Atomistic simulations of void migration under thermal gradient in UO2 / Tapan G. Desai in Acta materialia, Vol. 58 N° 1 (Janvier 2010)  

Public ISBD [article]  inActa materialia > Vol. 58 N° 1 (Janvier 2010) . - pp. 330–339 Titre : Atomistic simulations of void migration under thermal gradient in UO2 Type de document : texte imprimé Auteurs : Tapan G. Desai, Auteur ; Paul Millett, Auteur ; Michael Tonks, Auteur Année de publication : 2010 Article en page(s) : pp. 330–339 Note générale : Métallurgie Langues : Anglais (eng) Mots-clés : Molecular dynamics simulation Thermal gradient Void migration Uranium dioxide Nuclear Résumé : It is well known that within a few hours after startup of a nuclear reactor, the temperature gradient within a fuel element causes migration of voids/bubbles radially inwards to form a central hole. To understand the atomic processes that control this migration of voids, we performed molecular dynamics (MD) simulations on single crystal UO2 with voids of diameter 2.2 nm. An external temperature gradient was applied across the simulation cell. At the end of the simulation run, it was observed that the voids had moved towards the hot end of the simulation cell. The void migration velocity obtained from the simulations was compared with the available phenomenological equations for void migration due to different transport mechanisms. Surface diffusion of the slowest moving specie, i.e. uranium, was found to be the dominant mechanism for void migration. The contribution from lattice diffusion and the thermal stress gradient to the void migration was analyzed and found to be negligible. By extrapolation, a crossover from the surface-diffusion-controlled mechanism to the lattice-diffusion-controlled mechanism was found to occur for voids with sizes in the μm range. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S1359645409006077 [article] Atomistic simulations of void migration under thermal gradient in UO2 [texte imprimé] / Tapan G. Desai, Auteur ; Paul Millett, Auteur ; Michael Tonks, Auteur . - 2010 . - pp. 330–339. Métallurgie Langues : Anglais (eng) in Acta materialia > Vol. 58 N° 1 (Janvier 2010) . - pp. 330–339 Mots-clés : Molecular dynamics simulation Thermal gradient Void migration Uranium dioxide Nuclear Résumé : It is well known that within a few hours after startup of a nuclear reactor, the temperature gradient within a fuel element causes migration of voids/bubbles radially inwards to form a central hole. To understand the atomic processes that control this migration of voids, we performed molecular dynamics (MD) simulations on single crystal UO2 with voids of diameter 2.2 nm. An external temperature gradient was applied across the simulation cell. At the end of the simulation run, it was observed that the voids had moved towards the hot end of the simulation cell. The void migration velocity obtained from the simulations was compared with the available phenomenological equations for void migration due to different transport mechanisms. Surface diffusion of the slowest moving specie, i.e. uranium, was found to be the dominant mechanism for void migration. The contribution from lattice diffusion and the thermal stress gradient to the void migration was analyzed and found to be negligible. By extrapolation, a crossover from the surface-diffusion-controlled mechanism to the lattice-diffusion-controlled mechanism was found to occur for voids with sizes in the μm range. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S1359645409006077

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