The Study of Pre-Oxidation and Low Temperature Sintering Mechanism to Uo_2+x Pellets

Abstract:

Uranium dioxide powders were surface pre-oxidation treated. Phases and properties of the powders after pre-oxidation treatment were investigated by DSC-TG、XRD、BET and Dilatometer. The results show that there is a little of U₃O₇ in uranium dioxide powders by pre-oxidation treatment at 240°C for 8h in air, UO₂ powders will transform into U₃O₈ at 382°C for 8h in air. The shrinkage temperature of the uranium dioxide pellets after pre-oxidation treatment decreased from 1200°C to 580°C, densification rate (ΔL/L) increased also from 1.52×10^-4/K to 3.08×10^-4/K. The mechanism of low temperature sintering to pre-oxidation UO_2+x pellets was explained by simplified point defect model and densification equation. The UO_2+x diffusion coefficient, , is much higher than which of UO₂. The densification equation is expressed by , and the factor A is according to , a=16.23658, b=0.04247 and c=-2.18802×10^-5.

• Periodical: Advanced Materials Research (Volume 1053)
• Pages: 80-86
• DOI: https://doi.org/10.4028/www.scientific.net/AMR.1053.80
• Online since: October 2014
• Authors: Rui Li
• Keywords: Densification Mechanism, Hyper-Stoichiometry, Low Temperature Sintering, Point Defect Model, Surface Pre-Oxidation, Uranium Dioxide

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