in Figure 3.6 (if a simple decay proportional to t-'-? had been used as shown in the dotted line in Figure 3.6 then 1,f(t) would amount to simply Itt), Figure 3.7 is used only for calculating the dose accumulating betweenthe timeof arrival and H+ 50 hours. This dose is, if time of arrival is ta, 50 50 ta 1 fee at=1 ftw) at—1, f 0) dt =1, [ x60) -x¢ta)] tA 1 i Thus, the desired accumulated dose can be obtained by subtracting two abscissas of Figure 3.7. From Figure 3.6 a computational coefficient, summarizing the effect of decay after H + 12 hours, has been taken and entered in Column 7 of Table 3.5 opposite each measurement. 3.4.5 Local Dose at 3 Feet Elevation at the Synoptic Time H + 12 Hours. Column 8 is the result of multiplying Column 7 and Column 6, that is, reducing the data of Column 6 to the synoptic time H + 12 hours. 3.4.6 Local Dose at 3 Feet Elevation at the Synoptic Time H + 1 Hour. Column 9 is the result of reducing the local data to another synoptic time, H + 1 hour; this was done by multiplying Column 8 by the common decay factor 22.7. The solid curve of Figure 3.6 showsthat fallout at H + 1 hour has 22.7 times the activity present at H + 12 hours. 3.4.7 Effect of Time of Arrival and of Ocean Currents on Synoptic Presentation. Figure 3.8 and Table 3.4 are derived from an estimate supplied by NRDL of the time when fallout arrived at the sea surface as a function of distance from the point of detonation. Figures 3.9 and 3.10 summarize what is known about currents in this area. For simplicity, the assumption was taken of a constant mean current from east to west, and the fallout time of arrival function of Figure 3.8 was utilized; the ship’s track was displaced so as to present a hypothetical track indicating where the ship should have found the fallout if the water were stationary; that is, the locus of fallout on a hypothetical, firm catchment plane. : Unfortunately, local ocean currents had not been studied in detail by anyone during the immediate period, so an unknown amount of distortion is introduced here into the final fallout picture. Nevertheless, the fallout area is large, and there is evidence that the chosen velocity and direction are good representative values for the area as a whole. The ship’s track thus displaced so as to indicate where fallout would have been found on dry land, is shown as a solid line in Figure 2.5. 3.4.8 Plotting Fallout Contours of Iso--Dose-Rate. Along this “dry-land” track were distributed the measured radiation intensities given in Column 8 of Table 3.5; that is, the intensity at 3 feet elevation and H +12 hours. rate were linked to the similar numbers. Finally, contour lines showing iso-dose- These contour lines are in Figure 3.11. The contours are identified by letters and the numerical values of dose rate are listed in Table 3.6. Area inside of each contour is given. 46 The same contour map applies to