Hostname: page-component-848d4c4894-8kt4b Total loading time: 0 Render date: 2024-07-07T14:41:33.252Z Has data issue: false hasContentIssue false

The Boom Clay geochemistry: Natural evidence

Published online by Cambridge University Press:  21 March 2011

M. De Craen*
Affiliation:
Belgian Nuclear Research Centre (SCK•CEN), Waste and Disposal Department, Boeretang 200, B-2400 Mol, (Belgium)
Get access

Abstract

In Belgium, the Boom Clay is studied as the reference formation for geological disposal of high-level radioactive waste and spent fuel. As the Boom Clay is considered as the main barrier for radionuclide migration/retention, a thorough characterisation of the clay and its pore water was done. This facilitates better understanding of the long-term geological processes and the distribution of the trace elements and radionuclides.

From a mineralogical/geochemical point of view, the Boom Clay is considered as a rather homogeneous sediment, vertically as well as laterally. It is composed of detrital minerals, organic matter and fossils. Minerals are mainly clay minerals, quartz and feldspars. Minor amounts of pyrite and carbonates are also present. Small variations in mineralogical/geochemical composition are related to granulometrical variations. The radiochemical study indicates that the Boom Clay is in a state of secular radioactive equilibrium, meaning that the Boom Clay has not been disturbed for a very long time.

Pore water sampling is done in situ from various piezometers, or by the squeezing or leaching of clay cores in the laboratory. These three pore water sampling techniques have been compared and evaluated. Boom Clay pore water is a NaHCO3 solution of 15 mM, containing 115 mg·1−1 of dissolved natural organic carbon. Some slight variations in pore water composition have been observed and can be explained by principles of chemical equilibrium.

Type
Research Article
Copyright
Copyright © Materials Research Society 2006

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. Vandenberghe, N. (1978) Sedimentology of the Boom Clay (Rupelian) in Belgium. Verhand. Kon. Acad. Wetenschappen België, XL, 147, pp. 137.Google Scholar
2. Echelpoel, E. Van (1991) Kwantitatieve Cyclostratigrafie van de Formatie van Boom (Rupeliaan, België) - De Methodologie van het onderzoek van Sedimentaire Cycly via Walshanalyse. Unpublished PhD. K.U.Leuven.Google Scholar
3. Craen, M. De, Delleuze, D., Volckaert, G., Sneyers, A. and Put, M. (2000) The Boom Clay as natural analogue. SCK•CEN Restricted contract report to ONDRAF/NIRAS for the period 1997-1999, Contract CCHO-98/332, KNT 90 98 1042, R-3444, Mol, Belgium.Google Scholar
4. Craen, M. De, Wang, L. and Weetjens, E. (2004) Natural evidence on the long-term behaviour of trace elements and radionuclides in the Boom Clay. SCK•CEN Restricted contract report to ONDRAF/NIRAS for the period 2000-2003, Contract CCHO 2000-773/00/00, KNT 90 01 1467. R-3926, Mol, Belgium.Google Scholar
5. Craen, M. De (2005) Geochemical characterisation of specific Boom Clay intervals. SCK•CEN Restricted contract report to ONDRAF/NIRAS, Contract CO 90 01 1467.01 – CCHO 2004-2470/00/00, R-4080, Mol, Belgium.Google Scholar
6. Craen, M. De, Wang, L., Geet, M. Van and Moors, H. (2004) The geochemistry of Boom Clay pore water at the Mol site, status 2004. SCK•CEN Scientific Report. BLG 990.Google Scholar
7. Craen, M. De, Swennen, R. and Keppens, E.M. (1999) Petrography and geochemistry of septarian carbonate concretions from the Boom Clay Formation (Oligocene, Belgium). Geologie en Mijnbouw 77, 6376.Google Scholar
8. Craen, M. De, Swennen, R., Keppens, E.M., Macaulay, C.I. and Kiriakoulakis, K. (1999) Bacterially mediated formation of carbonate concretions in the Oligocene Boom Clay of Northern Belgium. Journal of Sedimentary Research 69, 10981106.Google Scholar
9. Brookins, D.G. (1987) Sandstone uranium deposits: analogues for surf disposal in some sedimentary rocks. Natural Analogues in Radioactive Waste Disposal - A Symposium, Symposium Proceedings, volume 2 (Ed. by Côme, B. & Chapman, N.A.), Brussels, 28-30/04/1987CEC, Report nr EUR 11037 EN.Google Scholar
10. Menager, M.-T., Parneix, J.-C., Petit, J.-C. and Dran, J.-C. (1988) Migration of U, Th and REE in an Intragranitic Hydrothermal System: Implications for the Mobility of Actinides Around a Radwaste Repository. Radiochimica Acta, 44/45, 291297.Google Scholar
11. Petit, J.-C. (1991) Natural Analogue Aspects of Radionuclide Transport in the Geosphere. Radiochimica Acta, 52/53, 337340.Google Scholar
12. Yoshida, H., Monsecour, M. and Basham, I.R. (1991) Use of Microscopic Techniques in Migration studies on Boom Clay. Radiochimica Acta, 52/53, pp. 133138.Google Scholar
13. Faure, G. (1986) The U-series Disequilibrium Methods of Dating. In: Principles of Isotope Geology. Second edition (ed. Faure, G.), Chap. 21, John Wiley & Sons.Google Scholar
14. Ivanovich, M., Latham, A.G. and Ku, T.-L. (1992) Uranium-series disequilibrium applications in geochronology. In: Uranium-series disequilibrium: Applications to Earth, Marine, and Environmental Sciences. Second edition (eds. Ivanovich, M. & Harmon, R.S.), Chap. 3, pp. 6294. Clarendon Press, Oxford.Google Scholar
15. Ivanovich, M., Latham, A.G., Longworth, G. and Gascoyne, M. (1992) Applications to radioactive waste disposal studies. In: Uranium-series disequilibrium: Applications to Earth, Marine, and Environmental Sciences. Second edition (eds. Ivanovich, M. & Harmon, R.S.), Chap. 17, pp. 583630. Clarendon Press, Oxford.Google Scholar
16. Dickin, A.P. (1995) Radiogenic Isotope Geology. Cambridge University Press.Google Scholar
17. Fleischer, R.L.(1988) Alpha-recoil damage: Relation to isotopic disequilibrium and leaching of radionuclides. Geochim. Cosmochim. Acta, 52, 14591466.Google Scholar
18. Osmond, J.K. and Ivanovich, M. (1992) Uranium-series mobilization and surface hydrology. In: Uranium-series disequilibrium: Applications to Earth, Marine, and Environmental Sciences. 2nd edition (eds. Ivanovich, M. & Harmon, R.S.) Clarendon Press Oxford, 259289.Google Scholar