Grain boundary migration across compositional complexity; A Molecular dynamics study from binary alloys to high-entropy alloys

Shiotani, Kohei; Niiyama, Tomoaki*; Shimokawa, Tomotsugu*

Acta Materialia, 321, p.122762_1 - 122762_12, 2026/12

https://doi.org/10.1016/j.actamat.2026.122762

no abstracts in English

Synergistic strength-ductility enhancement in carbide-free FeMnCoNiC high entropy alloys via interstitial carbon solution

Fang, W.*; Liu, C.*; Yoshida, Shuhei*; Peng, T. X.*; Xu, P. G.; Han, Y.*; Li, J.*; Yin, F.*; Tsuji, Nobuhiro*

Materials Science & Engineering A, 977, p.151109_1 - 151109_12, 2026/12

https://doi.org/10.1016/j.msea.2026.151109

Immobilisation mechanisms of simulated radioactive colloidal wastes in alkali-activated metakaolin-based geopolymers

Shi, D.*; Niu, X.*; Elakneswaran, Y.*; Li, A.*; Kikuchi, Ryosuke*; Hiraki, Yoshihisa; Sato, Junya; Osugi, Takeshi; Walkley, B.*

Journal of Nuclear Materials, 633, p.156997_1 - 156997_12, 2026/11

https://doi.org/10.1016/j.jnucmat.2026.156997

Interactions between U-Zr-O and concrete near the melting range of concrete

Sudo, Ayako; Sato, Takumi; Nagae, Yuji

Journal of Nuclear Materials, 632, p.156936_1 - 156936_16, 2026/10

https://doi.org/10.1016/j.jnucmat.2026.156936

Current molten corium concrete interaction codes are based on large-scale tests in which core materials interact with concrete and the initial temperature of the molten pool is below 2000C. Suboxides such as U-Zr-O may react with concrete at lower temperatures near the melting range of concrete. Investigating the reactions between core materials and concrete near the melting range of concrete is essential for advancing severe accident analyses. As a result of small-scale reaction tests between concrete and U-Zr-O under an Ar atmosphere at 1200C and 1300C, held for 2 hours, a Si-Zr-U-O layer was formed at the reaction interface. At 1500C, held for 2 hours, three layers were formed: (i)Si-Zr-U-O layer, (ii) (U,Zr)O and concrete, and (iii) Si-Zr metallic precipitates. The thermodynamic analysis, indicate that Ca dissolves in (U,Zr)O, whereas U is not predicted to be present in the Si-Zr-U-O layer. These discrepancies arise because the calculations assume complete mixing of the core materials and concrete. The present study demonstrated that, within the temperature range of 1200C-1500C, the reaction layer formed between U-Zr-O and concrete became thicker with increasing temperature, and that the composition of the reaction layer could not be adequately predicted by thermodynamic calculations alone.

A Unified predictive framework for precipitation in Fe-Cr-Al alloys based on effective diffusion length; From dense-cascade irradiation to thermal aging

Abe, Yosuke; Sasaki, Taisuke*; Yamashita, Shinichiro; Okubo, Nariaki; Ukai, Shigeharu

Acta Materialia, 317, p.122580_1 - 122580_15, 2026/09

https://doi.org/10.1016/j.actamat.2026.122580

Fe-Cr-Al alloys for accident-tolerant fuel cladding can embrittle through precipitation, yet ion-to-neutron extrapolation has remained unsolved. We built an atom probe tomography database of 80 conditions from 12 alloys, integrated 170 published entries, and developed a unified framework using the effective diffusion length from point-defect theory as a parameter-free scalar encoding dose rate, dose, temperature, and time. Machine-learning models with only Cr, Al, and the effective diffusion length predicted volume fraction and number density across irradiation types, but not precipitate size or composition - a limit attributed to ballistic mixing. A non-monotonic Al effect (5 at.% promoting precipitation) was also identified, defining a composition window to avoid in cladding design.

