FRACTIONATION VERSUS PARTICLE TYPE IN NUCLEAR SURFACE SHOT Ch/IALL BOY. Differences in Radiochemical Composition Between Fritted and Spheroidal Particles

Spheroidal and fritted particles of three size classes from closein fallout samples collected from Small Boy were separated by hand. Analysis of spheroidal and fritted groups fror the > lU00-u and the 35O-7OO-U size classes showed that spheroidal particles had higher specific activities than the fritted particles; however this difference was less pronounced for the smaller size groups. Contrary to reported observations on debris from a high-yield coral-surface bnrst, all groups showed comparable degrees of fractionation for radionuclides with raregas precursors. The Small Boy shot conditions were unique, however, and this ,homogeneity may not occur in more typical silicate-surface bursts. Ru^°° and Sbl5 were alike in behavior, but the data for these radionuclides do not correlate like those for rare-gas descendants. The necessity of adopting multidimensional correlations remains to be evaluated.