The role of charge and ionic radius on fission product segregation to a model UO2 grain boundary

Hong, Minki; Uberuaga, Blas P.; Phillpot, Simon R.; Andersson, David; Stanek, Christopher R.; Sinnott, Susan B.

doi:10.1063/1.4798347

Cited by 23 publications

(14 citation statements)

References 23 publications

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“…However, we find that ionic valence has a somewhat stronger influence on the dopant segregation as compared to ionic size. Hong et al [48] reported the segregation energies of several fission products to a UO2 grain boundary and attributed the prepensity of segregation to ionic charge, ionic radius, and the particular segregation site. Analogous to the trend reported here, they found that fission products with similar ionic charge as the host uranium ion exhibit weaker segregation, while those with dissimilar ionic charge segregate more strongly.…”

Section: Discussionmentioning

confidence: 99%

Stabilization of MgAl2O4 spinel surfaces via doping

et al. 2016

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Surface structure of complex oxides plays a vital role in processes such as sintering, thin film growth, and catalysis, as well as being a critical factor determining the stability of nanoparticles. Here, we report atomistic calculations of the low-index stoichiometric magnesium aluminate spinel (MgAl2O4) surfaces, each with two different chemical terminations. High temperature annealing was used to explore the potential energy landscape and provide more stable surface structures. We find that the lowest energy surface is {100} while the highest energy surface is {111}. The surfaces were subsequently doped with three trivalent dopants (Y 3+ , Gd 3+ , La 3+) and one tetravalent dopant (Zr 4+) and both the surface segregation energies of the dopants and surface energies of the doped surface were determined. All of the dopants reduce the surface energy of spinel, though this reduction in energy depends on both the size and valence of the dopant. Dopants with larger ionic radius tend to segregate to the surface more strongly and reduce the surface energy to a greater extent. Furthermore, the ionic valence of the dopants seems to have a stronger influence on the segregation than does ionic size. For both undoped and doped spinel, the predicted crystal shape is dominated by {100} surfaces, but the relative fraction of the various surfaces changes with doping due to the unequal changes in energy, which has implications on equilibrium nanoparticle shapes and therefore on applications sensitive to surface properties.

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Section: Discussionmentioning

confidence: 99%

Stabilization of MgAl2O4 spinel surfaces via doping

et al. 2016

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“…Nerikar et al attempted to map the Xe segregation properties onto the strain obtained from atomistic simulations, but, although some correlation was found, it was difficult to quantitatively predict the segregation energy from the local strain [42]. This may be related to the importance of electrostatic effects in these systems [55]. Fig.…”

Section: Segregation Datamentioning

confidence: 99%

Multiscale simulation of xenon diffusion and grain boundary segregation in UO2

Andersson

Tonks

Casillas

et al. 2015

Journal of Nuclear Materials

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In light water reactor fuel, gaseous fission products segregate to grain boundaries, resulting in the nucleation and growth of large intergranular fission gas bubbles. The segregation rate is controlled by diffusion of fission gas atoms through the grains and interaction with the boundaries. Based on the mechanisms established from earlier density functional theory (DFT) and empirical potential calculations, diffusion models for xenon (Xe), uranium (U) vacancies and U interstitials in UO 2 have been derived for both intrinsic (no irradiation) and irradiation conditions. Segregation of Xe to grain boundaries is described by combining the bulk diffusion model with a model for the interaction between Xe atoms and three different grain boundaries in UO 2 (Σ5 tilt, Σ5 twist and a high angle random boundary), as derived from atomistic calculations. The present model does not attempt to capture nucleation or growth of fission gas bubbles at the grain boundaries. The point defect and Xe diffusion and segregation models are implemented in the MARMOT phase field code, which is used to calculate effective Xe and U diffusivities as well as to simulate Xe redistribution for a few simple microstructures.

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“…Capabilities of the picosecond acoustic can be further expanded by taking into consideration recent reports where the structure of interface resulted in additional modifications to the Brillouin oscillations, (31,37) such as modulation in amplitude and emergence of a phase lag 12 upon propagation through a distinct layer. We speculate that these effects can be leveraged to study impurity segregation at grain boundaries using picosecond ultrasonics.…”

Section: Discussionmentioning

confidence: 99%

“…In this regard, grain boundaries attract impurities and other defects that have further implications on determining material behavior. (12) Additionally the boundaries themselves undergo motion under external stimuli such as mechanical deformation, radiation and high temperatures. (7,13) Grain boundary motion and the associated change in crystal misorientation across the boundary can significantly influence transport and mechanical properties.…”

Section: Introductionmentioning

confidence: 99%