Colloid and Radionuclide Retardation (CRR) - Experimental Approach Phase 2

CRR Phase 2 activities

Task 5
More detailed hydraulic and tracer tests with radionuclides and bentonite colloids were conducted in the test shear zone at the Grimsel Test Site (GTS). The test equipment was modified in order to minimise radionuclide sorption and flow field disturbances during injection, long term sampling and monitoring.

Task 6
Data interpretation and modelling of field and laboratory experiments lead to a continuous updating of the conceptual model generated during Phase 1. Testing (and further development) of different reactive transport codes and thermodynamic and kinetic databases continue. This allows an assessment of both the applicability of the tested codes to in-situ conditions and the transferability of data from the laboratory to the field.

Task 7
As with previous active experiments in Grimsel, radioprotection was taken into account and discussed with HSK.

Task 8
During the period of each tracer test, water samples have been collected for radionuclide and colloid analyses. A certain amount of radionuclide and colloid analyses were carried out in real time to allow an up-to-the-minute overview of the test, but the major proportion of the analysis was conducted later in the laboratory.

Task 9
The in-situ injection consisted of two down hole injections of radionuclides with

i) Grimsel groundwater and
ii) Grimsel groundwater with bentonite colloids.

The tracer was injected as a pulse and the concentrations of some of the injected radionuclides and bentonite colloids at the outlet have been monitored on-line until the concentrations of radionuclides and colloids drop below detection limits.

Task 10
Supporting laboratory experiments (e.g. column experiments) are still carried out within Phase 2 in order to investigate kinetic effects on the sorption and reversibility of the sorption of the radionuclides onto the bentonite colloids.

Task 11
Excavation of the flow field was not performed as the remaining radionuclide concentration in the flow field was too low (the recovery was partly increased due to the presence of the colloids too).

Task 12
Radiochemical and surface analysis not performed as no overcoring was done

Task 13
Documentation / reporting


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.