Kinetics of MgO dissolution and buffering of fluids in the Waste Isolation Pilot Plant (WIPP) repository

DOE has proposed to add MgO to backfill in the WIPP repository to stabilize pH and reduce gas pressures and spallation. Experiments show that MgO dissolution rates are proportional to surface area, nearly independent of pH, and decrease with increasing dissolved NaCl. The probably repository MgO dissolution rate will be 10 to 20 micromol m2/min. Simulations indicate that MgO dissolution will buffer pH and provide stabilizing cement; however, under highly reducing conditions MgO will not control total gas pressures. Adding oxidizing agents or materials containing oxidized species, for example anhydrite, to the backfill, might control gas pressures