Mass Transfer & Porous Media (MTPM) - Andra

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P/MTPM/6borehole was capped with a conical concrete plug and retained by a reinforced steel lid. The lid is helddown by rock anchors designed to withstand over 5000 tonnes of force. Additional instruments recordvariations in the relative humidity of the clay, the total stress and porewater pressure at the borehole wall,the temperature, any upward displacement of the lid and the restraining forces on the rock anchors.The state-of-the-art experimental monitoring and control systems for Lasgit are housed in the “GasLaboratory” which is a self-contained unit designed and assembled by BGS within a modified shippingcontainer. A customised graphical interface based on National Instruments LabVIEW TM software enablesremote control and monitoring to be undertaken by staff at BGS Headquarters in Keyworth and also allowsthe project's international partners to access data using their desktop computers. Lasgit will provide theindustry with important new information on the mechanics of gas flow in buffer bentonite. The numericdata will be used in the development and validation of process models aimed at repository performanceassessment.RESULTSThe Lasgit deposition hole was closed on the 1st February 2005 signifying the start of the hydration phase.At present monitored porewater pressures within the clay remain rather low ranging from 100 kPa to430 kPa. This is in contrast to the water pressure measured at the face of the deposition hole which rangesfrom 1160 kPa to 2575 kPa. Monitored radial stress around the canister continues to increase steadilyranging in value from 1500 kPa to 5130 kPa, with an average value of 3900 kPa. Analysis of thedistribution in radial stress shows a narrow expanding zone of elevated stress propagating verticallyupwards from the base of the hole. Stress measurements on the canister surface indicate radial stresses inthe range 4430 kPa and 4630 kPa, which are comparable with the values of radial stress monitored on therock face. Axial stress is significantly lower at 3200 kPa. Axial stress within the clay ranges from 4488 kPato 5750 kPa and is non-uniformly distributed across the major axis of the emplacement hole. The averageaxial total stress within the bentonite is now greater than the initial pre-stress applied by the lid. Movementand distortion of the steel retaining lid has occurred following the installation and initial closure ofpackered intervals within the pressure relief holes. Estimates of effective stress (swelling pressure) at therock face suggest values in the range of 180 to 3240 kPa with an average of around 2075 kPa. Suction datafrom devices located within the buffer above and beneath the canister indicate that a significant amount ofthe clay remains in suction.Analysis of the flow data from the artificial hydration system suggests a disproportionately large flux fromthe canister filters compared to the hydration mats. This can be explained by a number of factors includingcompression of the filter mats (i.e. a reduction in permeability) or a zone of elevated permeability aroundthe canister.During 2007 a preliminary gas injection history will be performed with a view to verifying the operationand data reduction methodologies for the experiment, providing qualitative data on hydraulic and gastransport parameters. The test will be designed in such a way as to minimise the effect of reintroducinggas and will be performed in one of the lower filter arrays where the bentonite is locally saturated. Theremaining filters on that level will be isolated from the artificial hydration system and their pressureallowed to evolve to provide temporal data on local porewater pressures within the buffer clay.Simultaneously artificial hydration will continue through all remaining canister filters and hydration mats.The test has now been in successful operation for in excess of 740 days and continues to yield high qualitydata amenable to the development and validation of process models aimed at repository performanceassessment.Page 434INTERNATIONAL MEETING, SEPTEMBER 17...>...18, 2007, LILLE, FRANCECLAYS IN NATURAL & ENGINEERED BARRIERSFOR RADIOACTIVE WASTE CONFINEMENT
P/MTPM/7SIMULATING THE GEOCHEMICALCOUPLING BETWEEN VITRIFIED WASTE,CANISTER AND NEAR-FIELDON THE ALLIANCES PLATFORMO. Bildstein 1 , E. Piault 1 , L. Trotignon 1 , P. Montarnal 2 , E. Deville 2CEA – Direction de l’Energie Nucléaire1. DTN/SMTM/Laboratoire de Modélisation des Transferts dans l’Environnement – Bât. 307 – CECadarache – 13108 St Paul lez Durance – France2. DM2S/SFME/Laboratoire de Modélisation des Transferts en Milieu Solide –CE Saclay – 91190Gif sur Yvette - FranceINTRODUCTIONThe simulation of the alteration of waste glass and associated geochemical interactions in the near field ofa deep geological disposal is an important issue for evaluating the long term release of fission products andactinides in the geosphere. Among difficulties encountered when attempting such simulations is the factthat the glass and iron canister cannot, as opposed to the clay barriers or to the host rock, be consideredas true porous media (Bildstein et al., 2006, 2007). Description of the coupling of geochemical fluxes atthe interface between alteration fronts moving inside materials and the porous surrounding rock thereforerequires specific adaptation and development in the simulation tools.The approach described here was developed in the Alliances simulation platform (Bengaouer et al., 2003)in order to represent with a greater accuracy the successive and progressive alteration of thick iron canistersand waste glass blocks in the HLW near-field.SIMULATION APPROACHThe underlying idea for the selected approach stems from the observation that in usual reactive transportsimulation tools, the reaction rates affecting solid phases are computed from local chemical conditions, i.e.inside a given discretization cell. Also, usual reactive transport simulation tools assume that all cells arepart of the porous medium and contain fluid. In order to avoid complex adaptative mesh approaches, asimple algorithm was devised in which a solid phase reacts according to the conditions prevailing in thesurrounding cells. The dissolution of a mineral at a specific location would, for instance, depend on thechemical conditions in nearby cells. This approach enables to describe the progression of a dissolution frontin a non porous solid and is in addition easily adaptable to 2D and 3D geometries and to situations in whichmultiple layers of heterogeneous and non porous materials are present. The chemical coupling between theporous medium, the progressively larger alteration zone (corrosion products, gel) and the local zone wherethe matrix begins to dissolve are described using the reactive transport algorithm implemented in theplatform.TESTS AND APPLICATIONSTests are presented in 1D and 2D geometry with a simplified chemistry in order to demonstrate thetopographic capabilities of this new approach (Fig. 1). A more complex application is then presented,showing the evolution in 1D geometry of the interface between argillite and a thick carbon steel overpack.INTERNATIONAL MEETING, SEPTEMBER 17...>...18, 2007, LILLE, FRANCECLAYS IN NATURAL & ENGINEERED BARRIERSFOR RADIOACTIVE WASTE CONFINEMENTPage 435
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 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
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P/MTPM/31Furthermore, Van Loon et a
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P/MTPM/32RESULTSResults show that,
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P/MTPM/33Clay modellingPore size di
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P/MTPM/341.60E-11f H2-d total (kg.m
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P/MTPM/350.50η R ()0.400.300.200.1
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P/MTPM/36200Bq/g1801601401201008060
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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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