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Andersson, Anders D.

Publications and source records attributed to Andersson, Anders D..

4 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2014

Simulation of xenon, uranium vacancy and interstitial diffusion and grain boundary segregation in UO 2

In light water reactor fuel, gaseous fission products segregate to grain boundaries, resulting in the nucleation and growth of large intergranular fission gas bubbles. Based on the mechanisms established from density functional theory (DFT) and empirical potential calculations 1, continuum models for diffusion of xenon (Xe), uranium (U) vacancies and U interstitials in UO 2 have been derived for both intrinsic conditions and under irradiation. 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. All models are implemented in the MARMOT phase field code, which is used to calculate effective Xe and U diffusivities as well as redistribution for a few simple microstructures.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2013

A molecular dynamics study of anisotropy and the effect of Xe on UO 2 thermal conductivity

In this report we first investigate the effect of Xe on UO 2 thermal conductivity via molecular dynamics simulations. This property is studied both as function of temperature and for different concentrations and configurations of Xe atoms (randomly dispersed and in gas bubbles). The largest decrease of the thermal conductivity is obtained for randomly distributed Xe atoms, which is due to high defect scattering and thus decreasing phonon mean free path. Second we demonstrate several different manifestations of anisotropic UO 2 thermal conductivity, including discontinuities between the conductivity of bulk UO 2 separated by asymmetric grain boundaries and variations of the conductivity along different crystallographic directions in single crystals of UO 2 . These results are validated against recent experiments on UO 2 single crystals.

36 MATERIALS SCIENCE↗