Rad Safe surveys and Project 2.5a surveys. Comparison3 of these valuee were done by converting all measurements to mr/hr at 0 + 4 days after the detonations. This period was selected because these island survey measurements were felt to be more valid than at earlier times when the majority of the survey readings were obtained by helicopter at verious heights above the surface. Conversion of all measurements to 0 + 4 days was meade by usine the composite gamma field decay curve in Fig. 5.1. Although this decay curve was constructed from both theoretical and experimental eveluation of Shot 1 deta, its use in reducing deta from Shots 2,3,4, and 5 does not introduce arpreciable error as is shown by & comparison of the experimental anc theoretical decay curves for these shots.12/ It does introduce some error into the Shot 4 celculetions hecause of the significantly different capture to fission ratios existing for Shot 6. The ratio of actual gamma fields to measured activity found in the totel collectors located on the atoll islands was not a constant for the many islands evaluated. Figure 4.1, a plot of field readings to readings as determined from the total collectors, was constructed by considering all data that were available; this included msasure- ments from Shots 1,3,4, and 6, A curve was fitted to the data which indicated a 1 to 1 ratio at high levels of activity and a 10 to 1 ratio where the total collector measurements were of low intensity. This curve was extrapolated at total collector levels below 1.0 mr/hr with a constant slope inilicating a 10 to 1 ratio between field survey moasurements and total collector measurements. Since this variable ratio was found to be independent of the shot detonated, it is reasonable to believe that the explanation for the variance is inherent in the characteristics of the collecting instrument. The fallout in areas of high residual gamma activity were those where the larger particles predominated. These particles with cozipara- tively high rates of fall apnarently do not tend to follow the streanlines about the collector. This tendency may explain the higher collect- ing efficiency resulting in those areas of high residual gamma fields. The fact that the ratio of gamma field measurements +o panma measurements from the total collector approaches 1 in the areas of high gamme activity is fortuitously coincidental. The activity collected in the total collectors emnloyed et the lagoon stations was converted to equivalent infinite field values by using the curve in Fig. 4.1. All data were then converted to r/hr et 1 hr using the composite gamma decay curve in Fig. 5.3. A similar evaluation of the gummed paper collectors was made. The curve in Fig. 4.2 was constructed using data from Shots 1, 3, and 6 to determine the ratio of gamma infinite field measurements made with survey inst~ments to those made on the gummed papers with the 47 gamma donization chamber. A constant ratio of 2 to 1 was determined for this collecting device, The gummed paper measurements from lagoon and free-floating sea stations were then corrected to infinite field values at © # 4 days by use of Fig. 4.2 and then converted to r/hr at 1 hr using the composite gamma decay curve in Fig. 5.3. aan, DO 47