Atmospheric Assessment

These are codes used to calculate atmospheric relative concentrations (X/Q) in support of assessments required by Title 10 of the U.S. Code of Federal Regulations (10 CFR) Part 50.



Software under active development which aims to combine multiple RAMP codes into one easy to use package.

Currently have two efforts underway for SIERRA

  • Atmospheric Dispersion Models:
    • ARCON2.0
    • PAVAN
    • NRCDose3 (XOQDOQ)
  • Source Term:
    • GALE
    • Advanced reactor source terms


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.


A control room.

ARCON is a computer code used to calculate atmospheric relative concentrations (X/Q) in support of control room habitability assessments required by 10 CFR Part 50, Appendix A, General Design Criterion 19. It uses hourly meteorological data and the atmosphere’s influence (i.e., dilution and dispersion) in the vicinity of buildings to calculate the relative concentration at control room air intakes. These concentrations would be exceeded no more than five percent of the time and calculated for averaging periods ranging from one hour to 30 days in duration.