Mass Transfer & Porous Media (MTPM) - Andra

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P/MTPM/39APPLICATIONSCORE 2D has been extensively used to model laboratory and in situ experiments including CERBERUSExperiment in Boom clay (Samper et al. 2006), interpretation of the Redox Zone Experiment in a fracturezone of the Äspö site (Molinero and Samper, 2004; Molinero et al. 2004; Molinero and Samper, 2006),inverse reactive transport of laboratory experiments and coastal aquifers (Dai and Samper, 2004; 2006),evaluation of oxygen consumption in a HLW repository (Yang et al., 2007) and stochastic cation exchangeand reactive transport in aquifers (Samper and Yang, 2006). Codes of CORE series have been used alsowithin the context of performance assessment in the following projects: ENRESA 2000, ENRESA 2003,BENIPA, NFPRO and PAMINA.ACKNOWLEDGEMENTSThis work was supported by the Spanish Nuclear Waste Company (ENRESA) through contracts # 770045and 770125, the European Union through Projects NF-PRO (FI6W-CT-2003-02389) and FUNMIG (FP6-516514), the Spanish Ministry of Science and Technology (CICYT Projects HID98-282 and REN 2003-8882), Xunta de Galicia (Incentives PGIDT04PXIC11801PM and PGIDT05PXIC11801PM) and theUniversity of La Coruña through a research scholarship awarded to the first author. Development ofCORE 2D V4 has relied on previous versions of CORE as well as on other earlier versions such asTRANQUI developed by T. Xu with support from J. Samper and C. Ayora. We acknowledge all peopleinvolved in all stages of CORE developments.References:Dai Z. and J. Samper. 2004, Inverse problem of multicomponent reactive chemical transport in porousmedia: Formulation and Applications Water Resources Research, Vol 40, W07407, doi:10.1029/2004WR003248.Dai Z., Samper, J., 2006. Inverse modeling of water flow and multicomponent reactive transport in coastalaquifer systems. J. of Hydrol. Vol. 327, Issues 3-4, 447-461.Molinero J., Samper, J., 2004, Groundwater Flow and Solute Transport in Fracture Zones: An ImprovedModel for a Large-Scale Field Experiment at Äspö (Sweden), J. Hydraulic Research. Vol. 42, 2004,Extra Issue, 157-172.Molinero, J., Samper, J., 2006. Modeling of reactive solute transport in fracture zones of granitic bedrocks.J. Cont. Hydrol., 82, 293–318.Molinero, J., Samper, J., Yang, C., Zhang, G., 2004. Biogeochemical reactive transport model of the Redoxzone experiment of the Äspö hard rock laboratory (Sweden). Nuclear Technology 48(2), 151-165.Samper, J., R. Juncosa, J. Delgado and L. Montenegro, 2000, CORE2D: A code for non-isothermal waterflow and reactive solute transport, Users manual version 2, Universidad de La Coruña, Techn. Publ.ENRESA, 131 pp.Samper, J., G. Zhang and L. Montenegro, 2006a. Coupled microbial and geochemical reactive transportmodels in porous media: Formulation and Application to Synthetic and In Situ Experiments, Journal ofIberian Geology, Vol 32(2), 211-217.Samper, J., Yang, C., Naves, A., Yllera, A., Hernández, A., Molinero, J., Soler, J.M., Hernán, P., Mayor,J.C. & Astudillo, J., 2006b, A fully 3-D anisotropic numerical model of the DI-B in situ diffusionexperiment in the Opalinus Clay formation. Physics and Chemistry of the Earth 31, 531-540.Zhang, G., 2001, HydroBioGeochemical Models in Porous Media, Ph.D. Dissertation University of LaCoruña, Spain, 368 pp.Yang, C., 2006, Conceptual and numerical coupled Thermal-Hydro-Bio-Geochemical models for threedimensionalporous and fractured media, University of La Coruña.Yang, C., Samper, J., Molinero, J., and Bonilla, M., 2007, Modelling geochemical and microbialconsumption of dissolved oxygen after backfilling a high level radioactive waste repository. Journal ofContaminant Hydrology, in press.Page 500INTERNATIONAL MEETING, SEPTEMBER 17...>...18, 2007, LILLE, FRANCECLAYS IN NATURAL & ENGINEERED BARRIERSFOR RADIOACTIVE WASTE CONFINEMENT
