1. NAME AND TITLE

PAVAN2: Atmospheric Dispersion Code System for Evaluating Accidental Radioactivity Releases from Nuclear Power Stations.

2. CONTRIBUTOR

Pacific Northwest National Laboratory, Richland, Washington, through the US Nuclear Regulatory Commission, Rockville Maryland, USA..

3. CODING LANGUAGE AND COMPUTER

FORTRAN; Linux, MacOS and Windows OS are supported (RSICC ID: C00879PCX8600).

4. NATURE OF PROBLEM SOLVED

PAVAN2 estimates down-wind ground-level air concentrations for potential accidental releases of radioactive material from nuclear facilities. Options can account for variation in the location of release points, additional plume dispersion due to building wakes, plume meander under low wind speed conditions, and adjustments to consider non-straight trajectories. It computes an effective plume height using the physical release height which can be reduced by input terrain features.

5. METHOD OF SOLUTION

Using joint frequency distributions of wind direction and wind speed by atmospheric stability, the program provides relative air concentration (X/Q) values as functions of direction for various time periods at the exclusion area boundary (EAB) and the outer boundary of the low population zone (LPZ). Calculations of X/Q values can be made for assumed ground-level releases or elevated releases from free-standing stacks. The X/Q calculations are based on the theory that material released to the atmosphere will be normally distributed (Gaussian) about the plume centerline. A straight-line trajectory is assumed between the point of release and all distances for which X/Q values are calculated.

6. RESTRICTIONS OR LIMITATIONS

The code cannot handle multiple emission sources.

7. TYPICAL RUNNING TIME

The running time depends on the case and the calculation parameters.

8. COMPUTER HARDWARE REQUIREMENTS

Should work on any Windows platform.

9. COMPUTER SOFTWARE REQUIREMENTS

None listed

10. REFERENCE

T. J. Bander, "PAVAN: An Atmospheric Dispersion Program for Evaluating Design Basis Accidental Releases of Radioactive Materials from Nuclear Power Stations," NUREG/CR-2858 (November 1982).

11. CONTENTS OF CODE PACKAGE

The package is transmitted digitally as a zip file that includes Windows executables, documentation, source and sample problems.

12. DATE OF ABSTRACT

August 2025