1. NAME AND TITLE

IONMIG: Code System for Radionuclide Migration Calculations.

2. CONTRIBUTOR

Sandia National Laboratories, Albuquerque, New Mexico.

3. CODING LANGUAGE AND COMPUTER

Fortran 77; Cray, Vax, CDC and IBM.

4. NATURE OF PROBLEM SOLVED

IONMIG is used to calculate the far-field transport of decaying radionuclides through a porous medium by diffusion and convection. It was specifically developed in support of the U. S. Subseabed Disposal program. For user specified velocity and temperature fields the convection-diffusion equation is solved in a sorbing porous medium. The sorption may be a function of species type, concentration, vertical position and local temperature. The formulation used is applicable to two-dimensional planar or axisymmetric geometries. Zero flux conditions are assumed at all but the upper boundaries.

5. METHOD OF SOLUTION

MacCormac's method, which is an explicit two-step finite difference technique, is used to solve the transient two-dimensional center differenced advection-diffusion equation. Linear and bilinear functional forms are used to represent the variation of equilibrium sorption coefficient with temperature and concentration. Input and output are unnormalized and are in metric units.

6. RESTRICTIONS OR LIMITATIONS

Comparison with analytic solutions of simple problems which test the diffusion, convection and radioactive decay terms of the transport equation show good overall agreement. When concentrations fall several orders of magnitude below the peak value, the accuracy of the code diminishes due to descretization error and numerical diffusion. When convection is significant, there is some pulse distortion and phase lag caused by operating below a Courant number of unity. These problems are accentuated when coupled with a variable equilibrium distribution coefficient.

7. TYPICAL RUNNING TIME

The sample problem takes 2.25 minutes on the IBM 3033.

8. COMPUTER HARDWARE REQUIREMENTS

The code runs on VAX 11/750, CDC 7600, Cray 1 and IBM computers.

9. COMPUTER SOFTWARE REQUIREMENTS

A Fortran 77 compiler and the International Mathematical and Statistical Library software are required.

10. REFERENCE

A. J. Russo, "A User's Manual for the Radionuclide Migration Code IONMIG," SAND83-1276 (November 1984).

11. CONTENTS OF CODE PACKAGE

Included is the referenced document and one (1.2MB) DOS diskette including the source file, sample input and output.

12. DATE OF ABSTRACT

May 1988.