Leach Rates and Thermal Properties of Lead-Iron Phosphate Glass Waste Forms

Abstract

Lead-iron phosphate (LIP) glasses loaded with a simulated high-level nuclear waste were studied on their leach rates and thermal properties. The obtained results showed that the phosphate glass matrix consisting of lead monoxide, phosphorus pentoxide and ferric oxide of 56:35:9w/0 is able to vitrify the waste, pretreated with formic acid to remove Zr, to about 15 w/0 at 950°C. The leach rate of the vitrified waste glass was in the order of 10−7 g/cm2.d at 110°C, which is low compared with that of the borosilicate glass waste form. Increasing the phosphorus pentoxide content of the matrix to higher than 35% enabled it to produce the glass form with the waste near 20 w/0 at 950°C, but this increase rendered the glass waste form more soluble than the former. Thermal properties such as thermal expansion coefficient, critical cooling rate for vitrification and temperatures of glass transition, softening and maximum rate of crystallization were measured and discussed. Removing Na ions from wastes improves consi...