查看更多>>摘要：Recrystallization annealing of warm-pilgered FeCrAl tubes was the key to reduce the cracking and control the microstructure and properties of the cladding tube. The recrystallization and texture evolution of warm-pilgered FeCrAl tubes were investigated. The recrystallization kinetics and textural evolution during annealing were characterized using microhardness measurements and electron backscatter diffraction. The 3D-microstructure of the warm-pilgered FeCrAl tube exhibited heterogeneous deformed grains of alpha-fiber and gamma-fiber orientation. The significant anisotropy results in different recrystallization kinetics in the axial and circumferential directions of the tube. The mirostructure maintains a stable grain size of similar to 22 mu m and an aspect ratio of 1.8 in the axial and circumferential directions within 0-600 min annealing time. The stable microstructure is due to the dispersion of fine Laves phase particles in the ferrite matrix. Quantitative texture analysis shows that the alpha-fiber texture decreased significantly and the gamma-fiber increased after recrystallization. During the annealing process, the alpha-fiber strong point texture component {112}< 110 > turns into{223}< 110 > and the gamma-fiber component {111}< 110 > turns into {111}< 112 >. The recrystallization and texture evolution of warm-pilgered FeCrAl tube is of great significance to preparation and microstructure control of final cladding tube. (c) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：Geopolymers are promising candidates for nuclear-waste immobilization, and more specifically for the immobilization of radioactive cesium. Low-Si metakaolin-based geopolymers cured at temperatures of 40 degrees C in the presence of Cs ions generate a mixture of amorphous and crystalline phases including a Cs-bearing zeolite F phase. Using a combination of Cs-133 solid-state NMR and X-ray powder diffraction measurements we were able to show that Cs preferentially binds to zeolite F even when zeolite F is not the dominant phase in the matrix. Moreover, post-leaching NMR experiments indicate that zeolite F binds Cs more efficiently than the remaining crystalline or amorphous phases. Tailoring geopolymer formulations so that a large fraction of zeolite F is generated may therefore be a promising route for the production of immobilization matrices for cesium. (C) 2022 Elsevier B.V. All rights reserved.
Eckelmeyer, Kenneth H.Romig, A. D., Jr.Ludtka, Gerard M.Mackiewicz-Ludtka, Gail...
28页
查看更多>>摘要：The effect of Ti content on age hardening and the resulting mechanical properties are described for gamma- quenched U-Ti alloys containing 0.3 to 2.0 wt.%Ti. Age hardening occurs between similar to 50 and similar to 450 degrees C. Over aging occurs at higher temperatures by cellular decomposition. Age hardening kinetics suggest that different mechanisms occur depending on Ti content and initial microstructure. Strengthening in alpha'a acicular martensites begins by the formation of Ti clusters which evolve into thin U2Ti disc shaped precipitates and later mature into continuous U2Ti rods beginning at peak hardness. The mechanism of hardening in alpha'(b) banded martensite is more elusive, as significant hardening occurs where atomic mobility is lower than that required for precipitate formation, similar to that reported for age hardening in alpha''(b) banded martensite in U-6%Nb. The activation energy for aging varies with Ti content and microstructure. In fully martensitic alloys containing 0.75 to 2.0%Ti it is in the vicinity of similar to 44 kcal/mole (184 kJ/mole). But it is lower in alloys containing less than 0.6%Ti where quenched microstructures are less than fully martensitic. Tensile ductility is high prior to aging, decreases with age hardening, is effectively zero at peak hardness, and remains low in overaged conditions. Attractive combinations of strength and ductility are best obtained in alloys containing 0.6 to 1.0%Ti which have been partially aged to fractional