Colloid and Radionuclide Retardation (CRR) - Experimental Approach Phase 1

CRR Phase 1 activities

Task 1: Preliminary calculations/review

  • 1a Solubility, speciation and retardation of dissolved radionuclides in the experimental shear zone were predicted by means of geochemical and coupled (geochemical / transport) codes.
  • 1aa Microbial surface complexion modelling.
  • 1b The stability of 'near-field' colloidal suspensions in different types of bentonite/host rock interface groundwaters was predicted (see also Task 2). Existing data on natural colloid populations at the site were evaluated.
  • 1c The stability of radiocolloids was predicted (literature study).
  • 1d Calculations of the flow-field conditions and transport simulations, based on different flow field geometries, were carried out.

Task 2: Detailed & long-term laboratory experiments

  • 2a In-situ solubility of radionuclides was determined from batch experiments. Kd values for the radionuclides were determined in Grimsel groundwater in contact with different solids.
  • 2b The stability of near-field derived colloids (e.g. bentonite colloids) in the experimental shear zone was assessed.
  • 2c The stability of radiocolloids was investigated in the lab, involving batch experiments with ZrO2.
  • 2d Flow and transport in simulated or actual shear zone core, investigating dissolved solute, colloid, and rock interactions over time periods comparable to the duration of the field test, were initiated.
  • 2e The interaction of tracers with the downhole equipment was tested.
  • 2f On-line colloid detection of colloids was refined.

Task 3: Field work

  • 3a New boreholes were drilled into the MI shear zone and hydraulic and uranine tracer tests were performed.
  • 3b Groundwater samples for microbial identifications were taken and analysed.
  • 3c In-situ water sampling was carried out in order to better define the natural colloid population of the Grimsel groundwater.

Task 4: Conceptual modelling

  • 4 Existing data on the shear zone flow system are integrated with the Phase I results to define the detailed design for the in-situ test. The conceptual model will be continuously updated and revised as new data are generated in the field and in the laboratory.


Colloid and Radionuclide Retardation Experiment - Experimental Approach

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.