Investigation of mineralogy, porosity and pore structure of Olkiluoto bedrock


Spent nuclear fuel from TVO’s (Teollisuuden Voima Oy) and Fortum’s nuclear power plants will be deposited deep in the crystalline bedrock in Olkiluoto, Western Finland. The bedrock needs to be well characterized to assess the risks inherent to the waste disposal at the site. If radionuclides (RN) are transported, it happens via water conducting fractures. Retardation may occur either by diffusion into stagnant pore water or by immobilization on mineral surfaces of the rock matrix. RN’s retardation from flowing water is linked to parameters defining porosity and microscopic rock pore structure, such as pore size distribution, connectivity, tortuosity and constrictivity, and by the mineralogy and chemical nature of the minerals and charge of the pore surfaces.

In this work, centimeter scale rock cores from Olkiluoto were investigated. The work is part of the in situ project REPRO (Experiments to investigate Rock Matrix Retention Properties) where the diffusion and sorption of RN are studied experimentally. Porosity and pore structures were characterized with the PMMA autoradiography method and polarized microscopy, which was used also to ascertain the mineralogy of the samples.

The results show that the rock from the REPRO site has low porosity with a mean value of 0.5% and a range of 0.1–1.5%. Rock heterogeneity explains the variation of porosity values. Correlation between the porosity and the mineralogy was found. Areas of high porosity correspond to areas of altered minerals, such as cordierite, biotite and plagioclase, which cover spatially between 10 and 20% of the rock volume

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  1. 1.

    Möri, A., et al., 2003. The Nagra-JNC in situ study of safety relevant radionuclide retardation in fractured crystalline rock. IV: the in situ study of matrix porosity in the vicinity of a water conducting fracture. Technical Report 00–08. Nagra, Wettingen/Switzerland

    Google Scholar 

  2. 2.

    Norton, D., Knapp, R., 1977. Transport phenomena in hydrothermal systems: the nature of porosity. American Journal of Science 277, 913–936.

    Article  Google Scholar 

  3. 3.

    Toropainen, V., 2012 Core Drilling of REPRO Drillholes in ONKALO at Olkiluoto 2010-2011, May 2012 Posiva Working Report, 78

  4. 4.

    International Society for Rock Mechanics, Commission on standardization of laboratory and field tests., International Journal of Rock Mechanics, Mining Science & Geomechanical Abstracts (1979) 16, 141–156

    Google Scholar 

  5. 5.

    Hellmuth, K-H., Siitari-Kauppi, M. and Lindberg, A., (1993) Journal of Contaminant Hydrology (1993), 13, 403–418

    CAS  Article  Google Scholar 

  6. 6.

    Hellmuth, K.-H., Lukkarinen, S. and Siitari-Kauppi, M., Isotopenpraxis. Isotopes in Environmental and Health Studies (1994), 30, 47–60

    CAS  Article  Google Scholar 

  7. 7.

    Hellmuth, K.-H. and Siitari-Kauppi, M., Klobes, P., Meyer, K., Goebbels, J., J. Applications, Phys. Chem. Earth A (1999), Vol. 24, No. 7, 569–573 10.1016/S1464-1895(99)00081-2

    Article  Google Scholar 

  8. 8.

    Siitari-Kauppi, M., Flitsiyan, E.S., Klobes, P., Meyer, K. and Hellmuth, (1998). Progress in Physical Rock Matrix Characterization: Structure of the Pore Space. In: I.G. McKinley, C. McCombie (edits.), Scientific Basis for Nuclear Waste Management XXI, Mat. Res. Soc. Symp. Proc. 506, 671–678

    CAS  Google Scholar 

  9. 9.

    Sammaljärvi, J., Jokelainen, L., Ikonen, I. and Siitari-Kauppi, M., Engineering Geology (2012) 135–136, 52–59

    Article  Google Scholar 

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Correspondence to Juuso Sammaljärvi.

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Sammaljärvi, J., Lindberg, A., Ikonen, J. et al. Investigation of mineralogy, porosity and pore structure of Olkiluoto bedrock. MRS Online Proceedings Library 1665, 31–37 (2014).

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