Pipe and grain boundary diffusion of He in UO2

COT Galvin and MWD Cooper and PCM Fossati and CR Stanek and RW Grimes and DA Andersson, JOURNAL OF PHYSICS-CONDENSED MATTER, 28, 405002 (2016).

DOI: 10.1088/0953-8984/28/40/405002

Molecular dynamics simulations have been conducted to study the effects of dislocations and grain boundaries on He diffusion in UO2. Calculations were carried out for the 100, 110 and 111 < 110 > edge dislocations, the screw < 110 > dislocation and Sigma 5, Sigma 13, Sigma 19 and Sigma 25 tilt grain boundaries. He diffusivity as a function of distance from the dislocation core and grain boundaries was investigated for the temperature range 2300-3000 K. An enhancement in diffusivity was predicted within 20 angstrom of the dislocations or grain boundaries. Further investigation showed that He diffusion in the edge dislocations follows anisotropic behaviour along the dislocation core, suggesting that pipe diffusion occurs. An Arrhenius plot of He diffusivity against the inverse of temperature was also presented and the activation energy calculated for each structure, as a function of distance from the dislocation or grain boundary.

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