Kinetic and thermodynamic controls on CsI-Mo gas-phase reactions under varying oxygen potentials

Shiotsu, Hiroyuki

Progress in Nuclear Energy, 195, p.106300_1 - 106300_11, 2026/05

https://doi.org/10.1016/j.pnucene.2026.106300

Refined spin Hamiltonian on the Cairo pentagonal lattice of BiFeO

Lenander, E. Y.*; Nielsen, F. B.*; Lass, J.*; Hansen, U. B.*; Krighaar, K. M. L.*; Preuss, A.*; Weber, T.*; Enderle, M.*; Jacobsen, H.*; Stuhr, U.*; et al.

Physical Review B, 113(1), p.014424_1 - 014424_14, 2026/01

https://doi.org/10.1103/3n7r-j7wd

Analysis of deposits inside "X-6 penetration" for the Unit 2 primary containment vessel at Fukushima Daiichi Nuclear Power Station

Yoneyama, Kai; Nitta, Ayako; Tanaka, Yasuyuki; Kodaka, Noriyasu; Kikuchi, Riku; Sakano, Takuma; Furuse, Takahiro; Sato, Soichi; Sambongi, Mitsuru; Tanaka, Kosuke

JAEA-Technology 2025-008, 44 Pages, 2025/12

JAEA-Technology-2025-008.pdf:4.3MB

At the TEPCO's Fukushima Daiichi Nuclear Power Station (1F), an investigation inside the reactors has been carried out. In order to safely carry out the decommissioning work such as fuel debris retrieval and building demolition, it is important to estimate the contamination in primary containment vessel for control the decommissioning planning and the worker radiation exposure levels. Therefore, the analysis of the deposit inside the penetration for the 1F Unit 2 primary containment vessel ("X-6 penetration") was performed to clarify the components and activity. The smears from the deposit were used for the analysis. Non-destructive analysis such as gamma-ray spectrometry, X-ray Fluorescence (XRF) and Scanning Electron Microscope-Energy dispersive X-ray spectroscopy (SEM-EDX) for the smear-samples were performed to determine the gamma-nuclides and the morphology of elements in the deposit. Furthermore, in order to evaluate the nuclides and nuclide composition of the deposit in detail, the smear-samples were dissolved and the quantitative analysis of gamma-nuclides, Sr-90, alpha-nuclides in the dissolved solution were conducted. The results (non-destructive analysis and quantitative analysis) were compared with the results of samples collected at different locations in the X-6 penetration in 2020. In the gamma-ray spectrometry as non-destructive analysis where the smears were analyzed directly, Co-60, Sb-125, Cs-134, Cs-137, Eu-154, Eu-155 and Am-241 were detected. In XRF results, Fe originating from construction material was detected as a major element and small amount of U and Zr originating from the fuel and fuel cladding were also detected. In SEM-EDX results, O and Fe were found as a major element of the deposit and U particles coexisting with Fe, Si, Cr, Ni and Zr were also found. These results were consistent with the SEM-EDX results of the samples collected in 2020. In radioactivity analysis, quantitative values for gamma-nuclides (Co-60, Sb-125, Cs-134, Cs-137, Eu-154, Eu-155), Sr-90, Pu-238, Pu-239+240, Am-241, Cm-244, U-235 and U-238 were obtained. Using the results, the ratios of radioactivity based on Cs-137 and U-238 were calculated. Both sets of the ratios were compared to the calculated value of the Unit 2 fuel composition from ORIGEN.

Induction of large in-plane uniaxial magnetic anisotropy for Co-Fe-B-Pt thin films by magnetic field annealing

Yamazaki, Takumi*; Ishitani, Yugo*; Nakada, Katsuyuki*; Sasaki, Tomoyuki*; Endo, Yasushi*; Takanashi, Koki; Seki, Takeshi*

Journal of Applied Physics, 138(23), p.233905_1 - 233905_11, 2025/12

https://doi.org/10.1063/5.0300010

High stabilization of pentavalent uranium on magnetite nanoparticles evidenced by high-energy-resolution X-ray absorption spectroscopy

Yomogida, Takumi; Scaria, J.*; Fablet, L.*; Tokunaga, Kohei; Dei, Shuntaro; Higashi, Kotaro*; Kawamura, Naomi*; Takahashi, Yoshio*; Marsac, R.*

Chemical Communications, 61(91), p.17926 - 17929, 2025/11

https://doi.org/10.1039/D5CC04540A

This paper presents insights into the influence of magnetite stoichiometry (0 R = Fe(II)/Fe(III) 0.5) on the surface reduction of U(VI) to U(V) and U(IV), as a key parameter controlling U redox speciation in natural settings. Although R can readily change due to the oxidation of structural Fe(II) or proton/ligand-promoted dissolution, prior studies have not quantified U(V) when assessing these effects. We employed U L-edge HERFD-XANES spectroscopy to investigate the electronic structure of U on magnetite with varying stoichiometries and observed a peak splitting of U(V) on magnetite. Our results demonstrate the high stability of U(V) species under a wide range of conditions, and after 10 days on magnetite by the combination of MCR-ALS analysis. A key finding is that structural Fe(II), whose abundance depends on pH and redox conditions, plays a critical role for in the stabilization of U(V) on magnetite.

