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Kondo, Masatoshi*; Kitamura, Yoshiki*; Kawarai, Atsushi*; Saito, Shigeru; Obayashi, Hironari
Corrosion Science, 262, p.113646_1 - 113646_14, 2026/04
The corrosion resistance of FeCrAl alloy APMT (Fe-21Cr-5Al-3Mo) in flowing lead-bismuth eutectic (LBE) was investigated by corrosion tests performed at 723 K using a non-isothermal forced convection loop. The oxygen concentration in flowing LBE was controlled at 1
10
wt%. No severe corrosion or erosion was detected on the specimens exposed to flowing LBE for 2000 h and 4000 h. Multiple oxide layers consisting of Fe-rich, Cr-rich and Al-rich sub-layers were formed in situ on the surface of APMT during the corrosion tests, which effectively suppressed corrosion and erosion. The oxide layers were intentionally removed by gentle abrasion prior to re-immersion and the specimens were then re-immersed in flowing LBE for an additional 2000 h. The oxide layers were spontaneously re-formed in situ on the abraded surface. This behavior indicates a self-healing capability. The results of micro-scratch tests indicated that the in-situ formed multiple oxide layers exhibited high adhesion strength in the shear direction after the 2000 h corrosion test.
Toigawa, Tomohiro; Hotoku, Shinobu; Kumagai, Yuta; Abe, Yuma*; Oyama, Kanichi*; Fukaya, Hiroyuki; Ban, Yasutoshi; Kida, Takashi; Hasegawa, Satoshi*; Nakano, Masanao*; et al.
Journal of Nuclear Science and Technology, 63(3), p.322 - 327, 2026/03
Times Cited Count：0 Percentile：0.00The effect of temperature on hydrogen production generated from radiolysis was investigated to determine the associated implications for nuclear fuel reprocessing safety. The hydrogen yield from radiolysis of plutonium nitric acid solution was measured at temperatures up to the boiling temperature of the solution. The results showed no notable temperature dependence even under boiling conditions. The impact of solution agitation on hydrogen production was also assessed, which revealed minor differences in the hydrogen yield between static and agitated conditions at room temperature. These findings suggest that high temperatures or boiling the solution do not considerably enhance hydrogen generation, and provide crucial information for accurately modeling hydrogen risks under severe accidents.
Th as a long-life 
Ac generator using the experimental fast reactor JoyoSasaki, Yuto; Maeda, Shigetaka; Fukasawa, Tetsuo*; Takaki, Naoyuki*
Journal of Nuclear Science and Technology, 63(2), p.154 - 165, 2026/02
Times Cited Count：0 Percentile：0.00In recent years, targeted alpha therapy, which utilizes Ac combined with antibodies or peptides that selectively accumulate in cancer cells, has garnered attention in the field of nuclear medicine. To meet the resulting increasing demand for Ac, exploring alternative production methods is essential. While several researchers, including the authors, have explored production methods using 
Ra as a raw material, challenges remain, such as the limited availability of Ra, difficulties in handling it, and the requirement for regular irradiation. To address these challenges, the authors focused on developing a production strategy for a long-life Ac generator using 
Th as a raw material and the experimental fast reactor Joyo. A detailed investigation was conducted, encompassing chemical processing after irradiation, target availability, and production yields, including the most probable values and associated uncertainties. Results revealed that although enrichment of the raw material and long-term irradiation are required, Ac can be produced in quantities comparable to its current global supply. Furthermore, this research has shown that the THOREX method, which is already in practical use, be applied to effectively separate by-products such as fission products and radioactive materials from thorium during the chemical processing after irradiation, as revealed by a literature survey.
Kondo, Ryoichi; Yamamoto, Akio*; Endo, Tomohiro*
Journal of Nuclear Science and Technology, 63(2), p.142 - 153, 2026/02
Times Cited Count：0 Percentile：0.00The flux distribution tallies using proper orthogonal decomposition, called POD tallies, have been developed to address issues of high-fidelity Monte Carlo simulations. The POD tallies can reduce both dimensionality and statistical error. The present study verifies the applicability of the POD tallies to sub-pin level flux distribution in the two-dimensional C5G7 benchmark. Statistical error estimation is also proposed by applying the circular block bootstrap method to the POD tallies to estimate the statistical error of the flux distribution in a single Monte Carlo calculation. In the verification, the dimensionality of the finely discretized distribution is reduced by more than 90% compared with conventional cell tallies. The statistical error is reduced by more than half as the average value of all tally regions. The proposed approach is confirmed to properly estimate the statistical error of flux distribution considering both the inter-cycle correlation and the correlation between the expansion coefficients of different POD orders.
