same distance from ground zero, sametime. and presumablyfallout arrived at both at about the A slightly greater penetration is evident at this later time. Table 3.3 and the right hand curve on Figure 3.4 show the result of lowering the instru~ ment to the full extent of the electric cable at a much later time at Station Y- 6. Here penetration had proceeded below 80 meters and uniform mixing above this depth was evi- dent. 3.4.2 Conclusions Regarding Penetration Progress. From Figure 3.4 it is apparent that fairly uniform penetration to at least 80 meters was soon established, and the BT data indicates that ultimate penetration below 100 meters was highly unlikely. To illustrate what is believed to be the extent of penetration at any time, Figure 3.5 was constructed by drawing a straight line betwcen the estimated time of arrival (5 hours) at Stations Y - 1 and Y - 2 and the two experimental points, and continuing to the depth of the thermocline (100 meters). This estimate of downward progress is needed for computations and is, of course, only a rough estimate; but it can be pointed out that there is still other evidence indicating that it is not absurdly inaccurate. For example, the water analyses at Station Y - 3, which was occupied about 42 hours after detonation, indicates that mixing had attained the depth of 80 to 90 meters. This datum fits the graph of Figure 3.5 well enough. Nevertheless, the fact that time of arrival and fallout at any station is not well established experimentally makes it futile to attempt to perfect the penetration estimate any further. 3.4.3 Computations of Total Local Fallout. From the knowledge of the vertical distri- bution of activity a process of summation leads to an estimate of how muchactivity might have been caught on a hypothetical plane fixed at mean sea level. From consideration of geometry, energy distribution, and scattering laws, a further estimate could be arrived at as to what radiant flux would have existed at an elevation 3 feet above the hypothetical catchmentplane. Details of the mathematical and physical considerations leading to the derivation are discussed in detail in Appendix C, and Column 6 of Table 3.5 lists the numerical values of this local datum corresponding to each field measurement. 3.4.4 Estimate of Radioactive Decay. The solid curve in Figure 3.6 is from an estimate of the progress of decay of radioactivity following Shot 5 supplied by NRDL forthe purpose of making a synoptic report of these field findings; the dotted line shows, for graphical comparison, a decay proportional to time raised to the usual negative 1.2 exponent. No measurements suitable for decay evaluation were made during Shot 5. The solid line between H + 1 and H + 3 hours is based on estimates made at NRDL from calculated gammaionization decay curve, using fission product plus induced activities. The solid line after H + 3 hours is based on measurements made by NRDL from Shot 1, How Island gamma-time-intensity record and AN/PDR-39 readings. The justification for using Shot 1 data lies in the similarity of capture to fission ratios for the two shots. Figure 3.7 is a convenient curve for computing total dose and was derived by graphi- cally integrating Figure 3.6. t (hours) since detonation is The total dose accumulated between H + 1 hour and the time t Dit) =];Sf f(t) dt = 1,X (t) 1 where X(t) = abscissa of Figure 3.7 and, where I, is the dose rate at H + 1 hour, and | whereI,f(t) expresses the instantaneous value of dose rate corresponding to the solid line 35 (Text continued on Page 46)