Fuel debris criticality analysis technology using non-contact measurement method (Contract research); FY2023 Nuclear Energy Science & Technology and Human Resource Development Project

Collaborative Laboratories for Advanced Decommissioning Science; Institute of Science Tokyo*

JAEA-Review 2025-010, 62 Pages, 2025/08

JAEA-Review-2025-010.pdf:3.63MB

The Collaborative Laboratories for Advanced Decommissioning Science (CLADS), Japan Atomic Energy Agency (JAEA), had been conducting the Nuclear Energy Science & Technology and Human Resource Development Project (hereafter referred to "the Project") in FY2023. The Project aims to contribute to solving problems in the nuclear energy field represented by the decommissioning of the Fukushima Daiichi Nuclear Power Station, Tokyo Electric Power Company Holdings, Inc. (TEPCO). For this purpose, intelligence was collected from all over the world, and basic research and human resource development were promoted by closely integrating/collaborating knowledge and experiences in various fields beyond the barrier of conventional organizations and research fields. The sponsor of the Project was moved from the Ministry of Education, Culture, Sports, Science and Technology to JAEA since the newly adopted proposals in FY2018. On this occasion, JAEA constructed a new research system where JAEA-academia collaboration is reinforced and medium-to-long term research/development and human resource development contributing to the decommissioning are stably and consecutively implemented. Among the adopted proposals in FY2021, this report summarizes the research results of the "Fuel debris criticality analysis technology using non-contact measurement method" conducted from FY2021 to FY2023. The purpose of research was to improve the fuel debris criticality analysis technology using non-contact measurement method by the development of the fuel debris criticality characteristics measurement system and the multi-region integral kinetic analysis code. It was performed by Institute of Science Tokyo, Tokyo City University, National Institute of Advanced Industrial Science and Technology, and Nagaoka University of Technology. We developed the fuel debris criticality characteristics measurement system which has a two layer structure surrounding a canister containing fuel debris fragments with He proportional counters. The operational validation and performance evaluation were performed on the developed detector system. We have demonstrated the feasibility and accuracy of measuring the amount of fissile material and water content. MIK2.0-MVP code, which can calculate fission reaction rate attributed to both prompt and delayed neutrons and also can take the movement of fuel debris into calculation, was developed. After parallelizing the tally process of C() function, MIK2.0-MVP code will be applicable to weakly coupled reactors which include moving fuel debris particles if a supercomputer will be used for the tally process of C() function and if the coupling of MIK2.0-MVP code with MPS will be weak.

Fundamental mechanisms of discontinuous deformation in metals for cryogenic-environment applications

Kim, Y. S.*; Kang, T.*; Hong, S.-K.*; Brechtl, J.*; Lebyodkin, M.*; Cheng, Y.-H.*; Huang, E.-W.*; Liaw, P. K.*; Harjo, S.; Gong, W.; et al.

Acta Materialia, 292, p.120970_1 - 120970_16, 2025/06

https://doi.org/10.1016/j.actamat.2025.120970

Numerical analysis of a potential Reactor Pressure Vessel (RPV) boundary failure mechanism in Fukushima Daiichi Nuclear Power Station Unit-2

Li, X.; Yamaji, Akifumi*; Sato, Ikken*; Yamashita, Takuya

Annals of Nuclear Energy, 214, p.111217_1 - 111217_13, 2025/05

https://doi.org/10.1016/j.anucene.2025.111217

Robustness of ferromagnetism in van der Waals magnet FeGeTe to hydrostatic pressure

Wang, Y.*; Zeng, X.-T.*; Li, B.*; Su, C.*; Hattori, Takanori; Sheng, X.-L.*; Jin, W.*

Chinese Physics B, 34(4), p.046203_1 - 046203_6, 2025/03

https://doi.org/10.1088/1674-1056/adb26f

Two-dimensional van der Waals ferromagnet FeGeTe (FGT) holds a great potential for applications in spintronic devices, due to its high Curie temperature, easy tunability, and excellent structural stability in air. In this study, we have performed high-pressure neutron powder diffraction (NPD) up to 5 GPa, to investigate the evolution of its structural and magnetic properties with hydrostatic pressure. The NPD data clearly reveal the robustness of the ferromagnetism in FGT, despite of an apparent suppression by hydrostatic pressure. As the pressure increases from 0 to 5 GPa, the Curie temperature is found to decrease monotonically from 225(5) K to 175(5) K, together with a dramatically suppressed ordered moment of Fe, which is well supported by the first-principles calculations. Although no pressure-driven structural phase transition is observed up to 5 GPa, quantitative analysis on the changes of bond lengths and bond angles indicate a significant modification of the exchange interactions, which accounts for the pressure-induced suppression of the ferromagnetism in FGT.

Feasibility study of reactor radiation photon spectroscopy in Fugen for nuclear decommissioning

Kaburagi, Masaaki; Miyamoto, Yuta; Mori, Norimasa; Iwai, Hiroki; Tezuka, Masashi; Kurosawa, Shunsuke*; Tagawa, Akihiro; Takasaki, Koji

Journal of Nuclear Science and Technology, 62(3), p.308 - 316, 2025/03

https://doi.org/10.1080/00223131.2024.2417786