A Study of Defect Behaviour in UO₂ using Adaptive Kinetic Monte Carlo Simulation

Laura Swansbury

Mark Bankhead

National Nuclear Laboratory Ltd.


Radiation damage in MOX fuel can result in the formation of defects. Understanding defect behaviour on an atomic-scale is important for elucidating structural changes that can ultimately result in fuel swelling and cracking. Atomic-scale defect structures can be generated using radiation cascade simulation. While molecular dynamics (MD) is commonly employed for studying atomic-scale systems, the disparity between the timescales over which simulations can run and the timescales over which defects anneal inhibits its use. Instead, techniques that can run over longer timescales are required. Time-accelerated methods such as Adaptive Kinetic Monte Carlo (AKMC) can run over longer timescales. AKMC modelling has been used in this work to study defect migration in UO2 and work toward understanding defect migration in MOX fuel. Trends in anion and cation transitions as a function of temperature, activation energy and atom hop distances have been explored. Subsequent mechanical stress/strain calculations also shed light on the impact of defects on the mechanical properties of UO2/MOX.

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Wednesday – 15th September 2021
Laura Swansbury