Investigating eutectic behavior and material relocation in BC-stainless steel composites using the improved MPS method

Ahmed, Z.*; Wu, S.*; Sharma, A.*; Kumar, R.*; Yamano, Hidemasa; Pellegrini, M.*; Yokoyama, Ryo*; Okamoto, Koji*

International Journal of Heat and Mass Transfer, 250, p.127343_1 - 127343_17, 2025/11

https://doi.org/10.1016/j.ijheatmasstransfer.2025.127343

Nickel binding with magnetite nanoparticles

Fablet, L.*; Pdrot, M.*; Choueikani, F.*; Kieffer, I.*; Proux, O.*; Pierson-Wickmann, A.-C.*; Cagniart, V.*; Yomogida, Takumi; Marsac, R.*

Environmental Science; Nano, 12(5), p.2815 - 2827, 2025/05

https://doi.org/10.1039/d4en01114g

Nickel is an omnipresent trace element in the environment. Due to its high affinity for iron oxide nanoparticles, its elimination from soils and water by these nanoparticles represents an interesting strategy, specially by magnetites, which is naturally present in the environment. However, the interactions between Ni and magnetite are poorly understood, because of the difficulty to control the stoichiometry (Fe(II)-to-Fe(III) ratio) of magnetite. The behavior of Ni in the presence of magnetite nanoparticles with different stoichiometries, in aqueous solution and inert atmosphere, are probed by adsorption experiments and X-ray Absorption Spectroscopy. This study helps predicting the interactions between Ni and magnetite in environmental conditions, which can be used for the development of efficient remediation strategies.

Characterization of the thorium-229 defect structure in CaF crystals

Takatori, Sayuri*; Pimon, M.*; Pollitt, S.*; Bartokos, M.*; Beeks, K.*; Grneis, A.*; Hiraki, Takahiro*; Homma, Tetsuo*; Hosseini, N.*; Leitner, A.*; et al.

New Journal of Physics (Internet), 27(4), p.043024_1 - 043024_10, 2025/04

https://doi.org/10.1088/1367-2630/adce22

Recent reports on laser excitation of the low-energy thorium-229 (Th) nuclear isomeric state in calcium fluoride single crystals render this system a promising candidate for a solid-state nuclear clock. However, experimental characterization of the microscopic ion arrangement around the doped Th and its electronic charge state, crucial for the precise control of the clock transition and assessing the solid-state clock's performance, remains an unresolved task. This study uses X-ray absorption fine structure spectroscopy of Th:CaF to investigate the charge state and coordination environment of doped Th. The results indicate that Th is doped with a 4+ valence at the substitutional site of the Ca ion, with charge compensated provided by two F ions located at interstitial sites adjacent to Th.

Magnetite stoichiometry (Fe(II)/Fe(III)) controls on trivalent chromium surface speciation

Scaria, J.*; Pdrot, M.*; Fablet, L.*; Yomogida, Takumi; Nguyen, T. T.*; Sivry, Y.*; Catrouillet, C.*; Pradas del Real, A. E.*; Choueikani, F.*; Vantelon, D.*; et al.

Environmental Science & Technology, 59(11), p.5747 - 5755, 2025/03

https://doi.org/10.1021/acs.est.4c12899

Understanding and predicting the interaction mechanisms between chromium and magnetite is of particular interest to elucidate the biogeochemical behavior of Cr in the environment and to develop optimal soil remediation and water treatment strategies. However, while the elimination of the most toxic form of (Cr(VI)) by its reduction to Cr(III) has widely been documented, elucidating the exact mechanism involved in Cr(III) sorption to magnetite has attracted less attention. This study examined the interaction of Cr(III) solution with 10 nm-sized magnetites, whose stoichiometries were carefully defined and preserved in anaerobic conditions. This study reveals the joint effects of pH and magnetite stoichiometry on Cr(III) sorption mechanism, and that Cr(III)-(hydr)oxide precipitation is not necessarily the driving process of Cr(III) elimination from solutions. These results will help predict the fate and transport of chromium, as well as developing magnetite-based chromium remediation processes.

