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Journal Articles

Numerical analysis of a potential Reactor Pressure Vessel (RPV) boundary failure mechanism in Fukushima Daiichi Nuclear Power Station Unit-2

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)

Journal Articles

Achievements and status of the STRAD project for radioactive liquid waste management

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, 2025/05

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.

JAEA Reports

Investigation of chemical substances affect the fluidity of paste on cement solidification

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.

Journal Articles

Establishment of a practical methodology for evaluating equieffective dose of individual patients based on RT-PHITS

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)

Journal Articles

A Lightweight shape-memory alloy with superior temperature-fluctuation resistance

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:2 Percentile:88.78(Multidisciplinary Sciences)

Journal Articles

Multiple metamagnetic transitions in the helical antiferromagnet CeVGe$$_{3}$$

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)

Journal Articles

Large-eddy simulation analysis on the area of influence of local hilly terrains on plume dispersion released from a stack

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 ($$H$$). 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$$H$$ valley) cases. The effect of the leeward hill on the flow field was negligible when the valley width was greater than 10$$H$$. In the area beyond 20$$H$$ 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$$H$$.

Journal Articles

Effect of sea salt on the interaction between simulated corium and concrete

Sudo, Ayako; Sato, Takumi; Takano, Masahide

Journal of Nuclear Science and Technology, 9 Pages, 2025/00

 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.

Journal Articles

Feasibility of individual dosimetry using RT-PHITS for patients with SPECT/CT imaging after $$^{177}$$Lu-DOTATATE peptide receptor radionuclide therapy

Miwa, Kenta*; Kakino, Ryo*; Sato, Tatsuhiko; Furuta, Takuya; Miyaji, Noriaki*; Yamao, Tensho*; Yamashita, Kosuke*; Terauchi, Takeshi*

Physical and Engineering Sciences in Medicine, 9 Pages, 2025/00

 Times Cited Count:0

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 $$^{177}$$Lu-DOTATATE peptide receptor radionuclide therapy.

Journal Articles

Separating urban heat island circulation and convective cells through dynamic mode decomposition

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 ($$sim$$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.

Journal Articles

New insight on the thermal impact on cementitious materials due to high-temperature with water supply; Continuous expansive spalling in water

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)

Journal Articles

Study on microwave power dependency of electron spin resonance spectrum of carbonate radicals in teeth

Iwami, Satone*; Yamashita, Takuma*; Mitsuyasu, Yusuke*; Ono, Kenta*; Oka, Toshitaka; Takahashi, Atsushi*; Kino, Yasushi*; Sekine, Tsutomu*; Shimizu, Yoshinaka*; Chiba, Mirei*; et al.

KEK Proceedings 2024-6, p.91 - 95, 2024/12

We aim to improve the detection limit of the ESR dosimetry method. In this study, the saturation behavior of each radical was investigated by varying the microwave power during ESR measurement. Based on the difference in spin relaxation time between carbonate radicals and native radicals, it is expected that the signal-to-noise ratio improves and the detection limit can be lowered when the microwave power is increased to 4.0 mW.

Journal Articles

Improved multicomponent analysis method for electron spin resonance spectra of gamma-irradiated tooth enamel

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.

Journal Articles

Overview of PHITS Ver.3.34 with particular focus on track-structure calculation

Ogawa, Tatsuhiko; Hirata, Yuho; Matsuya, Yusuke; Kai, Takeshi; Sato, Tatsuhiko; Iwamoto, Yosuke; Hashimoto, Shintaro; Furuta, Takuya; Abe, Shinichiro; Matsuda, Norihiro; et al.

EPJ Nuclear Sciences & Technologies (Internet), 10, p.13_1 - 13_8, 2024/11

The latest updates on PHITS, a versatile radiation transport code, focusing specifically on track-structure models are presented. Track structure calculations are methods used to simulate the movement of charged particles while explicitly considering each atomic reaction. Initially developed for radiation biology, these calculation methods aimed to analyze the radiation-induced damage to DNA and chromosomes. Several track-structure calculation models, including PHITS-ETS, PHITS-ETS for Si, PHITS-KURBUC, ETSART, and ITSART, have been developed and implemented to PHITS. These models allow users to study the behavior of various particles at the nano-scale across a wide range of materials. Furthermore, potential applications of track-structure calculations have also been proposed so far. This collection of track-structure calculation models, which encompasses diverse conditions, opens up new avenues for research in the field of radiation effects.

Journal Articles

Complete genome sequence of ${it Thiomicrospira}$ sp. strain V2501 isolated from 250 m below the ground level in Horonobe, Hokkaido, Japan

Ueno, Akio*; Sato, Kiyoshi*; Tamamura, Shuji*; Murakami, Takuma*; Inomata, Hidenori*; Tamazawa, Satoshi*; Amano, Yuki; Miyakawa, Kazuya; Naganuma, Takeshi*; Igarashi, Toshifumi*

Microbiology Resource Announcements (Internet), 13(11), p.e00108-24_1 - e00108-24_4, 2024/11

Journal Articles

Development of a multi-scale meteorological Large-eddy simulation model for urban thermal environmental studies; The "City-LES" Model Version 2.0

Kusaka, Hiroyuki*; Ikeda, Ryosaku*; Sato, Takuto; Iizuka, Satoru*; Boku, Taisuke*

