Ko, JaehwanKim, Jong WooMin, Hyeong WooKim, Yonghee...
24页
查看更多>>摘要：A B S T R A C T This article reviewed the near-term development status of accident tolerant fuel (ATF) cladding to increase the safety of nuclear power generation. The key to near-term development is to secure enhanced accident tolerance beyond the performance of zirconium alloys without compromising the stability of zirconium alloys during normal operation. The near-term techniques proposed in the literature include sputtering, arc ion plating, filtered cathodic vacuum arc deposition (FCVAD), pulsed laser deposition (PLD), chemical vapor deposition (CVD), spray, 3D laser coating, swaging, and electroplating. Among the manufacturing methods of enhanced ATF cladding, the process methods for near-term development are reviewed in this article on the basis of practical considerations. In addition, the performance of the ATF cladding manufactured using the above process methods are comparatively analyzed, and the oxidation resistance at high temperature is examined. Finally, future research areas such as mass production for several m-long tubes, thickness uniformity on the curved surface of the tube and forming a protective layer on the inner surface of the tube are discussed. So far, Cr coating using PVD is the most practical manufacturing technology for near-term development of ATF cladding.(c) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：There are a number of important challenges facing the nuclear industry including the extension of the fuel cycle of traditional UO2 fuel and the adoption of non-oxide ceramic fuel forms in both light water reactors (LWRs) and advanced reactors. Atomic scale processes govern thermophysical properties and the evolution of defects within nuclear fuel, and their impact on key fuel performance metrics, such as mar -gin to melting and fission gas release. Here a review is presented of atomic scale simulation effort s to provide physics-based materials models in support of fuel performance modeling. (C)& nbsp;2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：Stress corrosion cracking (SCC) growth behaviors of 309L and 308L stainless steel claddings in simulated pressurized water reactor primary water at 325 ? and 350 ? were investigated by compact tension specimens and correlated to the oxide film properties in terms of microstructure. SCC growth rates of 308L were much lower than those of 309L. 309L showed typical intergranular SCC characteristics. The high SCC resistance of 308L was related to the low oxidation rate and crack tip retardation due to the presence of highly networked ferrites. The lower Cr content, as well as less and sparsely distributed delta-ferrite phases in 309L than in 308L, led to more severe local oxidation penetration beneath the metal/inner oxide interface and more porous inner oxide, therefore, contributed to its enhanced SCC growth in 309L. The SCC growth rate results by compact tension specimens are consistent with those by slow strain rate tests. (C)& nbsp;2022 Published by Elsevier B.V.
Huang, S. S.Guan, H. Q.Zhong, Z. H.Miyamoto, M....
7页
查看更多>>摘要：Recent studies have shown that equiatomic CoCrFeMnNi high-entropy alloy (HEA) has excellent mechanical properties and irradiation resistance. However, upon neutron irradiation, He is always generated as a byproduct. In this study, the irradiation resistance of thin-film CoCrFeMnNi HEA samples irradiated by He ions at 773 K was compared with that of stainless steel 304 (SS304), which as the same crystal structure. Although the formation of He bubbles was observed during irradiation in both alloys, the He bubble density of the CoCrFeMnNi HEA was lower than that of SS304 under the same exposure conditions. The simulation of the effect of He on the formation of vacancy clusters in the CoCrFeMnNi HEA was carried out based on first-principles calculations. The results show that the He atom significantly improved the stability of the vacancy clusters in the CoCrFeMnNi HEA. Thus, even in the CoCrFeMnNi HEA, irradiation formed stable He-vacancy clusters that decreased the irradiation resistance compared with irradiation without He.(c) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：Helium exposure is known to induce severe damages in tungsten materials, which are often linked with the aggregation of helium at vacancies. Yet even for the simplest case of monovacancies, a complete atomistic understanding of helium aggregation is not available, with relevant structures and energetics being largely uncharted and contended. Here, starting with comprehensive ab initio molecular dynamics (AIMD) simulations, we systematically investigated helium aggregation in a tungsten monovacancy (Vac-He-n with n = 1-13), revealed the spatial distribution and correlations for helium atoms. A great number of structures, constructed by manual helium insertion based on empirical knowledge or extracted randomly from the AIMD trajectories, were then examined with density functional theory minimizations to identify the most stable ones. These calculations provide reliable structures and energies for Vac-He-n clusters, thus were used as critical benchmarks to evaluate five commonly used tungsten-helium empirical potentials. This work presents accurate atomistic insights toward helium aggregation in a tungsten monovacancy, offering a reliable reference for selecting interatomic potentials to simulate helium induced damages. (C)& nbsp;2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：Under intensive irradiation of ultrafast laser and swift ions, a metal material like tungsten is not in electronic ground state but in excited states. In the excited states, the properties of system intriguingly evolve with the degree of excitation. Revealing how its properties change with the degree of excitation and uncovering the physical nature in the change of properties are of great importance for application of the metal materials in some extreme environment. In this work, through performing tight-binding calculations on the electronically-excited tungsten containing edge dislocation, we found that as the electronic excitation of the system becomes heavier, its bulk modulus, shear modulus, and Young's modulus become worse, and its ductility gets better first and then turns to be worse. We proposed that this behavior is originated from the bond strength weakened by the electronically-excited states between atoms. Furthermore, it is found that during the evolution of these elastic properties, a solid-solid phase transition in the system happens at the electronically-excited state with electronic excitation energy of around 1.21 eV. We revealed that such a structural phase transition is driven essentially by exciting two soft phonon modes.(c) 2022 Elsevier B.V. All rights reserved.