P/MTPM/40HYPERFILTRATION OF METAL SOLUTIONSTHROUGH LOW-PERMEABILITY MEDIAAND ITS EFFECTSON HYDRAULIC CONDUCTIVITYG. Houben 1 , F. Wagner 11. BGR - Bundesanstalt für Geowissenschaften und Rohstoffe, Stilleweg 2, 30655 Hannover,Germany (georg .houben@bgr.de)INTRODUCTIONMaterial of low hydraulic conductivity and high surface charge are likely to exhibit osmotic (membrane)behaviour. Two solutions of differing salt content separated by a membrane tend to equilibrate theconcentration gradient by flow of water to the high concentration side. As a result one can measure anosmotic pressure gradient. Pressures in excess of this osmotic pressure applied at the high salinity sidecause hyperfiltration (or reverse osmosis): water molecules pass the membrane relatively uninhibited whilethe dissolved ions remain behind and become concentrated at the high-pressure side. This process is usedcommercially in desalination plants. Osmosis and reverse osmosis have long been suspected to also occurin geological environments, especially in and around low permeability media, such as clays andargillaceous rocks.Observations in desalination plants have shown that often precipitates form on the high-pressure side ofthe membranes. This occurs when solute ion concentrations exceed the dissolution product of its salts.Precipitation of salts in pore spaces leads to a decrease in porosity and thus also in hydraulic conductivity.This hydraulic self-sealing limits further solute migration and decreases the amount of dissolved mobilesalts. Potentially the precipitates may be re-dissolved, e.g. after a later pressure-drop.Hyperfiltration (reverse osmosis) and precipitation of minerals from the hyperfiltrated solution areprocesses that potentially decrease radionuclide output from leaky radioactive waste containers and lowerthe hydraulic conductivity of the geotechnical barrier and the near-field. Hydrogen gas originating fromcorroding containers is envisaged to be the driving pressure source. In this study we tried to assess theeffects of precipitation and potential re-dissolution on hydraulic conductivity.EXPERIMENTAL CONCEPTThe processes of hyperfiltration and salt precipitation were successfully demonstrated using nickel sulphatesolutions of differing saturations (10, 30, 50, 70, 90 %), different hyperfiltration flow rates (1, 2, 3, 5 ml/min),and the cretaceous fine-grained Obernkirchen Sandstone as substitute low-permeability material (K = 5·10 -8to 1·10 -9 m/s, mean porosity = 17 %). The initial hydraulic conductivity was determined previously using bidistilledwater and several flow rates. After the hyperfiltration, the reversibility of the observed conductivitydamage was tested by pumping distilled water at increasing flow rates. Pressures and flow rates and electricalconductivity of the effluent were measured continuously and stored digitally.RESULTS AND INTERPRETATIONPrecipitates were found in small (mm sized) layers at the high-pressure side of the samples where theycreate zones of lowered hydraulic conductivity. Generally their conductivity is two to three orders ofmagnitude lower than initial. In our experiments the mass of precipitates is very small compared to thedissolved amount which was passed through the membrane.Hyperfiltration-induced precipitates and the resulting lowering of hydraulic conductivities were observedat solute saturations as low as 10 %. Nevertheless, at saturations higher than 50 % both the precipitatedINTERNATIONAL MEETING, SEPTEMBER 17...>...18, 2007, LILLE, FRANCECLAYS IN NATURAL & ENGINEERED BARRIERSFOR RADIOACTIVE WASTE CONFINEMENTPage 501
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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
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P/MTPM/10Figure 1: Horizontal cross
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P/MTPM/11n t (mol)as received8 10 -
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P/MTPM/1210,9Degree of saturation (
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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-
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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
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Page 72 and 73: P/MTPM/350.50η R ()0.400.300.200.1
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Page 76 and 77: P/MTPM/37Argilite (ionic strength 0
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Page 84 and 85: P/MTPM/41Figure 1: Thermal conducti
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Page 88 and 89: P/MTPM/43The available data are con
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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
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