To save content items to your account,
please confirm that you agree to abide by our usage policies.
If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account.
Find out more about saving content to .
To save content items to your Kindle, first ensure email@example.com
is added to your Approved Personal Document E-mail List under your Personal Document Settings
on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part
of your Kindle email address below.
Find out more about saving to your Kindle.
Note you can select to save to either the @free.kindle.com or @kindle.com variations.
‘@free.kindle.com’ emails are free but can only be saved to your device when it is connected to wi-fi.
‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.
95Mo magic-angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy is surprisingly sensitive to the local environment of tetrahedral molybdate species. A series of compounds related to expected crystallization products in nuclear waste glasses are probed to calibrate their spectral characteristics. Glasses formed with fast and slow quenching show a glassy peak corresponding to tetrahedral molybdate species. With slow quenching, a prominent sharp peak is observed, representing crystallinity. In sodium-borosilicate glasses with 2.5 mol% MoO3, the sharp peak corresponds to pure crystalline sodium molybdate. Cesium-sodium and lithium-sodium borosilicate glasses with Mo show crystalline peaks as well, and suggest that NMR may potentially be used to characterize mixed-cation molydates and more complex phase assemblages. While precise quantification of Mo in different phases is likely to be time-consuming, reasonable estimates can be obtained routinely, making 95Mo MAS NMR a useful tool for investigating phase separation and crystallization in model nuclear waste materials.
In the characterisation of amorphisation or local disordering due to actinide radiation damage, nuclear magnetic resonance (NMR) spectroscopy is attractive because it is element specific and equally sensitive to local structure in crystalline and amorphous materials. Here, we have applied high-resolution solid-state NMR spectroscopy (magic-angle spinning) to radiation damaged natural minerals containing 238U/232Th to determine the ‘number fraction’ of amorphous material (fa) through spin-counting techniques. In samples with a known alpha dose, the number of atoms displaced per alpha decay may be determined from an integration of the spectrum. A protocol for performing similar radiological magic-angle spinning experiments on plutonium containing ceramic samples with an activity of > 5 GBq isp described. Results obtained have allowed data from ancient, radiation damaged mineral samples of ZrSiO4 (238U/232Th) to be compared with modern 238/239Pu doped ceramic ZrSiO4 samples. The number of atomic displacements per alpha particle from 239Pu is similar to that for 238U/232Th (4980 ± 300/α). At lower ?-doses there are significant differences in the amorphous volume fraction (observed by density and x-ray diffraction) and the number fraction of displaced atoms (as measured by NMR) as a function of cumulative dose. These differences arise from local density considerations that manifest themselves in the local structure of the amorphous and crystalline phases. Using ab initio simulations of the damaged crystalline and amorphous regions, the magnetic response of these structures and hence the NMR shifts can be compared with experiment to reveal the nature of radiation induced changes occurring at the local scale.
Email your librarian or administrator to recommend adding this to your organisation's collection.