The experiments performed for this research were completed to produce solid
cerium oxide microspheres by an internal gelation sol-gel process. The motivation for
this work was to develop a process that would enable the fabrication of a storage or
transmutation form for the plutonium and transuranics (TRU) from the Uranium
Extraction Plus (UREX ) used fuel reprocessing process. This process is being
investigated by the Department of Energy (DOE) and the Advanced Fuel Cycles
Initiative (AFCI) through the Nuclear Energy Research Initiative.
The internal gelation production of cerium oxide involves the combination of
hexamethylenetetramine (HMTA), urea, and cerium nitrate solutions at ~100oC.
Microspheres were produced by injection of a broth solution into a flowing stream of hot
silicone oil. The captured microspheres were aged, washed, and then underwent
Thermogravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC), and XRay
Diffraction (XRD) analysis. The process variables examined in this study include
the concentrations of HMTA, urea and cerium nitrate, the process temperature, the postgelation
aging time, and the product washing conditions. Over a series of 70 experiments, it was determined that a broth solution
containing a mixture of 1.45 M cerium nitrate and 1.65 M HMTA and urea (1:1 ratio)
solutions produced the best cerium oxide microspheres. The spheres were aged for 30 to
60 minutes and then washed in hexane to remove the silicone oil and a subsequent series
of ammonium hydroxide washes to remove unreacted product and to fully gel the
microspheres.
Through DSC analysis it was determined that excess wash or unreacted product
may be removed by an exothermic reaction at approximately 200oC. The XRD analysis
of unheated spheres showed the presence of cerium oxide with additional cerium-bearing
organics. Following heating, the microspheres were completely converted to cerium
oxide.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/ETD-TAMU-2008-12-83 |
| Date | 14 January 2010 |
| Creators | Wegener, Jeffrey J. |
| Contributors | McDeavitt, Sean M. |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Thesis |
| Format | application/pdf |
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