Colloid Formation and Migration (CFM) Phase 1

The sealing of the tunnel surface was one of the major experimental tasks in Phase I and was accomplished through the installation of a steel tunnel-packer (6 m long and 3.5 m in diameter), fondly referred to as the CFM "yellow submarine".

A series of preparation tracer tests have been performed within the shear zone to evaluate suitable flow fields for the colloid migration experiment, namely:

• Assessment of advective travel times
• Assessment of recovered tracer mass
• Estimation of dispersion parameters in the shear zone flow fields

A laboratory group and a modelling group were established within the framework of the CFM project.

The CFM laboratory group is working on the following issues:
Colloid generation (physical erosion, geochemical alteration etc.)
Colloid transport/retardation and stability (filtration effects, sedimentation, groundwater chemistry)
Radionuclide association (colloid-RN binding, reversibility, radio-colloids)
Bentonite intercomparison (MX-80, Febex, Kunigel)

The CFM modelling group has focussed its activities on:

• Supporting the in situ tests
• Initiating PA relevant studies on colloid generation and on colloid-facilitated radionuclide transport (including irreversibility of sorption and matrix diffusion/filtration effects)

The next step in the CFM project is the detailed planning of the bentonite/tracers/radionuclide emplacement at the start of Phase II in 2008.