Unveiling post-deformation transformation mechanism and ferrite microstructure evolution for tailoring mechanical properties of low-carbon martensitic steels

Tong, Z.*; Xia, C.*; Li, W.*; Ding, W.*; Guo, B.*; Min, N.*; Gong, W.; Harjo, S.; Tsuji, Nobuhiro*

Journal of Materials Science & Technology, 266, p.127 - 140, 2026/09

https://doi.org/10.1016/j.jmst.2025.12.004

Accurate prediction of oxygen solution enthalpy in liquid sodium with SCAN-family machine-learning potentials

Gil, J.; Itakura, Mitsuhiro; Kobayashi, Keita

Computational Materials Science, 273, p.114924_1 - 114924_10, 2026/08

https://doi.org/10.1016/j.commatsci.2026.114924

Accurate impurity thermodynamics is important for modeling corrosion and mass transport in liquid metals, but direct first-principles simulations are computationally expensive. We combined SCAN-family density-functional calculations with machine-learning molecular dynamics to evaluate oxygen solution enthalpy in liquid sodium. Machine-learning interatomic potentials trained on SCAN, rSCAN, and rSCAN data enabled extensive liquid-state sampling at near-first-principles accuracy. The calculated values agreed with experimental estimates without empirical corrections to molecular oxygen. This suggests that the main error in the conventional PBE method arises from the gas-phase oxygen reference rather than the liquid-state description. The results demonstrate an accurate and scalable approach to impurity thermodynamics in liquid metals.

A Study of high-temperature UO-Zr interactions in the presence of magnetite and ferrous melt

Zubekhina, B.; Pshenichnikov, A.; Takano, Masahide

Journal of Nuclear Materials, 630, p.156701_1 - 156701_11, 2026/08

https://doi.org/10.1016/j.jnucmat.2026.156701

Antiferromagnetic order and crystalline electric field in noncentrosymmetric hexagonal RuAs ( = Sm and Yb)

Hirose, Yusuke; Tsukui, Hiroki*; Kato, Yuta*; Shono, Rina*; Honda, Fuminori*; Aoki, Dai*; Settai, Rikio*

Physical Review Materials (Internet), 10(8), p.084407_1 - 084407_8, 2026/08

https://doi.org/10.1103/nr4t-wypp

Mechanistic insights into volatile ruthenium tetroxide formation during evaporation-to-dryness accidents of high-level liquid waste

Yoshida, Naoki; Amano, Yuki; Yoshida, Ryoichiro; Ono, Takuya; Tashiro, Shinsuke; Yamane, Yuichi

Journal of Hazardous Materials, 513, p.142332_1 - 142332_20, 2026/07

https://doi.org/10.1016/j.jhazmat.2026.142332

Volatile ruthenium tetroxide (RuO) formed during evaporation-to-dryness accidents (EDA) of high-level liquid waste (HLLW) combines high chemical toxicity with radiotoxicity from isotopes such as Ru and Ru, making it a primary hazard in nuclear-fuel reprocessing. This study experimentally elucidates the mechanisms governing RuO formation while testing the validity of the pragmatic nitrosyl-ruthenium ([RuNO]) surrogate model, an experimental model that assumes Ru in HLLW exists as [RuNO], and evaluates gaseous Ru release using nitric acid solutions of [RuNO], commonly used in RuO release assessments by comparing it with the behavior of simulated HLLW (s-HLLW). We systematically investigated potential pathways, including oxidation by liquid-phase nitric acid (HNO(l)), gas-phase nitric acid (HNO(g)), and oxygen (O); thermal decomposition of [RuNO]; and matrix effects of coexisting nitrates. The results identify oxidation by activated HNO(l), oxidation by HNO(g) and thermal decomposition of [RuNO] as the principal routes to RuO, with HNO(g) playing a far more significant role than previously recognized. Crucially, the RuO release profile from s-HLLW differed markedly from that predicted by the [RuNO] surrogate model, demonstrating that this model fails to capture the complex matrix effects and time-dependent chemical changes of Ru species inherent to real HLLW. These findings have significant implications for improving the accuracy of hazard assessments related to RuO release during HLLW EDAs, particularly by highlighting the limitations of commonly used [RuNO] surrogate models.