Calculation method for gamma-dose rates from spherical puffs

The Lagrangian puff-models are widely used for calculation of the dispersion of atmospheric releases. Bask output from such models are concentrations of material in die air and on die ground. The most simple method for calculation of die gamma dose from die concentration of airborne activity is based on semi-infinite cloud model. This medwd is however only applicable for points far away from die release point The exact calculation of die cloud dose using dK volume integral requires significant computer time. The volume integral for die gamma dose could be approximated by using die semi-infinite cloud model combined wiu correction factors. This type of calculation procedure is very fast, but usually the accuracy is poor doe to die fact that dc same correction factors are used for ail isotopes. The authors describe a more elaborate correction method. This mediod uses precalculated values of die gamma-dose rate as a function of die puff dispersion parameter (Or) and die distance from die puff centre for four energy groups. The release of energy for each radionuclide in each energy group has been calculated and tabulated. Based on diese tables and a suitable interpolation procedure die calculation of gamma doses lakes very short time and is almost independent of die number of radionuclides.