Liu, X. -Y.Matthews, C.Jiang, W.Cooper, M. W. D....
15页
查看更多>>摘要：TRISO fuel particles are candidates for use in next generation reactors including gas reactors, fluoride salt-cooled high temperature reactors, and micro-reactors. The UCO fuel kernel consists of a uranium dioxide (UO2) and uranium carbide mixture. The addition of UC2 helps suppress the formation of carbon monoxide gas, which led to failures during initial TRISO development. The addition of uranium carbide alters the chemistry of the UO2 kernel, which is known to influence performance parameters such as fission gas diffusivity, although the impact has not been quantified and no models exist that take the change in chemistry into account. Therefore, better understanding and more accurate models of the impact of chemistry on fuel performance are of high priority. In this paper, a first-principles density functional the-ory (DFT) and empirical potential based multi-scale study has been carried out to model the diffusivity of fission gas xenon (Xe) in UCO TRISO fuel kernels. The focus is on the UO2 component in the UCO fuel kernels, as that represents the largest volume fraction of the fuel kernels. The study relies on DFT and empirical potential calculations to determine Xe and point defect properties, which are then used in ther-modynamic and kinetic models to predict diffusion for intrinsic conditions. In addition, the information is utilized in cluster dynamics simulations using the Centipede code to estimate the impact of irradiation on defect transport. The presence of UC2 or UC2-x in the UCO fuel kernels is shown to have a substantial impact on the UO2 non-stoichiometry by inducing oxygen vacancies and driving UO2 sub-stoichiometric, which causes much slower Xe diffusion in UCO compared to light water reactor UO2 fuel. The application of this model in fuel performance simulations using the Bison code is also demonstrated. (C)& nbsp;2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：As the leading candidate of plasma-facing materials, tungsten is expected to withstand the influx of D-T plasma in future fusion reactors, which is known to cause damages to tungsten surface and give rise to T fuel retention. In this work, based on accurate density functional theory parameterization, we carried out a series of object kinetic Monte Carlo (OKMC) simulations to study the retention behavior of H isotopes in W. By directly comparing our simulations with existing experiments, we show that the OKMC model can accurately describe H implantation and desorption behavior in W, with excellent agreements found between experimental/simulated H annealing curves, thermal desorption spectra, and fluence dependence. Our OKMC model reveals primary trapping sites of H in these experiments, provides deeper understanding for experimental results, and offers quantitative theoretical assessment for H implantation and desorption in W.(c) 2022 Elsevier B.V. All rights reserved.
Barashev, Alexander V.Zhao, QiangWang, QingyuYan, Qiang...
9页
查看更多>>摘要：A B S T R A C T The delta hydrides formation in zirconium cladding under irradiation and thermal aging is studied by the rate theory modeling. The precipitates may lead to cracking of the clad and are investigated both exper-imentally and theoretically. The rate theory studies published so far are based on the well-established classical nucleation theory, but use several assumptions, e.g. of homogeneous hydride nucleation mode and spherical shape of precipitates, which contradict observations. In this work we continue the develop-ment of the hydride precipitation model by taking into consideration the observed preferential nucleation of the platelet-shaped hydrides on grain boundaries, and analyze the importance of such modifications by comparing calculations performed with different approaches. We also extract information from the literature on the hydrogen solution energy and alpha Zr / delta hydride interface energy, which define the hydrogen-hydride binding energy as a function of precipitate size, and show that the observed hy-dride size and density are well described with the use of the capillary approximation. The difference in precipitation kinetics during thermal annealing of samples with pre-existing level of hydrogen and under irradiation to the same final hydrogen concentration is elucidated. This improves our understanding of the factors affecting hydride formation in the clad.Published by Elsevier B.V.
查看更多>>摘要：Herein, the defect features under irradiation in the Fe-C system are studied by an Object Kinetic Monte Carlo (OKMC) model. The model was based on recent parameters and was validated by comparing the numerical estimates with the experimentally obtained defect features in neutron-irradiated iron. Systematic simulations of defects evolution at 70 ? in a wide range of dose rates from 10(-8) to 10(-4) dpa/s were carried out. The simulation results demonstrate that at the lower dose range (< 0.02 dpa), a higher dose rate irradiation leads to a higher interstitial-loop density and irradiation hardening. In contrast, the dose rate does not obviously influence the defect features at the high dose range. Defect features under two carbon concentrations 50 and 100 appm show a similar dose-rate effect, and a higher carbon concentration leads to a higher interstitial loop density and irradiation hardening. We attribute the dose rate effect change with dose to the competition between sinks absorption and SIAs-vacancies annihilation. Based on the interaction model of < 100 > production, the ratio of < 100 >-type interstitial loops is higher at the higher dose rate irradiation, consistent with the experimental results. (C)& nbsp;2022 Elsevier B.V. All rights reserved.
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