Two-dimensional nuclide decay chain transport in a fractured porous mediumby a control volume approach

A general two-dimensional numerical solution for nuclide transport through fractured porous rock is introduced. A main advantage of the model over pre vious models is that it is based on a physically exact approach by utilizin g a control volume formulation method in which the differential governing e quation can be directly integrated over each control volume. Assuming a lin ear sorption isotherm, nuclide transport of arbitrary decay chain length du e to advection and dispersion along thin rigid parallel fractures wall into the matrix is considered. To verify the model and to illustrate its usabil ity and exactness in simulating multi-member chain decay and transport, a t hree-member decay chain U-234 --> Th-230 --> Ra-226 is chosen. The results for various cases are compared with available analytical solutions. Since t he model can employ variable temporal and spatial discretization, larger pr actical problems associated with geological repository systems can be addre ssed with significant savings in computational resources. (C) 1999 Elsevier Science Ltd. All rights reserved.