CHAPTER 17 upwind from Umbrella surface zero, which indicated a recorded 3-min dose of 604 r, while at 6740 ft dowmwind of surface zero, the detector (calculated to be 55 inches deep) recorded only ea milliroentgen dose. No depth-penetration measurements are available for Shot Umbrella, and water sampling is mentioned only_briefly. Analysis of sea water collected in the lagoon 75 min after burst was carried out by separating the isotopes detected into two groups, particulate (0.45) and either soluble or colloidol («< 0.45), It was found that N, was present in high amounts in both groups, and several other isotopes were present in lesser amounts. For shot ¥enoo S20 ft in deep water), contaminated-water dose rates at li-ft de near the ships are unavailable because the starting signals were not received on the instrumented ships. For Wahoo, on the underwater GITR's at 3900 ft and 4100 ft from surface zero, dose rates peaked briefly at over 2000 r/hr at about 8.5 min and 1400 r/nr at 6.3 min, respectively. These dose rates are considered to have been due to waterborne radioactive material. The cumulative doses up to 3 min on the same GITR's, calculated to have been floating at about 12 and 18 inches below the surface, respectively, were about 16 r and 4 r. An experiment ®! whose objective was "investigating the dispersal in time and sea of the contamination resulting from Shot Wahoo" resulted in meager information. As the USS REHOBOTH cruised the area for several days -_ after shot time, the ses-water intake of the ship was monitored for contamination, mumerous depth-penetration measurements of activity were made, and Nevy radiac survey-instrument readings were taken at the bow. Some information was obtained on the dimensions of the radioactive pool with time, and of the radiation levels measured by the bow survey meters, which "viewed s large solid angle but were shielded from the nearby water surfaces." These readings probably represent the field at the bow due to waterborne activity, and were used to indicate the size of the contaminated surface layer of water. The first post-shot dose-rate-va-depth readings of the scintillation detectors, taken at about H + 3 hr at about 3 naut mi downwind of surface zero, indicated a maximim of about 4000 counts/sec at the surface, about 2400 counts/sec at depths from about 5 to 35 ft., and then decreased to about 250 counts/sec at a 60-ft depth, According to the radium-calibration curve given in Ref. 81, these measurements cor- respond to about 1 mr/hr, 0.6 mr/hr, and 0.06 mr/hr, respectively, if it is assumed that an error has been made in labeling the abscissa of the calibration curve. The maximum in-situ level encountered, about 16,000 counts/sec at depths of 90 to 130 ft (at H + 28 hr, about 5 naut mi down- wind of surface zero), correspond to about 10 or/hr on the calibration curve. The sea-water-monitor ionization-chamber results are presented in terms of amperes vs time, but no method of conversion to mr/hr is presented except for the statement that "current readings could be con- verted to mr/hr if certain assumptions are made." It was concluded that the base surge distributed a large amount of activity in the upper water layers, over an area of about 1 mi in radius, and prevailing winds carried the contaminated aerosol in a westerly direction to form an initial 17-95 Lawn mee eee ere: