Mass Transfer & Porous Media (MTPM) - Andra

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P/MTPM/31Furthermore, Van Loon et al. (2003) studied effective diffusion coefficients of tritiated water (HTO) inOpalinus Clay and compared their results with effective diffusion coefficients of HTO for a series ofargillaceous rocks (e.g. London Clay, Boom Clay, Wellenberg Marl, Tournemire Toarcian shale). Theyconcluded that the effective diffusion coefficients can be satisfactorily described using Archie’s law withan exponent of around 2.5.DATA ANALYSISBoth dissimilar data sets (Grathwohl, 1998; Van Loon et al., 2003) indicate that Archie’s law might beapplied for the estimation of the effective diffusion coefficients in argillaceous rocks. However, the valueof the accessible or transport-through porosity, respectively, is often not known and therefore Archie’s lawwill result in imprecise estimates for effective diffusion coefficients. Hence, in the current study, data oneffective diffusion coefficients and transport porosities will be collected from diffusion studies (e.g.Henrion et al., 1991; De Cannière et al., 1996; Decostes et al., 2007) performed on various argillaceousrocks (e.g. Opalinus Clay, Callovo-Oxfordian argillites and Boom Clay).RESULTS AND INTERPRETATIONComprehensive data sets on diffusion of different tracers (anions, cations and neutral species) inargillaceous rocks will be presented and the applicability of Archie’s law for clays and clay stones will bethoroughly discussed in context of the diffusion (or transport) accessible porosity. The relevance for safetyassessment of potential radioactive waste repositories will be highlighted.References:Blum, P. (2000): “Sorption- and diffusion behaviour of organic compounds in Israelian and EuropeanChalk“. MSc-Thesis, Applied Geology, University of Karlsruhe.Boving, T.B., Grathwohl, P. (2001): “Tracer diffusion coefficients in sedimentary rocks: correlation toporosity and hydraulic conductivity”. Journal of Contaminant Hydrology, 53, 85-100.De Cannière P., Moors H., Lolivier P., De Preter P., Put M. (1996): “Laboratory and in situ migrationexperiments in Boom Clay”. Nuclear Science and Technology, EUR16927, EC, Luxembourg.Descostes, M., Blin, V., Bazer-Bachi, F., Meier, P., Grenut, B., Radwan, J., Schlegel, M.L, Buschaert, S.,Coelho, D., Tevissen, E. (2007): “Diffusion of anionic species in Callovo-Oxfordian argillites andOxfordian limestones”. Submitted to Applied Geochemistry.Grathwohl, P. (1998): “Diffusion in Porous Media”. Kluwer Academic Publishers, London.Henrion, P.N., Put, M.J., Van Gompel, M. (1991): “The influence of compaction on the diffusion of nonsorbedspecies in Boom Clay”. Radioactive Waste Management and the Nuclear Fuel Cycle, 16 (1), 1-14.Van Loon, L.R., Soler, J.M., Jakob, A., Bradbury, M.H. (2003): “Effect Effect of confining pressure on thediffusion of HTO, 36 Cl − and 125 I − in a layered argillaceous rock (Opalinus Clay): diffusion perpendicularto the fabric”. Applied Geochemistry, 18, 1653-1662.Page 484INTERNATIONAL MEETING, SEPTEMBER 17...>...18, 2007, LILLE, FRANCECLAYS IN NATURAL & ENGINEERED BARRIERSFOR RADIOACTIVE WASTE CONFINEMENT
P/MTPM/32COMPARISON BETWEEN RADIALDIFFUSION AND LEACHING FORDETERMINING CHLORIDE AND SULPHATEIN TOURNEMIRE ARGILLITE PORE WATERCh. Wittebroodt 1, 2 , S. Savoye 1 , P. Jacquier 3 , C. Beaucaire 3 , F. Bensenouci 1, 4 ,H. Pitsch 3 , P. Gouze 2 , J.-L. Michelot 41. IRSN - Institut de Radioprotection et de Sûreté Nucléaire, BP n°17, 92262 Fontenay-aux-roses,France (charles.wittebroodt@irsn.fr, sebastien.savoye@irsn.fr, helmut.pitsch@irsn.fr,fethi.bensenouci@irsn.fr)2. Géosciences Montpellier, Université de Montpellier 2, CNRS, 34095 Montpellier cedex 5, France(philippe.gouze@msem.univ-montp2.fr)3. CEA – Commissariat à l’Energie Atomique, Saclay, DEN/DANS/DPC/SECR/L3MR, Bât. 450,91191 Gif-sur-Yvette, France (philippe.jacquier@cea.fr, catherine.beaucaire@cea.fr,)4. UMR IDES CNRS-Université Paris-Sud, Bât. 504, 91405 Orsay, France(jean-luc.michelot@u-psud.fr)INTRODUCTIONArgillaceous rocks are considered as potential host rocks for radioactive waste repositories. The FrenchInstitute of Radioprotection and Nuclear Safety (IRSN) develops experimental research programs in suchgeological formations at the Tournemire site (Aveyron, France). One of the objectives of this project is toevaluate the radionuclide migration through an argillaceous formation (argillites+marls) similar to thosestudied elsewhere for radioactive waste disposal. In order to estimate the confinement properties of suchrocks, it is crucial to characterize the chemical composition of their pore water and its possible verticalvariation. Because the argillite porosity is very low (less than 10%) it is impossible to extract directly thewater from the rock sample. Therefore, in the present study, we focused on the determination of mobileanion contents (sulphate and chloride) by means of two indirect approaches: the first one based on diffusionand the second one on leaching. After comparing both methods on a single stratigraphic level, weinvestigated the vertical distribution of anion contents from the upper Toarcian level down to the lowercalcareous aquifer.EXPERIMENTAL CONCEPTThe comparison between the out-diffusion method and the leaching method was carried out on samplescollected from an argon-drilled borehole, located in the upper Toarcian level. The samples wereimmediately sealed in evacuated Al-coated plastic bags under an argon atmosphere and stored in a glovebox to limit oxidation of pyrite which could induce an increase of the sulphate amount in the pore water.For the same reasons, all further handlings were carried out in a glovebox( ∼ 1 ppm O 2 ).Radial diffusion cells whose design is described in Savoye et al. (2006) were filled with a syntheticsolution (i) with a chemical composition as close as possible to that of the pore water and (ii) spiked withbromide in order to estimate the anion accessible porosity. Anion concentrations were monitored untilachievement of equilibrium. At this stage, the concentrations of all major dissolved cations (Na + , K + , Ca 2+ ,Mg 2+ ) and anions (Br - , Cl - , SO 4 2- , HCO 3 - /CO 3 2- ) were measured in order to verify the charge balance.Leaching experiments were performed with deionised water in a glove box with controlled partial pressureof CO 2 equal to 10 -2.4 atm, which is assumed to correspond to the in situ condition (Beaucaire et al.,submitted).The leaching experiments lasted either 24 hours, 7 or 21 days and four solid/liquid ratios, i.e.0.04, 0.25, 0.6 and 1 g/g, were investigated.INTERNATIONAL MEETING, SEPTEMBER 17...>...18, 2007, LILLE, FRANCECLAYS IN NATURAL & ENGINEERED BARRIERSFOR RADIOACTIVE WASTE CONFINEMENTPage 485
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Poster [MTPM]Mass Transfer & Porous
Page 4 and 5:
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
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 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 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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