1. NAME AND TITLE

DPCT: A Deterministic-Probabilistic Model For Contaminant Transport

2. CONTRIBUTORS

Nuclear Regulatory Commission, Washington, D.C.

Oak Ridge National Laboratory, Oak Ridge, Tennessee.

3. CODING LANGUAGE AND COMPUTER

FORTRAN 77; CDC Cyber, Cray XMP.

4. NATURE OF PROBLEM SOLVED

DPCT is designed to simulate mass transfer by ground water movement in a vertical section of the earth's mass. The model can account for convection, dispersion, radioactive decay, and cation exchange for a single component.

5. METHOD OF SOLUTION

The hybrid deterministic-probabilistic model is used. The hybrid method addresses the fundamental problem of describing the spread of a large number of moving reference particles within a region. It is impossible to represent individual particle motion in exact mathematics. Statistical features provide a basis for representing an idealized pattern of motion. Because the individual particle position is known, one can easily determine the distribution of contaminant mass. This distribution can be expressed in terms of concentrations. The actual pattern of ground water flow is described by the ground water velocity field. A velocity is calculated for each reference particle in the region by interpolating values from the two-dimensional grid of velocities. Dispersion is accounted for in the particle motion by adding a random component to the deterministic motion. By summing the mass carried by each particle in a given cell and by determining the volume of water in the cell, it is possible to calculate contaminant concentrations within the region. When only convective and dispersive processes act, the quantity of mass is constant. However, when there is radioactive decay or cation exchange, the quantity of mass is decreased. The solution of the ground water flow equation and the dispersion-convection equation is subject to boundary conditions.

6. RESTRICTIONS OR LIMITATIONS

The model is sufficiently general to enable the user to specify virtually any type of water table or geologic configuration, and a variety of boundary conditions.

7. TYPICAL RUNNING TIME

The code was tested on a Cray XMP/14 under UNICOS. The sample problem took 1.28 seconds of CPU time.

8. COMPUTER HARDWARE REQUIREMENTS

The code will run on the CDC Cyber computers and the Cray computers.

9. COMPUTER SOFTWARE REQUIREMENTS

The code is written in FORTRAN 77. On the Cray, the compiler used was CFT77 under the UNICOS operating system.

10. REFERENCES

a. Included in the package:

A Deterministic-Probabilistic Model For Contaminant Transport, NUREG/CR-1609, prepared by F. W. Schwartz and A. Crowe for US-NRC, Washington, D.C., August 1980.

11. CONTENTS OF CODE PACKAGE

Included are the referenced document and one DS/HD 5.25-inch diskette (1.2 MB), containing the source code, sample input and output.

12. DATE OF ABSTRACT

January 1991.