Mass Transfer & Porous Media (MTPM) - Andra

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P/<strong>MTPM</strong>/26heterogeneous distribution of 238 Pu on the inlet surface of the clay sample and also along the cut crosssection. In the OPA porewater Pu(V) dominates speciation. If the OPA porewater is circulated over the clayinlet surface, Pu(IV) becomes dominant.These ongoing investigations will provide the necessary basis for credible description of sorbingradionuclide mobility in clay for the nuclear waste disposal safety case.Reference:Van Loon, L. R., Soler, J. M., and Bradbury, M. H., 2003. Diffusion of HTO, Cl-36(-) and I-125(-) inOpalinus Clay samples from Mont Terri - Effect of confining pressure. J. Contam. Hydrol. 61, 73-83.Page 474INTERNATIONAL MEETING, SEPTEMBER 17...>...18, 2007, LILLE, FRANCECLAYS IN NATURAL & ENGINEERED BARRIERSFOR RADIOACTIVE WASTE CONFINEMENT
P/<strong>MTPM</strong>/27DIFFUSION OF H 2 OAND ELECTRO-OSMOSISIN WATER-SATURATED COMPACTEDNA-MONTMORILLONITE USING H 2 18 OAS A TRACERShingo Tanaka 1 , Tomohiro Higashihara 2 , Natsuko Noda 1 , Seichi Sato 1 ,Tamotsu Kozaki 1 , Haruo Sato 3 , Koichiro Hatanaka 31. Division of Energy and Environmental Systems, Graduate School of Engineering, HokkaidoUniversity, Kita 13 Nish 8, Sapporo 060-8628, Japan2. Civil Engineering Research Laboratory, Nuclear Fuel Cycle Backend Research Center, CentralResearch Institute of Electric Power Industry, 1646 Abiko, Abiko-shi, Chiba-ken 270-1194,Japan3. Horonobe Underground Research Unit, Geological Isolation Research and DevelopmentDirectorate, Japan Atomic Energy Agency, Horonobe-cho, Techio-gun, Hokkaido 098-3207,JapanINTRODUCTIONCompacted bentonite will be used as buffer material in Japanese high-level radioactive waste disposal. Thematerial has high sorption coefficients based on cation exchange and quite low hydraulic permeabilityresulting in diffusion control. Therefore, the properties are quite suitable for long-term safety assessment.The mechanistic understanding of cation diffusion is still needed for the assessment and design of anengineered barrier system using the bentonite, in which the thermodynamic and kinetic properties of waterand ions existing in interlayer and pore in the bentonite are quite important. In the present study, the kineticbehavior of water, such as migration rate and broadening, was studied by diffusion, electromigration, andelectro-osmosis, using H 2 18 O as a tracer.EXPERIMENTALSodium montmorillonite (Kunipia F) powder was used to prepare the water-saturated compactedmontmorillonite. The powder was dried and compacted into pellets of 20 mm in diameter and 20 mm indepth with having dry densities of 1.0, 1.2, and 1.4 Mg/m 3 . The pellets sandwiched with sintered stainlesssteelfilters in acrylic cells were immersed in a 0.1 M NaClO 4 solution. They were kept for 30 days tosaturate the montmorillonite with the solution after evacuation to remove gas. Then some of the pelletswere equilibrated with H 2 18 O enriched water. Couples of a H 2 18 O enriched pellet and a normal pellet wereused as specimens for the diffusion experiments. The couples were kept at 298 K for 24 h to allow todiffuse H 2 18 O. On the other hand, the specimens for the electro-osmosis experiments consist of two H 2 18 Oenriched pellets and two normal pellets in series. The experimental setup for electro-osmosis is givenelsewhere [1]. A constant current of 20 mA was applied to the series of the pellets as the H 2 18 O enrichedones are in the anode side and the ones including normal water are in the cathode side. The polarizationwas carried out for 4-6 h at 298 K. The electric potential gradient was 260 V/m, which was checked usingreference Ag/AgCl electrodes in the initial stage of experiments. After the diffusion or electro-osmosisexperiments, concentration of H 2 18 O was measured as a function of distance from the contact plane betweenthe H 2 18 O enriched and normal pellets by isotope fractionation.RESULTS AND DISCUSSIONFigure 1 shows an example of the concentration profiles of H 2 18 O for the dry density of 1.0 Mg/m 3 obtainedafter applying the electric potential gradient. It indicates an electro-osmotic flow toward the cathode in themontmorillonite. The profile is well described by the following advection-dispersion equation,INTERNATIONAL MEETING, SEPTEMBER 17...>...18, 2007, LILLE, FRANCECLAYS IN NATURAL & ENGINEERED BARRIERSFOR RADIOACTIVE WASTE CONFINEMENTPage 475
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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 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 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
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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