**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.

**KEYWORDS: ** DIFFUSION THEORY; RADIONUCLIDES; WASTE MANAGEMENT