Journal of Advances in Modeling Earth Systems (Internet), 16(10), p.e2024MS004367_1 - e2024MS004367_38, 2024/10

 Times Cited Count:2 Percentile:65.39(Meteorology & Atmospheric Sciences)

To bridge the gaps between meteorological large-eddy simulation (LES) models and computational fluid dynamics (CFD) models for microscale urban climate simulations, the present study has developed a meteorological LES model for urban areas. This model simulates urban climates across both mesoscale (city scale) and microscale (city-block scale). The paper offers an overview of this LES model, which distinguishes itself from standard numerical weather prediction models by resolving buildings and trees at the microscale simulations. It also differs from standard CFD models by accounting for atmospheric stratification and physical processes. Noteworthy features of this model include: (a) the calculation of long- and short-wave radiations in three dimensions, incorporating multiple reflections within urban canopy layers using the radiosity method, and accounting for building and tree shadows in the simulations; (b) the provision of various heat stress indices (Universal Thermal Climate Index, Wet Bulb Globe Temperature, MRT, THI); (c) the assessment of the efficacy of heat stress mitigation measures such as dry-mist spraying, roadside trees, cool pavements, and green/cool roofs strategies; (d) the capability to run on supercomputers, with the code parallelized in a three-dimensional manner, and the model can also run on a graphics processing unit cluster. Following the introduction of this model, the study confirms its basic performance through various numerical experiments, including simulations of thermals in the convective boundary layer, coherent structure of turbulence over urban canopy, and thermal environment and heat stress indices in urban districts. The model developed in this study is intended to serve as a community tool for addressing both fundamental and applied studies in urban climatology.

Journal Articles

Construction of new polygon mesh-type phantoms based on adult Japanese voxel phantoms

Sato, Kaoru; Furuta, Takuya; Satoh, Daiki; Tsuda, Shuichi

PLOS ONE (Internet), 19(10), p.e0309753_1 - e0309753_26, 2024/10

 Times Cited Count:0 Percentile:0.00(Multidisciplinary Sciences)

The authors previously developed the adult male (JM-103) and female (JF-103) voxel phantoms with standard Japanese body sizes for dose assessment of radiation accidents and medical exposures. However, JM-103 and JF-103 were not applicable to dose assessment considering posture at the time of exposure due to limitations in description format and resolution. In this study, we developed the polygon mesh-type adult Japanese phantoms (male: JPM, female: JPF) based on JM-103 and JF-103. The detailed models of skin and lens with radiosensitive regions less than 1 mm thick were incorporated into JPM and JPF. The effective doses, and skin and lens (entire and radiosensitive regions) doses were calculated for external irradiation with photons or electrons in anterior-posterior geometry. It was confirmed that dose analysis results by JPM and JPF were consistent with the previous reports. In the future, we will develop a detailed dose assessment method for individuals, taking into account their postures at the time of exposure, by applying the posture deformation technique currently under development to the JPM and JPF.

Journal Articles

${it In vitro}$ and ${it in silico}$ study of biological effects on cancer cells in the presence of metallic materials during radiotherapy

Nagano, Takuya*; Matsuya, Yusuke; Kaida, Atsushi*; Nojima, Hitomi*; Furuta, Takuya; Sato, Kaoru; Yoshimura, Ryoichi*; Miura, Masahiko*

Journal of Radiation Research (Internet), 65(5), p.628 - 639, 2024/09

 Times Cited Count:0 Percentile:0.00(Biology)

In X-ray therapy, radiation regimen is planned to eliminate tumors while minimizing side effects on normal tissue. When irradiating the oral cavity, which includes dental metallic crowns, intense mucositis can occasionally be induced. However, the mechanism underlying the radiosensitization remains unclear. In this study, we investigated the radiosensitization mechanism using cell experiments and computational simulations. As a result, the enhancement ratio observed in the cell experiments was 1.2-1.4, which was found to be predominately attributed to local dose increase near metal. On the other hand, as a result of dose evaluation based on CT images as a preclinical test, it was found that the dose increase was underestimated due to the complex anatomical structure of the human body, and microscopic dose evaluation was necessary. This outcome contributes to the precise understanding of side effects on normal cells around metals.

Journal Articles

Missing-mass measurement of the $$^{12}$$C$$(K^-,K^+)$$ reaction at 1.8 GeV/$$c$$ with the Superconducting Kaon spectrometer

Ichikawa, Yudai; Fujita, Manami; Hasegawa, Shoichi; Imai, Kenichi*; Nanamura, Takuya; Naruki, Megumi; Sato, Susumu; Sako, Hiroyuki; Tamura, Hirokazu; Tanida, Kiyoshi; et al.

Progress of Theoretical and Experimental Physics (Internet), 2024(9), p.091D01_1 - 091D01_13, 2024/09

 Times Cited Count:0 Percentile:0.00(Physics, Multidisciplinary)

Journal Articles

MAAP code analysis for the in-vessel phase of Fukushima-Daiichi Nuclear Power Station Unit 1 and comparison of the results among Units 1 to 3

Sato, Ikken; Yoshikawa, Shinji; Yamashita, Takuya; Shimomura, Kenta; Cibula, M.*; Mizokami, Shinya*

Nuclear Engineering and Design, 422, p.113088_1 - 113088_24, 2024/06

 Times Cited Count:0 Percentile:0.00(Nuclear Science & Technology)

617 (Records 1-20 displayed on this page)