Due to procurement difficulties, no proper dye could be obtained in time for Shot 1, which produced great quantities of white coral fallout Attempts at separation of flour pellets and coral grains have proved to. be unreliable, making it impossible to determine the water-coral ratio of the fallout, 4a2el t ion of Activit th Particle Si _ Gross samples, therefore, were sieved,* waighed and counted, with the resulting sise-activity data of the mixture reported in Table 4.3. The size fractions indicated in the table were analyzed for Na by the wet ash method, capable of detecting 0.20 +0.05 yg of Na. Only background amounts of Na were found, Following the sieving runs, fallout samples from other collection devices were received, from which it was learned that most of the active coral particles, altered by heat and water to Ca(0H)o, were friable, a development casting doubt on the validity of the sieve-determined size distributions. A total of nine collection devices were exposed on Shot 1, of which Love cycled two trays (combined in Table 4.3), with one cycling at Oboe, Uncle, William, and Zebra. The remaining instmments, positioned at Fox, How, Nan, and Yoke, suffered various conbinations of malfunction due to blast damage and flooding. Spare parts, stock flour, and preloaded trays stored on Tare were destroyed by fire. ling was abandoned. 4.3 Further drop samp~ INDIVIDUAL PARTICLE COMPOSITION AND CHARACTERISTICS The work reported in this section was undertaken to obtain a description of the internal structure, chemical composition, and distribution of radioactivity within the radioactive fallout particles collected following Shot 1. A description of a likely mechanism of formation of the fallout particles is given. 4.3.1 Description Most of the particles studied were collected in sampling devices which were distributed in a comprehensive array over the lagoon and islands of Bikini atoll. The wind directions at shot time wer6 such that the main path of the fallout passed over many ofthe collecting stations. The particles selected for study were chosen from stations over as great an area as possible. The greatest number of particles were, however, chosen from stations in or near the path of heaviest fallout. Two techniques were used in studying the particles: X-ray di*fraction analyses of individual particles and the observation under the petrographic microscope of thin sections ground from individual par-~ ticles. 352/ * Mechanical agitation was employed for about 1 min, followed by manual sieving and brushing on the 50- and 60-mesh screens. 95