SwRI Center for Nuclear Waste Regulatory Analyses Program Brief: Development of a Multi-Phase Nonisothermal Coupled Thermal-Hydrological-Chemical Flow and Transport Simulator

Development of a Multi-Phase Nonisothermal Coupled Thermal-Hydrological-Chemical Flow and Transport Simulator

Reactive chemical transport through porous media modeled using MULTIFLO. In this example, fluid undersaturated with respect to the solid is injected at the left, it follows flow paths indicated by the arrows and causes the solid (blue) through which it is flowing to dissolve (hot colors).

For more information, contact:
Hakan Basagaoglu
(210) 522-3522
hbasagaoglu@swri.org

Southwest
Research
Institute

Sponsor: U.S. Nuclear Regulatory Commission

Principal Investigator: Scott Painter, Ph.D.
Point of Contact: Hakan Basagaoglu

Program Brief

Statement of Problem: The client required a multipurpose code to enable modeling of reactive flow and transport within geologic and anthropogenically altered systems. Specifically, the code needed to (i) handle chemical reactions among minerals, metals, aqueous components and gas phases; (ii) allow for changes in temperature, pressure, and moisture distribution in porous and fractured systems; and (iii) dynamically update resulting changes in porosity and permeability.

Approach and Accomplishments: The code MULTIFLO was developed to address this problem. MULTIFLO describes coupled thermal-hydrological-chemical processes in single- and dual-permeability systems in one, two, and three spatial dimensions. MULTIFLO is a general code for simulating multiphase, multicomponent transport processes in nonisothermal systems with chemical reactions and reversible and irreversible phase changes in solids, liquids, and gases. MULTIFLO takes into account aqueous speciation of solutes, gaseous speciation, kinetically controlled aqueous reactions, mineral precipitation and dissolution reactions, ion exchange, and sorption. The flow field, temperature, pressure, and saturation states respond to changes in porosity and permeability resulting from various chemical reactions in the system. In addition to Cartesian or cylindrical geometries, other coordinate systems and geometrically complex domains may be readily treated by directly reading the input data in an unstructured grid format. The code uses robust and computationally efficient transport algorithms and can be run with limited computer memory. Arbitrary user-specified variability in rock properties is accommodated, and time-dependent boundary conditions and internal heat sources and sinks may be specified.

Client Benefits: MULTIFLO provides a powerful, multipurpose tool that enables a wide range of system perturbations to be evaluated quantitatively. MULTIFLO has been successfully applied to diverse problems, including alteration of high-level waste forms, thermal effects on regional-scale groundwater flow, drift-scale seepage and flow, and hydrothermal alteration of ore deposits.