Construction of a Compton camera-equipped robotic system capable of moving autonomously towards the radiation source

Sato, Yuki; Kakuto, Takeshi*; Tanaka, Takayuki*; Shimano, Hiroyuki*

European Physical Journal; Special Topics, 235(4), p.949 - 958, 2026/04

https://doi.org/10.1140/epjs/s11734-025-01483-5

Development of computer program for detailed thermal-hydraulic analysis in a fast reactor fuel assembly, 3; Implementation and validation of hybrid-type k-/k- model

Kikuchi, Norihiro; Imai, Yasutomo*; Yoshikawa, Ryuji; Tanaka, Masaaki; Ohshima, Hiroyuki

JAEA-Data/Code 2025-017, 133 Pages, 2026/03

JAEA-Data-Code-2025-017.pdf:3.9MB

In a core design of sodium-cooled fast reactors (SFRs), it is necessary to confirm the integrity of fuel assemblies (FAs) in the core over a wide range of operating conditions. To evaluate the velocity and temperature distributions within the FAs in detail, we have been developing a detailed FA thermal-hydraulic analysis code named SPIRAL. In our previous works, we implemented numerical methods for fluid mechanics at isothermal conditions and turbulence models. Subsequently, we implemented turbulent heat transfer models for the evaluation of temperature distribution within the FAs, and validated them through experimental analyses mainly under high flow rate conditions. The thermal-hydraulics within the FAs varies depending on the operating conditions. Furthermore, the local Reynolds (Re) number within the FAs varies widely due to the influence of wire spacers spirally wound around the fuel rod. For this reason, it has been shown that standard and low Re number k-/k- models have difficulty reproducing the thermal-hydraulics in the laminar-turbulent transition region. Therefore, to reproduce the thermal-hydraulics over a wide Re number range, we developed a hybrid k-/k- model that combines the standard k-/k- model with the advantages of the low Re number k-/k- model. This paper describes the governing equations, constitutive equations derived from various turbulence models, their formularizations by the finite element method, their numerical treatment, and the treatment of boundary conditions. We also report the results of analyses conducted to validate the hybrid k-/k- model for predicting pressure drop and temperature distribution.

Investigating the N(,)O reaction rates via the F(,)F reaction

Kim, S. H.*; Chae, K. Y.*; Asai, Masato; Hirose, Kentaro; Sato, Tetsuya; Makii, Hiroyuki; Nishio, Katsuhisa; Orlandi, R.; Smallcombe, J.; Suzaki, Fumi; et al.

Journal of the Korean Physical Society, 6 Pages, 2026/00

https://doi.org/10.1007/s40042-026-01643-3

no abstracts in English

Neutron reflectometry study on the interfacial layer of epoxy resin to improve adhesion strength

Liu, Y.*; Miyata, Noboru*; Miyazaki, Tsukasa*; Shundo, Atsuomi*; Kawaguchi, Daisuke*; Tanaka, Keiji*; Aoki, Hiroyuki

ACS Applied Materials & Interfaces, 17(25), p.37311 - 37318, 2025/06

https://dx.doi.org/10.1021/acsami.5c07863

Development of numerical evaluation method for heat transportation with sodium mist in the cover gas region of sodium-cooled fast reactor

Hayakawa, Satoshi*; Hagiwara, Hiroyuki*; Imamura, Akira*; Onoda, Yuichi; Tanaka, Masaaki; Nakamura, Hironori*

Proceedings of 13th Korea-Japan Symposium on Nuclear Thermal Hydraulics and Safety (NTHAS13) (Internet), 8 Pages, 2024/11

In a sodium-cooled fast reactor, a cover gas region filled with argon gas is located above the sodium pool in the main vessel to prevent the hot sodium from contacting the structures. This region involves heat transportation by natural convection of the cover gas, radiation among liquid surface and structures, and sodium phase change between mist and vapor. In this study, the numerical evaluation method has been developed with a commercial CFD code, Fluent, incorporating the sodium mist transport and growth models, and the radiation scattering model. Simulations of a laboratory scale test with a cylindrical cover gas region was carried out for the validation of the method and showed that the temperature distribution and sodium mist concentration in the cover gas region are in good agreements with the test results. A simulation of a pool-type sodium cooled fast reactor has also conducted and the basic aspect of physical phenomena taking place in the cover gas region were evaluated.

