Characterization of phosphate glasses used in the immobilization of low-level radioactive wastes

The rate of lixiviation, thermal conductivity and mechanic resistance of several phosphate glasses (in the form of cylinders 1.8 cm diameter, 6 cm height) have been measured. The glass contains 7.3 to 34.54% of Al2O3, for simulating matrices of low level radioactive wastes (very small amounts of Hg, Fe and UO2 are also added). For the matrices which have been studied the rate of lixiviation ranges between 10-5 and 5x10-4 g cm-2 h-1, the thermal conductivity between 0.15 and 0.35 w.m-1 K-1 and the mechanic resistance between 0.26 and 0.56 J cm-2. These properties have been correlated with the conditions of melting and annealing of the glass (temperature, time, rate and cooling) and content of aluminium in the matrix. (author)