Molecular dynamics study on planar clustering of xenon in UO2

TL;DR

This study uses molecular dynamics to explore how xenon atoms cluster in UO2 fuel, revealing a stable planar distribution at high temperatures and its implications for fuel behavior under irradiation.

Contribution

It demonstrates the stability of planar xenon clustering in UO2 and assesses interatomic potentials against ab-initio results for large-scale deformation modeling.

Findings

Planar xenon configurations are (meta-) stable under thermodynamic perturbations.

Xenon atoms form a liquid-like, modulated layer near UO2 interfaces at 1000 K.

A planar defect loop persists after xenon release.

Abstract

Interatomic potentials of uranium dioxide are investigated on their applicability to model structural stabilities beyond fluorite phase by comparing with ab-initio results. A high pressure cotunnite phase and loosely stacking virtual crystal are involved in order to get a primary confidence for large-scale deformation modelings of UO2 under irradiation damages. The behavior of Xe atoms in UO2 fuel is studied with molecular dynamics simulations. Besides the ground state bubble geometry, we find that a planar distribution is also (meta-) stable for xenon under thermodynamic perturbations. The Xe atoms with a planar configuration are in a liquid state at a typical reactor temperature of 1000 K, which presents a modulated layer-structure near the interface with solid UO2. A planar defects loop remains after these Xe atoms are released out.