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Deposition of Calcium-Silicate-Hydrate Gel on Rough Surface of Granite from Calcium-rich Highly Alkaline Plume

Published online by Cambridge University Press:  27 March 2012

Yuichi Niibori ,
Kyo Komatsu  and
Hitoshi Mimura
Yuichi Niibori
Affiliation:
Dept of Quantum Science and Energy Engineering, Tohoku University, 6-6-01-2, Aza-Aoba, Aramaki, Aoba-ku, Sendai, 980-8589 Japan.
Kyo Komatsu
Affiliation:
Dept of Quantum Science and Energy Engineering, Tohoku University, 6-6-01-2, Aza-Aoba, Aramaki, Aoba-ku, Sendai, 980-8589 Japan.
Hitoshi Mimura
Affiliation:
Dept of Quantum Science and Energy Engineering, Tohoku University, 6-6-01-2, Aza-Aoba, Aramaki, Aoba-ku, Sendai, 980-8589 Japan.
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Abstract

Cement-based materials used in the construction of the repository for high/low level radioactive wastes may produce a highly alkaline calcium-rich groundwater (plume). The Ca ions react with soluble silicic acid, depositing calcium-silicate-hydrate (CSH) gel on the surfaces of the groundwater flow-paths and decreasing the permeability of the bedrock. Such a decrement of permeability may play a role in retarding the migration of radionuclides. In this study, the deposition behavior in a fracture was experimentally examined by using a micro flow-cell consisting of silicon plate (including a slit (60 mm×5 mm, or 60 mm×2 mm)) and granite-chip. The initial equivalent-aperture based on the square law was estimated in the range of 26 μm to 45 μm from the flow test of pure water.

In the experiments, a Ca(OH)2 solution of 6.36 mM (pH: 12.2 to12.5, including NaOH) was continuously injected into the flow system at a constant flow rate of 1 or 2 ml/h. The solution flowed on the surface of the granite-chip. In this study, we prepared two kinds of chips that differed in the treatment of the surface. One chip was roughly ground with #2000 sandpaper (hereinafter referred to as rough surface) and another was polished to mirror-like surface. As a result, on the rough surface the deposits of CSH gel appeared along flow-channels across mineral grain-boundaries, while the deposits on the mirror-like surface were relatively uniform. Furthermore, the permeability in the case of rough surface became smaller than that in the case of mirror-like surface, showing the repeats of rapid decrement and increment due to the relatively large roughness of the surface. In order to estimate the decrement degrees of permeability, a simple, one-dimensional mathematical model is proposed in this study.

Type
Articles
Information
MRS Online Proceedings Library (OPL) , Volume 1475: Symposium NW – Scientific Basis for Nuclear Waste Management XXXV , 2012 , imrc11-1475-nw35-p50
Copyright
Copyright © Materials Research Society 2012

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References

REFERENCES

1. Atkinson, A., AERE-R 11777, UKAEA (1985).Google Scholar
2. FEPC (Federation of Electric Power Companies of Japan) and JNC (Japan Nuclear Cycle development institute), JNC TY1400 2005-013, FEPC TRU-TR2-2005-02 (2005).Google Scholar
3. Chida, T. et al. ., Applied Geochemistry 22, 2810 (2007).10.1016/j.apgeochem.2007.06.018Google Scholar
4. Mäder, Urs K. et al. ., Journal of Geochemical Exploration, 90, 68 (2006).10.1016/j.gexplo.2005.09.006Google Scholar
5. Komatsu, K., Usui, H., Kadowaki, J., Niibori, Y., and Mimura, H., Proc. of 16PBNC (16th Pacific Basin Nuclear Conference), Paper No. P16P1167 (2008).Google Scholar
6. Ahn, J., Kawasaki, D., and Chambré, P. L., Nuclear Technology, 140, 94 (2002).10.13182/NT02-A3326Google Scholar
7. Haga, D., Niibori, Y., and Chida, T., Water Resour. Res., 35, 1065 (1999).10.1029/1998WR900111Google Scholar