ured at late times in the region of YAG 39 operations during Shots Navajo and Tewa (Method II). (The probe profiles were provided, with background contamination subtracted out and converted from microamperes to apparent milliroentgens per hour by F. Jennings, Project 2.62a, SIO. Measurements were made from the SIO vessel Horizon.) The integrated areas were converted to fissions per square foot by applying a factor expressing probe response in fissions per cubic foot. This factor was derived from the ratio at 200 hours of surface probe readings and surface sample dip counts from the samestation, after the latter had been expressed in terms of fissions using the direct dip counter-OCC fission content data mentioned above. These results are also listed in Table 4.6. The set of values for the YAG 39 decay tank labeled Method III in the sametable is based on direct radiochemical analyses of tank (and ocean surface) samples for Mo*® (Table B.30). The results of Methods I and I were obtained before these data became available and, accordingly, were accomplished without knowledge of the actual abundance distribution of molybdenum with depth in sea water. Table 4.7 is a summaryof the dip-to-fission conversion factors indicated by the results in Table B.30; those used in Methods I and II are included for comparison. It is noteworthythat, for the YAG 39, the ocean surface is always enriched in molybdenum, a result which is in agreement with the particle dissolution measurements described earlier (Figures 3.11 and 3.12); in this experiment Mo’, Np?**, and probably I'*! were shown to begin leaching out preferentially within 10 seconds. The tank value for Shot Zuni, where the aliquot was withdrawn before acidi- fying or stirring, shows an enrichment factor of ~ 3.5 relative to the OCC; acidification and stirring at Shot Tewa eliminated the effect. The slurry fallout from Shots Flathead and Navajo, however, shows only a slight tendency to behave in this way. Finally, Table 4.6 also lists the representative platform values obtained earlier, as well as the maximum values read from the platform-collection curves for the cases where deposition occurred under essentially single-wind conditions (Table 4.4). These values are included as a result of postoperation rainfall measurements made at NRDL (Table B.31). (Although the data have not received complete statistical analysis, the ratio of the maximum collection of rainfall by an OCC on the LST 611 platform to the average collection of a ground array of OCC trays is indicated to be 0.969 + 0.327 for a variety of wind velocities (Reference 75).) It may be seen by examination of Table 4.6 that the most serious discrepancies between ocean and shipboard collections arise in two cases: the YAG 39 during Shot Zuni, where the ocean/ OCC (maximum)ratio of ~ 2 may be attributed entirely to the fission/dip conversions employed —~assuming the OCC value is the correct average to use for a depth profile; and the YAG 39 during Shot Navajo, where the ocean/OCC ratio is ~10, but the tank radiochemical value and the Horizon profile value almost agree within their respective limits. While the OCC value appears low in this multiwind situation, the difference between the YAG 39 and Horizon profiles may be the background correction made by SIO. In the final analysis, the best and most complete data were obtained at the YAG 39 and Horizon stations during Shot Tewa. Here, preshot ocean surface backgrounds were negligibly small; equipment performed satisfactorily for the most part; the two vessels ran probeprofiles in sight of each other; and the Horizon obtained depth samples at about the same time. The YAG 39 did hot move excessively during fallout, and the water mass of interest was marked and followed by drogue buoys. In addition to the values reported in Table 4.6, the value 1.82 x 10!5 fissions/ft? Was obtained for the depth-sample profile, using the dip-to-fission factor indicated in Table 4.7. (Because of the variations in the fission conversion factor with the fractionation exhibited from Sample to sample, a comparison was madeof the integral value of the dip counts (dip counts/ Min)/2 liters) feet from the depth-sample profile with the OCC YAG 39-C-21 catch expressed N similar units. The ratio ocean integral/OCC-C-21 = 1.08 was obtained.) It may be seen that all values for this shot and area agree remarkably well, in spite of the fact that Method I measurements extend effectively down to the thermocline, some of the Method a Profiles to 500 meters, and the depth sample cast to 168 meters. If the maximum OCC catch 'S taken as the total fallout, then it must be concluded that essentially no activity was lost to depths greater than those indicated. Although the breakupof friable particles and dissolution 119 -