Numerical simulation of reactive processes in an experiment with partially saturated bentonite.
Bentonites are preferred materials for use as engineered barriers for high-level nuclear waste repositories. Simulation of geochemical processes in bentonite is therefore important for long-term safety assessment of those repositories. In this work, the porewater chemistry of a bentonite sample subject to simultaneous heating and hydration, as studied by Cuevas et al. [Cuevas, J., Villar, M., Fernández, A., Gómez, P., Martín, P., 1997. Porewaters extracted from compacted bentonite subjected to simultaneous heating and hydration. Applied Geochemistry 12, 473-481.], was assessed with a non-isothermal reactive transport model by coupling the geochemical software PHREEQC2 with the object-oriented FEM simulator GeoSys/RockFlow. Reactive transport modelling includes heat transport, two-phase flow, multicomponent transport and geochemical reactions in the liquid phase, i.e. ion exchange, mineral dissolution/precipitation and equilibrium reactions. Simulations show that the easily soluble minerals in bentonite determine the porewater chemistry. Temperature affects both two-phase flow and geochemical reactions. Porosity change due to dissolution/precipitation is low during the experiment. However, changes of the effective porosity caused by bentonite swelling can be very large. The simulated results agree well with the experimental data.
Xie
Mingliang
M
Center for Applied Geoscience, Chair of GeoSystemsResearch, University of Tübingen, Sigwartstr. 10. D-72076 Tübingen, Germany. mingliang.xie@uni-tuebingen.de
Bauer
Sebastian
S
Kolditz
Olaf
O
Nowak
Thomas
T
Shao
Hua
H
D001546:Bentonite / Q000737:chemistry*; D002021:Buffers; D011232:Chemical Precipitation; D003198:Computer Simulation; D006358:Hot Temperature; D007474:Ion Exchange; D008962:Models, Theoretical; D010539:Permeability; D016062:Porosity; D011850:Radioactive Waste; D012995:Solubility; D018505:Waste Management / Q000379:methods; D014872:Water Movements
D002021:Buffers; D011850:Radioactive Waste; D001546:Bentonite