Volatile Losses from Sphene Glass‐Ceramic and Borosilicate Glass Melts

Abstract

Heating experiments have been performed with titanosilicate glass melts to investigate possible losses of volatile radionuclides during preparation. The melts are precursors to sphene glass‐ceramics, the latter being candidate materials for immobilization of nuclear fuel recycle wastes. After the titanosilicate melts were heated for up to 24 h at 1300° and 1400°C, weight‐loss measurements and X‐ray fluorescence spectrometry analyses indicated that Cs, Mo, and, to a lesser extent, Na were the main contributors to the observed losses by volatilization. For comparison, similar experiments were performed with an AVM‐type borosilicate glass at temperatures of 1150° and 1250°C, when the viscosities are approximately equal to those of the titanosilicate melts at 1300° and 1400°C, respectively. The losses from the borosilicate glass were predominantly due to Na, B, Cs, and Mo volatilization and were generally higher than the corresponding losses from the titanosilicate glass, typically by factors of ∼4. Possible speciation of the volatile components in these glasses is discussed.