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Sun, R.; Abe, Yukiko; Atarashi-Andoh, Mariko; Koarashi, Jun
Soil Biology & Biochemistry, 218, p.110150_1 - 110150_12, 2026/07
Times Cited Count：0 Percentile：0.00(Soil Science)The role of minerals in soil carbon sequestration has been increasingly recognized. However, the mechanism by which mineral-associated organic matter (MAOM) resists microbial decomposition remains an open question. We prepared MAOM on amorphous allophane and crystalline kaolinite with different organic matter (OM) proxies, characterized the affinity strength of these associations using isothermal titration calorimetry and X-ray photoelectron spectroscopy, and quantified their microbial mineralization through aerobic incubation. We found that amorphous allophane displayed greater OM adsorption capacity due to its higher specific surface area; in contrast, crystalline kaolinite exhibited stronger binding with OM, consistent with its predominant inner-sphere complexation. Furthermore, lower MAOM mineralization was found corresponding to higher Langmuir affinity. This inverse relationship was more pronounced than the correlation with the amount of OM adsorbed by minerals. These findings suggest that the overall MAOM stability is controlled by a balance between binding strength and adsorption capacity. Namely, stronger binding affinity enhances microbial resistance of MAOM, while the abundance of mineral sites determines the amount of MAOM accessible for microbial decomposition. This study presents a novel mechanistic understanding of the MAOM dynamics and refines the prevailing perspective on MAOM persistence.
Omori, Takazumi; Fuyushima, Takumi; Sayato, Natsuki; Saito, Nagatsuki; Takabe, Yugo; Endo, Yasuichi; Inoue, Shuichi; Wojtania, G.*; Migdal, M.*; Takeuchi, Tomoaki; et al.
JAEA-Technology 2026-006, 47 Pages, 2026/06
JAEA-Technology-2026-006.pdf:3.01MB
Japan Materials Testing Reactor (JMTR), which served as the core facility for neutron irradiation research including materials research and radioisotope production, has been decommissioned. As a result, it has become difficult to continue conducting irradiation tests domestically, as well as to transfer the operational expertise and irradiation technologies associated with test reactors, to address these challenges, it was decided to initiate JMTR alternative irradiation, in which foreign irradiation reactors are utilized to partially substitute for JMTR's irradiation capabilities. As a first step, based on the "Arrangement between the National Centre for Nuclear Research and the Japan Atomic Energy Agency for Cooperation in Research and Development on Testing Reactor". The MARIA reactor (30 MW) owned by the National Centre for Nuclear Research (NCBJ) was selected as the neutron irradiation facility, a temperature control system, which is one of JMTR's irradiation technologies, was introduced into the MARIA reactor, and irradiation tests were conducted. The results of this irradiation test confirmed that the combination of the newly introduced temperature control device and the JMTR irradiation test system operates without issues even after an irradiation period exceeding 150 days, it was also demonstrated that the tests could be conducted while continuously measuring the thermocouple temperature inside the capsule during irradiation, as well as the output of the LVDT and SPGD. Furthermore, regarding the constant temperature control of the irradiation capsule at 300
C constant temperature control test, which is highly demanded in materials irradiation testing, was conducted, during reactor power increases, when temperature fluctuations become significant, temperature control was maintained within 
6.3C, while during power decreases, it was controlled within 26.0C. These results indicate that irradiation testing with irradiation temperature control system developed by JMTR, can also be performed in the MARIA reactor, it was confirmed that it can be offered as an alternative irradiation field.
Takeda, Shinichiro*; Katsuragawa, Miho*; Takahashi, Tadayuki*; Watanabe, Shin*; Chiu, I.-H.; Ninomiya, Kazuhiko*; Arai, Toshihiko*; Onishi, Mitsunobu*; Tampo, Motonobu*; Shimomura, Koichiro*; et al.
Analytical Chemistry, 98(24), p.17618 - 17626, 2026/06
Times Cited Count：0
LaNakabe, Rintaro; Endo, Shunsuke; Kambara, Wataru*; Kimura, Atsushi; Kobayashi, Ryuju; Oku, Takayuki; Sakai, Kenji; Shinohara, Takenao; Takahashi, Ryuta*; Tsuchikawa, Yusuke; et al.
JPS Conference Proceedings (Internet), 45, p.011066_1 - 011066_5, 2026/06
We evaluate the time-reversal invariance violation using previous neutron transmission data with polarized neutrons propagating through a transversely polarized La. By incorporating precise spin observables and the scattering amplitudes into our analysis, we preliminarily constrained the time-reversal invariance violating cross section.
