查看更多>>摘要：Liquid Lead-Lithium (PbLi) alloys are promising functional material which can act as both neutron multiplier and tritium breeder in liquid blanket of fusion reactors, however, their corrosion behavior on RAFM steel is still a challenge. In this work, the dissolution, diffusion, bonding and charging behavior of steel alloy elements in liquid PbLi were investigated by using the first principles molecular dynamics simulations. The dissolution order of the main alloy elements of RAFM steel dissolved into the liquid PbLi was Cr > Fe > V > Mn > Ta > W > C. O atom tend to bond with Li atom in liquid PbLi and the O dissolution energy had negative value of-3.84 eV. The binding energies of Y-O, Ti-O, Al-O, Si-O, Zr-O, Ta-C, V-C, Ta-N and V N pairs within liquid PbLi at temperature 500 degrees C show that related oxides/carbides/nitrides in RAFM steel do not likely to decompose and may not affect their dissolution corrosion behavior. These data can provide indispensable information for understanding the dissolution corrosion behavior of advanced RAFM steel in liquid PbLi. (c) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：Severe lattice distortions and rough energy landscapes were found in low-density, refractory AlNbTiVCrx (x = 0, 0.5, 1) high-entropy alloys (HEAs) via first-principles calculations. The corresponding samples were irradiated by 5 MeV Xe ions to fluences of 3.3 x 10(14) ions/cm(2) at 600 degrees C. Fundamental irradiation behaviors were studied using transmission electron microscopy and nanoindentation. No phase decomposition was found after irradiation as well as void. The irradiation-induced dislocation loop size decreases, and the density increases with the increasing Cr content. This finding is attributed to the fact that Cr aggravates lattice distortion and roughens energy landscapes in the AlNbTiVCrx system, which will interrupt the long-distance migration of self-interstitials and delay their accumulation. Nanohardness increments exhibit good consistency with the product of dislocation loop size and density. This work provides an insight into the combination of atomic simulation and irradiation experiments for better understanding of the irradiation behaviors of refractory HEAs, and a possibility to modify defect evolution by regulating the compositional complexity. (C) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：Despite Laves phase precipitate in advanced accident-tolerant FeCrAl alloys has been reported to have remarkable properties, its irradiation resistance and phase stability are unexplored largely. Here, we investigate the response of Laves phase precipitate in Fe-13.5Cr-4.7Al alloys through in-situ TEM observation during 400 keV Fe + irradiation with different cumulative dose at a wide temperature range from room temperature to 823 K. The detailed relationship between critical dose and temperature for the crystalline to-amorphous transformation was established. In the low temperature region (<= 748 K), the critical dose was almost independent of temperature, while at higher temperatures, the increase of temperature could significantly delay the amorphization process. Even when irradiated to 11.76 dpa at 823 K, no obvious dissolution of Laves phase precipitate was observed. It was observed for the first time that the Al in Laves phase precipitate and FeCrAl matrix would diffuse to phase boundary, resulting in the segregation of Al at phase boundary. (c) 2022 Elsevier B.V. All rights reserved.
Jiang, WenSpencer, Benjamin W.Hales, Jason D.Shields, Michael D....
18页
查看更多>>摘要：Statistical nuclear fuel failure analysis is critical for the design and development of advanced reactor technologies. Although Monte Carlo Sampling (MCS) is a standard method of statistical failure analysis for fuels, the low failure probabilities of some advanced fuel forms and the correspondingly large number of required model evaluations limit its application to low-fidelity (e.g., 1-D) fuel models. In this paper, we present four other statistical methods for fuel failure analysis in Bison, considering tri-structural isotropic (TRISO)-coated particle fuel as a case study. The statistical methods considered are Latin hyper cube sampling (LHS), adaptive importance sampling (AIS), subset simulation (SS), and the Weibull theory. Using these methods, we analyzed both 1-D and 2-D representations of TRISO models to compute failure probabilities and the distributions of fuel properties that result in failures. The results of these methods compare well across all TRISO models considered. Overall, SS and the Weibull theory were deemed the most efficient, and can be applied to both 1-D and 2-D TRISO models to compute failure probabilities. Moreover, since SS also characterizes the distribution of parameters that cause TRISO failures, and can consider failure modes not described by the Weibull criterion, it may be preferred over the other methods. Finally, a discussion on the efficacy of different statistical methods of assessing nuclear fuel safety is provided. (c) 2022 Elsevier B.V. All rights reserved.
Simon, P. -C. A.Aagesen, Larry K.Jiang, ChaoJiang, Wen...
11页
查看更多>>摘要：The silicon carbide (SiC) layer in tristructural isotropic (TRISO) fuel particles serves as a barrier to prevent the escape of fission products produced and not retained in the fuel kernel. The release of silver (Ag) is a concern due to the long half-life of the 110mAg isotope. However, accurately determining the fission gas release rate requires knowing the diffusion coefficient through the SiC layer. In this study, we leverage atomistic calculations of Ag diffusivity in SiC bulk and grain boundaries (GBs) to develop a mesoscale effective Ag diffusion coefficient (D-eff ) in SiC. Since GBs serve as pathways for Ag diffusion, D-eff is defined as a function of temperature and microstructure variables. In particular, the size of SiC grains in the direction perpendicular to diffusion is shown to significantly affect Ag diffusion. The prediction of the mechanistic, mesoscale approach falls within one order of magnitude of empirical values. The temperature and microstructure-dependent effective Ag diffusivity in SiC is implemented in the fuel performance code Bison with a correction factor to predict Ag release from AGR-1 TRISO fuel particles. We hereby quantify the impact of SiC grain size on Ag release and improve Bison's predictions.& nbsp;Published by Elsevier B.V.