Watanabe, Tomoaki; Aizawa, Naoto*; Chiba, Go*; Tada, Kenichi; Fujita, Tatsuya*; Yamamoto, Akio*
Journal of Nuclear Science and Technology, 63(2), p.166 - 186, 2026/02
Times Cited Count：0 Percentile：0.00A fast burnup calculation method based on neutron spectrum reconstruction is proposed. The method employs a reduced-order model (ROM), constructed using proper orthogonal decomposition (POD) and regression models, to estimate neutron spectra experienced by fuel during burnup. The ROM is built from snapshot data generated through detailed burnup and neutron transport simulations under various conditions. During burnup calculations, the ROM is used to rapidly reconstruct neutron spectra at each burnup step. These reconstructed spectra are then used to compute one-group cross sections from multi-group effective cross sections derived using background cross sections. The proposed method significantly reduces computational time by avoiding repeated neutron transport simulations. Its performance is demonstrated using a PWR UO
fuel pin model. Results show that, with the 6th-order POD, the method predicts nuclide inventories with an average error within 
5% compared to reference Monte Carlo calculations. Error analysis indicates that prediction accuracy is primarily limited by the regression models, rather than by the POD truncation or the multi-group cross section calculations.
Cs in stream water in forested catchmentsSakuma, Kazuyuki; Yoshimura, Kazuya; Nakanishi, Takahiro; Hayashi, Seiji*; Tsuji, Hideki*; Funaki, Hironori; Iijima, Kazuki
Science of the Total Environment, 1014, p.181397_1 - 181397_9, 2026/02
The Fukushima Daiichi Nuclear Power Plant accident released substantial radiocesium into terrestrial environments in 2011. Understanding the sources of dissolved radiocesium and the factors controlling its seasonal variation in stream water is crucial for assessing and mitigating environmental radioactive contamination. From 2015 to 2021, we investigated dissolved Cs concentrations and dissolved organic carbon (DOC) in stream water, spring water, groundwater, litter leachate, soil pore water, and infiltrated water. In the headwater area, dissolved Cs concentrations increased just after spring compared to the concentrations in the groundwater. During approximately three years of stream water monitoring, dissolved Cs concentrations correlated with water temperature, concentrations of DOC, and K
. A three-component mixture model revealed that stream water composition is derived mainly from groundwater, leaching from forest litter/surface soil, and soil pore water. The soil pore water particularly influenced summer stream water, likely due to the water table fluctuations with precipitation. The leaching water also influenced the summer stream water compared to the winter stream water. These findings suggest that seasonal variations in dissolved Cs are driven by temperature-dependent leaching from surface forest litter/soil and increased contributions from soil pore water. This study is the first to identify the sources and seasonal drivers of dissolved Cs in forested headwater streams.
Maeda, Makoto; Komeda, Masao; Toh, Yosuke
Nuclear Science and Engineering, 200(1), p.181 - 194, 2026/01
Times Cited Count：0 Percentile：0.00(Nuclear Science & Technology)Shim, S.-I.*; Hosaka, Atsushi
Proceedings of Science (Internet), 500, p.010_1 - 010_6, 2026/01
no abstracts in English
from QCD sum rulesSu, N.*; Chen, H.-X.*; Gubler, P.; Hosaka, Atsushi
Proceedings of Science (Internet), 500, p.076_1 - 076_6, 2026/01
Ishikawa, Takatsugu*; Hosaka, Atsushi; Gubler, P.; Sako, Hiroyuki; Tanida, Kiyoshi; 33 of others*
Proceedings of Science (Internet), 500, p.225_1 - 225_5, 2026/01
Fujii, Daisuke; Kawaguchi, Mamiya*; Tanaka, Mitsuru*
Proceedings of Science (Internet), 500, p.239_1 - 239_6, 2026/01
Elucidating the mechanisms by which quarks and gluons are confined within hadrons is the most fundamental challenge in QCD. To solve this problem, it is important to understand the role of quark and gluon condensation and the associated spontaneous symmetry breaking in making hadrons. Recently, the stress distribution inside the proton has become experimentally measurable. It is extracted from the gravitational form factors that characterize the matrix elements of the energy-momentum tensor for the proton. This stress distribution is the force that confines quarks and gluons inside hadrons, opening the way to approach the above issues from the viewpoint of stress distribution. In this talk, we investigate the contributions of phenomena reflecting chiral and scale symmetry breaking, such as quark and gluon condensation, to the pressure distribution inside the nucleon, and show that these contributions are essential for stabilizing the nucleon.
Fujii, Daisuke; Hosaka, Atsushi*; Iwanaka, Akihiro*; Sakai, Tadakatsu*; Tachibana, Motoi*
Proceedings of Science (Internet), 500, p.135_1 - 135_6, 2026/01
Understanding strongly coupled QCD matter remains challenging due to its non-perturbative nature. We study finite-density, zero-temperature QCD in a two-flavor hard-wall holographic model with nonzero quark mass. The dense phase is obtained by solving the classical equations of motion under a homogeneous ansatz. To relate bulk fields to boundary observables, we perform holographic renormalization and construct the dictionary, emphasizing the essential role of an IR boundary term at the hard-wall cutoff. Within this setup we uncover a baryonic phase with large baryon number density and a strongly suppressed chiral condensate. From these solutions we derive the equation of state and compute neutron-star mass-radius relations, finding stars above two solar masses over a broad parameter range.
