Diffusion of oxygen interstitials in UO_2+x using kinetic Monte Carlo simulations: Role of O/M ratio and sensitivity analysis

详细信息    查看全文

• 作者：Rakesh K. Behera^a ; ¹ ; ^{rakesh.behera@gatech.edu" class="auth_mail" title="E-mail the corresponding author} ; Taku Watanabe^b ; ² ; David A. Andersson^c ; Blas P. Uberuaga^c ; Chaitanya S. Deo^a ; ^{chaitanya.deo@me.gatech.edu" class="auth_mail" title="E-mail the corresponding author}
• 关键词：UO2+x ; UO2 ; Defects ; Diffusion ; Sensitivity analysis ; DFT ; kMC
• 刊名：Journal of Nuclear Materials
• 出版年：2016
• 出版时间：15 April 2016
• 年：2016
• 卷：472
• 期：Complete
• 页码：89-98
• 全文大小：2808 K

文摘

Oxygen interstitials in UO_2+x significantly affect the thermophysical properties and microstructural evolution of the oxide nuclear fuel. In hyperstoichiometric Urania (UO_2+x), these oxygen interstitials form different types of defect clusters, which have different migration behavior. In this study we have used kinetic Monte Carlo (kMC) to evaluate diffusivities of oxygen interstitials accounting for mono- and di-interstitial clusters. Our results indicate that the predicted diffusivities increase significantly at higher non-stoichiometry (x > 0.01) for di-interstitial clusters compared to a mono-interstitial only model. The diffusivities calculated at higher temperatures compare better with experimental values than at lower temperatures (< 973 K). We have discussed the resulting activation energies achieved for diffusion with all the mono- and di-interstitial models. We have carefully performed sensitivity analysis to estimate the effect of input di-interstitial binding energies on the predicted diffusivities and activation energies. While this article only discusses mono- and di-interstitials in evaluating oxygen diffusion response in UO_2+x, future improvements to the model will primarily focus on including energetic definitions of larger stable interstitial clusters reported in the literature. The addition of larger clusters to the kMC model is expected to improve the comparison of oxygen transport in UO_2+x with experiment.