Erosion dynamics of compacted raw or homoionic MX80 bentonite in a low ionic strength synthetic water under quasi-stagnant flow conditions
Source abstract
Abstract
Abstract Bentonite is planned to be used as a backfill material in deep geological repositories (DGR) notably for those to be established in crystalline rock. Potential erosion processes have to be clearly understood in order to properly assess its long-term barrier function. A likely scenario over the lifetime of a DGR in certain geographical locations is the intrusion of low mineralized glacial melt water through low transmissivity bedrock fractures that could interact with bentonite and favor release of clay colloids. The objective of this work was to determine the dynamic of erosion under a glaciation scenario for Na-exchanged, Na-Ca-exchanged, Ca-exchanged and raw bentonite. The different bentonite types cover different potential materials used for backfill and different stages of cation loading via cation exchange processes upon contact with groundwater of different composition. To this end, erosion experiments were carried out with highly compacted bentonite confined by a porous filter (20 μm) under dynamic conditions simulating the presence of a hydraulically active fracture filled with fault gauge and fracture filling minerals. The The erosion (clay colloid detachment) via a low mineralized groundwater flow was quantified by determining an average eluted mass loss rate (AMLR). AMLR values integrated over 1466 days (4 years) erosion time for the raw MX80 bentonite, the Na-MX80 and the Na-Ca-MX80 are at 0.019 ± 0.003 kg/y/m2, 0.245 ± 0.007 kg/y/m2 and 0.10 ± 0.02 kg/y/m2, respectively. Only by the sensitive ICP-MS analysis of clay-bound Th and U a tiny detachment of particles from Ca-MX80 could be identified, which shows the highest resistivity against erosion (0.004 ± 0.002 kg/y/m2). The experiments pointed to the swelling pressure as main driving force for colloid generation. A possible inhibiting effect of accessory minerals on erosion can also be deduced from this study. Assuming erosion via a groundwater flow from a single fracture intersecting a deposition hole filled with raw MX80 bentonite at an angle of 90o and with a fracture aperture of up to 200 μm, the present estimations indicated that under the given scenario the mass loss limit of 1200 kg bentonite will not be reached during the first 106 years.
Source: openaire · Quality: candidate unverified · Source record ↗
Research context
OpenAlex topics: Groundwater flow and contamination studies · Soil and Unsaturated Flow · Hydraulic Fracturing and Reservoir Analysis
SciVX discovery tags are terminology-based. OpenAlex topics are source-provided classifications.
References (58)
Show source-provided references
1. Size distribution analysis of colloid generated from compacted bentonite in low ionic strength aqueous solutions10.1016/j.clay.2014.04.025 ↗
2. Alonso, U., Missana, T., García-Gutiérrez, M., 2007. Experimental approach to study the colloid generation from the bentonite barrier to quantify the source term and to assess its relevance on the radionuclide migration, 2006 MRS Fall Meeting, Boston, MA, pp. 605–610.10.1557/PROC-985-0985-NN11-21 ↗
3. Erosion behaviour of raw bentonites under compacted and confined conditions: Relevance of smectite content and clay/water interactions10.1016/j.apgeochem.2018.04.012 ↗
4. Effect of clay-water interactions on clay swelling by X-ray diffraction10.1016/j.nima.2007.05.103 ↗
5. Long-term geochemical evolution of the near field repository: Insights from reactive transport modelling and experimental evidences10.1016/j.jconhyd.2008.09.021 ↗
6. Erosion of bentonite particles at the interface of a compacted bentonite and a fractured granite10.1016/j.enggeo.2007.02.002 ↗
7. Nuclear waste management special issue10.1180/S0026461X00006162 ↗
8. BelBar
9. Generation and sedimentation of colloidal bentonite particles in water10.1016/j.clay.2008.08.006 ↗
10. Swelling behavior of compacted bentonite with the presence of rock fracture10.1016/j.enggeo.2019.04.004 ↗
11. State of compacted bentonite inside a fractured granite cylinder after infiltration10.1016/j.clay.2020.105438 ↗
12. A review and comparison of fracture mineral investigations and their application to radioactive waste disposal10.1016/j.apgeochem.2008.12.036 ↗
13. Interaction of bentonite colloids with Cs, Eu, Th and U in presence of humic acid: a flow field-flow fractionation study10.1016/j.gca.2011.04.015 ↗
14. Physico-chemical characterisation data and sorption measurements of Cs, Ni, Eu, Th, U, Cl, I and Se on MX-80 bentonite
15. Rheological properties of clay material at the solid/solution interface formed under quasi-free swelling conditions10.1016/j.clay.2015.02.018 ↗
16. Analytical applications of photon correlation spectroscopy for size distribution measurements of natural colloidal suspensions: Capabilities and limitations10.1016/S0927-7757(96)03677-1 ↗
17. Kinetic determination of critical coagulation concentrations for sodium- and calcium-montmorillonite colloids in NaCl and CaCl2 aqueous solutions10.1016/j.jcis.2007.07.002 ↗
18. Determining pseudo-equilibrium of montmorillonite colloids in generation and sedimentation experiments as a function of ionic strength, cationic form, and elevation10.1016/j.jcis.2009.02.048 ↗
19. A robust model for pore-water chemistry of clayrock10.1016/j.gca.2009.07.021 ↗
20. Results of the colloid and radionuclide retention experiment (CRR) at the Grimsel Test Site (GTS), Switzerland - impact of reaction kinetics and speciation on radionuclide migration10.1524/ract.92.9.765.54973 ↗
21. Modelling coupled processes in bentonite: recent results from the UK's contribution to the Aspo EBS Task Force10.1180/minmag.2012.076.8.19 ↗
22. Johansson, B., Äikas, K., Autio, J., Hagros, A., Malmund, H., Rautakorpi, J., Sievänen, U., Wanne, T., Antilla, P., Raiko, H., 2002. Preliminary KBS-3H layout adaptation for the Olkiluoto site, Working report. POSIVA OY, Olki luoto, FI-27160 Eurajoki, Finland.
