Atmospheric dispersion of an elevated release in a rural environment: Comparison between field SF6 tracer measurements and computations of Briggs and ADMS models

The French Institute for Radiological Protection and Nuclear Safety (IRSN), in collaboration with VEOLIA (French environmental services company), conducted experimental campaigns to study atmospheric dispersion around an Energy Recycling Unit (EUR). The objectives were to study dispersion for an elevated release in a rural environment and to compare results with those of models. The atmospheric dispersion was studied by SF6 tracer injection into a 40 m high stack. Maximum values of experimental Atmospheric Transfer Coefficients (ATCmax) and horizontal dispersion standard deviations (σh) were compared to predictions from a first generation Briggs gaussian model as well as results from the latest generation ADMS 4.1 gaussian model. tral atmospheric conditions, the Briggs and ADMS models are in good agreement with experimental data in terms of ATC and σh. In unstable condition, for σh, both ADMS and Briggs models slightly overestimate the data for winter and summer conditions. In unstable conditions, ADMS and Briggs models overestimated ATCmax. The statistical evaluation of the models versus experimental data shows neither models ever meets all of the criteria for good performance. However, statistical evaluation indicates that the ADMS model is more suitable for neutral condition, and that the Briggs model is more reliable for summer unstable conditions.