CORRELATIONS ON DEBRIS FROM SILICATE BURSTS 73 INTRODUCTION In the summer of 1962, the U. S. Naval Radiological Defense Laboratory (NRDL) collected fallout from three shots at the Nevada Test Site (NTS)—Johnie Boy, Small Boy, and Sedan. Radiochemical studies were made of the debris from these shots and were reported.-3 During the past several months, we have made log—log correlations of these radiochemical results and have attempted some interpretation of them. Before the results are discussed, it seems appropriate to review the shot conditions since important differences existed among the three events. These differences undoubtedly had effects on the fractionation behavior of the fallout. SHOT CONDITIONS Small Boy was a low-yield shot fired from atop a 10-ft-high wooden tower above alluvial soil in Area 5 at NTS. NRDL collected many fallout* samples of debris at 43 stations within 8.7 miles of ground zero and took other samples on a line 15 miles from ground zero. Further samples were supplied by the University of California at Los Angeles sampling network at distances of 18, 27, 36, 52, and 70 miles. Four cloud samples were supplied by Los Alamos Scientific Laboratory. The discussion in this report is mainly restricted to samples from within 8.7 miles of ground zero and from the cloud samples. The number of samples used from each station varied, and many Samples were subdivided by sieving into seven fractions that were analyzed individually. A total of about 187 samples is dealt with here, all of which were analyzed for ™Sr, *°Sr, °!Y, and *Zr. In addi- tion, about one-third of them were analyzed for *°Mo, !"Ru, !%Ru, 138cg '8lcs, M9Ba Mice, M4ce, *Np, and 738Pu. Some of this last group of samples were also analyzed for I and ‘Te. The numbers quoted do not include a fairly large number of radiochemical analyses on samples used for solubility studies. NRDL’s participation in the Johnie Boy and Sedan shots was ona rather limited basis. Johnie Boy was a low-yield burst 23 in. below the surface of basaltic material in Area 18 at NTS. Forty-four fallout samples from the area out to about 1, miles from ground zero and two cloud samples were studied radiochemically. All of these were analyzed for Sr, Sr, *!y, and ®Zr, and about one-third of them were analyzed for the long list of nuclides previously given for the Small Boy samples. *As distinguished from cloud and air-filter samples.