Surrogate Model for Multi-Component Diffusion of Uranium through Opalinus Clay on the Host Rock Scale
Source abstract
Abstract
Multi-component (MC) diffusion simulations enable a process based and more precise approach to calculate transport and sorption compared to the commonly used single-component (SC) models following Fick’s law. The MC approach takes into account the interaction of chemical species in the porewater with the diffuse double layer (DDL) adhering clay mineral surfaces. We studied the shaly, sandy and carbonate-rich facies of the Opalinus Clay. High clay contents dominate diffusion and sorption of uranium. The MC simulations show shorter diffusion lengths than the SC models due to anion exclusion from the DDL. This hampers diffusion of the predominant species CaUO2(CO3)32−. On the one side, species concentrations and ionic strengths of the porewater and on the other side surface charge of the clay minerals control the composition and behaviour of the DDL. For some instances, it amplifies the diffusion of uranium. We developed a workflow to transfer computationally intensive MC simulations to SC models via calibrated effective diffusion and distribution coefficients. Simulations for one million years depict maximum uranium diffusion lengths between 10 m and 35 m. With respect to the minimum requirement of a thickness of 100 m, the Opalinus Clay seems to be a suitable host rock for nuclear waste repositories.
Source: crossref · Quality: baseline
Research context
OpenAlex topics: Radioactive element chemistry and processing · Groundwater flow and contamination studies · Radioactivity and Radon Measurements
SciVX discovery tags are terminology-based. OpenAlex topics are source-provided classifications.
Affiliations
GFZ German Research Centre for Geosciences, Fluid Systems Modelling, Telegrafenberg, 14473 Potsdam, Germany
Institute of Geosciences, University of Potsdam, Karl-Liebknecht-Str. 24-25, 14476 Potsdam-Golm, Germany
Funding
Bundesministerium für Bildung und Forschung · Helmholtz Association
References (51)
Show source-provided references
1. IAEA (2003). Scientific and Technical Basis for the Geological Disposal of Radioactive Wastes, International Atomic Energy Agency. Technical Report.
2. Nagra (2002). Project Opalinus Clay—Safety Report, Negra. Nagra Technical Report; NTB 02-05.
3. Scientific investigation in deep wells for nuclear waste disposal studies at the Meuse/Haute Marne underground research laboratory, Northeastern France10.1016/j.pce.2005.11.004 ↗
4. Transferability of geoscientific information from various sources (study sites, underground rock laboratories, natural analogues) to support safety cases for radioactive waste repositories in argillaceous formations10.1016/j.pce.2008.10.046 ↗
5. Multicomponent diffusion modeling in clay systems with application to the diffusion of tritium, iodide, and sodium in opalinus clay10.1021/es0629256 ↗
6. Multicomponent diffusion of a suite of tracers (HTO, Cl, Br, I, Na, Sr, Cs) in a single sample of Opalinus Clay10.1016/j.gca.2009.11.013 ↗
7. Surface Properties of Clay Minerals10.1016/B978-0-08-100027-4.00001-2 ↗
8. ‘Geo’chemical research: A key building block for nuclear waste disposal safety cases10.1016/j.jconhyd.2008.09.012 ↗
9. Mont Terri rock laboratory, 20 years of research: Introduction, site characteristics and overview of experiments10.1007/s00015-016-0236-1 ↗
10. Pearson, F.J., Arcos, D., Bath, A., Boisson, J.Y., Fernández, A.M., Gäbler, H.E., Gaucher, E.C., Gautschi, A., Griffault, L., and Hernán, P. (2003). Mont Terri Project—Geochemistry of Water in the Opalinus Clay Formation at the Mont Terri Rock Laboratory, Federal Office for Water and Geology (FOWG). Technical Report 5.
