Mass Transfer & Porous Media (MTPM) - Andra

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P/<strong>MTPM</strong>/350.50η R ()0.400.300.200.10180 200 220 240 260 280 300Depth (m)Figure 1: The product η R of the diffusion accessible porosity and the retardation factor for HCO 3– as afunction of depth at the Mol site (Mol-1 borehole). Experiments for which the water flow rate out of theclay core was not constant as a function of time are also surrounded with squares. For these experimentsthe parameter values are less reliable. The horizontal line indicates the average value η R = 0.26.CONCLUSIONSLike for HTO and I - , the transport parameters of HCO 3 - can be considered as constant in the depth rangebetween -191 m and -281 m in Boom Clay in the Mol-1 borehole. So, at the level of the Boom Formationat the Mol site, the Transition zone and the members of Putte and Terhagen appear to be homogeneous incontrast to the lower part of the Belsele-Waas member which is also characterised by a higher silt contentand a higher hydraulic conductivity.ACKNOWLEDGEMENTSThis work is scientifically and financially supported by ONDRAF/NIRAS the Belgian NationalRadioactive Waste Agency. Isabelle Wemaere is also gratefully acknowledged for her fruitful discussion.ReferencesAertsens M., Put M., Dierckx A. (2003) An analytical model for the interpretation of pulse injectionexperiments performed for testing the spatial variability of clay formations. Journal of ContaminantHydrology 61 , 423-436.Aertsens M., Wemaere I., Wouters L. (2004) Spatial variability of transport parameters in the Boom Clay.Applied Clay Science 26, 37-45.Page 492INTERNATIONAL MEETING, SEPTEMBER 17...>...18, 2007, LILLE, FRANCECLAYS IN NATURAL & ENGINEERED BARRIERSFOR RADIOACTIVE WASTE CONFINEMENT
P/<strong>MTPM</strong>/36DIFFUSION EXPERIMENTSIN CALLOVO-OXFORDIAN CLAYFROM THE BURE SITE, FRANCE:2 MODEL RESULTSJ. Samper 1 , Q. Yang 1 , M. García-Gutiérrez 2 , T. Missana 2 , M. Mingarro 2 ,Ú. Alonso 2 , J.L. Cormenzana 31. UDC-ETSICCP, Campus de Elviña s/n, 15192 La Coruña, SPAIN ( jsamper@udc.es )2. CIEMAT, Departamento de Medio Ambiente, Av. Complutense 22, 28040 Madrid, SPAIN(miguel.garcia@ciemat.es)3 . Empresarios Agrupados, Magallanes 3, 28015 Madrid, SPAIN (jcol@enresa.es)INTRODUCTIONClay formations are being considered potential host rocks for radioactive waste disposal in many countries.The French National Radioactive Waste Management Agency (ANDRA) is performing research at theMeuse/Haute-Marne Underground Research Laboratory (URL) located at Bure (300 km east of Paris) toevaluate the feasibility of constructing a high-level radioactive waste repository in Callovo-Oxfordian(COx) argillite formation. COx clay has a very small hydraulic conductivity and therefore moleculardiffusion is the main transport mechanism for radionuclides. Laboratory and in situ experiments are beingperformed to improve understanding of diffusion processes and determine key diffusion and retentionparameters. García-Gutiérrez et al. (2007, in this volume) presented a large-scale diffusion experimentperformed in a cylindrical sample of 30x30 cm. which overcomes problems of in situ experiments. A recompactedclay/radionuclide mixed solid source is placed in the centre of a large clay block, allowing thetracer to diffuse into the clay sample. At the end of the experiment, samples along vertical boreholes aretaken to get a 3D distribution of tracer activity. Here we present numerical models for the interpretationof experiments performed with HTO and 85 Sr 2+ for which data are already available. Figure 1 showsexperimental concentration profiles of HTO along vertical boreholes drilled from top to bottom of the largeblock at different radial distances from the tracer source. 24 of such concentration profiles were obtainedand used to test and calibrate the numerical model.NUMERICAL MODELSolid-source experiments have been interpreted using an inverse model with INVERSE-CORE (Dai andSamper, 2004). Given the symmetry with respect to sample axis, numerical interpretation can be performedwith 2-D axi-symmetric anisotropic models. Figure 1 shows the 2-D finite element grid used to model bothexperiments. Numerical model considers tow material zones: one for the re-compacted clay containing thesolid source and another for intact clay. Prior estimates of transport parameters for compacted clay areavailable from previous experiments. Therefore, those parameters are fixed. Interpretation of theexperiment aims then at estimating diffusion and sorption parameters of clay sample.Experiments have been modelled using an approach similar to that used for modelling diffusionexperiments in Opalinus clay (Samper et al., 2006). Numerical models have been used to: 1) Computenumerical sensitivities of concentrations to model parameters; and 2) Interpret real data. Here we reportthe results of the numerical interpretation of HTO and 85 Sr data. Model results indicate that COx clayexhibits mild diffusion anisotropy. In addition to optimum estimates of porosity, effective diffusioncoefficient and K d , inverse modelling of these experiments provides estimates of parameters uncertaintiesand approximate confidence intervals of parameter estimates. Sources of uncertainty related to propertiesof re-compacted clay and presence of a damaged zone around the central cylindrical source are alsoanalyzed.INTERNATIONAL MEETING, SEPTEMBER 17...>...18, 2007, LILLE, FRANCECLAYS IN NATURAL & ENGINEERED BARRIERSFOR RADIOACTIVE WASTE CONFINEMENTPage 493
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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
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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 70 and 71: P/MTPM/341.60E-11f H2-d total (kg.m
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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