Terricabras, Adrien J.Wang, LingRaftery, Alicia M.Nelson, Andrew T....
20页
查看更多>>摘要：Silicon nitride and zirconium nitride have been proposed as potential materials for multiple nuclear applications (inert matrix fuels, accident tolerant fuels, space nuclear power, fusion reactor design), yet knowledge on their behavior under irradiation remains limited. Ion irradiations were performed using 15 MeV Ni5+ ions on Si3N4 and ZrN samples, with midrange doses (around 3 mu m) from 1 to 50 dpa and temperatures from 300 to 700 degrees C. Volumetric lattice swelling was determined by grazing incidence X-ray diffraction, defect production and evolution were tracked using Transmission Electron Microscopy, and nanoindentation was performed to quantify the ceramics' mechanical properties evolution. The results from these irradiation studies on nitride ceramics help fill the current gap present in the literature. Behavior consistent with past work on irradiated Si3N4 was observed with respect to mechanical properties and defect formation up to 15 dpa and 500 degrees C. Failure of the grain boundary sintering aid in Si3N4 was observed above these conditions. Different behavior was observed in both nitrides at 50 dpa and 700 degrees C, where lattice swelling increased past potential saturation values. Unreported cavity formation was witnessed in both materials under all irradiation conditions, with stable number density and slight size increase above 15 dpa. The mechanism for the cavity formation remains to be determined. (c) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：In order to improve the high-temperature steam oxidation resistance of Zircaloy-4 for accident tolerant fuel claddings (ATF), Cr coatings with (200) preferred orientation were deposited by changing argon flow using closed field unbalanced magnetron sputtering. The influences of the argon flow on the microstructure and high-temperature steam oxidation properties of Cr coatings were studied systematically. The results indicate that Cr coatings exhibit obvious preferred orientation of Cr (200) especially for 30sccm argon flow due to more adatom easy aggregation on Cr (200) plane under more ion collisions. With the argon flow increases, the grains of Cr coatings gradually becomes compact and homogeneous, which causes the formation of thicker Cr 2 O 3 oxide layer and residual Cr layer on Cr coatings surface after 1200 degrees C high-temperature steam oxidation test at 8h. Above all, Cr coatings prepared by 30sccm argon flow still possess excellent steam oxidation resistance properties even after 12h exposure time. In addition, the high-temperature steam oxidation mechanism of 30sccm argon flow Cr coatings under different exposure time also was discussed in detail. The study about Cr (200) preferred orientation is expected to provide a new research idea for prolonging steam oxidation resistance and accident tolerant time. (c) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：Low-enriched ( similar to 19.75% 235 U) U-10Mo(wt%) foils were evaluated for both mechanical and thermophysical properties to establish baseline characteristics prior to irradiation testing. Cast U-10Mo ingots were sequentially hot and cold rolled to two different final foil thicknesses, resulting in different levels of cold work being present in the finished foils. The mechanical response of the U-10Mo foils was evaluated in the temperature range of 293-623 K. Increasing test temperatures resulted in decreases of both yield and ultimate tensile strength. Comparison of results to earlier work performed on depleted U-10Mo rolled foils indicates that the material in this study has lower strength and increased ductility. However, a comparison of the two different foil thicknesses in this study found that they were nearly identical in yield and ultimate tensile strength, differing by only 10-20 MPa ( < 2%). Thermal conductivity was calculated from the measurements of specific heat, linear thermal expansion, and thermal diffusivity from 323 to 1273 K on both thicknesses of the foils. These data were approximately 5-10% lower than previously published data above 573 K and were similar to data for temperature ranges below 573 K. Differences are likely related to differences in grain size and/or impurity content and variation in fabrication history. (c) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：S C Alloy 690TT tube samples with different sizes of internal bulge defect (IBD) are prepared by actual hydraulic tube expansion in field and their microstructure and stress corrosion cracking (SCC) behavior are studied in detail. The hardening level and residual strain increase as moving from the original area of the tube to the bulged area, and so as for the increasing of deformation sizes. Corrosion test with a duration of 20 0 0 h shows that the IBD area has higher SCC sensitivity than the original tube. In addition, IBD with larger size is more sensitive to SCC. (c) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：Irradiation of crystalline materials modifies their microchemistry and microstructure. This includes solute segregation toward defect sinks such as grain boundaries (GBs), a phenomenon commonly known as radiation-induced segregation (RIS). Unlike in coarse-grained alloys where GBs are nearly static, RIS is usually accompanied and affected by either thermal or irradiation-induced grain growth in nanocrystalline materials. This work presents a modeling study of concurrent grain growth and RIS in austenitic Fe-Cr-Ni adopting realistic 2D grain structures. RIS can be significantly affected by concurrent grain growth due to (i) increasing grain size, (ii) motion of GBs as defect sinks, and (iii) their combined effect. Consequently, RIS is enhanced by grain growth due to increased grain size and sink motion. More notably, RIS in nanocrystalline materials were found to induce grain-level compositional redistribution in addition to RIS at defect sinks, resulting in grain-size-dependent compositions in individual grains. Without concurrent grain growth, elements depleted at the sinks due to RIS, such as Cr in austenitic steels, will have lower concentrations in smaller grains than in larger grains. The opposite trend becomes true when concurrent grain growth takes place. The compositional difference in individual grains can be significant enough to affect local phase stability. These findings are not discernible with the classical 1D bicrystal model, and they highlight the different effects of RIS in nanocrystalline alloys compared to their coarse-grained counterparts.(c) 2022 Elsevier B.V. All rights reserved.
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