11. Hennig, T., Stockmann, M., and Kühn, M. (2020). Simulation of diffusive uranium transport and sorption processes in the Opalinus Clay. Appl. Geochem., 123.10.1016/j.apgeochem.2020.104777 ↗
12. Radionuclide behaviour in the near-field of a geological repository for spent nuclear fuel10.1524/ract.2012.1967 ↗
13. Description of input and examples for PHREEQC Version 3—A computer program for speciation, batch-reaction, one-dimensional transport, and inverse geochemical calculations
14. Molecular simulation of the diffusion of uranyl carbonate species in aqueous solution10.1016/j.gca.2010.06.007 ↗
15. Multispecies diffusion models: A study of uranyl species diffusion10.1029/2011WR010575 ↗
16. Constraining porewater chemistry in a 250 m thick argillaceous rock sequence10.1016/j.chemgeo.2016.04.006 ↗
17. Diffusion of U(VI) in Opalinus Clay: Influence of temperature and humic acid10.1016/j.gca.2013.01.027 ↗
18. Keesmann, S., Noseck, U., Buhmann, D., Fein, E., and Schneider, A. (2005). Modellrechnungen zur Langzeitsicherheit von Endlagern in Salz- und Granitformationen, Gesellschaft für Anlagen- und Reaktorsicherheit (GRS) mbH. Technical Report GRS-206.
19. Wersin, P., Gaucher, E.C., Gimmi, T., Leupin, O.X., Mäder, U.K., Pearson, F.J., Thoenen, T., and Tournassat, C. (2009). Geochemistry of Porewaters in Opalinus Clay at Mont Terri: Experimental Data and Modelling, Mont Terri Project. Mont Terri Project, Technical Report; TR 2008-06.
20. Bradbury, M.H., and Baeyens, B. (1997). Derivation of In-Situ Opalinus Clay Porewater Compositions from Experimental and Geochemical Modelling Studies, Nagra. Nagra Technical Report, NTB 97-07.
21. Biogeochemical processes in a clay formation in situ experiment: Part E—Equilibrium controls on chemistry of pore water from the Opalinus Clay, Mont Terri underground research laboratory, Switzerland10.1016/j.apgeochem.2011.03.008 ↗
22. CO2 data on gas and pore water sampled in situ in the Opalinus Clay at the Mont Terri rock laboratory10.1016/j.pce.2008.10.050 ↗
23. Biogeochemical processes in a clay formation in situ experiment: Part A—Overview, experimental design and water data of an experiment in the Opalinus Clay at the Mont Terri underground research laboratory, Switzerland10.1016/j.apgeochem.2011.03.004 ↗
24. Dissolved CO2 and alkane gas in clay formations10.1016/j.proeps.2015.07.021 ↗
25. Gaucher, E.C., Lassin, A., Lerouge, C., Fléhoc, C., Marty, N.C.M., Benoit, H., Tournassat, C., Altmann, S., Vinsot, A., and Buschaert, S. (2010). CO2 Partial Pressure in Clayrocks: A General Model, HAL (archive hal-00664967). Water-Rock Interaction WRI-13.
26. Bossart, P., and Thury, M. (2008). Characteristics of the Opalinus Clay at Mont Terri, Swiss Geological Survey. Reports of the Swiss Geological Survey, No. 3.
27. Predicting the uptake of Cs, Co, Ni, Eu, Th and U on argillaceous rocks using sorption models for illite10.1016/j.apgeochem.2015.05.006 ↗
28. Smart Kd-values, their uncertainties and sensitivities—Applying a new approach for realistic distribution coefficients in geochemical modeling of complex systems10.1016/j.chemosphere.2017.08.115 ↗
