Mass Transfer & Porous Media (MTPM) - Andra

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P/<strong>MTPM</strong>/23HA (µg/g)3002001000(a):pH 5U (mol/g)HAU in presence of HAU in absence of HA2x10 -71x10 -700 1 2 3 4 5Distance (mm)0 1 2 3 4 53x10 -62x10 -61x10 -6Distance from the high concentration boundary (mm)0U (mol/g)Figure 1: U and HA distribution in the clay plug at pH 5 (a) and pH 7 (b). (Absence of HA: 70 d (pH 5),64 d (pH 7); presence of HA: 78 d (pH 5 and 7)).HA (µg/g)3002001000(b): pH 7U (mol/g)2x10 -62x10 -61x10 -65x10 -7HAU in presence of HAU in absence of HA00 1 2 3 4 5Distance (mm)3x10 -62x10 -61x10 -60 1 2 3 4 5Distance from the high concentration boundary (mm)0U (mol/g)The diffusing low molecular fraction of HA diffusing through the clay plug was not found to transporturanium within the experimental duration. Possibly, the uranyl humate complex dissociates in the poresystem due to competition between humate and surface complexes. Alternatively, the mobile lowmolecular HA fraction is not able to complex U(VI) due to structural and functional dissimilarities.The in-diffusion profiles of both tracers are illustrated in Fig. 1. HA is immobilized at the highconcentration boundary. In presence of HA, the U(VI) concentration is permanently lower compared to theHA free system (see insets in Fig. 1). The bulk of U(VI) is immobilized in association with HA at thesolution-clay boundary. Comparing pH 5 and pH 7, a deeper penetration of U(VI) was observed at pH 5.This is in concordance with the penetration depth of HA, the complexing agent, and U(VI) in absence ofHA. From the diffusion profiles of U(VI) in presence of HA it becomes clear that HA penetrates the claydeeper than U(VI) (see Fig. 1). This is in agreement with the observed through-diffusion behavior of thelow molecular HA fraction.The migration of HA in clay is governed by diffusion. It is influenced by the colloidal behavior of HA.At higher clay bulk densities, size fractionation affects the diffusion parameters. In presence of HA colloidsU(VI) is immobilized in association with HA near the high concentration boundary.The German Federal Ministry of Economics and Technology funded this study under contract 02E9673.The technical assistance of Ch. Müller is gratefully acknowledged.References[1] Wold, S., Eriksen, T.E. (2005) Proceedings of the 2 nd International Symposium Clays in natural andengineered barriers for radioactive waste confinement. Tours, France, 14-18 March 2005, 547.[2] Wang, X. et al. (2005) Adsorption Science and Technology , 23, 801-811.[3] Maes, N. et al. (2004) Report SCK•CEN-BLG-988. SCK•CEN, Mol, Belgium.[4] Sachs, S. et al. (2004) Report FZR-399, FZ Rossendorf, Dresden, Germany.[5] Lead, et al. (2000) Environ. Sci. Technol. 34 , 1365-1369.Page 468INTERNATIONAL MEETING, SEPTEMBER 17...>...18, 2007, LILLE, FRANCECLAYS IN NATURAL & ENGINEERED BARRIERSFOR RADIOACTIVE WASTE CONFINEMENT
P/<strong>MTPM</strong>/24DIFFUSION OF TRITIATED WATERAND IONS THROUGH THE TOURNEMIREARGILLITE (FRANCE) IN PRESENCEOF ALKALINE FLUIDSI. Devol-Brown 1 , S. Motellier 2 , E. Tinseau 1 , D. Thoby 21. Institut de Radioprotection et de Sûreté Nucléaire, DEI/SARG/LETS, B.P. 6, 92265FONTENAY-AUX-ROSES CEDEX, FRANCE2. Commissariat à l’Energie Atomique, DRT/LITEN/DTNM/L2T, 17 rue des Martyrs, 38054GRENOBLE CEDEX 9, FRANCEHigh-pH plumes arising from cementitious leachates are known to alter the mineral assemblage of clayeyformations selected to play the role of natural barriers for radioactive waste repositories. Dissolution ofconstitutive minerals such as smectite and precipitation of secondary phases such as feldspar and zeolitehave been reported [1, 2]. These mineral changes are suspected to have a significant effect upon diffusivetransport properties, either enhancing or decreasing the mudrock ability for radioelement confinement. Forinstance, experiments performed under alkaline conditions have shown a decrease in water diffusion fluxesand an increase in cation fluxes [3].This study was designed to provide better understanding