Peter C. Burns
Nuclear materials used in weapons carry detectable chemical and isotopic signatures that may be useful for attribution. We are developing approaches for characterizing material that results from a nuclear weapon blast (post-detonation debris) so that it will be possible to determine the type of device used and its origin.
Our long-standing interest in the crystal chemistry of actinide compounds, especially U(VI) and Np(V) inorganic compounds, has lead us to focus attention on cation-cation interactions. In actinide chemistry, a cation-cation interaction is said to occur when an actinyl O atom of a given actinyl ion coordinates a second actinyl ion. These are common for Np(V), but much less so for U(VI). Where they do occur, they result in more framework structures with denser packing, and unusual materials properties.
We are interested in the complex topologies of inorganic actinide compounds, and specifically how the various structural units and interstitial complexes combine to form a wide range of natural and synthetic materials. We have arranged U(VI), Np(V) and Np(VI) compounds into structural hierarchies based on structural units, and developed graphical and anion-topology approaches to study their relationships.
We study uranium mineralogy and crystallography, as well as general mineralogy of interesting mineral groups. Our emphasis is on the structures, compositions, and occurrences of minerals, and relating the crystal structures to stabilities and mineral occurrences.
Our research focuses on several aspects of actinides, including their materials science, mineralogy, geochemistry, environmental transport, nanoscale control, and aspects of national security. We study natural uranium and thorium minerals, and a broad range of materials that we synthesize containing thorium, uranium, neptunium, or plutonium. We use many diffraction, scattering, and spectroscopic techniques to study actinides at various length scales.
In 2005 we discovered how to create the conditions for a complex family of nanoscale uranyl peroxide cage clusters to form spontaneously in aqueous solution. We crystallize these clusters for structure determination using X-ray diffraction, and study their properties in solution using DLS, SAXS, and ESI-MS. We have created and characterized more than 80 varieties of cage clusters that contain a broad range of chemical constituents. These clusters provide a unique and powerful means of controlling uranium in solution on the scale of several nanometers, which place them intermediate in size between solid materials and dissolved cations. Possible applications that we are developing include environmentally superior methods for nuclear fuel recycling and fabrication of nanocomposite nuclear fuels with accident resistant properties.
We are studying the inorganic controls of Np(V) mobility in the subsurface. Specifically, we are probing the extent to which Np(V) is co-precipitated into a variety of low-temperature minerals, where it can substitute at different cation sites or in interstitial locations.
Graduate Studies in Actinide Chemistry
Graduate Studies in Radiochemistry
Graduate Studies in Mineralogy
Graduate Studies in Geochemistry
Graduate Studies in Actinide Materials
Graduate Studies in Actinide Crystallography
The plastic 3D models of uranyl peroxide nanoclusters shown to the left were printed using ABS or PLA plastic and an UP! Mini, Flashforge Creator, or Makerbot Replicator 2 printer. The larger models are approximately 15 cm diameter.
Digital files were created using Crystalmaker 9.0, starting from the Crystallographic Information Files (CIF). The complete 3D computer model was exported from Crystalmaker as a DAE file, which was subsequently converted to an STL file before being imported into the printer control software.
Printing these models requires inclusion of significant supports that are removed by hand following completion. Printing a high-quality U60 model, as seen on the left, requires approximately 24 hours of printer time.
STL files are available by request (firstname.lastname@example.org)
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