Describing oxygen self-diffusion in PuO₂ by connecting point defect parameters with bulk properties

Abstract

The description of oxygen self-diffusion over a range of temperatures and pressures is important in PuO₂ for nuclear fuel applications. Although there are limited experimental studies describing oxygen self-diffusion in PuO₂, recent molecular dynamics studies extend the temperature range significantly. In the present study elastic and expansivity data is used in the framework of a thermodynamic model (known as the cBΩ model) to derive the oxygen self-diffusion coefficient in PuO₂ in the temperature range 1800–3000 K. In the cBΩ model the defect Gibbs energy is proportional to the isothermal bulk modulus (B) and the mean volume per atom (Ω). The derived results are in good agreement with the most recent experimental and molecular dynamics data. Importantly, the present study extends the applicability of the model to nuclear fuel materials for the first time, where point defect parameters and behaviour are difficult to determine, particularly at the temperatures considered here.