Influence of temperature and flow rate on alteration layer structure and leaching properties of simulated sulfur-containing borosilicate HLW glass under multi-field coupling effects

During long-term deep geological disposal process, high-level liquid waste (HLW) glass may be exposed to "Thermodynamics-Hydrodynamics-Mechanics-Chemistry" (THMC)multi-field coupling effects. The leaching properties of sulfur-containing borosilicate HLW glass at different temperatures (40-150 degrees C) and different flow rates (0.01-0.10 mL/min) under THMC coupling effects were studied in this work. The alteration layer structure of waste glass surface was also characterized. The results show that honeycomb-shaped phyllosilicate alteration layer forms after leaching in simulated groundwater and white block-shaped BaSO4 4 crystals appear on the glass surface at 90 degrees C after 28 d. The amount of BaSO4 4 crystals increases obviously at 150 degrees C. The leaching rates of B, Si, Cs and U elements increase with increasing temperature and flow rate. Particularly, the leaching rates of B, Si, Cs, and U under THMC coupling effects (90 degrees C, 0.01 mL/min, 10 MPa, pH=8.05) after 28 d in the simulated groundwater are 1.10 x 10-1, -1 , 1.73 x 10-1, -1 , 2.91 x 10-1, -1 , 3.79 x 10-1 -1 g center dot m-2 center dot d-1,-2 center dot d-1 , respectively.