fallout with particle size, zero-point environment, and time and distance of collection; (2) the chemical tory; E. R. Tompkins, Project Officer. The objective was to determine the chemical, physical, and radiochemical nature of fallout from Castle. This information is useful in deducing the mechanism of contaminant formation, evaluating radiological situations, developing radiological countermeasures, and interpreting field testa of and radiochemical nature of liquid failout; and (3) the manner in which decay rates are affected by variations in radiochemical] composition. The investigation of radiochemical properties of fallout were conducted in Bikini Atoll and Bikini La- countermeasures at Castle. Shot 1 produced a dry fallout. goon. Bikini Lagoon and land stations, and from islands in atolls 8 to 120 miles distant were obtained and analyzed. system which immediately separated the phases. Approximately 20 percent of the activity in the fallout from Shot 1 was associated with particles 3maller than 10 microns. A trend of decreasing specific activity with increasing particle size was The fallout from Shots 2, 4, 5, and 6 were chiefly liquid in the form of an extremely fine mist of aerosol. Samples from free-floating buoys, la- goon and land stations, and from the Project 6.4 YAG’s were analyzed for these events. The adverse effect of mixing upon the liquid and solid fallout was minimized by a new collection Samples from found in Shot 1 fallout beluw 50 microns. Fractionation of fission-product nuclides was found on Shots 1 and 3. Gross decay of Shot 1 fallout generally follow- Because rain was falling during the period of fallout after Shot 3 (detonated on Tare:, the material collected was a slurry. Water samples from the open sea were col- ed the equation I = kt?-°, and did not vary with par- ticle size. There was evidence of an unusually high Mo”fission yield on Shot 1. lected out to 200 miles from ground zero for Shots 5 and 6. The gammacount of fallout samples from Shota 1 and 3 was found to be associated with the solid frac- In order to predict the military effects of fallout from operational nuclear weapons, it was necessary firat to understand the basic dependence of these tion to the extent of 92 to 98 percent; for Shots 2 and phenomena on environmental and weapon character- gamma count. land and water detonations than from shots on the surface and below the surface, from various soil istics. Different effecta are to be expected from 4 the solid fraction contained 25 to 38 percent of the The remainder was found to be con- tributed mainly by emitters in the ionic state. Neptunium wag found as 65 +11 percent Np (IV) as averaged for Shots 1, 2, 3, and 4; the remainder wag types, and from different depths of water. found as Np (V + VI). of ground contamination. Iodine was found in the solid fraction of the fallout from Shota 1 and 3; it was also found in the liquid fraction of the fallout from Shots 2 and 4. In every The experimental nuciear devices in Castle were detonated in peculiar zeropoint environments which will be absent in the case of most operational weapons detonations. case, iodine appeared to be essentially in the —1 Project 2.7 “Distribution of Radioactive Fallout by Survey and Analysis of Contaminated Sea Water” oxidation state. Quantitative analyses were made on all samples recovered from Shots 1, 2, 3, and 4. Island coral, lagoon seawater, and lagoon-bottom materials were also analyzed. (WT-935), Scripps Institution of Oceanography; T. R. Folsom, Project Officer. The objective was to obtain fallout data in frce- The ytelds of U2" and vu, as well as that of U™, were sufficiently high to contribute significantly to the residual contamination radiation and to affect the gross beta- and gamma-decay curves. Analyses of all absorption curves show the presence of beta energies as high as 2.6 Mev at H + 15 hours (Shot 4), with the maximum beta energy decreasing to about 2 Mev atH +3toH+10 days. Lead absorption curves were analyzed into three apparent energies: 0.15 Mev (70 percent), 0.44 Mev (16 percent), and 1.3 Mev (14 percent)— averaged for the first four shots from H + 0.3 to H + 13 days ocean areas, a8 a result of the fallout phenomena ob- served following Shot 1. Operational and technical details were hastily contrived so that they could be put into effect for the latter phases of Castle. (WT-913), Chemical and Radiological Laboratories, Army Chemical Center; R. C. Tompkins, Project Officer. The objectives were to determine (1) the variations in chemical and radiochemical composition of solid Par- ticipation was concentrated on Shots 5 and 6, and both water-sampling and submerged-radiation-meter techniques were used. Isointensity contours were plotted as though the fallout had been received by a fixed plane at mean sea level. Dose rates at H + 1 or H + 12 hours were calculated at 3 feet above the fixed plane. These contours indicated that for Shot 5 total doses of 250 r or more could have been accu- Gamma spectra were taken of the fallout samples as a function of time for Shots 2, 3, and 4. Project 2.6b “Radiochemical Analysis of Fallout” Rainout may exert a considerable influence on the significance mulated throughout an area of about 5,000 mi?; for the smaller yield of Shot 6, the hazardous area was smaller. The two survey techniques gave similar results. The direct gamma-radiation meter was well suited for rapid surveys and depth-of-penetration measurements, while the water~sampling technique provided specimens for more-complete gam ma-spectrum and 110 other physical and radiochemical studies. It was