Colloid Formation and Migration : I-BET (In Rock Bentonite Erosion Test)

The I-BET is part of the CFM project and will be implemented end of 2018/ beginning 2019. The project is designed to study a larger volume of bentonite in a natural flow field. It is somewhat a follow-up project of the LIT, but without any radionuclide tracers. The I-BET project is composed of a cylindrical bentonite source (compacted MX-80 bentonite) of 220 mm diameter and 1.15 m length.

The expected swelling pressure of the bentonite is around 3.7 - 4.6 MPa. The source will be emplaced as rings around a steel mandril and sealed at both ends with packers. All interfaces will be equipped with multiple sensors to monitor the swelling pressure and the water content. Furthermore, dedicated monitoring boreholes were drilled to monitor the groundwater composition around the source and detect potential bentonite erosion. In a later stage, the monitoring boreholes allow, if desired, to increase the water flow by injecting water.

The project will be implemented in an existing 220 mm diameter borehole, which was initially drilled for the JGP (JAEA Grouting Project) and later overcored as test for the LCS (Long-term Cement Studies) experiment.

Bentonite source and the mapped fractures sml 

3D picture showing the bentonite source and the fractures mapped along the surrounding boreholes. The monitoring boreholes are shown in pink.

Schematic representation of the sensor layout sml 

Schematic representation of the sensor layout on the multiple interfaces.

Borehole image of the bentonite source borehole sml 

Borehole image of the bentonite source borehole with the major fractures shown as red lines.

The GTS underground facilities are also available to interested 3rd parties for underground testing and research. The GTS offers cost-effective access to a fully developed, well characterised underground research facility with round the year logistical support - please contact Dr. Ingo Blechschmidt, Head of the Grimsel Test Site, for further details.
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