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A Study of Rock Matrix Diffusion Properties by Electrical Conductivity Measurements

Published online by Cambridge University Press:  10 February 2011

Y. Ohlsson  and
I. Neretnieks
Y. Ohlsson
Affiliation:
Department of Chemical Engineering and Technology. Royal Institute of Technology. Stockholm, Sweden.
I. Neretnieks
Affiliation:
Department of Chemical Engineering and Technology. Royal Institute of Technology. Stockholm, Sweden.
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Abstract

Traditional rock matrix diffusion experiments on crystalline rock are very time consuming due to the low porosity and extensive analysis requirements. Electrical conductivity measurements are, on the other hand, very fast and larger samples can be used than are practical in ordinary diffusion experiments. The effective diffusivity of a non-charged molecule is readily evaluated from the measurements, and influences from surface conductivity on diffusion of cations can be studied. A large number of samples of varying thickness can be measured within a short period, and the changes in transport properties with position in a rock core can be examined.

In this study the formation factor of a large number of Äspö diorite samples is determined by electrical conductivity measurements. The formation factor is a geometric factor defined as the ratio between the effective diffusivity of a non-charged molecule, to that of the same molecule in free liquid. The variation of this factor with position along a borecore and with sample length, and its coupling to the porosity of the sample is studied. Also the surface conductivity is studied. This was determined as the residual conductivity after leaching of the pore solution ions. The formation factor of most of the samples is in the range 1E-5 to 1E-4, with a mean value of about 5E-5. Even large samples (4-13 cm) give such values. The formation factor increases with increasing porosity and the change in both formation factor and porosity with position in the borecore can be large, even for samples close to each other.

The surface conductivity increases with increasing formation factor for the various samples but the influence on the pore diffusion seems to be higher for samples of lower formation factor. This suggests that the relation between the pore surface area and the pore volume is larger for samples of low formation factor.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 556: Symposium QQ – Scientific Basis for Nuclear Waste Management XXII , 1999 , 767
Copyright
Copyright © Materials Research Society 1999

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References

REFERENCES

1. Parkhomenko., E.I. Electrical Properties of Rocks. Plenum Press. New York. 1967. Pp. 277.Google Scholar
2. Conca, J.L., Wright, J. Diffusion Coefficients in Gravel Under Unsaturated Conditions. Water Resources Research, Vol.26, No. 5, pp. 1055–1066. May 1990.Google Scholar
3. Ohlsson, Y., Neretnieks, I.. Some Evidence for Surface Ion Mobility in Rock. Accepted for publication in J. of Cont. Hydr. Vol.35, pp. 91–100. January 1999 Google Scholar
4. Skagius, K.. Diffusion of Dissolved Species in the Matrix of Some Swedish Crystalline Rocks. Ph.D. Thesis. Royal Institute of Technology. Stockholm, Sweden 1986 Google Scholar
5. Eriksen, T.E., Jansson, M.. SKB Technical Report TR-96-16. Sweden 1996.Google Scholar
6. Yamaguchi, T., Sakamoto, Y. and Senoo, M.. J. of Nucl. Sci. & Techn., 30 [8], pp. 796–803 Google Scholar
7. Johansson, H., Byegdrd, J., Skarnemark, G. and Skdåberg, M.. In Scientific Basis for Nuclear Waste Management XX, edited by Gray, W.J. and Triay, I.R. (Mater. Res. Soc. Proc. Vol 465 Boston MA 1996). pp. 871–878.Google Scholar
8. Lobo, V.M.M., Quaresma, J.L. Handbook of Electrolyte Solutions. Part B. Department of Chemistry, University of Coimbra, 3000 Coimbra. Elsevier Science 1989.Google Scholar
9. Weast, R.E., Astle, M.J.. CRC Handbook of Chemistry and Physics, pp. D-277-D-279. 60th ed. (CRC Press Inc. Boca Raton, Florida)Google Scholar
10. Conca, J.L., Apted, M., Arthur, R. In Scientific Basis for Nuclear Waste Management XVI, edited by Interrante, C.G. and Pabalan, R.T. (Mater. Res. Soc. Proc. Vol 294 Boston MA 1992). pp. 395–402.Google Scholar