Sulphur Systematics In Model Glass Compositions From West Valley

An attempt was made to optimise the redox conditions required for solubilising sulphates during glass melting for West Valley nuclear waste processing. Powdered NiS and Na2SO4 were added to two different frits. Recox state of each glass was monitored by measuring its Fe2+/Fe3+ ratio. In this sample, Ni was the dominant transition metal in the sulphide phase, but more Fe was included under low oxygen fugacity. Fe redox ratio was found to saturate at 1-3 under reducing conditions at melting temperatures of 1050-1250 deg C. Na2SO4 was added to assure an immiscible sulphate layer and thereby impose a processing constraint.