29. Dzombak, D.A., and Morel, F.M.M. (1990). Surface Complexation Modeling: Hydrous Feric Oxide, Jon Wiley and Sons.
30. Sorption mechanism of U(VI) on a reference montmorillonite: Binding to the internal and external surfaces10.1023/A:1013212130177 ↗
31. Sorption of U(VI) onto Opalinus Clay: Effects of pH and humic acid10.1016/j.apgeochem.2013.06.016 ↗
32. Modelling the sorption of Mn(II), Co(II), Ni(II), Zn(II), Cd(II), Eu(III), Am(III), Sn(IV), Th(IV), Np(V) and U(VI) on montmorillonite: Linear free energy relationships and estimates of surface binding constants for some selected heavy metals and actinide10.1016/j.gca.2004.07.020 ↗
33. Sorption of Eu(III)/Cm(III) on Ca-montmorillonite and Na-illite. Part 2: Surface complexation modelling10.1016/j.gca.2005.06.031 ↗
34. Bradbury, M.H., and Baeyens, B. (2005). Experimental and Modelling Investigations on Na-Illite: Acid-Base Behaviour and the Sorption of Strontium, Nickel, Europium and Uranyl, Nagra. Nagra Technical Report, NTB 04-02.
35. Sorption of radionuclides onto natural clay rocks10.1524/ract.2008.1556 ↗
36. Effect of the pore water composition on the diffusive anion transport in argillaceous, low permeability sedimentary rocks10.1016/j.jconhyd.2018.05.001 ↗
37. Obtaining the porewater composition of a clay rock by modeling the in- and out-diffusion of anions and cations from an in-situ experiment10.1016/j.jconhyd.2008.07.009 ↗
38. Multicomponent diffusion in clays
39. Solute transport solved with the Nernst-Planck equation for concrete pores with ‘free’ water and a double layer10.1016/j.cemconres.2017.08.030 ↗
40. Gratwohl, P. (1958). Diffusion in Natural Porous Media: Contaminant Transport, Sorption/Desorption and Dissolution Kinetics, Kluwer Academic Publishers.
41. Anion exclusion effects in compacted bentonites: Towards a better understanding of anion diffusion10.1016/j.apgeochem.2007.07.008 ↗
42. The diffusion of SO42- in Opalinus Clay: Measurements of effective diffusion coefficients and evaluation of their importance in view of microbial mediated reactions in the near field of radioactive waste repositories10.1016/j.apgeochem.2018.05.009 ↗
43. Effect of confining pressure on the diffusion of HTO, 36Cl- and 125I- in a layered argillaceous rock (Opalinus Clay): Diffusion perpendicular to the fabric10.1016/S0883-2927(03)00047-7 ↗
44. Mazurek, M., Alt-Epping, P., Bath, A., Gimmi, T., and Waber, H. (2009). Natural Tracer Profiles Across Argillaceous Formations: The CLAYTRAC Project, Nuclear Energy Agency and Organisation for Economic Co-Operation and Development. Technical Report.
45. A modified version of Archie’s law to estimate effective diffusion coefficients of radionuclides in argillaceous rocks and its application in safety analysis studies10.1016/j.apgeochem.2015.04.002 ↗
46. Diffusion of HTO, 36Cl- and 125I- in Opalinus Clay samples from Mont Terri: Effect of confining pressure10.1016/S0169-7722(02)00114-6 ↗
47. Zorn, T. (2000). Untersuchungen der Sorption von Uran(VI) an das Gestein Phyllit zur Bestimmung von Oberflächenkomplexierungskonstanten. [Ph.D. Thesis, Technische Universität Dresden].
48. Sorption behavior of U(VI) on phyllite: Experiments and modeling10.1016/S0169-7722(00)00151-0 ↗
49. Modeling uranium(VI) adsorption onto montmorillonite under varying carbonate concentrations: A surface complexation model accounting for the spillover effect on surface potential10.1016/j.gca.2017.09.049 ↗
50. U (VI) sorption on Ca-bentonite at (hyper)alkaline conditions – Spectroscopic investigations of retention mechanisms10.1016/j.scitotenv.2019.04.274 ↗
51. Multi-proxy facies analysis of the Opalinus Clay and depositional implications (Mont Terri rock laboratory, Switzerland)10.1007/s00015-018-0303-x ↗