Diffusion Measurements in Compacted Bentonite

Abstract

The diffusion of Cs, Sr, Am and Tc in compacted bentonite clay has been studied, using a diffusion cell where diffusion takes place axially from the center of a cylinder of the clay. The effect of addition of potential radionuclide getters to the clay (apatite for Am, pyrite, olivine, and Fe(s) for Tc) as well as using complexed (acetate) or colloidal Am has been studied.

The diffusivities obtained for Cs and Sr were very high − 9.0×10−13 m2/s and 2.6×10−12 m2/s, considering that if the effect of sorption on the clay is substracted the diffusivities would be 1.8×10−9 m2/s and 3.1×10−8 m2/s. These diffusivities are, however, maximum values as the concentration profiles do not follow the theoretical form for these nuclides. A small amount of the ions seems to migrate very fast, while the rest moves slower.

For Tc, that may be expected to be anionic and thus poorly sorbed, a diffusivity of 5.3×10−11 m2/s was obtained. Addition of Fe(s) decreases the diffusivity by one order of magnitude while olivine and pyrite have no measurable influence during the present contact times (2–3 months).

Americium is practically immobile.

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References

  1. 1.

    “Handling of Spent Nuclear Fuel and Final Storage of Vitrified High-Level Reprocessing Waste” and “Handling and Final Storage of Unreprocessed Spent Nuclear Fuel”, Kärnbränslesäkerhet (KBS) Stockholm 1977 and 1978.

  2. 2.

    B. Allard, K. Andersson, B. Torstenfeit, to be published.

  3. 3.

    A. Jacobsson, R. Pusch, “Egenskaper hos bentonitbaserat buffertmaterial” (Properties of bentonite based buffer substances), KBS-TR-32, Kärnbränslesäkerhet, Stockholm 1978 (in Swedish).

    Google Scholar 

  4. 4.

    U. Olofsson, B. Allard, K. Andersson, B. Torstenfeit, “Formation and Properties of Americium Colloids in Aqueous Systems” Proc. Mat. Res. Soc. Ann. Meeting, Boston Nov. 16–17, 1981.

  5. 5.

    B. Torstenfeit, K. Andersson, B. Allard, “Sorption of Sr and Cs on Rocks and Minerals. Part I: Sorption in Groundwater”, Report Prav 4.29, National Council for Radioactive Waste, Stockholm 1981.

    Google Scholar 

  6. 6.

    J. Crank, The Mathematics of Diffusion, (Oxford University Press, London 1956).

    Google Scholar 

  7. 7.

    R. C. Reid, J. M. Prausnitz, T. K. Sherwood, The Properties of Gases and Liquids, 3rd ed. (Mc Graw-Hill, New York 1977).

    Google Scholar 

  8. 8.

    I. Neretnieks, C. Skagius, “Diffusivitetsmätningar i våt lera. Na-lignosulfonat, Sr2+, Cs+” (Diffusivity measurements in wet compacted clay. Na-1ignosulphonate, Sr2+, Cs+), KBS-TR-87, Kärnbränslesäkerhet, Stockholm 1978 (in Swedish).

    Google Scholar 

  9. 9.

    T. Eriksen, A. Jacobsson, “Ion Diffusion Through Highly Compacted Bentonite”, KBS-TR-81-06, Kärnbränslesäkerhet, Stockholm 1981.

    Google Scholar 

  10. 10.

    B. Allard, G. Beall, “Sorption of Americium on Geologic Media”, Journ. Environmental Sci. and Health, 6 507 (1979).

    Google Scholar 

  11. 11.

    B. Allard, H. Kipatsi, B. Torstenfelt, “Technetium: Reduction and Sorption in Granitic Bedrock”. Radiochem. Radioanal. Letters 37 223 (1979).

    CAS  Google Scholar 

  12. 12.

    C. B. Amphlett, Inorganic Ion Exchangers, (Elsevier, Amsterdam 1964).

    Google Scholar 

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Correspondence to B. Torstenfelt.

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Torstenfelt, B., Andersson, K., Kipatsi, H. et al. Diffusion Measurements in Compacted Bentonite. MRS Online Proceedings Library 6, 295–302 (1981). https://doi.org/10.1557/PROC-6-295

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