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Alkali borosilicate glass is used to immobilise high-level radioactive waste generated from the reprocessing of spent nuclear fuel. However, poorly soluble waste products such as molybdenum present issues for long-term storage of the material, whereby phase separation of water-soluble crystalline aggregates truncate the glass network and offer leaching opportunities for the escape of radionuclides into the environment. Solid-state NMR is an effective technique for studying the phase separation in nuclear waste glasses, as it is able to distinguish glassy and crystalline environments using nuclei-specific probes. The presence of paramagnetic transition metal cations within the waste glass compromises the efficacy of NMR, as unpaired electrons can cause broadening and chemical shift effects. This work engages in a multinuclear magnetic resonance characterisation of paramagnetically-doped (by Cr2O3, MnO2, Fe2O3, NiO, or Nd2O3) model nuclear waste glasses and explores the partitioning of transition-metal components. Characterisation of the separated heterogeneous crystalline phase was accomplished principally by 133Cs, 23Na, and 95Mo NMR, where it was determined that Cr substitutes into mixed-alkali molybdates. Furthermore, paramagnetic broadening and relaxation effects were observed and quantified by 11B and 29Si NMR.

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The purpose of this work has been the determination of structure in solids using the technique of solid-state nuclear magnetic resonance spectroscopy. High-resolution (^31) p NMR spectra have been obtained for a range of phosphate species. A number of techniques have been applied to these systems including cross-polarization, magic angle spinning, and high power proton decoupling. Characterisation using additional NMR techniques such as (^1) H cramps has been carried out wherever possible. The results obtained yield molecular and crystallographic information consistent with data from X-ray diffraction when known. Shielding tensor components were determined from static and/or spinning spectra wherever possible. The phosphate species studied include a series of precipitated calcium phosphates. A particular model for the structure of amorphous calcium phosphate is favoured in the light of (^31) p NMR measurements. One sample showed NMR evidence for changes in composition whilst in the solid state. The origins of (^31) p NMR line widths in high-resolution solid-state spectra have been considered in some detail. Variation of (^31) p NMR linewidth as function of spinning rate has been noted for a number phosphate compounds. Multiple pulse techniques have been applied on the phosphorus channel with pleasing improvements in spectral resolution. Five solid binary phosphorus sulphides have also been studied using phosphorus MAS NMR, and the results compared to solution state data wherever possible. A number of anomalies between solution and solid-state data have been noted and discussed.

The push toward higher magnetic fields in MRI has consistently thrown up new challenges in hardware development. The recent development of a new generation of ultra-high field scanners for human imaging is no exception. The earch presented in this thesis aims to provide solutions to new technical challenges in radio-frequency probe design. All probe designs were developed for use at 7T on a Philips Acheiva full body scanner.

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