Yas and Rongerik Atolls from O hr through O ¢ 6 hr were used. Since the Erimary fallout was deposited over the area between Bikini Atoll and Rongelap Atoll within the first 8 hr, no extrapolation of the wind data was necessary for these particles. However no wind data after - H+ 6 hr were available for the area beyond the Ronzerik Atoll and a time extrapolation had to be ured in determining tae winds tnat fixed the particle trajectories there. In plotting the trajectories it became obvious that particles above 1000 pin diameter would fall very Near ground zero. Consequently, no calculations were made on tne 1000, 1500, and 2000 H particles. Figure 6.5 shows the terminal points of the 231 trajectories evaluated. The primary effect of the larger particles is evident. at distances close to ground zero, 6.2.5 Consideration of Cloud Dimensions The maximm lateral width of tne fallout area was determined by expendinr each particle's arrival voint to the diameter of the stem or cloud from which the particle originated. From the cloud photosraphy data the stem diameter was found tc te 6,6 miles, ihe stem heignt 60,000 ft, the cloud diameter 66 miles and the cloud height 100,000 ft at 0 +10 min. These dimensions were chosen altucugh the cloud contimed to exp.nd laterally efter 9410 min. For simplicity it was assumed in this model that the cloud and stem were cylinders havinz these dinensicns. “his evaluation essunes no clouc diffusion with tine, but fully considers shear. 6.2.6 Determination of Axis of Symmetry of tae Sellout Pattern From the swath of points (Fig. 6.5) the direction of fallout was determined. Since the particle arrival points hud a narrow spread it seened reasonable to construct an axis about waich the fallout was Symmetrical. Such a symmetrical. fallout pattern results only if the upper wints have the necessary configuration for so restricting the particle trajectories. The time of arrivel of the particles was also calculated, Table 6.6. Some of the calculated trajectories of the smaller particles starting at hish elevationc did not reach the surface until many uours after the main bedy of material nad ceposited. These arrival points indicative of secondary fellout were not corsidered in the determination of the axis of symmetry. 6.2.7 Construction of the Fallout Pattern Using the established axis of symmetry of fallout in conjurction wita the measured levels of gamma activity on the availeble atolls a complete fallovt pattern (r/ar at 1 hr) was constructed as presented in Fig. 6.6. This patlern shows the levels of fallout thoit would exist on an infinite land plane shouid the basic assumptions used in the definition of the experimental model nold. It is important to note that this pattern was constructed solely on ccnsideration of the ganna field Measurencnts and the axis of symmetry: however, there is otaer supporting