and Rongerik Atolls from 0 hr through 0 ¢ 6 hr were used. Since the primary fallout was deposited over the aree between Bikini Atoll and Rongelap Atoll within tne first 8 hr, no extrapolation of the wind data was necessary for these particles. ~S However no wind data after d+ 6 hr were available for tne area beyond the Ronzerik Atoll and a time extrapolation had to be ured in deternining tue winds taat fired the particle trajectories tnere. In plottinz the trajectories it be~ came obvious that particles above 1000 win diameter would fall very Near ground zero. Consequently, no calculations were made on tae 1000, 1500, and 2000 H particles. Firure 6.5 shows the terminal points of the 231 trajectories evaluated. The primary effect of the larser particles is eviden at distances close to ground zero, 6.2.5 Consideration of Cloud Dimensions S The maximm lateral width of tne fallout area was determined by expanding each particle's arrival point to the diameter of the stem or cloud from which the particle originated. From the cloud photocraphy data the stem diameter wes found te te 4.6 miles, the stem heigat 60,000 ft, the cloud diameter 66 miles and the cloud height 100,000 ft at 0 #10 min. These dimensions were ciosen altucugh the cloud continued to exp-nd laterally efter 9410 min. For simplicity it was assumed in taois model that the cloud and stem were cylinders havinz tnece dinensicns. “his evoluation essumcs no clouc diffusion with time, but fully considers shear. 6.2.6 Determination of Axis of Symmetry of tae Tellout 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 seemed reasonable to construct an axis about wnich the fallout was Symmetrical. Such a symmetrical fallout pattern results only if the upper wines have the necessary configuration for co 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 high elevationc did not reach the surface until many nours after the main Ledy of material nad ceposited. ‘nese arrival points indicative of seconcary fallout were not corsidered in the determination of the axis of symmetry. 6.267 Construction of the Fallout Pattern Using the established axds of symmetry of fallout in conjurction wita the measured levels of vamma activity on the availeble atolls a complete fallovt pattern (r/or at 1 hr) was constructed as presented in Fig. 6.6. This patlern shows the Icvels of fallout tnit would exist on an infinite land plane shouid the basic assumptions used in the defini- tion of the experimental model sold. It is important to note that this pattern was constructed solely on censideration of the gamma field measurements and the axis of ¢:rmmetry: however, there is otaer supporting 85 \ ~ 2