CHAPTER 17 Wahoo, and many total doses were registered on film packs. Also, many of the base-surge dose-rate records were measured by GITR's located on coracles that were floating in the water.2¢ These coracle records best describe free-field dose rates, where the free field is defined as the gamma field near the water surface, ynmodified by any projections above that eurface. Since the GITR's were only a few feet above the water surface, it is estimated that some of them were washed by the water and some of the records include radiation from contaminated water. However, the dose contribution from the water is separable from the total dose because some of the coracles were also equipped with underwater GITR's; thus the above- and below-surface GITR records could often be compared with each other and with available shipboard records. Inspection revealed that most of the coracle records can be considered equivalent to readings at unshielded locations on a ship's deck. cords led to the conclusion given in Ref. 33, Analysis of the re- which deals specifically with shipboard rediation, that "at least 95 percent and 98 percent for Shots Jmbrella and Wahoo, respectively, of the total doses observed on the unwashed decks were due to remote-source (i.e., transit) radiation.” Base-surge dose rates were recorded at times ranging from less than oN 30 sec to more than 20 min after buret.3% 33 Peak dose rates as high as 100,000 r/hr and total transit doses as high as 1000 r were recorded. At Shot Umbrella, on the EC-2 at 1650 ft crosswind, a dose of over 1000 r was recorded, with a peak dose rate of more than 100,000 r/hr at less than 1 min after burst. Aboard the DD-592 at 3000 ft downwind, @ dose of over 500 r wes recorded, with a similarly high peak rate of about 100,000 r/hr at 30 sec. On the DD-592 at 7900 ft downwind, a dose of only 65 r was recorded with « peak rate of about 5500 r/hr at 100 sec, At 8hot Wahoo, aboard the EC-2 located 2300 ft upwind from surface zero, & peak dose rate of 17,500 r/hr was recorded at 0.75 min after burst, and a transit dose of about 300 r was accumleted within 30 min. Aboard the DD-593 at 8900 ft downwind, a peak dose rate of about 9000 r/hr was recorded at about 5 min after burst, and the transit dose was 300 r. Dose rates were recorded aboard ship until 6 hr after burst. After passage of the base surge, rates were quite low, characteristically being less than 1 r/hr at times later than 1 hr after burst (all ships used washdown ). ration Wi : One dose-rate history recorded aboard the YAG-39 at 13 to oO min after burst3/ mst have been due to transit radiation @lone, since no deposit material was collected in that time interval. The peak recorded dose rate was approximately 600 r/hr, when the ship was about 23,000 ft from surface zero. Some transit radiation was recorded the following day at extremely low levels. ne ST AVAILABLE COPY 17-37 cme me ee ee cee me ge “ae