Speaker
Prof.
Nicolas DACHEUX
(University of Montpellier)
Description
Due to the concomitant formation of oxygen vacancies in the fluorite structure, it was found that the incorporation of trivalent lanthanide elements in ThO2 or CeO2 strongly affect their chemical durability during dissolution or leaching tests [1-4]. On the contrary, the impact of such elements on the dissolution of UO2 remains largely unknown. For this purpose, several lanthanide – uranium mixed based samples incorporating 1 to 20 mol.% of a mixture of lanthanide elements (with the mole ratio : 13 % La ; 7.4 % Y ; 25.6 % Ce ; 12 % Pr ; 42 % Nd) were prepared through quantitative oxalate precipitation. After conversion to the final oxides then sintering, they were characterized from chemical and microstructural points of view and finally submitted to multiparametric dissolution tests in several nitric acid solutions and at various temperatures. Contrarily to Th- and Ce-based mixed oxides, the presence of lanthanide elements in UO2 did not affect significantly the normalized dissolution rates in concentrated nitric acid solutions (C > 1M). On the contrary, the effect was more important in less concentrated solutions (e.g. a factor or 100 compared to pure UO2 observed in 0.5M HNO3) when the role of surface-controlling reactions on the overall dissolution become predominant. Such observations related to the macroscopic description of the dissolution were connected to in operando following of the evolving solid/liquid interface that underlined the preferential dissolution of lanthanide enriched grain boundaries and triple junctions.
1. Horlait, D. et al., Inorg. Chem., 51, 3868-3878, 2012
2. Horlait, D. et al., J. Nucl. Mater., 429, 237-244, 2012
3. Horlait, D. et al., J. Mater. Chem. A, 2, 5193-5203, 2014
4. Claparede, L. et al., Inorg. Chem., 50, 11702-11714, 2011
Primary author
Prof.
Nicolas DACHEUX
(University of Montpellier)
Co-authors
Dr
Claire Lavalette
(AREVA NC / BG aval)
Dr
Laurent Claparede
(University of Montpellier)
Dr
Renaud Podor
(ICSM)
Dr
Stéphanie Szenknect
(ICSM)
Dr
Theo Cordara
(ICSM)
Dr
adel mesbah
(ICSM Marcoule, France)
