such small magnitude that decay is greater than build-up. Another check on the validity of the analysis using the experi- memvel model was a comparison of the particle size distribution as measured from sanples collected on the atolls and the size distribution that would be expected from consideration of the trajectories of the particles. Table 6.7 tabulates the measured particle size distribution found in samples from the atolls as taken from the data presented in Chapter 5, TABLE 6.7 - Shot 1, Measured Particle Size Station Bikini Ailinginae Rongelap Village Rongelap North End Rongelaep, Kabelle Utirik Smallest Particle (1) Largest Particle (4) az a5 >1000 10 126 16 172 16 16 394 518 6 134 Geometric Mean (4) 112 60 70 45 The calculated trajectories showed particles from 2000 to 100 2 arrived as primary fallout within the Bikini Lagoon. This fact agrees very well with the measured size distribution shown in Table 6.7. Consideratiun of the cloud diameter and stem diameter, in the experimental model, on the arrival points of the particle trajectories indicates particles from 150 to 75 H diameter would arrive at the north end of Rengelap «ith the limit of the 250 particles falling approximately 10 nautical miles north of Rongelap Atoll. The steep gradient of particle size distritution in a north-south line is also clearly indi-~ cated from the model study which agrees sell with the size distribution found at Ailinginae some 15 nautical miles south of north Rongelap. Also the calculated size limits the particles arriving at a distance or 300 nautical miles to a maximm diameter of 75 » as compared to a measured geometric mean size of 45 He The only discrepancy of say magnitude between observed data and those calculated from the experimental model is that no fallout arrived at Utirik based on the medel analysis. It must be realized that at this distance the model analysis is weakest because the wind data used were extrapolated as being constant fron 0 + 6 br to 0 + 20 hr, the latter being the time of arrival of fallout at a distance of approxlMately 300 nautical miles. This extrapolation was necessary because no wind data for periods beyond 0 + 6 hr was available at the time of this analysis. Even better corrslation of measured to calculated particle size would be obtained if a larger cloud diameter were used in the experi- mental modei. For this analysis the value used of 66 nautical mies was conservatively chosen; Project $.1 cloud dimension data indicate 89