Diffusion in amorphous chromia doped uranium dioxide

Megan Owen1

M.J.D. Rushton1, L.J. Evitts1, A.Claisse2, M.Puide2, W.E. Lee1, and S.C. Middleburgh1

1Bangor University
2Westinghouse Electric Sweden Ltd.

Grain boundaries in UO₂ may become amorphous in nature, as additives migrate to the more favourable grain boundaries. Additives such as Cr₂O₃ and Al₂O₃ are initially added to the fuel to promote grain growth during sintering, increasing the burn-up of the fuel pellet. Other advantages of additives include reducing fission gas release and pellet-cladding mechanical interaction [1]. The impacts of diffusion along amorphous doped UO₂ grain boundaries differ dependent on temperature, with low temperature diffusion (< 1200 °C) controlling the creep rate, and higher temperature diffusion (> 1200 °C) impacting grain interchanges, impurity diffusion, and grain boundary pinning [2]. This work focuses on modelling the diffusivity of constituent species of Cr₂O₃ doped amorphous UO₂ at a range of concentrations and temperatures. Results from this work can provide a further understanding to amorphous doped UO₂ grain boundaries, and how additives have an impact on the mechanical properties of the fuel pellet.

[1] T. Matsuda, Y. Yuasa, S. Kobayashi, and M. Toba, “Characteristics of Fuel Pellet with Additive of Al and Si.” Nuclear Fuel Industries Ltd., Osaka.
[2] A. A. Solomon, C. S. Yust, and N. H. Packan, “Primary creep of UO₂ and the effect of amorphous grain boundary phases,” J. Nucl. Mater., vol. 110, no. 2–3, pp. 333–342, 1982, doi: 10.1016/0022-3115(82)90163-5.

Event Timeslots (1)

Wednesday – 15th September 2021
Megan Owen