Fabrication and characterization of MCC approved testing material: ATM-11 glass

ATM-11 glass is designed to be representative of defense high-level waste glasses that will be produced by the Defense Waste Processing Facility at the Savannah River Plant in Aiken, South Carolina. It is representative of a 300-year-old nuclear waste glass and was intended as a conservative compromise between 10-year-old waste and 1000-year-old waste. The feedstock material for this glass was supplied by Savannah River Laboratory, Aiken, SC, as SRL-165 black frit to which was added Ba, Cs, Mo, Nd, Ni, Pd, Rb, Ru, Sr, Te, Y, and Zr, as well as 241Am, 237Np, /sup 239+240/Pu, 151Sm, 99Tc, and depleted U. The glass was melted under the reducing conditions that resulted from the addition of 0.7 wt% graphite during the final melting process. Nearly 3 kg of ATM-11 glass were produced from a feedstock melted in a nitrogen-atmosphere glove box at 12500C in Denver Fire Clay crucibles. After final melting, the glass was formed into stress-annealed rectangular bars 1.9 x 1.9 x 10 cm nominal size. Twenty-six bars were cast with a nominal weight of about 100 g each. The analyzed composition of ATM-11 glass is tabulated. Examination of a single transverse section from one bar by reflected light microscopy showed random porosity estimated at 0.4 vol% with nominal pore diameters ranging from ∼5 μm to 175 μm. A distinct randomly distributed second phase was observed at a very low concentration in the glass matrix as agglomerated, metallic-like clusters. One form of the aggregates contained mainly a high concentration of iron, while a second form had regions of high nickel concentration, and of high palladium concentration. All aggregates also contained a low concentration of technetium and/or ruthenium. An autoradiograph of the sample provided an indication of the total radionuclide ditribution. X-ray diffraction analysis of this same sample indicates that the glass probably contained 5 wt% crystalline material