Image analysis study of crystallization in two glass compositions of nuclear interest

Few prior studies of the crystallization properties of nuclear glass compositions have focused on the quantification of crystallization rates and the kinetics associated with heat treatments. We have quantified the crystallization of both apatite and powellite in two glass compositions containing simulated fission products using an image analysis technique based on SEM images. Samples are first heat treated at different temperatures (from 600 to 900 °C) and for different durations (from 1 h to 388 h). SEM images are then acquired and the image analysis technique is applied to quantify crystallization by extracting a few relevant crystal morphological parameters. These results permit a quantitative comparison of crystallization in the two glass compositions: nature of crystals, morphologies, thermal domains of crystallization, crystallization rates and kinetics are compared. Results show that image analysis is a suitable method when crystals are homogeneously distributed in the glass matrix. However, this technique should be used carefully in the case of a heterogeneous distribution of crystals in the material.