1 CALCULATION OF THE CONCENTRATION OF ANY RADIONUCLIDE DEPOSITED ON THE GROUND BY OFFSITE FALLOUT FROM A NUCLEAR DETONATION Harry G. Hicks Division of Nuclear Chemistry Lawrence Livermore National Laboratory, Livermore, Ca, 94550 ABSTRACT A method is described to calculate the dry deposition on the around of any radionuclide in offsite fallout from a nuclear weapons test. The method depends upon the calculation of a source term (microcuries per square meter of fission and activation products), the use of concentration-to-exposure-rate conversion factors, and normalization to a measured external exposure rate. Fractionation is treated explicitly by elimination of a fraction of the refractory elements from the source term. available measurements. Calculations are in agreement with