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

抄録

Lead-iron phosphate (LIP) glasses loaded with a simulated high-level nuclear waste wen. 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 15w/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 35w/0 enabled it to produce the glass form with the waste near 20w/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 considerably both the leach rate and the thermal stability of the LIP glass waste form.