In-plane movement of isolated poly(methacrylate) chains on a hydrophilic solid surface

Kawano, Masayuki*; Morimitsu, Yuma*; Liu, Y.*; Miyata, Noboru*; Miyazaki, Tsukasa*; Aoki, Hiroyuki; Kawaguchi, Daisuke*; Yamamoto, Satoru*; Tanaka, Keiji*

Macromolecules, 57(14), p.6625 - 6633, 2024/07

https://doi.org/10.1021/acs.macromol.4c00724

Validation of the hybrid turbulence model in detailed thermal-hydraulic analysis code SPIRAL for fuel assembly using sodium experiments data of 37-pin bundles

Yoshikawa, Ryuji; Imai, Yasutomo*; Kikuchi, Norihiro; Tanaka, Masaaki; Ohshima, Hiroyuki

Nuclear Technology, 210(5), p.814 - 835, 2024/05

https://doi.org/10.1080/00295450.2023.2249707

In the study of safety enhancement on advanced sodium-cooled fast reactor, it is essential to clarify the thermal-hydraulics under various operation conditions in a fuel assembly (FA) with the wire-wrapped fuel pins to assess the structural integrity of the fuel pin. A finite element thermal-hydraulics analysis code named SPIRAL has been developed to analyze the detailed thermal-hydraulics phenomena in a FA. In this study, the numerical simulations of the 37-pin bundle sodium experiments at different Re number conditions, including a transitional condition between laminar and turbulent flows and turbulent flow conditions, were performed to validate the hybrid turbulence model equipped in SPIRAL. The temperature distributions predicted by SPIRAL was consistent with those measured in the experiments. Through the validation study, the applicability of the hybrid turbulence model in SPIRAL to thermal-hydraulic evaluation of sodium-cooled FA in the wide range of Re number was confirmed.

Neutron reflectometry analysis of condensed water layer formation at a solid interface of epoxy resins under high humidity

Liu, Y.*; Miyata, Noboru*; Miyazaki, Tsukasa*; Shundo, Atsuomi*; Kawaguchi, Daisuke*; Tanaka, Keiji*; Aoki, Hiroyuki

Langmuir, 39(29), p.10154 - 10162, 2023/06

https://doi.org/10.1021/acs.langmuir.3c01091

Development plan for coupling technology between high temperature gas-cooled reactor HTTR and hydrogen production facility, 1; Overview of the HTTR heat application test plan to establish high safety coupling technology

Nomoto, Yasunobu; Mizuta, Naoki; Morita, Keisuke; Aoki, Takeshi; Okita, Shoichiro; Ishii, Katsunori; Kurahayashi, Kaoru; Yasuda, Takanori; Tanaka, Masato; Isaka, Kazuyoshi; et al.

Proceedings of 30th International Conference on Nuclear Engineering (ICONE30) (Internet), 7 Pages, 2023/05

Analysis of the activities of the website "Question and Answer about radiation in daily life" after the accident at the Fukushima Daiichi Nuclear Power Plant and some lessons learned from it; To pass on this experience to the future

Kono, Takahiko; Tanaka, Masato*; Tanaka, Hitomi*; Shimo, Michikuni*; Torii, Hiroyuki*; Uno, Kazuko*

Journal of Radiation Protection and Research, 47(3), p.167 - 179, 2022/09

https://doi.org/10.14407/jrpr.2021.00346

After the accident at the Fukushima Daiichi Nuclear Power Plant, artificial radionuclides such as radioactive cesium and iodine were released into the environment. It caused great anxiety not only in the vicinity of the Fukushima Daiichi Nuclear Power Plant but also in other regions of the world. Some members of the Japan Health Physics Society (JHPS), a leading academic society in Japan in the field of radiation protection, volunteered to establish a website called "Question and Answer about radiation in Daily Life" shortly after the accident to help reduce the residents anxiety about the health effects of radiation. In August 2011, Committee for "Question and Answer about radiation in Daily Life" was established in JHPS, making the website-related activities a responsibility of JHPS. The Q&A website continued to respond to the questions from the general public with expertise and sincerity until February 2013 when the Committee members decided to end the activities because the number of questions received had gradually decreased with the passage of time. This paper aims to introduce the following: the activities of the Q&A website during the two years (2011-2013), the stance chosen for the activities, the information related to the website activities and the analysis of Twitter data. Building on the experience and the knowledge obtained from the activities, it also discusses issues and experiences that can be utilized in the initial response to emergencies for radiation protection experts as well as other fields.