Atmospheric Dispersion Codes

[Jim Hardeman <Jim_Hardeman@mail.dnr.state.ga.us>]

Fellow RADSAFEr's and REPLANer's ...

I am currently reviewing radiological emergency preparedness
documents in which the facility operator uses the results of
far-field (> 10 km) atmospheric dispersion calculations as the
primary, perhaps even sole, basis for an emergency
classification. For example, if the calculated dose is 900
mrem, the facility operator will declare a Site Area
Emergency ... if the calculated dose is > 1000 mrem, the
facility operator will declare a General Emergency. 

My training and experience has led me to conclude that
far-field atmospheric dispersion calculations are only accurate
to an order of magnitude at best, and probably to 2-3 orders
of magnitude. However, I don't have any hard citations for this.

Do any of you know of references that I might look at with
regard to the "accuracy" of far-field atmospheric dispersion
codes as verified by comparisons to field measurements ...
regardless of the "contaminant" released? Is my assessment
of the "accuracy" of these codes in the right ballpark?

Thanks in advance for your help!!

Jim Hardeman, Manager
Environmental Radiation Program
Environmental Protection Division
Georgia Department of Natural Resources
4244 International Parkway, Suite 114
Atlanta, GA 30354
(404) 362-2675  fax: (404) 362-2653
Jim_Hardeman@mail.dnr.state.ga.us