hardening levels no greater than-similar to 0.6. This corresponds to the very early stages of aging, associated with clustering and the earliest stages of U2Ti disc formation. Alloys containing 0.45%Ti or less are not as responsive to age hardening. Alloys containing 1.5 and 2.0%Ti can be aged to higher strengths, but extreme quench rate sensitivity prevents them from being effectively heat treated in realistic section thicknesses. (c) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：In this study, high flux irradiated and surveillance high Ni and Mn and low Cu welds identical to those of the belt-line region of Ringhals R4 were subjected to annealing at temperatures between 390 and 455 degrees C for 24-30 h, in order to study the dissolution of irradiation induced clusters and possible matrix defects using hardness testing and atom probe tomography. It was found that the cluster characteristics did not change during annealing at 390 degrees C, meaning that the size, number density and composition of the clusters, which mainly consist of Ni and Mn, did not change. Thus, the observed decrease in hardness during annealing of the high flux irradiated material is believed to be due to dissolution of matrix defects that were stable at the operating temperature. Cluster dissolution was observed after annealing at 410 degrees C in the high flux irradiated material, leaving around 10% of the original clusters. These clusters contained more Cu and less Ni and Mn than before annealing. The cluster dissolution at temperatures above 400 degrees C correlated with the decrease in hardness. The larger clusters of the surveillance material required a higher temperature or longer time to be dissolved compared to the clusters of the high flux material.(c) 2022 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license ( http://creativecommons.org/licenses/by/4.0/ )
查看更多>>摘要：In this study, TP316H steel was subjected to quench-polish-quench (QPQ) salt bath nitriding at different times. The effects of QPQ on the fretting wear behavior of TP316H steel at varying temperatures in liquid sodium were investigated. The results show that QPQ treatment significantly improves the wear resistance of TP316H due to the high hardness nitride layer. The main fretting wear mechanism of nitrided samples in liquid sodium is diffusion-tribo-oxidation-rediffusion. QPQ 90 with a thicker nitride layer has the best wear resistance, although the nitride layer cracks in high-temperature liquid sodium. As a result, QPQ treatment may be a viable option for combating the wear of TP316H steel in liquid metals.(c) 2022 Elsevier B.V. All rights reserved.
Jin, Hyung-HaRyu, I. SeulKim, SangeunKwon, Junhyun...
10页
查看更多>>摘要：The role of microstructures on the overall yield strength of garter-spring coil X-750 alloy used for the fuel channel structure in the Canada deuterium uranium reactor is investigated in this study. We perform a comprehensive characterization of the residual microstructures in the garter-spring coil X-750 alloy and heat-treated plate X-750 alloys using electron microscopy. Simultaneously, we perform small-scale mechanical tests and bulk mechanical tests to evaluate the yield strength of the compact garter-spring coil component. We compare the mechanical property data obtained via the micro-bending measurement method and derive a correlation between each measured data point to assess the increase in yield strength. The gamma' ordering phase contribution is the most crucial factor in strengthening, followed by dislocation density and boundary-decorated precipitates in the garter-spring coil X-750 alloy. We quantitatively evaluate the effects of the gamma' ordering phase and initial dislocation density on the yield strength of the garter spring coil X-750 alloy because they significantly affect the change in the mechanical properties in the irradiation environment. (C)& nbsp;2022 The Author(s). Published by Elsevier B.V.& nbsp;
Jiang, WenSingh, GyanenderHales, Jason D.Toptan, Aysenur...
