Atomistic simulations of void migration under thermal gradient in UO2
It is well known that within a few hours after startup of a nuclear reactor, the temperature gradient within a fuel element causes migration of voids radially inwards to form a central hole. To understand the atomic processes that control this migration of voids, we performed molecular dynamics (MD) simulations on single crystal UO2 with voids of diameter 2.2 nm. An external temperature gradient was applied across the simulation cell. At the end of the simulation run, it was observed that the voids had moved towards the hot end of the simulation cell. The void migration velocity obtained from the simulations was compared with the phenomenological equations. Surface diffusion of the slowest moving specie, i.e., uranium, was found to be the dominant mechanism for void migration. The contribution from lattice diffusion and thermal stress gradient to the void migration was analyzed and found to be negligible. By extrapolation, a crossover from the surface-diffusion controlled mechanism to the lattice-diffusion controlled mechanism was found to occur for voids with sizes in the ?m range.
- Research Organization:
- Idaho National Laboratory (INL)
- Sponsoring Organization:
- DOE - NE
- DOE Contract Number:
- AC07-05ID14517
- OSTI ID:
- 970633
- Report Number(s):
- INL/JOU-09-17004
- Journal Information:
- Acta Materialia, Journal Name: Acta Materialia Journal Issue: 1 Vol. 58; ISSN 1359-6454; ISSN ACMAFD
- Country of Publication:
- United States
- Language:
- English
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