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

Sulphur transport and dry deposition over Europe described by a simple Langrangian dispersion model.

A simple Lagrangian dispersion model is described and applied to sulphur pollution over Europe. The model calculations are based on available SO2-emission data for Europe, and wind observations in the 850 mb surface. A special case is reported where the presence of computed large-scale SO2 and SO4 plumes are verified by concentration data from aircraft sampling and from the LRTAP sampling network. For stations in this network, computed and observed daily mean SO2 and SO4 concentrations are compared for a period of six months. Based on this comparison SO dry deposition patterns for Europe are calculated, using computed mean concentrations and a deposition velocity of 0.8 cms-1

Wet and dry sulphur deposition patterns over Europe for the period 13.12.73-29.3.74

On days with precipitation, a relation is established between mean SO4-concentrations measured in precipitation at some LRTAP-stations and mean SO2-concentrations, calculated with an one-layer Lagrangian dispersion model. The time period on which this relation is based is 107 days, 13th December, 1973 to 29th March, 1974. Using this relation, together with model calculations and the amount of precipitation analysed as fields every 12 hours, we have estimated the wet deposition field of SO4 over Europe for the period. Estimating the dry deposition field of SO2 by the same methode as in ref. (1), and assuming the dry deposition of sulphate particles to be small, we have added dry deposition of SO2 and wet deposition of SO4 to give the calculated total deposition of sulphur. We have compared these estimates with the emissions

A simple Lagrangian dispersion model applied to sulphur pollution over Europe

A simple Lagrangian dispersion model is described and applied to sulphur pollution over Europe. The model calculations are based on available SO2-emission data for Europe, and wind observations in the 850 mb surface. A special case is reported where the presence of computed large-scale SO2 and SO4 plumes are verified by concentration data from aircraft sampling and from the OECD sampling network. For stations in this network, computed and observed daily mean SO2 and SO4 concentrations are compared for a period of six months. Based on this comparison an SO2 dry deposition pattern for Europe for 1974 is calculated, using computed mean concentrations and a deposition velocity of 0.8 cms-1