Atmospheric Dispersion of Radioactive Debris Released in Case of Nuclear Explosion Using the Norwegian Snap Model

Severe Nuclear Accident Program (SNAP) has been developed at the Norwegian Meteorological Institute (met.no) for modelling dispersion of radioactive debris in case of nuclear accidents. The model has been tested based on the data available from the Chernobyl accident as well as from the ETEX experiments. The main user of model results is the Norwegian Radiation Protection Authority (NRPA) which is responsible for calculating doses in case of a real accident. The model is fully operational for NRPA as well as for met.no. Following a request from NRPA, the SNAP model was modified in such a way that not only dispersion from nuclear accidents can be simulated, but dispersion from nuclear explosions as well. The source term for the model run in case of nuclear explosion has been developed based on cooperation among Scandinavian countries. The source term includes mainly particles of different size and density, which are subject to dry and wet deposition during atmospheric transport. Description of the model and examples of the simulations related to hypothetical nuclear explosions are presented and discussed.