Notice Board

The Department of Chemistry &  Biochemistry Presents: 

Dr. Scott Kroeker

Department of Chemistry
University of Manitoba

Through a Glass Darkly:  How NMR Spectroscopy is Improving Nuclear Waste Disposal

 Thursday, Oct. 6, 2016

12:15 – 1:30pm
C610, UHall

All are Welcome

Nuclear fission offers a valuable alternative to fossil fuels for power generation. However, waste immobilization is a complicated problem which demands highly durable wasteforms capable of retaining radioactive ions for up to a million years. Borosilicate glasses are used worldwide for this purpose but waste loading is limited by the solubility of ions such as molybdenum and chromium. Due to the large number of components in typical waste streams, the precipitated phases vary in composition and structure, limiting the applicability of diffraction methods. This presentation will illustrate the use of multinuclear magnetic resonance spectroscopy in the study of complex heterogeneous inactive nuclear waste materials containing up to 20 oxide components. These phase assemblages contain mixed-alkali compounds and substitutionally disordered chromates and 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 in geologic repositories.

 Scott Kroeker is a Professor of Chemistry at the University of Manitoba. His NMR-centred research program focuses on the characterization of disordered inorganic solids. He gained his first exposure to magnetic resonance during his undergraduate degree at the University of Winnipeg, where he did medical research using in vivo MR imaging and spectroscopy. His master’s degree was carried out under the tutelage of Ted Schaefer, where he used ultrahigh-resolution NMR spectroscopy and MO calculations to study the conformational behaviour of benzene derivatives in solution. His Ph.D. in Physical and Theoretical Chemistry was obtained from Dalhousie University in 1999 in the solid-state NMR research group of Roderick Wasylishen. After an NSERC PDF at Stanford University in the Department of Geological and Environmental Sciences studying glasses and minerals with Jonathan Stebbins, he took up an Inorganic Chemistry faculty position at the University of Manitoba in 2001. Since then he has developed a research program focusing principally on the structure of oxide glasses for applications including solid-state electrolytes, non-linear optics and nuclear waste disposal. He is a founding member of the Manitoba Institute of Materials and works closely with the National Ultrahigh-Field NMR Facility for Solids. As an EPSRC visiting professor at the University of Cambridge (2007-08), he became interested in high-temperature NMR spectroscopy and recently returned from a research fellowship at Le Studium Institute of Advanced Studies in Orléans (2015-16) doing in situ NMR at CEMHTI (Conditions Extrême et Materiaux: Haute Température et Irradiation).