LaNakabe, Rintaro; Endo, Shunsuke; Kambara, Wataru*; Kawamura, Shihori; Kimura, Atsushi; Kobayashi, Ryuju; Oku, Takayuki; Okudaira, Takuya*; Sakai, Kenji; Shinohara, Takenao; et al.
Progress of Theoretical and Experimental Physics (Internet), 2026(6), p.063D01_1 - 063D01_15, 2026/06
Times Cited Count：0We report the first constraint on time-reversal invariance violating (TRIV) effects in polarized neutron transmission through a transversely polarized La target. We formulate the transmission asymmetry within the density matrix formalism, explicitly incorporating the forward scattering amplitude of La including tensor polarization terms up to third-rank. The formalism is applied to existing transmission data originally obtained to measure the spin-dependent cross section near the 
~eV 
-wave resonance. Since these data were not optimized for P-odd/T-odd observables, the attainable sensitivity is intrinsically limited; nevertheless, they provide a useful test of the formalism on real experimental data. No statistically significant TRIV signal is observed. By analyzing the global 
structure in the parameter space, we obtain an upper limit of 
at the 90% confidence level. This corresponds to an upper limit on the resonance-averaged TRIV cross section of 
. These results validate the present theoretical framework and provide guidance for future dedicated TRIV searches in polarized neutron transmission experiments.
Fujiwara, Yusuke; Nakajima, Kunihiro; Urabe, Kohei; Nagatsuka, Kentaro; Asano, Kazuhito; Shimizu, Atsushi; Noguchi, Hiroki; Sato, Hiroyuki; Ohashi, Hirofumi; Sumita, Junya; et al.
JAEA-Technology 2026-001, 43 Pages, 2026/05
JAEA-Technology-2026-001.pdf:2.93MB
High Temperature Gas-cooled Reactors (HTGRs) have excellent safety features and can supply high-temperature heat without emitting carbon dioxide, and therefore are expected to stably produce large amounts of hydrogen to contribute carbon neutrality by 2050. The pertinent material for the "Basic Policy for GX Realization" shows the development process for the HTGR demonstrator with the goal of starting operation in the 2030s. Meanwhile, to achieve net-zero, the UK government has started the Advanced Module Reactor (AMR) Research, development and demonstration (RD&D) programme with the aim of starting operations of the HTGR demonstrator in the early 2030s. Against this background, with the aim of early deployment of HTGR technology, Japan Atomic Energy Agency (JAEA), in collaboration with the United Kingdom National Nuclear Laboratory (UKNNL), aims to demonstrate Japanese HTGR technology outside Japan and reflect the development of HTGR demonstrator in the UK to Japan. This document summarizes the results of a market survey of HTGR products and surveys of industrial infrastructure in the UK, the environment and social conditions of Hartlepool, a candidate construction site, with the aim of contributing to the design study of the HTGR demonstrator in the UK (UKJ-HTR).
Kawabe, Tomosaburo*; Sano, Yoshihiko*; Kuwahara, Fujio*; Uesawa, Shinichiro; Yoshida, Hiroyuki
Dai-63-Kai Nihon Dennetsu Shimpojiumu Koen Rombunshu (Internet), 1 Pages, 2026/05
To estimate the thermal behavior of fuel debris inside the Primary Containment Vessels (PCVs) of TEPCO's Fukushima Daiichi Nuclear Power Station, a simulation method has been developed using the JUPITER code with porous medium models. However, it has been found that the selection of models and parameters according to the internal structure of the porous media significantly affects the accuracy of simulation results, highlighting the need for appropriate model selection strategies. In this study, we focus on packed beds with particles as one form of porous media and investigate a methodology for determining model parameters that characterize their flow behavior. Systematic knowledge of packed beds with heterogeneous particle size ratios and packing structures remains limited, and comprehensive organization accounting for structural differences has not yet been fully established. Therefore, numerical simulations were employed to evaluate the permeability and Forchheimer coefficient of packed beds with different particle size ratios and packing structures. Based on the obtained results, a method for appropriately determining these parameters according to the structural characteristics of packed beds is proposed, and insights are provided that contribute to improving the accuracy of flow analysis models in porous media.
