Evaluating thermal stability of rare-earth containing wasteforms at extraordinary nuclear disposal conditions

The thermal stability and crystallization behaviors of La2O3 containing B2O3-CaO–Al2O3 glass waste forms were investigated to evaluate the stability of waste form during emergencies in deep geological disposal. For glasses containing 15% La2O3, LaBO3 phases were observed as major crystals from 780 °C and exhibited needlelike structures. Al, Ca, and O were homogeneously distributed throughout the entire specimen, while some portions of B and La were concentrated in some parts. By differential thermal analysis at various heating rates, the activation energy for grain growth and the crystallization rate of LaBO3 were calculated to be 12.6 kJ/mol and 199.5 kJ/mol, respectively. These values are comparable to other waste forms being developed for the same purpose.