A new fallout prediction model.

The standard method for the calculation of nuclear weapon fallout radiation doses and dose rates in operational type studies for the last 20 yr has been the computer algorithm known as WSEG-10. WSEG-10 uses empirical functions rather than numerical analyses and computes fallout dose (rates) in seconds or less on modern computers. WSEG-10 has long been criticized for its inability to allow for variations in the activity-particle size distribution of the fallout, for its inability to account for fractionation and for the absence of realistic settling rates. At the other end of the scale, the Defense Land Fallout Information Code, DELFIC, is currently used for research work and as a comparison standard. DELFIC produces fallout footprints on the ground by numerical integration, employing discrete cells in space, time and particle size. A new fallout prediction method is presented here which, unlike WSEG-10, does allow variations in activity with particle size, does account for fractionation and does model variable settling rates. This new model, like WSEG-10 but unlike DELFIC, computes in seconds or less. Some results are presented and compared to DELFIC and to WSEG results. Additionally, this new model will treat the far-field problem of interest in a massive strategic attack which cannot be easily done using DELFIC.