1. NAME AND TITLE

DUST-BNL: Disposal Unit Source Term by One-Dimensional, Transient, Finite-Difference, Subsurface Release and Transport of Solute Contaminants.

AUXILIARY ROUTINES:

DUSTIN: Menu driven input preprocessor for DUST

GRAFXT: Menu driven graphical output processor for DUST

IOSWTCH: Utility for putting output files into spreadsheet format

2. CONTRIBUTOR

Brookhaven National Laboratory, Upton, New York.

3. CODING LANGUAGE AND COMPUTER

FORTRAN-77; IBM PC's and compatibles, 386 or 486 processor (C00634/PC386/00).

4. NATURE OF PROBLEM SOLVED

DUST solves for release and transport of contaminants from containerized wastes. Each container may have unique properties (i.e., time to failure or localized failure, e.g., pitting) and each waste form may have unique release properties. Release from the waste form is limited by one of four physical or chemical restraints: solubility, diffusion, dissolution, and surface wash-off with partitioning. The release from the waste form acts as a source for transport in the advection/dispersion equation. Transport is modeled in one-dimension through the groundwater pathway from subsurface disposal. RNUCL.DAT, database of half-lives, solubility limits, and atomic mass for selected radionuclides, is included in this package.

5. METHOD OF SOLUTION

The advection/dispersion transport equation with spatially varying sources (waste forms) is solved using the method of finite-differences. Advancement in time is achieved using the fully implicit backward Euler scheme. An option exists which permits an analytical solution to the advection equation with spatially varying sources. This procedure is an extension of the mixing-cell cascade models. Radioactive decay and sorption processes are included in either model. Container performance is calculated through empirical correlations and user-supplied input data. Waste form release characteristics are simulated with geometry-dependent (rectangular or cylindrical waste forms) analytical solutions to the diffusion equation. Dissolution is modeled through an input value specifying yearly fractional release rate and rinse release with partitioning is simulated using user-supplied values. In all cases, checks are made to prevent solubility limits from being exceeded.

6. RESTRICTIONS OR LIMITATIONS

One-dimensional.

Maximum problem size is 1000 time steps and 500 computational points. These can be readjusted by redimensioning the code.

Maximum number of waste containers and waste forms is 300.

Maximum number of materials is 10 (i.e., number of regions with different transport properties).

Water flow is treated through tabular input. Flow rates must be estimated by other computer codes.

Simulates only a single-species.

Changes in chemistry over time are not modeled.

7. TYPICAL RUNNING TIME

For a problem with 100 computational points and 100 time steps the run time is less than 5 seconds on a 486/50 IBM PC compatible.

8. COMPUTER HARDWARE REQUIREMENTS

An IBM PC or compatible with a minimum of a 386 processor. 500K of RAM of available conventional RAM is required for execution. Approximately 4 MB of disk space is required for the entire code package.

9. COMPUTER SOFTWARE REQUIREMENTS

The GRAFXT utility was compiled using the Lahey Fortran v5.0 graphics library. You will need this compiler if you recompile the source for GRAFXT. The included executables are bound with the Phar Lap DOS extender and do not require the Lahey Fortran package to execute.

10. REFERENCES

a: Included in documentation:

T. M. Sullivan, "DUST - Disposal Unit Source Term: Data Input Guide," NUREG/CR-6041, BNL-NUREG-52375 (May 1993).

b: Background information:

T. M. Sullivan, "Selection of Models to Calculate the LLW Source Term," NUREG/CR-5773, BNL-NUREG-52295 (October 1991).

11. CONTENTS OF CODE PACKAGE

The referenced document and one DS/HD (1.44 MB) diskette are included. The diskette, written in a DOS compressed, self-extracting file, contains the source files, executables, sample input and output, and an information file.

12. DATE OF ABSTRACT

July 1995.