structures at high temperatures and high pressures. Neutron diffraction is the most powerful tool for determining the occupation sites and occupancies of hydrogen atoms dissolved in a metal lattice. Structural parameters, including hydrogen occupation sites and occupancies, are refined via Rietveld analysis for neutron diffraction data. We present our expertise in Rietveld refinement of iron hydrides accumulated over 10 years.

Damage on a solid-liquid interface induced by the dynamical behavior of injected gas bubbles in flowing mercury

Kogawa, Hiroyuki; Wakui, Takashi; Futakawa, Masatoshi

Fluids (Internet), 10(1), p.3_1 - 3_15, 2025/01

https://doi.org/10.3390/fluids10010003

Microbubbles have been applied in various fields. In mercury targets of spallation neutron sources, where cavitation damage is a crucial issue for the life estimation, microbubbles are injected into the mercury to absorb the thermal expansion of the mercury caused by the pulsed proton beam injection and reduce the macroscopic pressure waves, and result in reducing the damage. Recently, when the proton beam power was increased and the amount of injected gas bubbles was increased, unique damage morphologies were observed on solid-liquid interface. Detailed observation and numerical analyses revealed that the microscopic pressure emitted from the gas bubbles contracting is sufficient to form pit damage; i.e. the directions of streak-like defects which are formed by connecting pit damage coincides with the direction of gas bubble trajectories, and the distances between pits was understandable taking the natural period of gas bubble vibration into account. This indicates that the gas microbubbles to reduce the macroscopic pressure waves have potential to be inceptions of the cavitation damage due to the microscopic pressure emitted from gas bubbles. To completely mitigate the damage, we have to consider the two effects of injecting gas bubbles; reducing macroscopic pressure waves and microscopic pressure due to bubble dynamics.

Nuclear heating and damage data in JENDL-5 neutron ACE library

Konno, Chikara

JAEA-Conf 2024-002, p.80 - 85, 2024/11

https://doi.org/10.11484/jaea-conf-2024-002

The official ACE files of JENDL-5 were released in December, 2022. The neutron ACE file of JENDL-5 was mainly produced with the FRENDY code, while the data on nuclear heating and damage (heating number, damage production energy) were done with the NJOY2016.65 code modified for JENDL-5. This presentation explains the modified points of NJOY2016.65 and the data on nuclear heating and damage in the neutron ACE file of JENDL-5.

Study on the evaluation methodology of the radioactivity concentration in low-level radioactive concrete wastes generated from JPDR

Aono, Ryuji; Haraga, Tomoko; Kameo, Yutaka

JAEA-Technology 2024-006, 48 Pages, 2024/06

JAEA-Technology-2024-006.pdf:1.77MB

In the future, radioactive waste which generated from nuclear research facilities in Japan Atomic Energy Agency are planning to be buried for the near surface disposal. It is necessary to establish the method to evaluate the radioactivity concentrations of the radioactive wastes. In this work, we studied the evaluation methodology of the radioactivity concentrations in concrete waste generated from JPDR. In order to construct the evaluation methodology of the radioactivity concentration, the validity of the evaluation methods was confirmed by mainly theoretical calculation and using the result of radiochemical analysis. Correcting the theoretical calculations using results of nuclide analysis, it is possible to evaluate the radioactivity concentrations of nuclides preliminary selected.

Perpendicular magnetic anisotropy of thin films

Takanashi, Koki; Seki, Takeshi*

Magune, 19(3), p.100 - 106, 2024/06

Perpendicular magnetic anisotropy of thin films currently plays an important role in spintronics as well as magnetic recording. Regarding perpendicular magnetic anisotropy, in this article, the fundamentals, the research history, and the recent research trends are reviewed, showing specific examples with perpendicular magnetization such as magnetic multilayers, ordered alloy films, rare earth-transition metal amorphous alloy films, and inhomogeneous or granular films. The physical origins for perpendicular magnetic anisotropy, including interface anisotropy due to structural symmetry breaking, magnetoelastic anisotropy due to strain, bulk-type magnetocrystalline anisotropy, and directional pair ordering of atoms, are discussed in each example.