Computational Geosciences

, Volume 19, Issue 3, pp 535–550 | Cite as

Benchmark reactive transport simulations of a column experiment in compacted bentonite with multispecies diffusion and explicit treatment of electrostatic effects

  • P. Alt-Epping
  • C. Tournassat
  • P. Rasouli
  • C. I. Steefel
  • K. U. Mayer
  • A. Jenni
  • U. Mäder
  • S. S. Sengor
  • R. Fernández
ORIGINAL PAPER

Abstract

Bentonite clay is considered as a potential buffer and backfill material in subsurface repositories for high-level nuclear waste. As a result of its low permeability, transport of water and solutes in compacted bentonite is driven primarily by diffusion. Developing models for species transport in bentonite is complicated, because of the interaction of charged species and the negative surface charge of clay mineral surfaces. The effective diffusion coefficient of an ion in bentonite depends on the ion’s polarity and valence, on the ionic strength of the solution, and on the bulk dry density of the bentonite. These dependencies need to be understood and incorporated into models if one wants to predict the effectiveness of bentonite as a barrier to radionuclides in a nuclear repository. In this work, we present a benchmark problem for reactive transport simulators based on a flow-through experiment carried out on a saturated bentonite core. The measured effluent composition shows the complex interplay of species transport in a charged medium in combination with sorption and mineral precipitation/dissolution reactions. The codes compared in this study are PHREEQC, CrunchFlow, FLOTRAN, and MIN3P. The benchmark problem is divided into four component problems of increasing complexity, leading up to the main problem which addresses the effects of advective and diffusive transport of ions through bentonite with explicit treatment of electrostatic effects. All codes show excellent agreement between results provided that the activity model, Debye-Hückel parameters, and thermodynamic data used in the simulations are consistent. A comparison of results using species-specific diffusion and uniform species diffusion reveals that simulated species concentrations in the effluent differ by less than 8 %, and that these differences vanish as the system approaches steady state.

