Mixtures of simulated Hanford low-activity aqueous waste and glass precursor additives were heat treated at various temperatures up to 1000°C and characterized using X-ray diffraction, X-ray fluorescence spectroscopy, scanning electron microscopy, gas chromatography mass spectroscopy, and inductively coupled plasma – mass spectroscopy. It was found after heating the simulant mixture up to 700°C, the majority of the sodium nitrite present in the original waste reacted with the silica and perhaps boron species in the additives to form C– and N-containing gases, oxygen gas, and lower melting phases which contributed to the observed batch volume expansion beginning at these temperatures. Elemental analyses of minor components in the simulant mixture showed that I, Cl, and S exhibited significant losses during heating, presumably due to volatilization or entrainment. For the case of I, nearly 90% on an elemental basis was lost from the simulant mixture after processing to 1000°C, whereas Re exhibited less than 40% loss.