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Yoshimura, Kazuo; Doda, Norihiro; Tanaka, Masaaki; Fujisaki, Tatsuya*; Murakami, Satoshi*
Annals of Nuclear Energy, 226, p.111896_1 - 111896_11, 2026/02
At the Japan Atomic Energy Agency, a multilevel simulation (MLS) methodology which enables consistent evaluation from whole plant behavior to local phenomena in the plant components is being developed to attempt plant design and enhance the safety of sodium-cooled fast reactors. To validate the coupling method in the MLS system, the 1D-CFD coupling method using Super-COPD for 1D plant dynamics analysis and Fluent for multi-dimensional CFD analysis was applied to the analyses of loss of flow tests in EBR-II. It was confirmed that it could predict multi-dimensional thermal-hydraulic phenomena such as thermal stratification in the upper plenum, Z-shaped pipe, and cold pool, holding the whole plant behavior simultaneously. Moreover, the applicability of the 1D-CFD coupling method to the evaluation of the phenomena in natural circulation conditions was confirmed by comparing the results of the 1D-CFD couple analyses and the measured data.
Kawaguchi, Munemichi*; Ikeda, Asuka; Saito, Junichi
Annals of Nuclear Energy, 226, p.111880_1 - 111880_9, 2026/02
Times Cited Count：0Wang, Z.; Shibamoto, Yasuteru
International Journal of Heat and Mass Transfer, 255(Part 1), p.127701_1 - 127701_16, 2026/02
Times Cited Count：0
underwater radiation monitoring detectorJi, W.*; Lee, E.*; Ji, Y.-Y.*; Ochi, Kotaro; Yoshimura, Kazuya; Funaki, Hironori; Sanada, Yukihisa
Nuclear Engineering and Technology, 58(2), p.103933_1 - 103933_6, 2026/02
We aimed to validate the performance of an in situ underwater radiation detector, MARK-U1 (Monitoring of Ambient Radiation of KAERI - Underwater), was used to estimate 
Cs activity concentration in river and reservoir sediment at predicted sites of contamination. Additionally, underwater core samples were collected to measure the radioactivity using a high-purity germanium (HPGe) detector. To estimate radioactivity, a conversion factor was derived by comparing the measured spectrum and Cs activity in the sample. A Monte Carlo N-Particle (MCNP) simulation was conducted to determine the effective source geometry for in situ measurement. The simulation results correlated well with the on-site MARK-U1 monitoring results, with a deviation of 31.62%. These findings validate the performance of the in situ detector. This device can therefore be used to estimate Cs activity concentration in the underwater sediment via on-site monitoring, without requiring sample collection.
Qin, T. Y.*; Hu, F. F.*; Xu, P. G.; Zhang, R.*; Su, Y. H.; Ao, N.*; Li, Z. W.*; Shinohara, Takenao; Shobu, Takahisa; Wu, S. C.*
International Journal of Fatigue, 202, p.109233_1 - 109233_16, 2026/01
Ueki, Taro
Progress in Nuclear Energy, 191, p.106007_1 - 106007_11, 2026/01
Times Cited Count：0Criticality analysis of continuously mixed random media is crucial for safely retrieving fuel debris. Initially, a Monte Carlo method was established using the Incomplete Randomized Weierstrass Function (IRWF) to model a single-mode inverse power law power spectrum. However, image analysis showed that oxide debris mock-ups require a more complex model. To address this, a new function called the Randomized Fourier Series (RFS) was developed to represent arbitrary power spectra. RFS is versatile, incorporating Brownian motion models and aiding reactor physicists in analyzing various scenarios. Numerical results compare the fluctuation of neutron multiplication factor in various media generated by RFS and IRWF, identifying the spectral range most affecting k
.
Chong, Y.*; Tsuru, Tomohito; Gholizadeh, R.*; Minor, A. M.*; Tsuji, Nobuhiro*
Acta Materialia, 301, p.121523_1 - 121523_12, 2025/12
Twinning is essential for achieving large ductility in hexagonal close-packed (HCP) titanium alloys that inherently lack independent slip systems due to an asymmetrical HCP crystal structure. Unfortunately, twinning is in principle suppressed by a trace amount of interstitial oxygen, resulting in a substantially deteriorated ductility in titanium. However, the underlying mechanism remains in dispute so far. Here, we report a systematic multiscale study on the twinning/detwinning behaviors of Ti-O alloys that provides a clear mechanistic view of how interstitial oxygen inhibits twinning. We reveal for the first time that oxygen atoms segregate to both {10
2}
2} compression twin boundaries using atom probe tomography. Combined with theoretical simulations that unravel a strong pinning effect of oxygen atoms on twin boundary due to an oxygen shuffling mechanism, we explain the distinctive migration abilities of twin boundaries in Ti-O alloys at different temperatures. The insights from our experimental and computational work provide a rationale for the design of titanium alloys with increased tolerance to variations in interstitial impurity content, with significant implications for more widespread use of this high strength, light weight material.
