Microstructural evolution and mechanical hardening of Cr-coated MDA cladding under high-dose Fe ion irradiation

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

https://doi.org/10.1016/j.jnucmat.2026.156513

Quantitative analysis of ionization quenching in CaF:Ce using PHITS track-structure simulations

Hirata, 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

https://doi.org/10.1016/j.radmeas.2026.107651

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.

Development of Ra in the sea water collection technology for production of medical tracer Ac-225

Oguri, Kaori; Arai, Yoichi; Watanabe, So; Seko, Noriaki*; Hoshina, Hiroyuki*

Annual Research Report 2024 (Physical Science, Engineering), p.269 - 278, 2026/03

https://www.saltscience.or.jp/information/research_list/2023research_list.html

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.

Temperature effect on radiolytically generated hydrogen yield from a plutonium nitric acid aqueous solution

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

https://doi.org/10.1080/00223131.2025.2541067

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.

Microbial survivability during repeated extreme dry-wet cycles determines CO emissions after rewetting of dried soils in humid temperate forests

Nakayama, Masataka*; Suzuki, Yuri; Abe, Yukiko; Taniguchi, Takeshi*; Atarashi-Andoh, Mariko; Koarashi, Jun; Nagano, Hirohiko*

Biogeochemistry, 169(2), p.15_1 - 15_15, 2026/02

https://doi.org/10.1007/s10533-026-01310-6

Role of Alkyl Chain Branching in the Self-Assembly of Nitrilotriacetamide-Based Lanthanide Extractants

Ueda, Yuki; Kobayashi, Toru; Nakamura, Satoshi; Ban, Yasutoshi; Kaneta, Yui; Nabatame, Nozomi; Micheau, C.; Tokunaga, Kohei; Nakabe, Rintaro; Kaneko, Masashi*; et al.

Langmuir, 42(1), p.1613 - 1626, 2026/01

https://doi.org/10.1021/acs.langmuir.5c05651

Understanding the structural factors governing the metal ions selectivity of solvent extraction systems is crucial for developing advanced processes for partitioning and transmutation of high-level radioactive waste. Here, we systematically investigated the effect of alkyl side-chain branching in nitrilotriacetamide (NTAamide) extractants on the extraction of lanthanum (La) and neodymium (Nd), chosen as representative lanthanides. Four extractants having each eight carbon atoms as one of the amide chains with identical molecular weights but different degrees of alkyl branching were examined. Distribution ratios were measured as a function of HNO concentration, and the local coordination structures of La and Nd were analyzed by extended X-ray absorption fine structure (EXAFS), while supramolecular aggregation in the organic phase was characterized by small-angle neutron scattering (SANS). EXAFS analysis revealed that the inner-sphere coordination environment of La and Nd was essentially unaffected by the degree of alkyl branching. In contrast, SANS results showed that extractants with fewer branched alkyl groups formed larger aggregates at low HNO concentrations, particularly in the case of Nd, where aggregation was found to facilitate extraction and prevent precipitation of poorly soluble complexes. These findings demonstrate that alkyl branching strongly influences supramolecular aggregation, which in turn governs extraction behavior. This work highlights the potential of nanoscale structural control as a new design concept for improving selectivity in lanthanide and actinide solvent extraction systems.

Possible transition from silandic to aluandic andosols with acidification as evidenced by detailed profile investigation of two well-preserved forest andosols in Japan

Alam, M. M.*; Yamakita, Eri*; Inoue, Yuzuru*; Koarashi, Jun; Atarashi-Andoh, Mariko; Abe, Yukiko; Nakayama, Masataka*; Mori, Yuki*; Hiradate, Shuntaro*

Soil Science and Plant Nutrition, 72(1), p.55 - 66, 2026/01

https://doi.org/10.1080/00380768.2025.2511803

Phase diagram of the polystyrene/near-critical water system

Shibata, Motoki*; Takenaka, Mikihito*; Motokawa, Ryuhei; Kumada, Takayuki; Ueda, Yuki; Miyazaki, Tsukasa*; Nakanishi, Yohei*; Abe, Jun*; Iwase, Hiroki*; Shibayama, Mitsuhiro*; et al.

Polymer, 340, p.129203_1 - 129203_7, 2025/12

https://doi.org/10.1016/j.polymer.2025.129203

Run function confirmation of the quadrupedal robots in JAEA facilities targeted for act on special measures concerning nuclear emergency preparedness

Watanabe, Kaho; Nishiyama, Yutaka; Imahashi, Masaki; Taguchi, Yuji; Iitsuka, Yoshinobu; Ouchi, Takuya; Inoue, Shuichi; Kozawa, Takayuki; Nemoto, Takahiro; Sugaya, Takashi; et al.

JAEA-Testing 2025-001, 56 Pages, 2025/11

JAEA-Testing-2025-001.pdf:2.61MB

There is an emergency response team against 7 nuclear facilities (JRR-3 in Nuclear Science Research Institute, Tokai Reprocessing Plant (TRP) in Nuclear Fuel Cycle Engineering Laboratories, JMTR, HTTR and Joyo in Oarai Research and Development Institute, Prototype Fast Breeder Reactor Monju, Fugen Decommissioning Engineering Center) accidents of Japan Atomic Energy Agency (JAEA). The team is in Naraha Center for Remote Control Technology Development (NARREC). On site surveys which are about the situations and the access entering route of the 7 site emergencies were conducted by the team in 2021. And the results of the surveys made the team get two Spot (quadrupedal robots) in 2022. This is because the team thought using Spot gave operators the less exposure than using crawler robots which had been belonged to the team. After that it was confirmed that the Spot have the ability to respond to the emergency on the route of each facility in 2023. This report shows the results of the Spot's run function (= shooting videos, running oversteps, running up and down stairs, and so on) confirmation about 6 facilities (JRR-3, JMTR, HTTR, Joyo, Monju and Fugen).

Study of operation above half-integer random resonance in the J-PARC RCS

Kojima, Kunihiro; Harada, Hiroyuki; Okabe, Kota; Chimura, Motoki; Saha, P. K.

Proceedings of 16th International Particle Accelerator Conference (IPAC25) (Internet), p.2244 - 2247, 2025/11

https://doi.org/10.18429/JACoW-IPAC2025-WEPS003

In the 3-GeV rapid cycling synchrotron of the Japan Proton Accelerator Research Complex, the beam power ramp-up aiming to surpass the design of 1 MW enhances the space charge effect and pushes the beam toward the structure resonance. To mitigate the beam loss, the operating point is required to be apart from the structure resonance corresponding to the beam power ramp-up, although any changes in the operating point lead to an increase in the beam loss due to the approach to other resonances. We recently compensated the horizontal half-integer resonance located just above the current operating point to address this issue, and we are now ready to explore a higher tune region than that. We confirmed in a tune survey that the vertical half-integer and linear sum resonances are substantially excited. In addition, the linear sum resonance is found to be well compensated by making a vertical local bump in the arc section.