14页
查看更多>>摘要：The ability of tri-structural isotropic (TRISO) fuel to contain fission products is largely dictated by the quality of the manufacturing process, since most of the fission product release is expected to occur due to coating layer failure in a small number of particles containing defects. The Bison fuel performance code has capabilities to predict failure in individual particles, accounting for the presence of defects, and to apply statistical analysis methods to compute the probability of failure in a set of fuel particles. Bison has recently undergone significant development both to improve its physical representations of fuel particle behavior and to improve the efficiency of its statistical failure calculations. Physical model improvements include new capabilities to account for the pressure generated by fission gases on inner pyrolytic carbon (IPyC) crack surfaces and to use local material coordinate orientation to accurately incorporate the anisotropy in the material properties in aspherical particles. To improve statistical modeling efficency, a direct integration approach which involves directly integrating the failure probability function associated with statistically varying parameters has been developed. The direct integration approach is much more efficient than the Monte Carlo (MC) schemes commenly employed, and allows Bison to directly run high dimensional fuel performance models, which improves the accuracy of failure probability calculations. A set of benchmark problems is considered here to compare the MC and direct integration approaches, and a statistical failure analysis of compacts in the Advanced Gas Reactor (AGR)-2 experiments is performed using the direct integration approach.(c) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：The U-Zr phase diagram has been the subject of many recent studies, particularly for the development of metallic fuels for future fast reactors. The so-called delta-UZr2 phase is part of this renewed interest as it is likely to be formed during irradiation of U-Zr10wt% fuel. Although this phase has been the subject of several structural studies, there is a single experimental determination of its enthalpy of formation by dissolution calorimetry. Most of the Calphad and DFT models of this phase rely on this value to support their validation. In this paper, we propose a reinterpretation of this measurement which tends to show that the original interpretation of the authors was probably wrong. Our reinterpretation leads to a new endothermic estimate of the standard enthalpy of formation of delta-UZr2 which is discussed in relation to the other data of the U-Zr system. The need for new heat capacity and formation enthalpy measurements is highlighted. The present work does not invalidate the most recent CALPHAD descriptions.(c) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：Understanding atomic-scale mechanisms of dislocation interacting with irradiation-induced nanosized voids is vital to predict in-service performances of nuclear components. In reality, multiple dislocations can sequentially interact with one void, namely, the already sheared void can be further sheared by incoming dislocations; however, previous work mostly focused on the first-time dislocation-void interaction and assumed that already sheared voids have the same hardening effects in subsequent interactions. Using atomistic simulations, this work studies the interaction mechanisms between a periodic array of voids and successively incoming edge dislocations, and corresponding hardening effects. Simulation results reveal that the sheared voids impede dislocation motion in the same manner as the unsheared ones do, but the resistance to dislocation glide could decrease with interaction times. As an edge dislocation is pinned by the void, a pair of screw dipole form on the dislocation. Then the screw arms move along the void surface through multiple-time cross-slip upon continuous shear deformation, until the dipole annihilate in or above the original slip plane at some critical stress, thereby releasing the dislocation. These atomic processes are also accompanied with absorbing vacancies from the void and climbing up of dislocation segment in each interaction event. Hardening effect of the sheared voids can be progressively weakened due to decreasing void size when interaction times exceeding some value. The hardening effects of sheared voids can be quantified by a modified Bacon-Kocks-Scttergood model, if adopting an effective diameter that is calculated from the major axis of the dislocation-void intersection region rather than the constant diameter of the unsheared void.(c) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：90Sr is one of the most heat-generating fission products in used nuclear fuel. Because of its chemical stability as an oxide, it is tricky to separate Sr from used nuclear fuel without separating nuclear materials. Here we report on thermodynamic behavior of one of the primary contributors of decay heat, SrO, by investigating the reactions in molten salt systems. We study the respective influences of the KCl molar fraction and temperature on the dissolution behavior of SrO in molten LiCl-KCl salts: a widely used-salt composition owing to its low melting point and wide electrochemical window. Our results reveal that the solubility of SrO is relatively low in the eutectic LiCl-KCl at 773 K, compared to the other temperatures (823 K to 923 K) and the solubility decreased with increasing molar fraction of KCl (0 to 0.6) in LiCl at 923 K. Sr4OCl6 is produced by the dissolution of SrO in LiCl-KCl, and was confirmed by applying X-ray analyses. The results can be utilized to design a molten salt leaching process to separate high heat-generating fission products without proliferation issues, thereby reducing the environmental footprint during final waste disposal. (C) 2022 Elsevier B.V. All rights reserved.
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