Calculate relative ground-level air concentrations (χ/Q)

Reactor towers

PAVAN is a computer code used to estimate relative ground-level air concentrations (X/Q) for the assessment of potential accidental releases of radioactive material from nuclear facilities. These assessments are required by 10 CFR Part 50 and 10 CFR Part 100. PAVAN uses joint frequency distributions of wind direction and wind speed by atmospheric stability to estimate relative air concentration values for specific averaging time periods at specified distances. In particular, the averaging time periods range from one hour to 30 days in duration, and the distances usually correspond to the exclusion area boundary and the outer boundary of the low population zone.

The model is based on a straight-line Gaussian model that assumes the release rate is constant for the entire period of the release. PAVAN can account for variation in the location of release points, plume meander under low wind speed conditions, additional plume dispersion due to building wakes, and adjustments to consider non-straight trajectories.