Rock-Matrix Diffusion and its Implications for Radionuclide Migration

D. A. Lever and M. H. Bradbury
Theoretical Physics and Chemical Technology Divisions, AERE Harwell, Oxfordshire OXl1 0RA

Abstract: Diffusion into the rock matrix is potentially an important retardation mechanism for nuclides leached from an underground radioactive waste repository in a fractured hard rock. A technique for measuring the intrinsic diffusion coefficient and rock capacity factor is briefly described. Simple solutions to migration model equations are used, together with diffusion results and typical hydrogeological parameters, to estimate the impact of matrix diffusion on radionuclide migration. It is shown that retardation factors in excess of 100 and reductions in the peak concentration by 3–4 orders of magnitude are possible for non-sorbed ions, which would otherwise be carried by the flow and not retarded at all.

Keywords: radionuclides • radioactive waste • diffusion

Mineralogical Magazine; April 1985 v. 49; no. 351; p. 245-254; DOI: 10.1180/minmag.1985.049.351.11
© 1985, The Mineralogical Society
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