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Yamane, Towa*; Inatsu, Masaru*; Kawano, Jun*; Sato, Takuto; Kusaka, Hiroyuki*
Agricultural and Forest Meteorology, 379, p.111052_1 - 111052_9, 2026/03
This study aims to obtain fundamental information on birch pollen deposition data by field observation for the high-resolution, accurate pollen modeling. On the peak dispersal day in 2024, simple pollen collectors were installed just below and at three downwind points of an isolated birch tree line in Ebetsu, Hokkaido, Japan. Meteorological observation were also conducted at the site during the days. The birch pollen captured on slide glasses was imaged by a microscope. We first developed the automatic pollen counting technique by applying a machine learning algorithm YOLO to the images. This technique was validated by comparison with subjective counting, and we successfully achieved the automatic counting that has never been done before. The results suggested that the pollen count was highest in the point 200 m downstream from the tree line and diurnal variations were observed at all distances. A simple linear regression analysis of pollen count and meteorological factors revealed a significant positive correlation with temperature. Additionally, a positive correlation with wind speed was also found only at the point just below the tree line. The large-eddy simulation with the pollen advection supported the observation results, though the pollen deposition position was more concentrated near the tree in the simulation.
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.
Tamatsukuri, Hiromu; Kozawa, Tatsuya*; Mitsuda, Setsuo*; Fujihara, Masayoshi; Kinjo, Katsuki*; Nawa, Kazuhiro*; Wu, H.-C.*; Sato, Taku*; Yano, Shinichiro*
Physical Review B, 112(18), p.184115_1 - 184115_8, 2025/11
Sato, Takuto; Nakayama, Hiromasa; Satoh, Daiki
Journal of Nuclear Science and Technology, 17 Pages, 2025/09
Times Cited Count：0 Percentile：0.00We developed a framework for rapid monitoring of radioactive plumes in the vicinity of nuclear facilities based on a quick and practical high-resolution atmospheric dispersion simulation method that combines a large-eddy simulation (LES) model pre-simulation database (pre-sim DB) of wind conditions and onsite meteorological observation results, as proposed by the previous study. However, this framework was not quantitatively demonstrated using measurement data. In this study, we evaluated the performance of the wind condition reproduction and plume dispersion analysis methods. Air dose rates observed at monitoring posts around the stack were compared with the values reproduced by the method using the pre-sim DB, and the reproducibility of both air dose rate and flow field was discussed. The pre-sim DB-based method successfully captured the temporal variation of air dose rates at the monitoring posts, though it tended to overestimate the peak values. Particularly when the vertical wind shear was pronounced, the method using the pre-sim DB could cause significant errors. This is likely because the method relies on wind conditions from a single observation point, which inherently limits its ability to represent vertical wind shear within the pre-sim DB. Despite these limitations, particularly in reproducing complex wind fields, the method utilizing the pre-sim DB offers a valuable and practical tool for rapid dose rate simulation due to its lower computational cost compared to unsteady simulations using an LES model.
Ito, Ayumi*; Kanno, Tatsuya*; Iwama, Takayuki*; Ueda, Shigeru*; Sato, Takumi; Nagae, Yuji
Annals of Nuclear Energy, 217, p.111333_1 - 111333_14, 2025/07
In the Fukushima Daiichi Nuclear Power Station Unit 2, the formation of a metallic pool, mainly comprising Fe and Zr, has been proposed as a mechanism contributing to the failure of the reactor pressure vessel. This study focuses on material interactions during the early core degradation that led to metallic pool formation in the late phase of the in-vessel degradation process. Initially, two compositions, Fe-87Zr and Fe-15Zr (at%), were heated to the liquidus temperature of 1723 K, dropped onto SS at lower temperatures, and the metallographic structure of the reaction products was examined. Subsequently, the Fe-87Zr melt at temperatures ranging from 1723 to 1873 K was dropped onto oxidized SS to evaluate the influence of the oxide layer on degradation. This study confirmed that the liquidus temperatures of all intermetallic compounds were below 2000 K, and the metallic debris could be a source of the "metallic pool formation" predicted by recent severe accident analysis.