A Study of the correlation function

Abreu, L. M.*; Gubler, P.; Khemchandani, K. P.*; Martnez Torres, A.*; Hosaka, Atsushi

Physics Letters B, 860, p.139175_1 - 139175_7, 2025/01

https://doi.org/10.1016/j.physletb.2024.139175

France-Japan collaboration on severe accident studies in sodium-cooled fast reactors, 2; Methodologies and calculations of severe accident phases

Sogabe, Joji; Ishida, Shinya; Tagami, Hirotaka; Okano, Yasushi; Kamiyama, Kenji; Onoda, Yuichi; Matsuba, Kenichi; Yamano, Hidemasa; Kubo, Shigenobu; Kubota, Ryuzaburo*; et al.

Proceedings of International Conference on Nuclear Fuel Cycle (GLOBAL2024) (Internet), 4 Pages, 2024/10

In the frame of France-Japan collaboration, the calculational methodologies were defined and assessed, and the phenomenology and the severe accident consequences were investigated in a pool-type sodium-cooled fast reactor.

Circular polarization measurement for individual gamma rays in capture reactions with intense pulsed neutrons

Endo, Shunsuke; Abe, Ryota*; Fujioka, Hiroyuki*; Ino, Takashi*; Iwamoto, Osamu; Iwamoto, Nobuyuki; Kawamura, Shiori*; Kimura, Atsushi; Kitaguchi, Masaaki*; Kobayashi, Ryuju*; et al.

European Physical Journal A, 60(8), p.166_1 - 166_10, 2024/08

https://doi.org/10.1140/epja/s10050-024-01392-6

Study on eutectic melting behavior of control rod materials in severe accidents of sodium-cooled fast reactors, 4; Analyzing Eutectic Melting and Relocation Dynamics in BC-stainless steel using the Moving Particle Semi-Implicit (MPS) Method

Ahmed, Z.*; Wu, S.*; Pellegrini, M.*; Okamoto, Koji*; Sharma, A.*; Yamano, Hidemasa

Proceedings of 14th International Topical Meeting on Nuclear Reactor Thermal-Hydraulics, Operation, and Safety (NTHOS-14) (Internet), 14 Pages, 2024/08

The analysis show that once eutectic reaction occurs, the boron diffuses into the stainless steel (SS) wall. Melting initiates at the BC and SS interface, with melt flow following SS cladding penetration. Also, we observed that as temperature rises, a proportional increase in the boron concentration within the melt. The updated MPS method indicated a computational capability of the eutectic reaction model used to effectively analyze control rod eutectic reactions, simulating severe accidents, and its subsequent relocation to understand the effect of BC ingress into the core.

Coulomb spike model of radiation damage in wide band-gap insulators

Costantini, J.-M.*; Ogawa, Tatsuhiko

Quantum Beam Science (Internet), 8(3), p.20_1 - 20_16, 2024/08

https://doi.org/10.3390/qubs8030020

A novel Coulomb spike concept is applied to the radiation damage induced in LiF and SiO with about the same mass density (2.65 g cm) by Ni and Kr ions of 1.0-MeV/u energy for about the same electronic energy loss (10 MeV/um). The distribution of ionizations and electrostatic energy gained in the electric field by the ionized atoms is computed with the PHITS code for both targets. Further, the atomic collision cascades induced by these low energy hot ions of about 500 eV are simulated with the SRIM2013 code. It is found that melting is reached in a small volume for SiO due to the energy deposition in the subthreshold events of nuclear collisions induced by the Si and O ions. For LiF, the phonon contribution to the stopping power of the lighter Li and F ions is not sufficient to induce melting, even though the melting temperature is lower than for SiO. The formation of amorphous domains in SiO is likely after fast quenching of the small molten pockets, whereas only point defects may be formed in LiF.

Eutectic melting and relocation behavior of BC pellet-stainless steel under radiative heating

Ahmed, Z.*; Sharma, A. K.*; Pellegrini, M.*; Yamano, Hidemasa; Kano, Sho*; Okamoto, Koji*

Ceramics International, 50(10), p.17665 - 17680, 2024/05

https://doi.org/10.1016/j.ceramint.2024.02.256

In this study, we identified two distinct failure mechanisms: the separation of stainless steel from the BC pellet, resulting in the formation of a later melting drop, and the fracture of the BC pellet into multiple pieces, possibly due to thermal stress. The visualization technique and thermal interfacial resistance analysis precisely captured the eutectic temperature.