TRANSURANIC ELEMENTS AT BIKINI ATOLL 543 



Fig. 1 Approximate locations of nuclear tests at Bikini Atoll. 



and E in Fig. 1). Devices detonated on barges at Bikini under these conditions contained 

 large quantities of iron and coral which were used as barge ballast (Adams, Farlow, and 

 Schell, 1960). Spherical particles (< 1 jum) of "dicalcium ferrite" (2 CaO X Fe203) 

 formed from vaporization of the barge and ballast contained about 85% of the 

 radioactivity in the fallout droplets (Schell, 1959); the saturated sodium chloride (sea 

 salt) droplets, in which these insoluble solids were suspended, contained the remaining 

 15% of the measured radioactivity (Farlow and Schell, 1957). 



The second common site was the shallow water or island environments where the 

 largest tests were conducted (sites B, J, G, I, C, and H in Fig. 1). From explosions of this 

 type, Adams, Farlow, and Schell (1960) found that condensation of the vaporized 

 materials typically occurred as impurities into and on the surfaces of the coral soils swept 

 into the fireball, which produced two distinct types of fallout particles, spherical and 

 angular. The spherical particles consisted of CaO, which was partially hydrated to 

 Ca(0H)2 . A surface coating of Ca(0H)2 and/or CaCOa was present owing to the reaction 

 of the particles with water vapor and atmospheric COo during the fallout. These particles 

 were formed by high-temperature (>2570°C) vaporization of coral with subsequent 

 condensation of the oxide as spherical particles, which lost their normal porosity. The 

 radioactivity was almost uniformly distributed throughout the particles. The angular 

 particles consisted of Ca(0H)2 with a thin outer coating of CaCOa. Some of these 

 particles contained unmelted coralline sand fragments as the central core; the bulk of the 

 radioactivity was in the outer carbonate shell. The angular shape of these particles, the 

 lack of incorporated radioactivity, and the presence of occasional unmodified sand grains 

 suggested that these particles were formed from nonvolatilized coral that had been heated 

 enough to melt and decarbonate (800 to 900°C) while incorporating only an outer 

 surface of condensing radionuclides. Occasionally 10-jL/m and smaller oxide spherical 