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, 72(3), p.289 - 300, 2026/05
Times Cited Count：0 Percentile：0.00(Plant Sciences)
O solutionKumagai, Yuta; Kusaka, Ryoji; Takano, Masahide; Watanabe, Masayuki
Journal of Nuclear Materials, 625, p.156553_1 - 156553_7, 2026/04
Times Cited Count：0 Percentile：0.00(Materials Science, Multidisciplinary)Uranium-zirconium oxide solid solution, (U, Zr)O, is a representative matrix phase found in fuel debris formed during severe nuclear reactor accidents. Understanding its chemical behavior in oxidative aqueous environments is important for evaluating the potential release of radionuclides during water contact. In this study, we investigated the reactivity of (U, Zr)O with hydrogen peroxide (HO) in pure water to assess its resistance to oxidative dissolution, because HO is the dominant oxidant produced by water radiolysis. The dissolution behavior of uranium and zirconium was monitored through repeated HO exposure experiments, and the solid phases were characterized using Raman micro-spectroscopy and X-ray diffraction. Kinetic modeling was performed to interpret experimental data. The results showed that uranium dissolution occurred initially but decreased significantly upon repeated HO exposure, while zirconium dissolution proceeded more slowly. Raman analysis revealed only minor surface changes, with limited formation of uranyl peroxide phases. The kinetic simulation reproduced the experimental trends by assuming a small fraction of redox-active surface sites. These findings suggest that the observed durability of (U, Zr)O against HO-induced oxidative dissolution is not due to the formation of a protective surface layer, but rather reflects the limited redox reactivity of most of the surface. This study provides a quantitative basis for understanding the HO-induced oxidation of (U, Zr)O in water, relevant to the long-term behavior of fuel debris.
Mohamad, A. B.; Chen, J.*; Ioka, Ikuo*; Suzuki, Eriko; Kondo, Keietsu; Abe, Yosuke; Yamashita, Shinichiro; Okubo, Nariaki; Nemoto, Yoshiyuki; Okada, Yuji*; et al.
Journal of Nuclear Materials, 625, p.156513_1 - 156513_9, 2026/04
Times Cited Count：0 Percentile：0.00(Materials Science, Multidisciplinary)
-containing porous hydrogel via freeze-crosslinking for efficiency and salt-robust dye DecolorizationSugita, Tsuyoshi; Ueda, Yuki; Nakabe, Rintaro; Mori, Masanobu*; Nankawa, Takuya; Sekine, Yurina
Journal of Photochemistry and Photobiology A; Chemistry, 473, p.116773_1 - 116773_9, 2026/04
Times Cited Count：0 Percentile：0.00(Chemistry, Physical)We developed a WO-embedded hydrogel (WFG) by freeze-cross-linking that retained high activity even in the presence of coexisting salts. Confocal laser scanning microscope revealed interconnected channels < 200 
m. ensuring good water permeability, and contrast-matching small-angle neutron scattering showed that the secondary particle size of embedded WO (~300 nm) matched that in aqueous suspension. Under visible-light irradiation, WFG decolorized indigo carmine (INC) 1.5-fold increase in rate than suspended WO and 3.7-fold increase in rate than a WO-coated glass plate. Coexisting salts (NaNO, NaCl, Na
SO
, NaHPO) altered the decolorization efficiency; NaNO and NaSO enhanced, whereas Cl
and HPO suppressed the reaction, indicating that ionic strength and anion-species affect contact efficiency and charge transfer.
:Ce using PHITS track-structure simulationsHirata, Yuho; Kai, Takeshi; Ogawa, Tatsuhiko; Matsuya, Yusuke; Sato, Tatsuhiko; Watanabe, Kenichi*; Kato, Takumi*; Kawaguchi, Noriaki*; Yanagida, Takayuki*
Radiation Measurements, 193, p.107651_1 - 107651_8, 2026/04
Times Cited Count：0 Percentile：0.00(Nuclear Science & Technology)CaF:Ce has a high potential to be used as a dosimeter due to its high optically stimulated luminescence (OSL) intensity. However, when phosphors such as CaF:Ce are irradiated with swift ions, the OSL intensity per dose decreases due to quenching effects. Traditionally, quenching effects in phosphors have been evaluated based on energy deposition density, using linear energy transfer (LET) as a metric. However, the relationship between quenching effects and LET varies with ion type, complicating unified evaluations. The track structure in PHITS can precisely simulate the radiation interactions. In this study, we simulated the detector response of CaF:Ce irradiated with swift-ions and compared these results with experimental data. The comparison suggests that the quantum yield of OSL is a critical parameter influencing the quenching effect in CaF:Ce. These findings are expected to contribute to the development of improved phosphor detectors.
