Influence of the atmospheric dispersion model modifications on the results of the German Reactor Risk Study

Improvements of the atmospheric dispersion model of the German Reactor Risk Study (GRS), Phase B, are presented. Washout model variations show the need of a realistic as well as practicable modeling. Emphasis is further given to the lift off criterion in the plume rise model, to the height dependent dispersion parameters and to the mixing layer height. The partially antagonistic effects of these modifications on the results of the Reactor Risk Study (in terms of early and late fatalities) are discussed. (orig.)