Séminaire du 10 Avril 2012 à 14H30

NMR STUDIES OF NUCLEAR WASTE MATERIALS: CUTTING THROUGH COMPOSITIONAL AND MORPHOLOGICAL COMPLEXITY

Scott KROEKER (Dept. of Chemistry, University of Manitoba, Winnipeg, Manitoba, Canada, R3T 2N2)

Salle de Conférence (401), 4ème étage, Tour 23, Couloir 22-23

IMPMC, Université P. et M. Curie, 4, Place Jussieu, 75005 Paris

Résumé :

Multinuclear magnetic resonance spectroscopy is used to identify and quantify devitrification products in heterogeneous model nuclear waste materials containing up to 19 oxide components. These complex phase assemblages contain mixed-alkali compounds and substitutionally disordered chromate/molybdates. The presence of paramagnetic ions complicates the NMR analysis but also provides valuable information about the partitioning of species amongst phases. Hydration reactions appear to play a critical role in the formation of some precipitates which may impact the long-term chemical durability of these materials. Circumventing the formation of such phases requires knowledge of the high-temperature behaviour of the melt and the formation mechanisms during cooling. High-temperature magic-angle spinning NMR is used to characterize phase transformations and reactions amongst devitrification products during cooling, under conditions mimicking those of industrial processes and long-term storage.

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