Mass Transfer & Porous Media (MTPM) - Andra

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P/<strong>MTPM</strong>/341.60E-11f H2-d total (kg.m-2.s -1 )1.40E-111.20E-111.00E-118.00E-126.00E-1250 ans250 ans1000 ans4500 ans5000 ans20 000 ans50 000 ans100 000 ans4.00E-122.00E-120.00E+000 2 4 6 8 10 12 14 16 18 20Figure 2: Dissolved Hydrogen flux along radial axis.r (m)7Pg (MPa)65433 jours2 ans50 ans250 ans1000 ans4500 ans5000 ans20 000 ans50 000 ans100 000 ans2100 10 20 30 40 50 60 70 80 90 100Figure 3: Gas pressure along radial axis.r (m)improve the numerical convergence rate is to impose at least a minimum degree of saturation, what meansthat some gas remains always in pores. Such modification of the constitutive equation may modify thenumerical answer. This question is discussed and a comparison of results obtained with different numericalstrategies is presented.References:Gerard, P., Charlier, R. & Collin, F. (2007): “On boundary conditions in tunnels under partial saturation”.Proc. 3 rd . Conf. Meeting “Clay in natural and engineered barriers for radioactive waste confinement”,ANDRA, Lille.Gerard, P., Charlier, R. & Collin, F. (2007) : “Couplage entre le comportement mécanique et le trasfert degaz autour des alvéoles et des scellements ”. Rapport ANDRAPage 490INTERNATIONAL MEETING, SEPTEMBER 17...>...18, 2007, LILLE, FRANCECLAYS IN NATURAL & ENGINEERED BARRIERSFOR RADIOACTIVE WASTE CONFINEMENT
P/<strong>MTPM</strong>/35VERTICAL DISTRIBUTION OF HCO 3–TRANSPORT PARAMETERS IN BOOM CLAYIN THE MOL-1 BOREHOLE (MOL, BELGIUM)M. Aertsens 1 , M. Van Gompel 1 , P. De Cannière 1 , N. Maes 1 , A. Dierckx 21. SCK•CEN, Boeretang 200, B-2400 Mol, Belgium ( marc.aertsens@sckcen.be )2. ONDRAF/NIRAS, Kunstlaan 14, B-1210 Brussels, BelgiumINTRODUCTIONBoom Clay is presently studied as a reference host formation for the disposal of high-level radioactivewaste in Belgium. This layer, situated between about -190 m and -290 m deep below the Mol site in thenortheast of Belgium, presents various characteristics favourable to the final disposal of radioactive waste.Apart from a very low hydraulic conductivity (around 2.5 × 10 -12 m s -1 ), it also has a strong sorptioncapacity for many radionuclides as well as self-sealing properties. A safety analysis of the radiological risksin the biosphere due to the release of radionuclides from the waste requires to calculate the transport rateof radionuclides in Boom Clay. Transport in the Boom Clay is mainly due to diffusion. Because of the verylow value of the hydraulic conductivity K and the very low vertical hydraulic gradient (about 2 %),advection is negligible and diffusion is dominant in the overall transport. The diffusive transport isdetermined by (1) the product η R of the diffusion accessible porosity η and the retardation factor R , and(2) the apparent dispersion coefficient D . Initially, these parameters have been determined on clay corestaken from the underground research facility in Mol, at a depth of -223 m. In 1997, a borehole (Mol-1)was drilled at the Mol site in order to cover the complete profile of the Boom Formation and to analyzethe detailed vertical distribution of the transport parameters of non-sorbed tracers as a function of depthand stratigraphy. By performing migration experiments on clay cores from Mol-1, the hydraulicconductivity in the direction perpendicular to the bedding plane, the η R product and the apparent dispersioncoefficient of iodide and tritiated water have been determined as a function of depth (Aertsens et al ., 2004).This study is completed by doing the same for H 14 CO - 3 . Other cored boreholes were drilled in northeastBelgium to evaluate the spatial distribution of some of these parameters at a larger scale.EXPERIMENTALFor each clay core, the hydraulic conductivity in the direction perpendicular to the bedding plane, the η Rproduct, and the apparent dispersion coefficient of H 14 CO - 3 are determined by performing migrationexperiments (Aertsens et al ., 2003) on compact clay cores. For an accurate determination of the migrationparameters, it is essential that during an experiment, the water flow rate out of a migration cell is keptconstant.RESULTS AND DISCUSSIONIn agreement with previous results (Aertsens et al ., 2004), the hydraulic conductivity between -191 m and-281 m can be considered as homogeneous with an average value around 2.5 × 10 -12 m s -1 . In this region,the product η R of H 14 CO 3 - can be considered as homogeneous as well, η R = 0.26 (standard deviation 0.03).This value lies between that of iodide, η R = 0.16 and that of HTO, η R = 0.37 (Aertsens et al., 2004). Thereason of the lower porosity of iodide and bicarbonate compared to HTO is due to anion exclusion becauseof the electrostatic repulsion by the negatively charged clay mineral surfaces. The higher η R value ofH 14 CO 3- compared to I - could be due to: (i) a different diffusion accessible porosity, or (ii) a slightretardation of H 14 CO 3 - .The apparent diffusion coefficient of H 14 CO 3- can be considered as homogeneous as well with a valuearound 6 × 10 -11 m 2 s -1 . This value complements the values obtained in a similar previous study (Aertsenset al., 2004) for HTO (2.3 × 10 -10 m 2 s -1 ), and iodide (1.4 × 10- 10 m 2 s -1 ).INTERNATIONAL MEETING, SEPTEMBER 17...>...18, 2007, LILLE, FRANCECLAYS IN NATURAL & ENGINEERED BARRIERSFOR RADIOACTIVE WASTE CONFINEMENTPage 491
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Poster [MTPM]Mass Transfer & Porous
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P/MTPM/1The free energy cost of for
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P/MTPM/3DIFFUSION OF IONS IN UNSATU
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P/MTPM/4POROUS MEDIA CHARACTERIZATI
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P/MTPM/5Oxalate ionsQuartzQuartz +P
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P/MTPM/6borehole was capped with a
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P/MTPM/7Initial state with glass an
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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 48 and 49: P/MTPM/23HA (µg/g)3002001000(a):pH
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 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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Mass Transfer & Porous Media (MTPM) - Andra

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