Long-range atmospheric dispersion of radioisotopes

The MESOS model has been used to study notional radioactive emissions from several sites in different EEC countries. Successive 3-h releases to the atmosphere of various nuclides have been simulated, as they disperse across Europe, using meteorological data bases covering two different years. The results have been used to generate annual average levels of contamination in air, and on the ground by dry and wet deposition; these levels have been combined with data on population distribution and food production to estimate collective doses arising from direct exposure and ingestion per unit released of each nuclide. For accident risk assessment cumulative probability distributions of exceeding various levels of contamination have been estimated at selected receptor points around each source for hypothetical unit releases over periods varying from 3 h to 7 days. Sample results are presented with accompanying analysis and interpretation, including a survey of conditions leading to high levels of contamination at a remote receptor point. (author)