of the phenomena that govern diffusion processesduring the transition between site and alkaline conditions. Experiments involving the use of “throughdiffusion”cells were performed to mimic the proceeding of an alkaline plume through different types ofclayey materials from the Tournemire experimental site (France). Three kinds of sliced rock material wereinvestigated for the diffusion of both water and major cations (sodium, potassium, calcium andmagnesium): i) an unfractured sample, ii) a sample with an opened fracture and iii) a sample with a largetectonic fracture.An equilibration procedure was required to i) (re-)saturate the rock with water and ii) force itsequilibration with a synthetic solution prior to diffusion experiments. It was performed by renewedcontacting of the clayey samples with the synthetic background solution every two weeks. Theprocedure was to be stopped when the composition of the withdrawn solution was similar to thatimposed by the synthetic solution, i.e. re-equilibration between the rock and the solution wascompleted. Once the equilibration steps completed, tritiated water (HTO) considered as a referencespecies was introduced in the upstream reservoir in order to deduce the HTO diffusion coefficientOFTFPyrite(a) (b) (c)Figure 1: Photographs of sliced samples (Ø = 6.3 cm) used in the through diffusion cells and displaying:(a) no fractures; (b) an opened fracture (OF); (c) a large tectonic fracture (TF).INTERNATIONAL MEETING, SEPTEMBER 17...>...18, 2007, LILLE, FRANCECLAYS IN NATURAL & ENGINEERED BARRIERSFOR RADIOACTIVE WASTE CONFINEMENTPage 469
Page 1: Poster [MTPM]Mass Transfer & Porous
Page 4 and 5: P/MTPM/1The free energy cost of for
Page 7 and 8: P/MTPM/3DIFFUSION OF IONS IN UNSATU
Page 9: P/MTPM/4POROUS MEDIA CHARACTERIZATI
Page 12 and 13: P/MTPM/5Oxalate ionsQuartzQuartz +P
Page 14 and 15: P/MTPM/6borehole was capped with a
Page 16 and 17: P/MTPM/7Initial state with glass an
Page 18 and 19: P/MTPM/8The mesh of the elementary
Page 20 and 21: P/MTPM/9Moreover, using another sam
Page 22 and 23: P/MTPM/10Figure 1: Horizontal cross
Page 24 and 25: P/MTPM/11n t (mol)as received8 10 -
Page 26 and 27: P/MTPM/1210,9Degree of saturation (
Page 28 and 29: P/MTPM/13RESULTSFirst, we estimated
Page 30 and 31: P/MTPM/142.5Energy (M eV)1.6 1.7 1.
Page 32 and 33: P/MTPM/15C/Co10.90.80.70.60.50.40.3
Page 34 and 35: P/MTPM/16ModelIrmayvG-M1vG-M2vG-M3T
Page 36 and 37: P/MTPM/17Figure 1: Experimental HTO
Page 38 and 39: P/MTPM/18Diffusion experiments were
Page 40 and 41: P/MTPM/19Figure 1: Used mesh for co
Page 42 and 43: P/MTPM/201.81.61.41.2upstream compa
Page 44 and 45: P/MTPM/21490Pressure [bar]0 10 20 3
Page 46 and 47: 134P/MTPM/22through-diffusion exper
Page 50 and 51: P/MTPM/24through each sample. The p
Page 52 and 53: P/MTPM/25FIRST RESULTSPreliminary c
Page 54 and 55: P/MTPM/26heterogeneous distribution
Page 56 and 57: P/MTPM/27Relative concentration (C-
Page 58 and 59: P/MTPM/280.75m0.25mTable 1: Cross s
Page 60 and 61: P/MTPM/29Figure 1: A. Scheme of the
Page 62 and 63: P/MTPM/30The presented theory is ex
Page 64 and 65: P/MTPM/31Furthermore, Van Loon et a
Page 66 and 67: P/MTPM/32RESULTSResults show that,
Page 68 and 69: P/MTPM/33Clay modellingPore size di
Page 70 and 71: P/MTPM/341.60E-11f H2-d total (kg.m
Page 72 and 73: P/MTPM/350.50η R ()0.400.300.200.1
Page 74 and 75: P/MTPM/36200Bq/g1801601401201008060
Page 76 and 77: P/MTPM/37Argilite (ionic strength 0
Page 78 and 79: P/MTPM/38-Samples cored at 12m were
Page 80 and 81: P/MTPM/39APPLICATIONSCORE 2D has be
Page 82 and 83: P/MTPM/40Figure 1: Sketch drawing o
Page 84 and 85: P/MTPM/41Figure 1: Thermal conducti
Page 86 and 87: P/MTPM/42Figure 2: Model of pore st
Page 88 and 89: P/MTPM/43The available data are con
Page 90 and 91: P/MTPM/44Figure 1: Spatial extensio
Page 92 and 93: P/MTPM/45Relative concentration / (
Page 94 and 95: P/MTPM/46Figure 2: Swelling pressur
Page 96 and 97: P/MTPM/47then used in the transport
Page 98:
P/MTPM/4820181614121086Gas pressure
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