ONLINE CALCULATION OF THE DISPERSION OF RADIOACTIVE SUBSTANCES IN AIRON THE BASIS OF A LAGRANGIAN MODEL

The Federal Land Bavaria introduced, in the year 1978, the first remot e monitoring system for nuclear reactors (KFU) in the world. A dispers ion model developed on the basis of Gaussian dispersion theory was inc orporated into this in the form of a systems module. In the third deve lopment stage of the Bavarian KFU system, a Lagrangian particle model is applied for the calculation of the dispersion of air-borne radioact ive releases. In the process of this, the influence factors arising fr om topographical and meteorological conditions, the nature of building s in close proximity to the nuclear power plant, and the variability o f emissions over time, are brought into the calculation, and the accur acy of the results is thus considerably increased. By means of a user- friendly menu design, graphic presentations of air concentration and g round contamination as well as the resulting radiation exposure are of fered for the immediate area within a range of 5 km, for a mid-range z one of up to 10 km distance, and for a more distant field within a rad ius of 50 km around the nuclear power plants, with, in each case, seve ral options for the background grid, providing information on administ rative borders, the road network, or the form of grid. The Lagrangian particle model has been in use in the Bavarian State Ministry for Deve lopment and Environmental Affairs in its off-line version, since the a utumn of 1996. The on-line version will, in 1997, be put into use with in the Bavarian KFU system.