These numbers are to be interpreted as the quantity of material that does not come down in the local area. The limits assigned are derived from the variability in the data. Qf the curves for the fraction of Mo™ left in the clouds, the one for the water-surface burst (Shot Walnut) shows to a considerable degree the behavior anticipated when the project was planned. On the reef shot, the points appear to be fluctuating around a fraction of 0.11, whereas “for the land-surtace detonation, there is insufficient data to do anything but extrapolate beyond 6.5 hours. Because it is likely that the fission ratios would be around initially, the curves shown for Oak and Koa maybe only the relatively flat part, which appears for Walnut at a later time. This seems to be consistent with what is surmised aboutthe cloud particle size distributlon for land and water shots. In addition to the samples from the light and variable wind layer, there were also 2 number of collections made on each shot at lower altitudes. Although not of direct application to the project objectives, the radiochemical data for these samples is instructive, because it shows how the nuclide composition of the particulate matter varied with altitude. Some of the samples came from the bottom portiona of the clouds, but those collected at the lowest altitudes may have been below the base of the mushroom and would perhaps be considered as fallout. Table 3.3 gives a summary of the Sr® and Cs"*' R-values for the three shots as related to altitude and time of collection. The R-values for the samples marked with an asterisk were calculated as gross figures from the R-values for the size-separated fractions. For the land-surface shot, the R-values showed a general increase with altitude, attaining values at 60,000 feet which were 10 (Sr) to 40 (Ca**’) times those expected forthe detonation. The water-surface shot R-values were relatively insensitive to altitude, and the enrichment factor was not more than 2 for either nuclide. Samples collected below 45,000 feet may be from the fallout. On the reef shot, it appears that the sampling aircraft were just entering the base of the cloud at the 55,000-foot level, because there was a sudden jump in the R-values at this point. The material collected at lower altitudes was depleted in both Sr® and Cs’*" and was not greatly different in composition from the fallout at 1,000 feet. It 1s also noted that the enrichmentfac- tors for both nuclides went through a maximum with time for the samples from the light and variable stratum. Several conjectures might be offered in explanation of this unexpected behavior with time. One of these is that some sampling might have been done at the lower boundary of the light and variable stratum where some of the particles collected had fallen below the Stratum where the rare gases were present. This could also be offered as a possible explana- tion for the late time rise in the ratio of molybdenum to krypton in Shot Oak. Somewhat similar data for the ratios of Mo" to Kr"® and Kr** to Kr"® for the first 4 hours following detonation is given in Table 3.4. The ratios of Mo” to Kr®* are also shown graphically in Figure 3.4. At the lower altitudes, the Mo was enriched and the Kr** depleted with respect to Kr 3.1.2 Fallout Data. The radiochemical data on the fallout samples may be used to obtain results for the distribution of Sr™ and Cs‘*’, which are complementary to those found from the cloud analyses. The fraction of the total Mo* formed in the explosion, which has left the cloud, is found by difference from the numbers given in Table 3.2. Multiplication of these fig- ures by the Sr® and Csa'*’ R-values for the fallout and division by the device R-values convert them to fractions ofthe two nuclides in the fallout. Table 3.5 lists results obtained in this way based on the averaged composition for the fallout. All the fallout samples from the land and reef shots show depletion of both Sr™ and Cs!" as compared to the detonation yields. This is most pronounced in the earliest samples. Material coming down at times later than 4 hours for the land shot and 6 hours for the reef shot is quite uniform in composition and exhibits little evidence of fall rate-dependent fractionation. The 4-hourfallout from the water-surface ‘shot is depleted in both Sr™ and Cs45’, but the 10- and 13-hour samples show an enrichment. composition. The two latter samples have nearly the same The failure of the 6- and 8-hour flight missions makes the data rather scanty in this case. These effects are brought out clearly by the listings in Table 3.6. 38