Abstract
This report describes the modelling of break-through curves from a series of two-tracer dynamic infiltration experiments, which are intended to complement larger scale experiments at the Nagra Grimsel Test Site. The tracers are {sup 82}Br, which is expected to be non-sorbing, and {sup 24}Na, which is weakly sorbing. The {sup 24}Na concentration is well below the natural Na concentration in the infiltration fluid, so that sorption on the rock is governed by isotopic exchange, exhibiting a linear isotherm. The rock specimens are sub-samples (cores) of granodiorite from the Grimsel Test Site, each containing a distinct shear zone. Best-fits to the break-through curves using single-porosity and dual-porosity transport models are compared and several physical parameters are extracted. It is shown that the dual-porosity model is required in order to reproduce the tailing part of the break-through curves for the non-sorbing tracer. The single-porosity model is sufficient to reproduce the break-through curves for the sorbing tracer within the estimated experimental errors. Extracted K{sub d} values are shown to agree well with a field rock-water interaction experiment and in situ migration experiments. Static, laboratory batch-sorption experiments give a larger K{sub d}, but this difference could be explained by the larger surface area available
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Smith, P A
[1]
- Paul Scherrer Inst. (PSI), Villigen (Switzerland)
Citation Formats
Smith, P A.
Modelling of laboratory high-pressure infiltration experiments.
Switzerland: N. p.,
1992.
Web.
Smith, P A.
Modelling of laboratory high-pressure infiltration experiments.
Switzerland.
Smith, P A.
1992.
"Modelling of laboratory high-pressure infiltration experiments."
Switzerland.
@misc{etde_10157662,
title = {Modelling of laboratory high-pressure infiltration experiments}
author = {Smith, P A}
abstractNote = {This report describes the modelling of break-through curves from a series of two-tracer dynamic infiltration experiments, which are intended to complement larger scale experiments at the Nagra Grimsel Test Site. The tracers are {sup 82}Br, which is expected to be non-sorbing, and {sup 24}Na, which is weakly sorbing. The {sup 24}Na concentration is well below the natural Na concentration in the infiltration fluid, so that sorption on the rock is governed by isotopic exchange, exhibiting a linear isotherm. The rock specimens are sub-samples (cores) of granodiorite from the Grimsel Test Site, each containing a distinct shear zone. Best-fits to the break-through curves using single-porosity and dual-porosity transport models are compared and several physical parameters are extracted. It is shown that the dual-porosity model is required in order to reproduce the tailing part of the break-through curves for the non-sorbing tracer. The single-porosity model is sufficient to reproduce the break-through curves for the sorbing tracer within the estimated experimental errors. Extracted K{sub d} values are shown to agree well with a field rock-water interaction experiment and in situ migration experiments. Static, laboratory batch-sorption experiments give a larger K{sub d}, but this difference could be explained by the larger surface area available for sorption in the artificially crushed samples used in the laboratory and by a slightly different water chemistry. (author) 13 figs., tabs., 19 refs.}
place = {Switzerland}
year = {1992}
month = {Feb}
}
title = {Modelling of laboratory high-pressure infiltration experiments}
author = {Smith, P A}
abstractNote = {This report describes the modelling of break-through curves from a series of two-tracer dynamic infiltration experiments, which are intended to complement larger scale experiments at the Nagra Grimsel Test Site. The tracers are {sup 82}Br, which is expected to be non-sorbing, and {sup 24}Na, which is weakly sorbing. The {sup 24}Na concentration is well below the natural Na concentration in the infiltration fluid, so that sorption on the rock is governed by isotopic exchange, exhibiting a linear isotherm. The rock specimens are sub-samples (cores) of granodiorite from the Grimsel Test Site, each containing a distinct shear zone. Best-fits to the break-through curves using single-porosity and dual-porosity transport models are compared and several physical parameters are extracted. It is shown that the dual-porosity model is required in order to reproduce the tailing part of the break-through curves for the non-sorbing tracer. The single-porosity model is sufficient to reproduce the break-through curves for the sorbing tracer within the estimated experimental errors. Extracted K{sub d} values are shown to agree well with a field rock-water interaction experiment and in situ migration experiments. Static, laboratory batch-sorption experiments give a larger K{sub d}, but this difference could be explained by the larger surface area available for sorption in the artificially crushed samples used in the laboratory and by a slightly different water chemistry. (author) 13 figs., tabs., 19 refs.}
place = {Switzerland}
year = {1992}
month = {Feb}
}