sp. nov., a novel hydrogen-producing bacterium isolated from a deep diatomaceous shale formationUeno, Akio*; Sato, Kiyoshi*; Tamamura, Shuji*; Murakami, Takuma*; Inomata, Hidenori*; Tamazawa, Satoshi*; Amano, Yuki; Miyakawa, Kazuya; Naganuma, Takeshi*; Igarashi, Toshifumi*
International Journal of Systematic and Evolutionary Microbiology, 75(6), p.006802_1 - 006802_11, 2025/06
Times Cited Count：0 Percentile：0.00(Microbiology)no abstracts in English
Sudo, Ayako; Sato, Takumi; Takano, Masahide
Journal of Nuclear Science and Technology, 62(6), p.573 - 581, 2025/06
Times Cited Count：0 Percentile：0.00(Nuclear Science & Technology)During the progression of the severe accident at the Fukushima Daiichi Nuclear Power Station, seawater flowed down and was predicted to react with molten corium and concrete. For the removal and storage of fuel debris, knowing the effects of seawater components on the characteristics of reaction products in the fuel debris is crucial. To understand changes in the microstructure of fuel debris, a reaction test was conducted by introducing sea salt to simulated corium and concrete under a temperature gradient. Among the components of sea salt, sulfur formed iron sulfide during metallic precipitation. Analysis of vaporized species indicated that most of Cl, some Na and K in the sea salt might volatilize during heating rather than react with simulated corium and concrete. Calcium and a small amount of Mg, Na, and K in the sea salt might be trapped in the silicate glass.
Li, X.; Yamaji, Akifumi*; Sato, Ikken*; Yamashita, Takuya
Annals of Nuclear Energy, 214, p.111217_1 - 111217_13, 2025/05
Times Cited Count：0 Percentile：0.00(Nuclear Science & Technology)Taniguchi, Takumi; Matsumoto, Saori; Hiraki, Yoshihisa; Sato, Junya; Fujita, Hideki*; Kaneda, Yoshihisa*; Kuroki, Ryoichiro; Osugi, Takeshi
JAEA-Review 2024-059, 20 Pages, 2025/03
JAEA-Review-2024-059.pdf:1.0MB
The basic performance required for solidifying waste into cement, such as fluidity before curing and strength after curing, is expected to be affected by the chemical effects of substances and components contained in the waste. The fluidity before curing and the strength properties after curing are greatly influenced by the curing speed of the cement. We investigated existing knowledge with a focus on chemical substances that affect the curing speed of cement. In this report, chemical substances that affect fluidity are broadly classified into inorganic substances such as (1) anion species, (2) metal elements such as heavy metals, (3) inorganic compounds as cement admixtures, and (4) organic compounds as cement admixtures. Based on the investigation, we actually added chemicals and measured the setting time. As a result, it was found that there are multiple mechanisms contributing to accelerated hardening. We investigated chemical substances that inhibit the curing reaction of cement, and were able to compile information to consider ingredients that are contraindicated in cement curing.
Sato, Tatsuhiko; Furuta, Takuya; Sasaki, Hidetaka*; Watabe, Tadashi*
EJNMMI Physics (Internet), 12, p.28_1 - 28_16, 2025/03
Times Cited Count：0 Percentile：0.00(Radiology, Nuclear Medicine & Medical Imaging)Arai, Yoichi; Watanabe, So; Nakahara, Masaumi; Funakoshi, Tomomasa; Hoshino, Takanori; Takahatake, Yoko; Sakamoto, Atsushi; Aihara, Haruka; Hasegawa, Kenta; Yoshida, Toshiki; et al.
Progress in Nuclear Science and Technology (Internet), 7, p.168 - 174, 2025/03
The Japan Atomic Energy Agency (JAEA) has been conducting a project named "Systematic Treatment of RAdioactive liquid waste for Decommissioning (STRAD)" project since 2018 for fundamental and practical studies for treating radioactive liquid wastes with complicated compositions. Fundamental studies have been conducted using genuine liquid wastes accumulated in a hot laboratory of the JAEA called the Chemical Processing Facility (CPF), and treatment procedures for all liquid wastes in CPF were successfully designed on the results obtained. As the next phase of the project, new fundamental and practical studies on primarily organic liquid wastes accumulated in different facilities of JAEA are in progress. This paper reviews the representative achievements of the STRAD project and introduces an overview of ongoing studies.
Song, Y.*; Xu, S.*; Sato, Shunsuke*; Lee, I.*; Xu, X.*; Omori, Toshihiro*; Nagasako, Makoto*; Kawasaki, Takuro; Kiyanagi, Ryoji; Harjo, S.; et al.
Nature, 638, p.965 - 971, 2025/02
Times Cited Count：9 Percentile：98.67(Multidisciplinary Sciences)
Jin, H.*; Choi, E. S.*; Wu, H.-C.*; Curro, N. J.*; Nawa, Kazuhiro*; Sato, Taku*; Kiyanagi, Ryoji; Ohara, Takashi; Klavins, P.*; Taufour, V.*
Physical Review B, 111(3), p.035103_1 - 035103_7, 2025/01
Times Cited Count：0 Percentile：0.00(Materials Science, Multidisciplinary)Sato, Takuto; Goger, B.*; Nakayama, Hiromasa
SOLA (Scientific Online Letters on the Atmosphere) (Internet), 21, p.17 - 23, 2025/01
Times Cited Count：0 Percentile：0.00(Meteorology & Atmospheric Sciences)In this study, we conducted large-eddy simulations of turbulent flows and plume dispersion over idealized two-dimensional double steep hills. In the simulations, we investigated the distribution patterns of the mean plume concentrations, considering various distances between the hills and emission sources. Our objective was to provide information on the area of influence of local hilly terrains on plume dispersion from the viewpoint of accuracy, i.e., determining if the conventional Gaussian plume model can accurately predict plume concentrations. The result showed that the clockwise circulation was dominant in the area between the windward and leeward hills (valley) when the valley width was less than 10 times the hill height (
). This circulation makes the flow close to the stack remain in the valley, resulting in the higher concentrations in the valley than in wider-valley (
10 valley) cases. The effect of the leeward hill on the flow field was negligible when the valley width was greater than 10. In the area beyond 20 from the crest of the windward hill, estimated plume spreads for all cases were similar, indicating that the area of influence of the hills was approximately 20.
