1. NAME AND TITLE

PAGAN 1.1: Code System for Performance Assessment Ground-water Analysis for Low-level Nuclear Waste.

2. CONTRIBUTOR

Sandia National Laboratories, Albuquerque, New Mexico.

3. CODING LANGUAGE AND COMPUTER

Fortran 77; IBM PC and compatibles.

4. NATURE OF PROBLEM SOLVED

The PAGAN code system is a part of the performance assessment methodology developed for use by the U. S. Nuclear Regulatory Commission in evaluating license applications for low-level waste disposal facilities. In this methodology, PAGAN is used as one candidate approach for analysis of the ground-water pathway. PAGAN, Version 1.1 has the capability to model the source term, vadose-zone transport, and aquifer transport of radionuclides from a waste disposal unit. It combines the two codes SURFACE and DISPERSE which are used as semi-analytical solutions to the convective-dispersion equation. This system uses menu driven input/out for implementing a simple ground-water transport analysis and incorporates statistical uncertainty functions for handling data uncertainties.

The output from PAGAN includes a time- and location-dependent radionuclide concentration at a well in the aquifer, or a time- and location-dependent radionuclide flux into a surface-water body.

5. METHOD OF SOLUTION

PAGAN uses a simple modelling approach to which the convective-dispersion equation is applied. The model for releases from a disposal unit is based on a cascade of mixing cells including leach mechanisms that can be used to analyze either surface-contaminated wastes or diffusion controlled releases.

6. RESTRICTIONS OR LIMITATIONS

The PAGAN code is not intended for complex analyses of ground-water transport.

7. TYPICAL RUNNING TIME

Execution times for the sample problems on a Northgate 486/66 were:

Sample problem Run time (approximate)

EX2A 6 seconds

EX2B 6 seconds

EX3 24 seconds

EX4A 7 seconds

EX4B 7 seconds

8. COMPUTER HARDWARE REQUIREMENTS

An IBM PC or compatible is required. A color monitor/adapter, 300K available conventional RAM, a math coprocessor, and hard disk are recommended.

9. COMPUTER SOFTWARE REQUIREMENTS

The system runs under DOS 3.31 or higher. The Fortran source files for PAGAN are included; however the SUNS (Sensitivity and UNcertainty Analysis Shell) portion of the source is not distributed. MS Fortran 5.1 compiler was used to create the executable included in the package.

10. REFERENCES

a: Included in documentation:

M. S. Y. Chu, "A Self-Teaching Curriculum for the NRC/SNL Low-Level Waste Performance Assessment Methodology," NUREG/CR-5539, SAND90-0585 WL (December 1990).

M. W. Kozak, "A Comparison Between Simple and Detailed Methods for Analyzing Releases of Radionuclides to Ground Water from Low-Level Waste Facilities," (February 1991).

b: Background information:

M. W. Kozak, M. S. Y. Chu, P. A. Mattingly, J. D. Johnson, and J. T. McCord, "Background Information for the Development of a Low-Level Waste Performance Assessment Methodology," NUREG/CR-5453, Vol. 5, SAND90-0375 WL (June 1990).

11. CONTENTS OF CODE PACKAGE

The referenced document and one DS/HD 3.5-in. (1.44 MB) diskette written in DOS format are included. The code package contains sample input and output and the PAGAN executables and the Fortran portion of the source.

12. DATE OF ABSTRACT

February 1994.

KEYWORDS: HYDRODYNAMICS; NUCLIDE TRANSPORT; LIQUID PATHWAY; WASTE MANAGEMENT;