Alam, M. M.*; Yamakita, Eri*; Inoue, Yuzuru*; Koarashi, Jun; Atarashi-Andoh, Mariko; Abe, Yukiko; Nakayama, Hiromasa; Mori, Yuki*; Hiradate, Shuntaro*
Soil Science and Plant Nutrition, 72(1), p.55 - 66, 2026/01
Alam, M. M.*; Yamakita, Eri*; Tamanna, S.*; Thae, E. P.*; Koarashi, Jun; Atarashi-Andoh, Mariko; Abe, Yukiko; Nakayama, Masataka; Mori, Yuki*; Hiradate, Shuntaro*
Soil Science and Plant Nutrition, 12 Pages, 2026/00
Masuda, Hiroto*; Yamane, Yuta*; Dohi, Takaaki*; Yamazaki, Takumi*; Modak, R.*; Uchida, Kenichi*; Ieda, Junichi; Kl
ui, M.*; Takanashi, Koki; Seki, Takeshi*
Advanced Science (Internet), 12(48), p.e14598_1 - e14598_9, 2025/12
by high-energy irradiationOtsuka, Shunya*; Sasajima, Yasushi*; Ishikawa, Norito
ECS Journal of Solid State Science and Technology, 14(12), p.124003_1 - 124003_9, 2025/12
Nakamura, Yuki*; Kojima, Yoshihiro*; Yamashita, Takuya; Shimomura, Kenta; Mizokami, Shinya
Journal of Nuclear Science and Technology, 62(12), p.1226 - 1230, 2025/12
Fukuda, Takanari; Yamashita, Susumu; Yoshida, Hiroyuki
Journal of Nuclear Science and Technology, 62(12), p.1264 - 1278, 2025/12
This study compared three interface capturing schemes (ICSs) for multi-phase flow simulations based on the VOF method, focusing on bubble volume conservation. The THINC/WLIC scheme showed significant VOF diffusion and underestimated total bubble volume, while the original THINC and PLIC conserved bubble volumes. Moreover, an analysis of THINC/WLIC based on a new visualization approach revealed that VOF fragments were ripped off by shear forces around interface, making it unsuitable for accurate void fraction prediction in boiling water reactors. The original THINC may be a viable alternative to PLIC due to its simplicity.
Hirota, Noriaki
Material Science and Technology of Japan, 62(6), p.192 - 196, 2025/12
In a high-temperature sulfuric acid environment, Alloy600 showed a high corrosion rate of 0.40 mm/year, while Alloy800H and 3Al-Ferrite exhibited much lower rates of 0.03 to 0.01 mm/year. Four-point bending tests revealed the stress to reach 0.2 % yield stress followed the order: 3Al-Ferrite 
Alloy600 Alloy800H. Bending strain at 80 % of 0.2 % yield stress was highest in Alloy800H and lowest in 3Al-Ferrite, indicating its low deformability. Post-corrosion microstructural analysis revealed that Alloy800H and 3Al-Ferrite formed thin oxide films with no cracks, whereas Alloy600, which developed a thick multilayered oxide film composed of Ni, Fe and Cr, exhibited open cracks. Electron Backscattered Diffraction (EBSD) and Grain Reference Orientation Deviation (GROD) maps confirmed intergranular crack growth and residual tensile stress in Alloy600. These findings indicate that Alloy600, primarily composed of Ni and Cr, formed a spallation and degradation oxide film and subsequently generated oxides that weakened the grain boundaries, thereby promoting the occurrence of Stress Accelerated Grain Boundary Oxidation (SAGBO).
Catumba, G.*; Hiraguchi, Atsuki; Hou, G. W.-S.*; Jansen, K.*; Kao, Y.-J.*; David Lin, C.-J.*; Ramos, A.*; Sarkar, M.*
Proceedings of Science (Internet), 466, p.145_1 - 145_10, 2025/12
The custodial Two-Higgs-Doublet-Model with SU(2) gauge fields is studied on the lattice. This model has the same global symmetry structure as the Standard Model but the additional Higgs field enlarges the scalar spectrum and opens the possibility for the occurrence of spontaneous symmetry breaking of the global symmetries. Both the spectrum and the running of the gauge coupling of the custodial 2HDM are studied on a line of constant Standard Model physics with cutoff ranging from 300 to 600 GeV. The lower bounds of the realizable masses for the additional BSM scalar states are found to be well bellow the W boson mass. In fact, for the choice of quartic couplings in this work the estimated lower mass for one of the BSM states is found to be about 
0.2 
and independent of the cutoff.
