Mass Transfer & Porous Media (MTPM) - Andra

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P/<strong>MTPM</strong>/13RESULTSFirst, we estimated ρ 1 of montmorillonite through T 1 measurements of dispersed montmorillonite sols andgels. A single T 1 value was observed for these uncompactedNot all have high water content – e.g. 6.7%sample illustrated below systems. The ( S/V ) pore in these systems is determined by the specific surface area,S 0 , of montmorillonite and the solid/liquid ratio by weight [(clay)/(water)], C ; that is, ( S/V ) pore =S 0 C ρ w ,where ρ w is density of bulk water. S 0 was measured as 700 m 2 /g by the EGME (ethylene-glycol-monoethylether)method (Kozaki et al., 1999). A simple linear regression analysis of C against 1/ T 1 for 13 sampleswith C...18, 2007, LILLE, FRANCECLAYS IN NATURAL & ENGINEERED BARRIERSFOR RADIOACTIVE WASTE CONFINEMENT
P/<strong>MTPM</strong>/14DIFFUSION COEFFICIENTS MEASUREMENTIN CONSOLIDATED CLAYS:A COMBINATION OF MICRO-SCALEPROFILING AND SOLID PORE STRUCTUREANALYSESU. Alonso 1 , T. Missana 1 , M. García-Gutiérrez 1 , A. Patelli 2 , M. Siitari-Kauppi 3 ,A. Leskinen 3 , Valentino Rigato 41. CIEMAT, Environmental Department, Avda. Complutense 22, Edif. 19 28040 Madrid, Spain(ursula.alonso@ciemat.es)2. CIVEN, Via delle Industrie 9, 30175 Venezia-Marghera, Italy3. University of Helsinki, Laboratory of Radiochemistry PO. Box 55, 00014 Helsinki, Finland4. LNL-INFN, Viale dell´Univresitá 2, 35020 Legnaro, Padova, ItalyConsolidated clays are considered suitable geological formations to host a high-level radioactive wasterepository. They are low permeability media and diffusion is the main mechanism for radionuclide (RN)transport. Thus, the determination of RN diffusion coefficients is required to evaluate the safety of the claybarrier. Experimental methods to measure diffusion coefficients for elements that suffer no or smallretardation exist but, almost no data are available for elements presenting high sorption onto the clay, asthe majority of actinides and several fission products.In this study, the nuclear ion beam technique Rutherford Backscattering Spectrometry (RBS) is tested toevaluate RN concentration profiles within the Opalinus consolidated clay from the Mont Terri rocklaboratory (Switzerland). This technique, widely used in material science is scarcely applied to measurediffusion coefficients in geological materials, and it is suited to evaluate concentration gradients of heavyelements in the near surface region (several micrometers) in samples mainly composed by light elements.To relate the measured apparent diffusion coefficients to the porosity of the clay samples, clay porosity wasdetermined by impregnation technique. Furthermore, the porestructure was studied in detail byelectronmicroscopy (SEM) on the impregnated sample. The poly-methylmethacrylate (PMMA) methodinvolves impregnation of clay samples here with 3 H labelled methylmethacrylate ( 3 H-MMA), irradiation forpolymerisation, autoradiography and optical densitometry evaluation of the tracer, by digital imageprocessingtechniques. In our samples, the average measured porosity was 19 %.Diffusion experiments were performed with Sr and Eu that are respectively low and strongly sorbingelements onto the clay. Commercial gold colloids of 2 nm in diameter were also selected, to define thelowest limit of diffusion coefficient within the clay. Colloid diffusion is expected to be hindered becauseof having higher diameter than solutes and because both the colloids and the clay are negatively charged.Papers were spiked with Sr or Eu solution or the 2 nm Au colloids suspensions and were placed on theclay samples previously hydrated with synthetic water (Pearson water), simulating the Opalinus clay porewater. Once the selected contact time passed (ranging from 5 minutes to 7 days), the traced-papers wereremoved, and the samples were analyzed by Rutherford Backscattering Spectrometry (RBS).As example, Figure 1 presents the RBS spectra obtained on the MtTerri clay samples after contact withEu (Figure 1- left) or Sr (Figure 1-right). Comparatively, in Figure 1 (left) undoubted asymmetric Eu peaksare detected in the RBS spectra indicating Eu access into the clay. In Figure 1 (left) the Eu peak shape israther narrow at higher channels, suggesting Eu retention on the surface caused by sorption, but also, theEu peak showed a tail going towards lower channels, indicating that Eu was going deeper in the sample.INTERNATIONAL MEETING, SEPTEMBER 17...>...18, 2007, LILLE, FRANCECLAYS IN NATURAL & ENGINEERED BARRIERSFOR RADIOACTIVE WASTE CONFINEMENTPage 449
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 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 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
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P/MTPM/38-Samples cored at 12m were
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P/MTPM/39APPLICATIONSCORE 2D has be
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P/MTPM/40Figure 1: Sketch drawing o
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P/MTPM/41Figure 1: Thermal conducti
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P/MTPM/42Figure 2: Model of pore st
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P/MTPM/43The available data are con
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P/MTPM/44Figure 1: Spatial extensio
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P/MTPM/45Relative concentration / (
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P/MTPM/46Figure 2: Swelling pressur
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P/MTPM/47then used in the transport
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P/MTPM/4820181614121086Gas pressure
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Mass Transfer & Porous Media (MTPM) - Andra

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