Diffusion of oxygen interstitials in UO2+x using kinetic Monte Carlo simulations: Role of O/M ratio and sensitivity analysis

JOURNAL OF NUCLEAR MATERIALS

卷:472

Article

Behera, Rakesh K.^1,4  Watanabe, Taku^2,5  Andersson, David A.³  Uberuaga, Blas P.³  Deo, Chaitanya S.¹ 

[1] Georgia Inst Technol, George W Woodruff Sch Mech Engn, Nucl & Radiol Engn Program, Atlanta, GA 30332 USA

[2] Georgia Inst Technol, Sch Chem & Biomol Engn, Atlanta, GA 30332 USA

[3] Los Alamos Natl Lab, Div Mat Sci & Technol, Los Alamos, NM 87545 USA

[4] Georgia Inst Technol, Sch Chem & Biochem, Atlanta, GA 30332 USA

[5] Samsung R&D Inst, Osaka, Japan

关键词: UO2+x;    UO2;    Defects;    Diffusion;    Sensitivity analysis;    DFT;    kMC;   

DOI  :  10.1016/j.jnucmat.2016.02.003

来源: Elsevier

【 摘 要 】

Oxygen interstitials in UO2+x significantly affect the thermophysical properties and microstructural evolution of the oxide nuclear fuel. In hyperstoichiometric Urania (UO2+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 diinterstitial 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 UO2+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 UO2+x with experiment. (C) 2016 Elsevier B.V. All rights reserved.

【 授权许可】

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