Misono, Toshiharu; Shiribiki, Takehiko*; Urabe, Yoshimi*; Sanada, Yukihisa
JAEA-Research 2025-014, 88 Pages, 2026/03
JAEA-Research-2025-014.pdf:7.52MB
An accident occurred at the TEPCO's Fukushima Daiichi Nuclear Power Station (1F) in 2011 and a large amount of radioactive materials were deposited around the 1F. Japan Atomic Energy Agency has continued to conduct research on the dynamics of radioactive materials after the accident. This report summarizes the results of the survey conducted in FY 2022 on the status of marine monitoring survey on radioactive substances. Furthermore, in order to evaluate the inflow of radioactive Cs from the river, the horizontal distribution of the radioactive Cs concentration on the surface sediment in front of the rivers was measured. As basic information on the effects of radioactive materials on marine products, the distribution status of fish was investigated. From these results, we estimated the distribution and its dynamics of radioactive Cs in the sediments in the front area on the 1F.
Oguri, Kaori; Arai, Yoichi; Watanabe, So; Seko, Noriaki*; Hoshina, Hiroyuki*
Annual Research Report 2024 (Physical Science, Engineering), p.269 - 278, 2026/03
Radium-226 (
Ra) has recently attracted attention as a source for the production of Actinium-225 (
Ac), which can be used for the alpha-particle treatment of cancer. Ra is present in approximately 10,000 tons in the sea. The amount of Ra in seawater could help patients with metastatic cancer around the world. Therefore, we focused on the extraction of Ra from seawater and examined an effective process for refining Ra. Due to the low concentration of Ra in seawater, only a few ppb, it has not received much attention in terms of economic point. Therefore, we focused on adsorbents prepared by Radiation-Induced Graft Polymerization to selectively collect Ra. In this study, we performed adsorption studies with Barium (Ba), homologs element of Ra, which may coexist with Ra in seawater.
Kim, M.; Yoshimura, Kazuya; Sakuma, Kazuyuki; Malins, A.*; Abe, Tomohisa; Nakama, Shigeo; Machida, Masahiko; Saito, Kimiaki
Journal of Environmental Radioactivity, 294, p.107931_1 - 107931_8, 2026/03
Times Cited Count：0 Percentile：0.00(Environmental Sciences)This study quantitatively evaluated the effects of non-decontamination human activities, such as traffic, on ambient dose rates in residential areas near the Fukushima Daiichi Nuclear Power Plant through field measurements and simulations. Field surveys showed that areas with higher traffic had greater reductions in 
Cs deposition, suggesting that vehicular movement may enhance cesium weathering. Monte Carlo simulations using 3D-ADRES confirmed that human activities accelerate the decrease in ambient dose rates on paved surfaces, with reductions of up to approximately 50%. These results indicate that non-decontamination human activities significantly contribute to lowering ambient dose rates.
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：1 Percentile：50.28(Nuclear Science & Technology)The 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.
Saito, Yoshika*; Ito, Naomi*; Abe, Toshiki*; Yamamoto, Chika*; Matsumoto, Chihiro*; Zhao, T.*; Moriyama, Nobuaki*; Yoshimura, Kazuya; Sanada, Yukihisa; Tsubokura, Masaharu*
Journal of Radiological Protection, 46(1), p.013502_1 - 013502_8, 2026/03
Times Cited Count：0 Percentile：0.00(Environmental Sciences)Saha, P. K.; Harada, Hiroyuki; Tamura, Fumihiko; Shobuda, Yoshihiro; Kojima, Kunihiro; Yoshimoto, Masahiro; Okita, Hidefumi; Okabe, Kota; Hatakeyama, Shuichiro; Nakanoya, Takamitsu; et al.
Proceedings of 22nd Annual Meeting of Particle Accelerator Society of Japan (Internet), p.549 - 553, 2026/03
Ueno, Katsuhiro; Ouchi, Kazuki; Watanabe, Masayuki
Results in Engineering (Internet), 29, p.109246_1 - 109246_10, 2026/03
Kumada, Takayuki; Nakabe, Rintaro; Nakagawa, Hiroshi
Teion Kagaku, 84, p.13 - 17, 2026/03
