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, 89(5), p.488 - 493, 2026/09

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

no abstracts in English

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.

Defect-free, high-performance support preparation via a novel rotary method for hydrogen-separation membranes in HI decomposition of the thermochemical iodine-sulfur process

Myagmarjav, O.; Noguchi, Hiroki; Tanaka, Nobuyuki; Kamiji, Yu; Sugimoto, Chihiro; Ishii, Katsunori; Nomura, Mikihiro*; Takegami, Hiroaki

International Journal of Hydrogen Energy, 198, p.152495_1 - 152495_9, 2026/01

https://doi.org/10.1016/j.ijhydene.2025.152495

Analysis of deposits inside "X-6 penetration" for the Unit 2 primary containment vessel at Fukushima Daiichi Nuclear Power Station

Yoneyama, Kai; Nitta, Ayako; Tanaka, Yasuyuki; Kodaka, Noriyasu; Kikuchi, Riku; Sakano, Takuma; Furuse, Takahiro; Sato, Soichi; Sambongi, Mitsuru; Tanaka, Kosuke

JAEA-Technology 2025-008, 44 Pages, 2025/12

JAEA-Technology-2025-008.pdf:4.3MB

At the TEPCO's Fukushima Daiichi Nuclear Power Station (1F), an investigation inside the reactors has been carried out. In order to safely carry out the decommissioning work such as fuel debris retrieval and building demolition, it is important to estimate the contamination in primary containment vessel for control the decommissioning planning and the worker radiation exposure levels. Therefore, the analysis of the deposit inside the penetration for the 1F Unit 2 primary containment vessel ("X-6 penetration") was performed to clarify the components and activity. The smears from the deposit were used for the analysis. Non-destructive analysis such as gamma-ray spectrometry, X-ray Fluorescence (XRF) and Scanning Electron Microscope-Energy dispersive X-ray spectroscopy (SEM-EDX) for the smear-samples were performed to determine the gamma-nuclides and the morphology of elements in the deposit. Furthermore, in order to evaluate the nuclides and nuclide composition of the deposit in detail, the smear-samples were dissolved and the quantitative analysis of gamma-nuclides, Sr-90, alpha-nuclides in the dissolved solution were conducted. The results (non-destructive analysis and quantitative analysis) were compared with the results of samples collected at different locations in the X-6 penetration in 2020. In the gamma-ray spectrometry as non-destructive analysis where the smears were analyzed directly, Co-60, Sb-125, Cs-134, Cs-137, Eu-154, Eu-155 and Am-241 were detected. In XRF results, Fe originating from construction material was detected as a major element and small amount of U and Zr originating from the fuel and fuel cladding were also detected. In SEM-EDX results, O and Fe were found as a major element of the deposit and U particles coexisting with Fe, Si, Cr, Ni and Zr were also found. These results were consistent with the SEM-EDX results of the samples collected in 2020. In radioactivity analysis, quantitative values for gamma-nuclides (Co-60, Sb-125, Cs-134, Cs-137, Eu-154, Eu-155), Sr-90, Pu-238, Pu-239+240, Am-241, Cm-244, U-235 and U-238 were obtained. Using the results, the ratios of radioactivity based on Cs-137 and U-238 were calculated. Both sets of the ratios were compared to the calculated value of the Unit 2 fuel composition from ORIGEN.

Speciation of cesium in a radiocesium-bearing microparticle emitted from Unit 1 during the Fukushima nuclear accident by XANES spectroscopy using transition edge sensor

Takahashi, Yoshio*; Miura, Hikaru*; Yamada, Shinya*; Sekizawa, Oki*; Nitta, Kiyofumi*; Hashimoto, Tadashi*; Yomogida, Takumi; Yamaguchi, Akiko; Okada, Shinji*; Itai, Takaaki*; et al.

Journal of Hazardous Materials, 495, p.139031_1 - 139031_19, 2025/09

https://doi.org/10.1016/j.jhazmat.2025.139031

In this presentation, we analyzed the chemical state of cesium in radiocesium-bearing microparticles (CsMPs) released during the 2011 Fukushima Daiichi Nuclear Power Plant accident using high-resolution X-ray absorption spectroscopy (XANES) and micro X-ray fluorescence (-XRF). The results identified two forms of cesium: one dissolved in glass and the other enriched on the surfaces of internal voids. The latter is considered to have originally existed as a gas and became concentrated during the cooling and solidification of the molten glass. These findings are crucial for understanding the formation process of CsMPs during the accident, as well as for future decommissioning and safety assessments.

Validation study on SFR core bowing codes using Joyo ex-core experiment data; Multiple duct bowing benchmark

Wozniak, N.*; Ohgama, Kazuya; Doda, Norihiro; Ota, Hirokazu*; Shemon, E.*; Feng, B.*; Uwaba, Tomoyuki; Futagami, Satoshi; Tanaka, Masaaki; Yamano, Hidemasa; et al.

Progress in Nuclear Science and Technology (Internet), 8, p.165 - 170, 2025/09

https://doi.org/10.15669/pnst.8.165

To enhance the accuracy of the safety evaluations for sodium-cooled fast reactors, it is necessary to develop a method that can realistically evaluate the reactivity changes induced by core deformation. In this context, Japan and the United States jointly conducted a benchmark analysis of thermal bowing experiments using multiple ducts from a Joyo-type fuel assembly. The aim was to confirm the validity of the core bowing analysis codes. Comparisons of analysis and experimental results demonstrated that the codes used by both countries were able to reasonably predict the thermal bowing of a row of assemblies in multiple duct configuration.

Core deformation reactivity with neutronics-thermal hydraulics-structural mechanics coupled analysis for FFTF LOFWOS Test #13

Doda, Norihiro; Kato, Shinya; Uwaba, Tomoyuki; Tanaka, Masaaki; Nakamine, Yoshiaki*; Igawa, Kenichi*; Iida, Masaki*

Proceedings of 21st International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-21) (Internet), 14 Pages, 2025/08

Accurate evaluation of reactivity feedback due to core deformation during power increases in sodium-cooled fast reactors requires comprehensive modeling of the interactions among neutronics, thermal-hydraulics, and core mechanics. To accurately consider these interactions, JAEA has developed an evaluation method that combines multiple analysis codes that model these phenomena in detail. In this study, the evaluation method was applied to the core analysis of the FFTF LOFWOS Test #13, and the analysis results of net reactivity were compared with the test results. The sensitivity analysis results of the core structural design parameters showed that the core bowing behavior has a significant effect on the temporal variation of net reactivity.

Surface and interfacial aggregation states in thin films of a polystyrene/polyrotaxane blend

Taguchi, Miki*; Miyata, Noboru*; Miyazaki, Tsukasa*; Aoki, Hiroyuki; Ozawa, Satoru*; Hasegawa, Ryuichi*; Morimitsu, Yuma*; Kawaguchi, Daisuke*; Yamamoto, Satoru*; Tanaka, Keiji*

Polymer Journal, 57(7), p.737 - 743, 2025/07

https://doi.org/10.1038/s41428-025-01030-y

Experimental studies on spatial resolution of a delay-line current-biased kinetic inductance detector

Vu, TheDang*; Shishido, Hiroaki*; Aizawa, Kazuya; Oku, Takayuki; Oikawa, Kenichi; Harada, Masahide; Kojima, Kenji M*; Miyajima, Shigeyuki*; Soyama, Kazuhiko; Koyama, Tomio*; et al.

Nuclear Instruments and Methods in Physics Research A, 1075, p.170425_1 - 170425_9, 2025/06

https://doi.org/10.1016/j.nima.2025.170425