Atomic-scale modeling of 1/2 (110)001 edge dislocations in UO₂ : Core properties and mobility

M Borde and M Freyss and E Bourasseau and B Michel and D Rodney and J Amodeo, JOURNAL OF NUCLEAR MATERIALS, 574, 154157 (2023).

DOI: 10.1016/j.jnucmat.2022.154157

The dislocation properties of UO 2 , the main nuclear fuel material, are important ingredients to model the mechanical properties and predict nominal and accidental operations of nuclear plant reactors. However, the plastic behaviour of UO 2 is complex with little known about dislocations and other extended defects. In this study, we use a combination of interatomic potential-based atomistic simulations and ab initio calculations to investigate the core structure and mobility of the 12 ( 110 ) 001 edge dislocation, which controls the plasticity of UO 2 single crystals. Various dislocation cores are obtained and compared, including the classical asymmetric Ashbee core and a so-far unreported core made of an alternation of both variants of the Ashbee core along the dislocation line. This new core, called here zigzag , is ubiquitous in molecular dynamics simulations at high temperature in the nominal-to-accidental transient regime (1600 to 2200 K). Molecular dynamics is also used to determine the velocity of the edge dislocation as a function of temperature and stress. A dislocation mobility law is adjusted from the simulations and provides an up-scaling ingredient central to the multi-scale modeling of UO 2 nuclear fuel mechanical properties. (c) 2022 Elsevier B.V. All rights reserved.

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