Kinetics of surface-layer formation on simulated nuclear waste glass

Waste glass immersed in water at high temperatures and pressures rapidly develops a surface layer. The growth of this layer was followed semiquantitatively using an optical interference technique. Growth rates were measured as a function of temperature and pressure in distilled water and 1% NaCl solution. Pressures of 25 to 85 x 105 Pa had no measurable effect at 2000C on glass immersed in water. At a pressure of 25 x 105 Pa the growth rate increased with temperature in both water and salt solution. The rates were described in terms of activation energies (83.4 kJ/mol for water and 53.0 for salt solution) with approximately equal rates in both solutions at 2400C. The rates of growth were linear in all cases. The surface layer began to exhibit cracks when its thickness exceeded approx. = 2.5 μm and it eventually spalled