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Diffusion in the Matrix of Granitic Rock Field Test in the Stripa Mine

Published online by Cambridge University Press:  28 February 2011

Lars Birgersson  and
Ivars Neretnieks
Lars Birgersson
Affiliation:
Royal Institute of Technology, Department of Chemical Engineering, S-100 44 Stockholm, Sweden
Ivars Neretnieks
Affiliation:
Royal Institute of Technology, Department of Chemical Engineering, S-100 44 Stockholm, Sweden
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Abstract

Three similar migration experiments in the matrix of granitic rock are presented. The experiments have been carried out in “undisturbed” rock, that is rock under its natural stress environment. Since the experiments were performed at the 360 m level (in the Stripa Mine), the rock was subjected to nearly the same conditions as the rock surrounding a nuclear waste repository as proposed in the Swedish concept (SKB).

A mixture of three non-sorbing (conservative) tracers, Uranine, Cr-EDTA and I−, were injected into the granitic rock matrix for time periods of months up to years. The subsequent overcorings of the injection holes showed that the tracers had in some cases migrated at least ≈ 400 mm (measuring limit) into the rock matrix for the experiment with the longest injection time. It could also be seen that there were large differences in migration distance into the rock matrix for samples taken fairly close to each other. One example where the tracers have diffused through fissure coating (filling) material located in “undisturbed” rock is also presented.

The results from all three experiments show that all three tracers have migrated through the disturbed zone close to the injection hole, through the fissure coating material and a distance into the “undisturbed” rock matrix.

These results therefore indicate that dissolved compounds may migrate into the rock matrix. This migration into the rock matrix will increase the area available for sorption of radionuclides significantly and may therefore increase the migration times for radionuclides by order(s) of magnitude.

Diffusivities and hydraulic conductivities obtained in this in-situ experiment compare well with those obtained in laboratory experiments.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 112: Symposium P – Scientific Basis for Nuclear Waste Management XI , 1987 , 189
Copyright
Copyright © Materials Research Society 1988

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References

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