Homogeneous glass processing region defined for a lanthanide borosilicate glass composition for the mobilization of plutonium using thorium as a surrogate

摘要

A ternary diagram showing the homogeneous glass processing region of a base frit, rare earth oxide and thorium oxide has been developed for a residence temperature of 1475 C. Thorium oxide was used as a plutonium surrogate. All ThO2 glasses that were processed included a 1:1 mole ratio of Th to Gd. Gadolinium is added to the glass as a neutron absorber. Forty individual glass compositions were melted at 1475 C for 4 to 6 hours with periodic stirring. Two glasses (B-20-25 and B-25-25) were processed with a ThO2 loading of 25 weight percent (oxide) without amorphous phase separation or crystalline species detected by X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) or Transmission Electron Microscopy (TEM). These were processed with 55 weight percent frit, 20 weight percent rare earth oxides and 50 percent frit, 25 percent rare earth oxides. Crystalline species that formed outside of the homogeneous glass processing region due to solubility limits or insufficient processing temperature were identified. Amorphous phase separation was detected and examined by TEM at high ThO2 loadings (20 to 30 weight percent oxide). The base frit was able to dissolve up to 65 weight percent rare earth oxides when thorium oxide was not present. Durability testing will be performed on three glasses from three different regions of the homogeneous glass processing region. Product Consistency Test (PCT) results are pending and will be added to this document under a future revision.