Lawrence Berkeley Laboratory, Report LBL-34868, November 1995.
EOS7R: Radionuclide Transport for TOUGH2
C. M. Oldenburg, and K. Pruess
Lawrence Berkeley National Laboratory, Earth Sciences Division
University of California, Berkeley, CA 94720
EOS7R provides radionuclide transport capability for TOUGH2.
EOS7R extends the EOS7 module (water, brine, and optional air) to model water,
brine, parent component, daughter component, and optional air and heat.
The radionuclide components follow a first-order decay law, and may adsorb
onto the solid grains. Volatilization of the decaying components is modeled by Henry's Law.
The decaying components are normally referred to as radionuclides, but they may in fact be
any trace components that decay, adsorb, and volatilize. The decay process need not be
radioactive decay, but could be any process that follows a first-order decay law,
such as biodegradation. EOS7R includes molecular diffusion for all components in
gaseous and aqueous phases using a simplified binary diffusion model.
When EOS7R is used with standard TOUGH2, transport occurs by advection and molecular diffusion
in all phases. When EOS7R is coupled with the dispersion module T2DM, one obtains T2DMR,
the radionuclide transport version of T2DM. T2DMR models advection, diffusion, and
hydrodynamic dispersion in rectangular two-dimensional regions. Modeling of radionuclide
transport requires input parameters specifying the half-life for first-order decay,
distribution coefficients for each rock type for adsorption, and inverse Henry's constants
for volatilization. Options can be specified in the input file to model decay in "inactive"
grid blocks and to read from standard EOS7 INCON files. We present a number of example
problems to demonstrate application and accuracy of TOUGH2/EOS7R. One-dimensional simulation
results agree well with analytical solutions. For a two-dimensional salt-dome flow problem,
the final distribution of daughter radionuclide component is complicated by the presence of
weak recirculation caused by density effects due to salinity.