Oizumi, Akito; Sagara, Hiroshi*
Annals of Nuclear Energy, 223, p.111677_1 - 111677_12, 2025/12
Times Cited Count：0 Percentile：0.00(Nuclear Science & Technology)This study aims to provide a new rational physical protection (PP) design method by using 
(
) and to design a rational PP system for a site of the transuranium fuel cycle with accelerator-drive systems (ADSs cycle) using the new method. First, the new rational PP design method with different PP design requirements for each was generalized based on the definitions of a national standard method defined by the US Department of Energy, the joint US-Japan study, and the International Atomic Energy Agency. A new PP categorization of Uranium (U), including U-234, which is abundant in the ADS cycle, was also developed based on . Second, a PP design was conducted for a general BWR site with MOX fuel and the ADS cycle site by using the new rational method. It was clarified that the highest overall of the items within the ADS cycle site was lower than that of the MOX fuel assembly within the BWR site. The BWR site was determined to be Category I requiring the inner area. The PP design requirement level of the ADS cycle site was determined to be Category II, which does not require an inner area, while the ADS cycle site would have been classified as Category I if the PP design had been conducted using the conventional method.
Dechenaux, B.*; Brovchenko, M.*; Araki, Shohei; Gunji, Satoshi; Suyama, Kenya
Annals of Nuclear Energy, 223, p.111555_1 - 111555_11, 2025/12
Times Cited Count：0 Percentile：0.00(Nuclear Science & Technology)Nakase, Masahiko*; Mishima, Ria; Abe, Takumi; Okamura, Tomohiro*; Asano, Hidekazu*
Annals of Nuclear Energy, 224, p.111569_1 - 111569_14, 2025/12
Nakagawa, Hiroshi; Ubbink, J.*
Food Hydrocolloids, 168, p.111453_1 - 111453_9, 2025/12
Times Cited Count：1 Percentile：0.00(Chemistry, Applied)The molecular mechanism of plant protein texturization under extrusion conditions was unraveled at the secondary structure level by decoupling the effects of heating, cooling and shearing on protein secondary structure. Upon heating without shearing, native alpha-helices and intramolecular-beta-sheets unfold to random domains, followed by the formation of intermolecular beta-sheets, inducing aggregation. During cooling, the intermolecular beta-sheets become increasingly ordered, and random domains partially fold into non-native beta-structures. Combined heating and shearing results in more extensive beta-sheets than heating alone. The resulting beta-rich structures provide for an entangled network of protein chains and a cohesive protein matrix.
Motegi, Kosuke; Shibamoto, Yasuteru; Hibiki, Takashi*
International Journal of Heat and Mass Transfer, 252, p.127451_1 - 127451_16, 2025/12
Times Cited Count：0 Percentile：0.00(Thermodynamics)Ji, Y.-Y.*; Joung, S.*; Ji, W.*; Ochi, Kotaro; Sasaki, Miyuki; Sanada, Yukihisa
Journal of Radiological Protection, 45(4), p.042501_1 - 042501_11, 2025/12
This study reports the development and field validation of KAERI's UAV-based gamma-ray spectrometry system equipped with LaBr
(Ce) detectors. Joint surveys with JAEA near FDNPP showed reliable dose rate estimation after applying altitude based attenuation correction, through discrepancies occurred in sloped terrain. Incorporating terrain data is recommended to enhance accuracy for emergency response applications.
Ota, Akira*; Ito, Sho*; Sonobe, Hideaki*; Ino, Susumu*; Choi, B.; Nishida, Akemi; Shiomi, Tadahiko
Nuclear Engineering and Design, 444, p.114403_1 - 114403_7, 2025/12
Times Cited Count：0no abstracts in English
Yoshikawa, Masanori; Seki, Akiyuki*; Okita, Shoichiro; Takaya, Shigeru; Yan, X.
