The influence of stoichiometry on compression creep of uranium dioxide single crystals

Seltzer, M. S.; Clauer, A. H.; Wilcox, B. A.

doi:10.1016/0022-3115(72)90127-4

Cited by 46 publications

(10 citation statements)

References 16 publications

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“…These straight dislocations are entangled at larger strains. Such observations have been confirmed by few studies for {100} and {110} slip modes [10], [12] that emphasize the relevance of lattice friction in UO2 at low and intermediate temperatures. However, no detail analysis about elementary dislocation processes (e.g.…”

Section: Introductionmentioning

confidence: 52%

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Crystal viscoplastic modeling of UO2 single crystal

Portelette

Amodeo

Madec

et al. 2018

Journal of Nuclear Materials

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The viscoplastic behavior of uranium dioxide (UO2) single crystal is of great interest to perform predictive multiscale modeling of the nuclear fuel. Here, a viscoplastic model is built considering dislocation glide in ½<110>{100} and ½<110>{110} slip systems. The constitutive law parameters are determined adjusting the temperature dependency of the experimental critical resolved shear stress for both principal slip modes. Crystal plasticity finite element simulations of single crystal compression tests show a reasonable agreement with experimental viscoplastic anisotropy of UO2. However, for specific orientations where ½<110>{111} slip is observed experimentally, significant differences remain between experimental and computed compression stresses. Therefore, the role of ½<110>{111} slip is investigated based on a parametric study that provides new insights on UO2 plastic deformation. Several parameterizations of ½<110>{111} slip are tested highlighting the complexity of UO2 viscoplastic behavior. Significant improvements are still required to explain all simulation-experiment gaps.

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Section: Introductionmentioning

confidence: 52%

“…In addition, Keller and collaborators show a slip system transition toward ½<110>{111} at 873 K in hyper stoichiometric UO2+x [13], [14]. Besides the temperature, the U/O ratio also influences the slip mode activity [10], [13], [14] but no quantitative dependency has been shown up to now.…”

Section: Introductionmentioning

confidence: 99%

Crystal viscoplastic modeling of UO2 single crystal

Portelette

Amodeo

Madec

et al. 2018

Journal of Nuclear Materials

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“…1, 4,5,7 The transition temperature from irradiation-induced [8][9][10] to thermal creep [11][12][13][14] is approximately 1100…”

Section: Introductionmentioning

confidence: 99%

“…• C. 4,8 Compared to the creep of metals, the creep behavior of UO 2 is much more complex, depending strongly on the O/M ratio 11,15 and, microstructural features 14,15 such as grain size and porosity, as well as temperature 4,11,14 and stress state 12,13,16 . Dozens of mechanisms have been proposed for the high temperature thermal creep.…”

Section: Introductionmentioning

confidence: 99%

“…Dozens of mechanisms have been proposed for the high temperature thermal creep. These mechanisms can be broadly classified into lattice diffusion controlled 1,11,14 , grain boundary diffusion 12,[17][18][19] , and dislocation glide/climb controlled diffusion. [12][13][14]16 In the case of UO 2 , lattice diffusion controlled creep, known as Nabarro-Herring creep, involves vacancy transport within grains, with the rate controlled by the diffusion of uranium vacancies.…”

Section: Introductionmentioning

confidence: 99%

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Impact of homogeneous strain on uranium vacancy diffusion in uranium dioxide

et al. 2015

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We present a detailed mechanism of, and the effect of homogeneous strains on, the migration of uranium vacancies in UO2. Vacancy migration pathways and barriers are identified using density functional theory (DFT) and the effect of uniform strain fields are accounted for using the dipole tensor approach. We report complex migration pathways and non-cubic symmetry associated with the uranium vacancy in UO2 and show that these complexities need to be carefully accounted for to predict the correct diffusion behavior of uranium vacancies. We show that under homogeneous strain fields, only the dipole tensor of the saddle with respect to the minimum is required to correctly predict the change in the energy barrier between the strained and the unstrained case. Diffusivities are computed using kinetic Monte Carlo (KMC) simulations for both neutral and fully charged state of uranium single and di-vacancies. We calculate the effect of strain on migration barriers in the temperature range 800 -1800 K for both vacancy types. Homogeneous strains as small as 2% have a considerable effect on diffusivity of both single and di-vacancies of uranium, with the effect of strain being more pronounced for single vacancies than di-vacancies. In contrast, the response of a given defect to strain is less sensitive to changes in the charge state of the defect. Further, strain leads to anisotropies in the mobility of the vacancy and the degree of anisotropy is very sensitive to the nature of the applied strain field for strain of equal magnitude. Our results suggest that the influence of strain on vacancy diffusivity will be significantly greater when single vacancies dominate the defect structure, such as sintering, while the effects will be much less substantial under irradiation conditions where di-vacancies dominate.

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