The Grimsel Migration experiment: field injection-withdrawal experiments in fractured rock with sorbing tracers

摘要

In the framework of the Migration Experiment at the Grimsel Test Site, Switzerland, breakthrough experiments with a conservative tracer, uranine, and sorbing cationic γ-emitting radionuclides(~22,24Na~+, ~85Rb~+, and ~137Cs~+)were carried out to test models of radionu- clide migration in the field. An array of bore holes drilled from an experimental drift penetrated a transmissive, water-saturated shear zone in a granodiorite. The shear zone consists of a set of fractures filled with a fine-grained porous fault gouge. A two bore hole injection-withdrawal ('dipole')flow field was superimposed on the natural hydraulic gradient and two different linear flow distances, 1.7and 4.9 m, were studied in detail.