Nuclear Engineering and Design, 444, p.114350_1 - 114350_9, 2025/12
Times Cited Count：0Morishita, Yuki; Nakama, Shigeo; Ochi, Kotaro; Urabe, Yoshimi*; Kanno, Marina*
Radiation Measurements, 189, p.107513_1 - 107513_6, 2025/12
Following the Fukushima Daiichi Nuclear Power Plant accident, radioactive cesium contamination posed a significant environmental concern. This study developed a compact gamma-ray spectrometer utilizing a Ce:GPS scintillator and a compact photomultiplier tube (PMT) for environmental monitoring. The spectrometer was designed to overcome limitations of traditional NaI(Tl) detectors, leveraging the non-hygroscopic nature and high energy resolution of Ce:GPS scintillators. Performance was evaluated through measurements of a Cs source and comparison with a commercial NaI(Tl) survey meter. The spectrometer's potential for effective and portable monitoring of radioactive cesium in contaminated environments was demonstrated. The system was tested using sealed sources, confirming its ability to detect the 662 keV photopeak of Cs with high accuracy. Field measurements in radiocesium-contaminated areas showed the spectrometer's effectiveness in detecting dose rate variations and high-dose hotspots. This portable, durable spectrometer shows promise for applications in environmental radiation monitoring and remote sensing technologies.
Dei, Shuntaro; Shibata, Masahito*; Negishi, Kumi*; Sugiura, Yuki; Amano, Yuki; Bateman, K.*; Wilson, J.*; Yokoyama, Tatsunori; Kagami, Saya; Takeda, Masaki; et al.
Results in Earth Sciences (Internet), 3, p.100097_1 - 100097_16, 2025/12
Interactions between cement and host rock in geological repositories for radioactive waste will result in a chemically disturbed zone, which may potentially affect the long-term safety. This paper investigates the chemical evolution at the interface between cement (Ordinary Portland Cement: OPC and Low Alkaline Cement: LAC) and mudstone after 11 years of in situ reactions at the Horonobe Underground Research Laboratory. The study combines various analytical techniques to identify the key reactions at the cement-rock interface, including cement dissolution, precipitation of secondary minerals such as calcite and C-(A-)S-H phases, cation exchange in montmorillonite and reduced porosity in mudstone. The study also highlights the effects of cement-mudstone interactions on radionuclide migration, such as reduction of diffusivity due to reduced porosity and enhancement of sorption due to incorporation into secondary minerals in the altered mudstone.
and Pb adsorptionNankawa, Takuya; Sugita, Asako; Fukakusa, Chihoko*; Yamada, Teppei*; Sekine, Yurina
Separation and Purification Technology, 378(3), p.134780_1 - 134780_9, 2025/12
We report a sustainable and chemical free strategy to fabricate sponge like chitosan hydrogels via freeze induced physical crosslinking using mild alkaline solutions, without toxic crosslinkers or synthetic additives. The resulting freeze crosslinked biomass-based chitosan sponge hydrogels exhibited interconnected macropores, high water permeability, excellent compressibility, and mechanical recoverability. These features enabled outstanding adsorption of hazardous heavy metals, achieving far better maximum capacities for Cu and Pb markedly surpassing conventional hydrogels. Notably, Cu adsorption induced visible color changes and enhanced mechanical strength, attributed to metal induced secondary crosslinking between amino and hydroxyl groups and adsorbed ions. Cu adsorption also led to a measurable increase in the Youngs modulus of the hydrogels, likely due to coordination with chitosan functional groups.
Otsuka, Naohiko*; Devi, V.*; Iwamoto, Osamu
Applied Radiation and Isotopes, 225, p.111903_1 - 111903_18, 2025/11
Times Cited Count：0 Percentile：0.00(Chemistry, Inorganic & Nuclear)Koarashi, Jun; Nagano, Hirohiko*; Nakayama, Masataka*; Atarashi-Andoh, Mariko; Nagaoka, Mika
Chemosphere, 389, p.144715_1 - 144715_11, 2025/11
Radiocesium (Cs) contamination poses a long-term ecological challenge, particularly in forest ecosystems. The role of soil microorganisms in determining its fate remains insufficiently understood. This study presents a dynamic assessment of microbial Cs retention, focusing on the complex interplay among microorganisms, organic matter, and clay minerals within the organic layer-mineral soil system. Our results show that rapid microbial cycling sustains a potentially bioavailable Cs pool in the organic layer. This microbial involvement diminishes as Cs activity concentrations in the organic layer decline. In the mineral soil, minimal microbial Cs retention was observed, suggesting an indirect role in facilitating Cs immobilization by clay minerals. Notably, microbial Cs retention in the organic layer is regulated by Cs availability, independent of region, forest type, and time since deposition. These findings provide a unified explanation for observed differences in Cs persistence in organic layers between European and Japanese forests.
