Mass Transfer & Porous Media (MTPM) - Andra

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P/<strong>MTPM</strong>/44Figure 1: Spatial extension of the cemented mineralogical alteration rim. Dehydration micro-cracks areproduced during sample preparation.35 OH 60 °C, 6 months30OH 60 °C, 12 months25% oxide201510500 5000 10000 15000 20000 25000distance from the alkaline source (µm)Figure 2: MgO % chemical profile measured by SEM-EDX, showing the development of the alteration rim.References:Savage, D. Walker, C., Arthur, R. and Rochelle, C. (2007). Alteration of bentonite by hyperalkaline fluids:A review of the role of secondary minerals. Physics and Chemistry of the Earth , Parts A/B/C. 32, 287-297Sánchez, L., Cuevas, J., Ramírez, S., Ruiz De León, D., Fernández, R., Vigil de la Villa, R. and Leguey, S.(2006). Reaction kinetics of FEBEX bentonite in hyperalkaline conditions resembling the cementbentoniteinterface. Applied Clay Science , 33, 2, 125-141.Page 510INTERNATIONAL MEETING, SEPTEMBER 17...>...18, 2007, LILLE, FRANCECLAYS IN NATURAL & ENGINEERED BARRIERSFOR RADIOACTIVE WASTE CONFINEMENT
P/<strong>MTPM</strong>/45TRANSPORT NUMBER OF SODIUM IONSIN WATER-SATURATED, COMPACTEDNA-MONTMORILLONITETomohiro Higashihara *, Kumiko Kinoshita, Yorimasa Akagi, Seichi Sato, Tamotsu KozakiDivision of Energy and Environmental Systems, Graduate School of Engineering, HokkaidoUniversity, Kita 13 Nishi 8, Sapporo 060-8628, Japan* Present address, Civil Engineering Research Laboratory, Central Research Institute of ElectricPower Industry, 1646 Abiko, Abiko-shi, Chibaken 270-1194, JapanINTRODUCTIONIn geologic disposal of both high-level radioactive wastes and a part of TRU wastes, compacted bentoniteis a promising material to be used for a buffer material. Radionuclides are not migrated by advection butby diffusion, because of very low hydraulic conductivity of the bentonite. It is important to clarify thediffusion process of the radionuclide as a part of a safety assessment of the geologic disposal.In the buffer material, the diffusion of the radionuclides may be affected by other ions in the groundwater,because the nuclides as ions diffuse in electrically neutral condition by coupling with counter ions.However, there are quite few reports in which the contribution of these counter ions to diffusion of ionsis examined. Nakazawa et al. (1999) suggested that the charge carrier of electrical conduction in the Namontmorilloniteis hydrogen ions rather than Na + ions. However, the major charge carrier in the compactedbentonite has not been clarified sufficiently, because their conclusion was based on the indirect methodsuch as measurement of electrical conductivities. Measurement of transport number is one of directmethods and is one of the most basic electrochemical properties of materials. The transport numbersuggests the contribution of counter ions to the migration of radionuclides. The purpose of this study is topropose an experimental method to determine the transport number of the Na + ions in the water-saturated,compacted Na-montmorillonite to examine possible counter ions to the diffusion of radionuclides in themontmorillonite.EXPERIMENTALThe Na-montmorillonite powder was compacted in an acrylic resin cells, 20 mm in diameter and20 mm in height. The clay columns were saturated with 0.1 M NaClO 4 solution. The transport numberwas determined using a moving boundary method. To estimate the transport number of Na + ions inthe montmorillonite, two processes are concerned with. One is electromigration of Na + ions. Themigration of the Na + ions was traced, using 22 Na + spiked as a thin layer. The other is the electroosmoticflow of pore water, because it is possible that the Na + ions migrate together with pore water.The flow of pore water was traced using dissolved helium, because the helium can be regarded as anon-sorbing tracer. For measuring the electro-osmotic flow, a part of the prepared columns weresaturated with dissolved helium by bubbling. The osmotic flow was measured using an inflection pointof helium distribution in the montmorillonite (Higashihara et al., 2004).RESULTSDispersivity parameters, which were obtained in these experiments, were 10 -5 m for Na + and 10 -3 m for He.This indicates that a property of the migration path for Na + ions is deferent from one for He. It is quitepossible that, in the montmorillonite, the Na + ions mainly migrate in interlayer space and/or on outersurface, and the He does in pore space, as was suggested previously by Higashihara et al. (2004).Therefore, it is considered that the migration of the Na + is not affected by the electro-osmotic flow. Thetransport numbers of Na + ions were determined taking no account of the contribution of the electro-osmoticflow.INTERNATIONAL MEETING, SEPTEMBER 17...>...18, 2007, LILLE, FRANCECLAYS IN NATURAL & ENGINEERED BARRIERSFOR RADIOACTIVE WASTE CONFINEMENTPage 511
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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
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P/MTPM/142.5Energy (M eV)1.6 1.7 1.
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P/MTPM/15C/Co10.90.80.70.60.50.40.3
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P/MTPM/16ModelIrmayvG-M1vG-M2vG-M3T
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P/MTPM/17Figure 1: Experimental HTO
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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
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 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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