Hayashi, Teppei*; Yamashita, Takuma*; Mitsuyasu, Yusuke*; Ono, Kenta*; Iwami, Satone*; Kino, Yasushi*; Sekine, Tsutomu*; Oka, Toshitaka; Takahashi, Atsushi*; Shimizu, Yoshinaka*; et al.
International Journal of Radiation Biology, 8 Pages, 2025/00
Times Cited Count：0 Percentile：0.00no abstracts in English
Yamashita, Takuma*; Hayashi, Teppei*; Mitsuyasu, Yusuke*; Ono, Kenta*; Iwami, Satone*; Kino, Yasushi*; Sekine, Tsutomu*; Oka, Toshitaka; Takahashi, Atsushi*; Shimizu, Yoshinaka*; et al.
International Journal of Radiation Biology, 8 Pages, 2025/00
Times Cited Count：1 Percentile：73.02(Biology)no abstracts in English
Lu-DOTATATE peptide receptor radionuclide therapyMiwa, Kenta*; Kakino, Ryo*; Sato, Tatsuhiko; Furuta, Takuya; Miyaji, Noriaki*; Yamao, Tensho*; Yamashita, Kosuke*; Terauchi, Takashi*
Physical and Engineering Sciences in Medicine, 9 Pages, 2025/00
Times Cited Count：1 Percentile：86.20(Engineering, Biomedical)Radiotherapy package based on Particle and Heavy Ion Transport code System (RT-PHITS) enables to calculate the 3-dimensional dose distribution inside patients using their individual SPECT/CT images coupled with the Monte Carlo radiation transport simulation. The objective of this study is to evaluate the feasibility of individual dosimetry based on RT-PHITS for patients after Lu-DOTATATE peptide receptor radionuclide therapy.
Sato, Takuto; Hino, Hideitsu*; Kusaka, Hiroyuki*
Atmospheric Science Letters, 25(12), p.e1279_1 - e1279_10, 2024/12
Times Cited Count：0 Percentile：0.00(Geochemistry & Geophysics)This study applies dynamic mode decomposition (DMD) to three-dimensional simulation results of urban heat island circulation (UHIC, which is horizontal circulation) and thermals (vertical convections). The aim of this study is to revisit how these phenomena coexist based on the characteristics of temporal changes in the flow field. We used DMD to obtain the dominant spatial patterns and information on temporal changes. One of the modes of horizontal wind, which does not change temporally (no oscillation or amplification), exhibits a spatial UHIC pattern. The unique feature of this UHIC mode is that there are small-scale striated structures (150-200 m) and large-scale convergence. The other modes are time-varying (oscillating and decaying) and represent smaller spatial-scale phenomena (150-250 m), such as thermals. The frequency of each mode takes various values, some of which are lower than the lifetime of thermals in accordance with the Deardorff convective scale (
10 min). These low-frequency modes showed striated structures similar to that observed in the UHIC modes. These results suggest that UHIC and thermals deform each other through components that vary in long temporal scales.
Miura, Taito*; Miyamoto, Shintoro*; Maruyama, Ippei*; Aili, A.*; Sato, Takumi; Nagae, Yuji; Igarashi, Go*
Case Studies in Construction Materials, 21, p.e03571_1 - e03571_14, 2024/12
Times Cited Count：0 Percentile：0.00(Construction & Building Technology)Yamashita, Takuma*; Iwami, Satone*; Mitsuyasu, Yusuke*; Ono, Kenta*; Oka, Toshitaka; Takahashi, Atsushi*; Kino, Yasushi*; Sekine, Tsutomu*; Shimizu, Yoshinaka*; Chiba, Mirei*; et al.
KEK Proceedings 2024-6, p.85 - 90, 2024/12
To clarify the radiation effects of the accident at the TEPCO's Fukushima Daiichi NPP on living organisms, it is important to accurately estimate the dose to each individual. We have developed a multi-component analysis program using random number optimization to extract only the components derived from carbonate radicals from the ESR spectra.
