Hostname: page-component-7c8c6479df-27gpq Total loading time: 0 Render date: 2024-03-27T16:35:48.037Z Has data issue: false hasContentIssue false

Migration Behavior of Bentonite Colloids through a Fractured Rock

Published online by Cambridge University Press:  01 February 2011

Yoshio Kuno
Affiliation:
kuno.yoshio@jaea.go.jp, Japan Atomic Energy Agency, Tokai-mura, Ibaraki, Japan
Hiroshi Sasamoto
Affiliation:
sasamoto.hiroshi@jaea.go.jp, Japan Atomic Energy Agency, Tokai-mura, Ibaraki, Japan
Get access

Abstract

Bentonite colloids released into groundwater from the buffer in a geological repository for high-level radioactive waste may influence the migration of radioactive elements in fractures of the host rock. In the present study, column experiments were carried out to investigate the migration behavior of bentonite colloids in artificially fractured granite. The objective of the study is to determine whether the colloids are filtered by the fracture, considering the effects of the fracture length and the ionic strength of transporting solutions. Results indicate that bentonite colloids are not filtered if the transporting solution is dilute (i.e., distilled water or 10-4 M NaCl solution). This is evidenced by the observed tendency for normalized colloid concentrations in the column effluent (C/C0) to rapidly approach 1. An initial increase in the breakthrough curves is also observed at early stages of migration experiments involving more concentrated solutions (10-3 M NaCl solution), but the curves later evolve to an approximate steady state with C/C0 < 1. The amount of filtered colloids tends to increase with increasing fracture length. These results suggest that bentonite colloids can be filtered by interactions between the colloids and fracture surfaces, and that these interactions are affected by the ionic strength of the transporting solution. This migration behavior is simulated by a model of colloid migration, taking into consideration the effects of colloid filtration by fracture surfaces. The information on the filtration of bentonite colloids would contribute to a more realistic assessment of colloid effects on radionuclide migration.

Type
Research Article
Copyright
Copyright © Materials Research Society 2009

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

REFERENCES

1. Pusch, R., SKB Technical Report TR-99–31, (1999).Google Scholar
2. van Olphen, H., An Introduction to Clay Colloid Chemistry, 2nd ed., (Krieger Publishing Co., 1991), pp. 92110.Google Scholar
3. Kuno, Y., Kamei, G. and Ohtani, H., Mat. Res. Soc. Proc., 713, 841 (2002).Google Scholar
4. Lu, N. and Mason, C. F. V., Appl. Geochem., 16, 1653 (2001).Google Scholar
5. Painter, S., Cvetkovic, V., Pickett, D. and Turner, D. R., Environ. Sci. Technol., 36, 5369 (2002).Google Scholar
6. Möri, A., Alexander, W. R., Geckeis, H., Hauser, W., Schäfer, T., Eikenberg, J., Fierz, T., Degueldre, C. and Missana, T., Colloids Surf. A: Physicochem. Eng. Aspects, 217, 33 (2003).Google Scholar
7. Schäfer, T., Geckeis, H., Bouby, M. and Fanghänel, T., Radiochim. Acta, 92, 731 (2004).Google Scholar
8. Missana, T., Alonso, Ú., García-Gutiérrez, M. and Mingarro, M., Appl. Geochem., 23, 1484 (2008).Google Scholar
9. Ibaraki, M. and Sudicky, E. A., Water Resour. Res., 31, 2945 (1995).Google Scholar
10. Alonso, Ú., Missana, T., Patelli, A. and Rigato, V., Phys. Chem. Earth, Parts A/B/C, 32, 469 (2007).Google Scholar
11. Kosakowski, G., J. Contam. Hydrol., 72, 23 (2004).Google Scholar