Solute transport in crystalline rocks at Aspo; II, Blind predictions, inverse modelling and lessons learnt from test STT1

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doi: 10.1016/S0169-7722(02)00136-5
Authors:Jakob, Andreas; Mazurek, Martin; Heer, Walter
Author Affiliations:Primary:
Paul Scherrer Institute, Waste Management Laboratory, Villigen, Switzerland
University of Bern, Switzerland
Volume Title:8th international conference on Chemistry and migration behaviour of actinides and fission products in the geosphere; Migration '01
Volume Authors:Kim, Jae-Il, editor; Geckeis, Horst
Source:Journal of Contaminant Hydrology, 61(1-4), p.175-190; 8th international conference on Chemistry and migration behaviour of actinides and fission products in the geosphere; Migration '01, Bregenz, Austria, Sept. 16-21, 2001, edited by Jae-Il Kim and Horst Geckeis. Publisher: Elsevier, Amsterdam, Netherlands. ISSN: 0169-7722
Publication Date:2003
Note:In English. 16 refs.; illus., incl. 3 tables
Summary:Based on the results from detailed structural and petrological characterisation and on up-scaled laboratory values for sorption and diffusion, blind predictions were made for the STT1 dipole tracer test performed in the Swedish Aspo Hard Rock Laboratory. The tracers used were nonsorbing, such as uranine and tritiated water, weakly sorbing 22Na+, 85Sr2+, 47Ca2+and more strongly sorbing 86Rb+, 133Ba2+, 137Cs+.Our model consists of two parts: (1) a flow part based on a 2D-streamtube formalism accounting for the natural background flow field and with an underlying homogeneous and isotropic transmissivity field and (2) a transport part in terms of the dual porosity medium approach which is linked to the flow part by the flow porosity. The calibration of the model was done using the data from one single uranine breakthrough (PDT3). The study clearly showed that matrix diffusion into a highly porous material, fault gouge, had to be included in our model evidenced by the characteristic shape of the breakthrough curve and in line with geological observations. After the disclosure of the measurements, it turned out that, in spite of the simplicity of our model, the prediction for the nonsorbing and weakly sorbing tracers was fairly good. The blind prediction for the more strongly sorbing tracers was in general less accurate. The reason for the good predictions is deemed to be the result of the choice of a model structure strongly based on geological observation. The breakthrough curves were inversely modelled to determine in situ values for the transport parameters and to draw consequences on the model structure applied. For good fits, only one additional fracture family in contact with cataclasite had to be taken into account, but no new transport mechanisms had to be invoked. The in situ values for the effective diffusion coefficient for fault gouge are a factor of 2-15 larger than the laboratory data. For cataclasite, both data sets have values comparable to laboratory data. The extracted Kd values for the weakly sorbing tracers are larger than Swedish laboratory data by a factor of 25-60, but agree within a factor of 3-5 for the more strongly sorbing nuclides. The reason for the inconsistency concerning Kds is the use of fresh granite in the laboratory studies, whereas tracers in the field experiments interact only with fracture fault gouge and to a lesser extent with cataclasite both being mineralogically very different (e.g. clay-bearing) from the intact wall rock. Abstract Copyright (2003) Elsevier, B.V.
Subjects:Alkali metals; Alkaline earth metals; Aquifers; Boreholes; Calibration; Cesium; Controls; Crystalline rocks; Cs-137; Diffusivity; Experimental studies; Granites; Igneous rocks; Isotopes; Matrix; Metals; Migration of elements; Mobility; Models; Na-22; Permeability; Plutonic rocks; Pollution; Porosity; Porous materials; Prediction; Preferential flow; Radioactive isotopes; Radioactive waste; Sodium; Solute transport; Sorption; Sr-85; Strontium; Theoretical models; Tracers; Transmissivity; Underground installations; Uranyl ion; Waste disposal; Aspo Hard Rock Laboratory; Europe; Kalmar Sweden; Scandinavia; Sweden; Western Europe
Record ID:2003043703
Copyright Information:GeoRef, Copyright 2018 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands
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