Keywords

Bentonite clay Reactive transport Electrical double layer 

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References

  1. 1.
    Pusch, R., Karnland, O., Hökmark, H.: GMM – a general microstructural model for qualitative and quantitative studies of smectite clays. SKB Technical Report 90-43. Swedish Nuclear Fuel and Waste Management Corporation, Stockholm, Sweden (1990)Google Scholar
  2. 2.
    Bolt, G.H, de Haan, F.A.M.: Anion exclusion in soil. In: G.H. Bolt (ed.) Soil Chemistry: B. Physico chemical Models. Elsevier, Amsterdam (1982)Google Scholar
  3. 3.
    Van Loon, L.R, Glaus, M.A., Müller, W.: Anion exclusion effects in compacted bentonites: Towards a better understanding of anion diffusion. Appl. Geochem 22, 2536–2552 (2007)CrossRefGoogle Scholar
  4. 4.
    Tournassat, C., Appelo, C.A.J.: Modelling approaches for anion-exclusion in compacted Na-bentonite. Geochim. Cosmochim. Acta 75, 3698–3710 (2011)CrossRefGoogle Scholar
  5. 5.
    Keller, L.M., Seiphoori, A., Gasser, P., Lucas, F., Holzer, L., Ferrari, A.: The pore structure of compacted and partly saturated MX-80 bentonite at different dry densities. Clays Clay Miner. 62, 174–187 (2014)CrossRefGoogle Scholar
  6. 6.
    Birgersson, M., Karnland, O.: Ion equilibrium between montmorillonite interlayer space and an external solution—consequences for diffusional transport. Geochim. Cosmochim. Acta 73, 1908–1923 (2009)CrossRefGoogle Scholar
  7. 7.
    Parkhurst, D.L., Appelo, C.A.J.: Description of input and examples for PHREEQC Version 3–a computer program for speciation, batch-reaction, one-dimensional transport, and inverse geochemical calculations. http://purl.fdlp.gov/GPO/gpo37078 (2013)
  8. 8.
    Steefel, C.I., Appelo, C.A.J., Arora, B., Jacques, D., Kalbacher, T., Kolditz, O., Lagneau, V., Lichtner, P.C., Mayer, K.U., Meeussen, J.C.L., Molins, S., Moulton, D., Shao, H., Šimu̇nek, J., Spycher, N., Yabusaki, S.B., Yeh, G.T.: Reactive transport codes for subsurface environmental simulation. Comput. Geosci. doi:10.1007/s10596-014-9443-x (2014)
  9. 9.
    Appelo, C.A.J, Wersin, P.: Multicomponent diffusion modeling in clay systems with application to the diffusion of tritium, iodide, and sodium in opalinus clay. Environ. Sci. Technol. 41, 5002–5007 (2007)CrossRefGoogle Scholar
  10. 10.
    Karnland, O., Olsson, S., Dueck, A., Birgersson, M., Nilsson, U., Hernan-Håkansson, T., Pedersen, K., Nilsson, S., Eriksen, T., Rosborg, B.: Long term test of buffer material at the Äspö hard rock laboratory, LOT project. Final report on the A2 test parcel. TR-09-29, SKB, www.skb.se. Stockholm, Sweden (2009)
  11. 11.
    Fernández, R., Mäder, U., Jenni, A.: Multi-component advective diffusive transport experiment in MX80 compacted bentonite: Method and results of 1st phase of experiment, Nagra Arbeitsbericht, NAB, 11-02. Nagra, Wettingen Switzerland (2011)Google Scholar
  12. 12.
    Mäder, U., Jenni, A., Fernández, R., de Soto, I.: Reactive transport in compacted bentonite: Porosity concepts, experiments and applications. Goldschmidt Conference Abstracts. (http://www.vmgoldschmidt.org/2012/index.htm) (2012)
  13. 13.
    Steefel, C.I., Maher, K.: Fluid-rock interaction: a reactive transport approach. Rev. Mineral. Geochem. 70, 485–532 (2009). doi:10.2138/rmg.2009.70.11 CrossRefGoogle Scholar
  14. 14.
    Mayer, K.U.: MIN3P user guide, University of British Columbia, Department of 413 Earth and Ocean Sciences (2010)Google Scholar
  15. 15.
    Lichtner, P.C.: FLOTRAN Users Manual: Two-phase non-isothermal coupled thermal-hydrologic-chemical (THC) reactive flow and transport code, Version 2. Los Alamos National Laboratory, Los Alamos, New Mexico (2007)Google Scholar
  16. 16.
    Molins, S., Trebotich, D., Steefel, C.I., Shen, C.: An investigation of the effect of pore scale flow on average geochemical reaction rates using direct numerical simulation. Water Resour. Res. 48, W03527 (2012). doi:10.1029/2011WR011404 CrossRefGoogle Scholar
  17. 17.
    Liu, C., Shang, J., Zachara, J.M.: Multispecies diffusion models: a study of uranyl species diffusion. Water Resour. Res. 47, W12514 (2011)Google Scholar
  18. 18.
    Applin, K.R.: The diffusion of dissolved silica in dilute aqueous solution. Geochimica et Cosmochimica Acta 51(8), 2147–2151 (1987)CrossRefGoogle Scholar
  19. 19.
    Li, Y.-H., Gregory, S.: Diffusion of ions in sea water and in deep-sea sediments. Geochimica et Cosmochimica Acta 38(5), 703–714 (1974)CrossRefGoogle Scholar
  20. 20.
    Tournassat, C., Neaman, A., Villieras, F., Bosbach, D., Charlet, L.: Nanomorphology of montmorillonite particles: Estimation of the clay edge sorption site density by low-pressure gas adsorption and AFM observations. Am. Mineral. 88(11-12), 1989–1995 (2003)Google Scholar
  21. 21.
    Bradbury, M.H., Baeyens, B.: Porewater chemistry in compacted re-saturated MX-80 bentonite. J. Contam. Hydrol. 61(1-4), 329–338 (2003)CrossRefGoogle Scholar
  22. 22.
    Appelo, C.A.J., Van Loon, L.R., Wersin, P.: Multicomponent diffusion of a suite of tracers (HTO, Cl, Br, I, Na, Sr, Cs) in a single sample of opalinus clay. Geochimica Et Cosmochimica Acta 74, 1201–1219 (2010)CrossRefGoogle Scholar

Copyright information

© Springer International Publishing Switzerland 2014

Authors and Affiliations

  • P. Alt-Epping
    • 1
  • C. Tournassat
    • 2
  • P. Rasouli
    • 3
  • C. I. Steefel
    • 4
  • K. U. Mayer
    • 3
  • A. Jenni
    • 1
  • U. Mäder
    • 1
  • S. S. Sengor
    • 5
  • R. Fernández
    • 6
  1. 1.Rock-Water Interaction Group, Institute of Geological SciencesUniversity of BernBernSwitzerland
  2. 2.BRGMOrleans Cedex 2France
  3. 3.Department of Earth and Ocean SciencesUniversity of British ColumbiaVancouverCanada
  4. 4.Lawrence Berkeley National LaboratoryBerkeleyUSA
  5. 5.Southern Methodist UniversityDallasUSA
  6. 6.Departamento de Geología y Geoquímica, Facultad de CienciasUniversidad Autónoma de MadridMadridSpain

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