0018933 evidence that the nuclidee in the larger pzrticles (3-12 p) were fracticnated, but these in particles smzller than 1 p were not (Reference 54). This method cf data analysis has been shown to be valid regardlees of the secondary reference nuclide, the primzry reference nuclide 2nd the reference event (Reference 6 }, 1,3 EXPERIMENTAL PROGRAM 1.3.1 Outline cf the Pregram, The foregoing discussion indicates thet further pregrees in the development of a realistic fallout model will © require zn improved knowledge of the structure of nuclear cleuds with respect to the vertical and radiz] distribution of particle size and radioactivity within the mushroom, Quantitative deta on the activity associated with particles in different size groups is also needed for estimation of the pertiticn of the weapon between Iccal end world-wide fzlovt, Project 2.8 Was established to attempt to obtein suck information from certain shots at Operation HARDTACK, It was planned to explore the cloud structure by In¢ins of air sampling rockets and to use both the rocket samples and also airecrett sainples collected from the cloud with the UCRL coincident szmp- ler for determinztion of the fzilout partition, Other aircreft flying zt 1000 feet were echeduled to collect falicut szmples to be used for the determi‘ nstion of the effect of particle size on fracticnztion and for ccrrcboratioa . 3F 3S