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Colloid and Radionuclide
Retardation Experiment (CRR)
Experimental Approach
Phase 2 |
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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 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
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