Rad Safe surveys and Project 2.5a surveys. Comparisons of these values were dene by converting 811 measurements to mr/hr at O + 4 days after the detonations, This veriod was selected because these island survey measurements were felt to he 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 méde by usins the composite gamma field decay curve in Fie. 5.1. Although this decay curve was constructed from toth theoretical and ex- perimental eveluation of Shot 1 deta, its use in reducing data from Shots 2,3,4, & comparison shots.12/ It cause of the for Shot 6, and 5 does not introduce aroreciable error as is shown by of the experimental ane theoretical decay curves for these does introduce some error into the Shot 4 crlculetions hesignificantly different capture to fission ratios existing The ratio of actual gamma fields to measured activity found in the total 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 consicering all data that were available; this included ments from Shots 1,3,4, and 6. msasure- 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 inticating a 10 to 1 ratio between field survey moasuremenzs and total collector measurements, Since this variable ratio was found to be independent of the shot detoneted, it is reasonable to believe thet 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 larecer particles predominated. These particles with conmaratively high rates of fall aprarently do not tend to follow the strearlines abvuut the collector. This tendency may explain the higher collect- ing efficiency resulting in those areas of high resicual pamma fields. The fact that the ratio of gamma rield measurements *o cama measurerents from the total collector approaches 1 in the areas of higs: gamma activity is fortuitously coincidental, The activity collected in the totel collectors emnloyed et the lagoon stations was converted to equivalent infinite “ield 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 mace with survey inst-uments to those made on the gummed papers with the 47 gamma fonization 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 velues at C # 4 days by use of Fig. 4e2 and then converted to r/hr at 1 hr using the composite gamma decay curve in Fig. 5.3. 47