23. Karnland, O., 2010. Chemical and mineralogical characterization of the bentonite buffer for the acceptance control procedure in a KBS-3 repository, in: SKB (Ed.), Internal Report TR-10-60, p. 29.
24. Karnland, O., Olsson, S., Nilsson, U., 2006. Mineralogy and sealing properties of various bentonite and smectite-rich clay materials. in: SKB (Ed.), Internal Report TR-06-30.
25. Detachment of colloidal particles from bentonites in water10.1016/j.clay.2007.04.008 ↗
26. Liu · 2006 · 43
27. Prediction of swelling pressures of different types of bentonite in dilute solutions10.1016/j.colsurfa.2013.05.068 ↗
28. Determination of the cation exchange capacity (CEC) of clay minerals using the complexes of copper(II) ion with triethylenetetramine and tetraethylenepentamine10.1346/CCMN.1999.0470315 ↗
29. Miller · 2000
30. Generation and stability of bentonite colloids at the bentonite/granite interface of a deep geological radioactive waste repository10.1016/S0169-7722(02)00110-9 ↗
31. Analysis of colloids erosion from the bentonite barrier of a high level radioactive waste repository and implications in safety assessment10.1016/j.pce.2011.07.088 ↗
32. Analysis of the stability behaviour of colloids obtained from different smectite clays10.1016/j.apgeochem.2018.03.010 ↗
33. Colloidal properties of different smectite clays: significance for the bentonite barrier erosion and radionuclide transport in radioactive waste repositories10.1016/j.apgeochem.2018.08.008 ↗
34. Erosion of sodium bentonite by flow and colloid diffusion10.1016/j.pce.2011.07.034 ↗
35. The colloid and radionuclide retardation experiment at the Grimsel Test Site: influence of bentonite colloids on radionuclide migration in a fractured rock10.1016/S0927-7757(02)00556-3 ↗
36. Predicting the swelling pressure of MX-80 bentonite10.1016/j.clay.2017.08.014 ↗
37. Montmorillonite colloids: I. Characterization and stability of dispersions with different size fractions10.1016/j.clay.2015.05.028 ↗
38. Montmorillonite colloids: II. Colloidal size dependency on radionuclide adsorption10.1016/j.clay.2016.01.017 ↗
39. Size characterization of bentonite colloids by different methods10.1021/ac010116t ↗
40. Use of bentonite for isolation of radioactive waste products10.1180/claymin.1992.027.3.08 ↗
41. Ravier, E., Buoncristiani, J.F., 2018. Glaciohydrogeology, in: Menzies, J., van der Meer, J.J.M. (Eds.), In Past Glacial Environments (Second Edition). Elsevier, pp. 431–466.10.1016/B978-0-08-100524-8.00013-0 ↗
42. A mechanism for bentonite buffer erosion in a fracture with a naturally varying aperture10.1180/minmag.2015.079.6.23 ↗
43. Filtering of clay colloids in bentonite detritus material10.1002/ceat.201000108 ↗
44. Long-term bentonite erosion in an artificial fracture under near-neutral advective conditions
45. Fracture-related hydrothermal alteration of metagranitic rock and associated changes in mineralogy, geochemistry and degree of oxidation: a case study at Forsmark, Central Sweden10.1007/s00531-008-0369-1 ↗
46. Schatz · 2013
47. Influence of exchangeable cation composition on the size and shape of montmorillonite particles in dilute suspension10.1346/CCMN.1982.0300105 ↗
48. Microstructural and swelling properties of Ca and Na montmorillonite: (in situ) observations with Cryo-TEM and SAXS10.1021/jp300531y ↗
49. Seher, H., 2011. Influence of colloids on the migration of radionuclides, PhD thesis, University of Heidelberg, Faculty of Chemistry and Earth Sciences ed, p. 252.
50. Colloid generation by erosion of compacted bentonite under different geochemical conditions
51. Shelton, A., Sellin, P., Missana, T., Schäfer, T., Červinka, R., Koskinen, K., 2018. BELBaR Synthesis report: Colloids and related issues in the long term safety case. In: Report, S.T. (Ed.).
52. SKB, 2010. Design and production of the KBS-3 repository., in: Svensk Kärnbränslehantering AB, S. (Ed.), SKB Internal Report.
53. SKB, 2011. Long-term safety for the final repository for spent nuclear fuel at forsmark, main report of the SR-site project. In: Svensk Kärnbränslehantering AB, S. (Ed.), SKB Technical Report.
54. SKB, 2011a. Long-term safety for the final repository for spent nuclear fuel at Forsmark, in: AB, S.K. (Ed.), Technical report, pp. 1–276.
55. SKB, 2011b. Long-term safety for the final repository for spent nuclear fuel at forsmark, in: AB, S.K. (Ed.), Technical report, pp. 287–549.
56. Smith, P., Schatz, T., Reijonen, H., Hellä, P., 2017. Chemical erosion and mass redistribution of bentonite in a KBS-3H repository, in: Posiva OY, O.l., FI-27160 Eurajoki, Finland (Ed.), Eurajoki, Finland, p. 168.
57. Workshop on copper corrosion and buffer erosion
58. Vieno, T., Ikonen, A.T.K., Vähänen, M., 2005. Plan for safety case of spent fuel repository at Olkiluoto, Proceedings – 10th International Conference on Environmental Remediation and Radioactive Waste Management, ICEM'05, pp. 629–635.