1,721,208 research outputs found
Microstructure and fuel performance analysis of U-Mo dispersion fuel irradiated at HANARO (Invited)
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Volatile Loss-free Radioactive Waste Immobilization by Cold Sintering of Iodosodalite, Hydroxyapatite, Aluminosilicate and Zeolite: Mechanisms and Applications
No full textCold sintering of as-dried nanostructured calcium hydroxyapatite without using additives
No full textA novel low-temperature densification method of nanocrystalline calcium hydroxyapatite (HAp) at a temperature as low as 200 degrees C with no liquid additives is investigated. To understand the underlying mechanism of the low-temperature sintering of hydroxyapatite, two types of lab-synthesized nanocrystalline HAp, dried (110 degrees C, 12 h) and calcined (1000 degrees C, 2 h), were subjected to cold sintering conditions (200 degrees C, 500 MPa) and compared thoroughly. The dried samples were found to be nanocrystalline, enveloped by an amorphous shell, whereas the calcined samples were fully crystalline, as confirmed by X-ray diffraction, transmission electron microscopy, and solid-state nuclear magnetic resonance techniques. A relative density of 98.8% was achieved for the dried samples; however, the calcined samples could not be sintered. This indicates a clear dependence of densification on the surface chemistry of the nanocrystals involving rearrangement and dehydration of the amorphous layer present on the surface of the nanocrystals under the influence of applied pressure and temperature. Moreover, the calcined sample, which had a fully developed crystalline structure, did not undergo sintering, even with the use of added water. Therefore, it is demonstrated that wet-precipitated and dried nanocrystalline HAp can be cold-sintered to full densification for applications in biomedical materials or radioactive waste immobilization of volatile radionuclides at a considerably low temperature, without the addition of sintering aids. (c) 2021 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
Finite-Element Simulation of Residual Stresses During the Processing of Lumped Burnable Absorber Fuel
No full textUO2-Gd2O3 fuel is mostly used as a burnable absorber fuel in the form of a homogenous mixture of Gd2O3 and UO2. More effective reactivity control can be achieved by lumping Gd2O3 within the UO2 because this enhances the spatial self-shielding factor of the burnable absorber fuel. The fabrication of lumped burnable absorber fuel containing lumped Gd2O3 spherical particles or compacts has been experimentally demonstrated using yttrium-stabilized zirconia (YSZ) as a UO2 fuel surrogate. Interfacial cracks or gaps forming under the interfacial stress that develops during the fabrication of the fuel can be eliminated by controlling the initial density of the lumped Gd2O3. In this study, this interfacial stress during the fabrication process was simulated using finite element methods. The effect of the size, shape, and initial density of the lumped Gd2O3 on the distribution and magnitude of the interfacial stress was investigated. The addition of Gd2O3 spherical particles resulted in a lower and more uniform interfacial stress distribution than the addition of cylindrical Gd2O3 compacts. The interfacial stress was increased with increasing Gd2O3 size and initial density. The calculated interfacial stress was compared with experimental results to estimate the threshold stress for crack development in a lumped burnable absorber fuel.
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