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Science and Technology of Nuclear Installations
Volume 2013 (2013), Article ID 827961, 17 pages
http://dx.doi.org/10.1155/2013/827961
Research Article

Radionuclide Transport in Fractured Rock: Numerical Assessment for High Level Waste Repository

1Graduate Program of Nuclear Engineering (COPPE), Federal University of Rio de Janeiro, 21941-841 Rio de Janeiro, RJ, Brazil
2Department of Nuclear Engineering, Polytechnic School, Federal University of Rio de Janeiro, 21941-841 Rio de Janeiro, RJ, Brazil

Received 4 June 2013; Revised 2 October 2013; Accepted 3 October 2013

Academic Editor: Eugenijus Ušpuras

Copyright © 2013 Claudia Siqueira da Silveira et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Deep and stable geological formations with low permeability have been considered for high level waste definitive repository. A common problem is the modeling of radionuclide migration in a fractured medium. Initially, we considered a system consisting of a rock matrix with a single planar fracture in water saturated porous rock. Transport in the fracture is assumed to obey an advection-diffusion equation, while molecular diffusion is considered the dominant mechanism of transport in porous matrix. The partial differential equations describing the movement of radionuclides were discretized by finite difference methods, namely, fully explicit, fully implicit, and Crank-Nicolson schemes. The convective term was discretized by the following numerical schemes: backward differences, centered differences, and forward differences. The model was validated using an analytical solution found in the literature. Finally, we carried out a simulation with relevant spent fuel nuclide data with a system consisting of a horizontal fracture and a vertical fracture for assessing the performance of a hypothetical repository inserted into the host rock. We have analysed the bentonite expanded performance at the beginning of fracture, the quantified radionuclide released from a borehole, and an estimated effective dose to an adult, obtained from ingestion of well water during one year.