Molecular dynamics simulation of energetic uranium recoil damage in zircon

R. Devanathan (1) , L. R Corrales (1) , W. J. Weber (1) , A. Chartier (2) , C. Meis (3)

1 PNNL - Pacific Northwest National Laboratory
2 CEA-DES (ex-DEN) - CEA-Direction des Energies (ex-Direction de l'Energie Nucléaire)
3 INSTN - Institut National des Sciences et Techniques Nucléaires

Defect production and amorphization due to energetic uranium recoils in zircon (ZrSiO$_4$), which is a promising ceramic nuclear waste form, is studied using molecular dynamics simulations with a partial charge model. An algorithm that distinguishes between undamaged crystal, crystalline defects and amorphous regions is used to develop a fundamental understanding of the primary damage state. The damage consists of under-coordinated Zr and polymerised Si leading to amorphization and phase separation on a nanometer scale into Zr-and Si-rich regions. This separation could play an important role in the experimentally observed formation of nanoscale ZrO$_2$ in ZrSiO$_4$ irradiated at elevated temperatures. The observed amorphisation and the associated volume expansion have the potential to enhance leaching of cations by providing diffusion pathways for cations and water molecules.

Keywords: Molecular dynamics; amorphisation; nuclear waste form; uranium

Domains: Nuclear Experiment [nucl-ex]

R. Devanathan, L. R Corrales, W. J. Weber, A. Chartier, C. Meis. Molecular dynamics simulation of energetic uranium recoil damage in zircon. Molecular Simulation, 2006, 32 (12-13), pp.1069-1077. ⟨10.1080/08927020600959929⟩. ⟨cea-02513503⟩