HR: 14:55h
AN: H13I-06    [Abstracts]
TI: Coupling diffusion and high-pH precipitation/dissolution in the near field of a HLW repository in clay by means of reactive solute transport models
AU: * Samper, J
EM: jsamper@udc.es
AF: University of La Coru¤a, Campus Elvi¤a s/n , La Coru¤a, 1592 Spain
AU: Font, I
EM: IFOH@enresa.es
AF: ENRESA, C/ RamĦrez de Arellano 15, Madrid, 28043 Spain
AU: Yang, C
EM: yang@iccp.udc.es
AF: University of La Coru¤a, Campus Elvi¤a s/n , La Coru¤a, 1592 Spain
AU: Montenegro, L
EM: montenegro@iccp.udc.es
AF: University of La Coru¤a, Campus Elvi¤a s/n , La Coru¤a, 1592 Spain
AB: The reference concept for a HLW repository in clay in Spain includes a 75 cm thick bentonite buffer which surrounds canisters. A concrete sustainment 20 cm thick is foreseen between the bentonite buffer and the clay formation. The long term geochemical evolution of the near field is affected by a high-pH hyperalkaline plume induced by concrete. Numerical models of multicomponent reactive transport have been developped in order to quantify the evolution of the system over 1 Ma. Water flow is negligible once the bentonite buffer is saturated after about 20 years. Therefore, solute transport occurs mainly by diffusion. Models account for aqueous complexation, acid-base and redox reactions, cation exchange, and mineral dissolution precipitation in the bentonite, the concrete and the clay formation. Numerical results obtained witth CORE2D indicate that the high-pH plume causes significant changes in porewater chemistry both in the bentonite buffer and the clay formation. Porosity changes caused by mineral dissolution/precipitation are extremely important. Therefore, coupled modes of diffusion and reactive transport accounting for changes in porosity caused by mineral precipitation are required in order to obtain realistic predictions.
DE: 5114 Permeability and porosity
DE: 1829 Groundwater hydrology
DE: 1832 Groundwater transport
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting