iw a7 bene. —elL. ti DNA 1240H-2 Tp mee ee te Pe a PA eA t . Mey ~ me oo ee ~ . A PAIGE, ~ meow ete ~ ~~ et 22 Oa “Tre : - Lak fe Ayo Shot Tewa . sya oe a. . ~ 7 ee , vv ce : ~f - IN rp ae? FF A “t 2 A . ‘7 ~ : ¢ — Sty, ‘ ryt fr ~ 40s Ae. torr oe wel 8 “: fy fe Pw C produced a visible fallout of radioactive particles in coral residue.42,6lFor this shot, the accumulsted deck dose in the unwashed ares of the YAG 40 to the end of washdown at H + 15.2 hours was 49.3 r, while in the washed area, a total of 10.3 r was recorded.4 2 The recorded dose in the unwashed area increased to 100 r by about 54 hr, indicating the effect of the deposited activity. Furthermore, it is estimated from the records in Ref. 4], that the deposited activity contributed about 95% of the total radiation dose recorded by 24 hr on the unwashed weather deck, an estimate in agreement with that of Operation Castle. 2. Underwater Bursts \ \ Operation Crossroads, Shot Baker: It was eatimated”’that deposit dose composed about 50% of the total radiation doses registered by film badges at exposed locations on ships at Shot Baker, and the remainder of ‘the dose was attributed to transit radiation from the base surge. It wae further estimated“’that residual activity was deposited on the ships by rainout from the mushroom head of the cloud, in a ring whose radius was slightly less than 1000 yards from surface zero. In the ring, the mean total dose level due to deposited material was 4000 r, of which 3500 r was attributed to fallout from the mehroom cloud. In the center ‘of the ring, deposit doses ranged down to below 1000 r. Table 1 of Enclosure J of Ref. 65 gives calculated estimates of first-hour doses (based on dose-rate readings) from material deposited on target ships. The ships were located at ranges varying from 500 to 2000 yards around surface zero, and first-hour dose estimates varied from 140 r, aboard the LCI-332 at 2000 yards E of surface zero, to 3850 r on the Pensacola at 500 yards SW of surface zero. Operation Hardtack: Large base surges were generated by Shots Umbrella and Wahoo, but no visible fallout occurred. Weather-deck dose and dose-rate data were obtained principally for Shot Umbrella, due to power failures on two test ships at Shot Wahoo. in 2 to 3 miles of surface zero. <All the test ships were with- Dose and dose-rate data were also obtained from the coracles, most of which were within 2 miles of surface zero, although a few were positioned at more than 4 miles from surface zero. During Shot Wahoo, 11 of the 16 coracles broke moorings. positions during the time of principal interest did not change more ‘Their 300 ft, although before recovery, several drifted k to 12 miles.-* than was concluded in Ref. 33 that practically no material was deposited aboard the test ships, since the dose rates fell from extremely high It to extremely low values with the passage of the base surge, and very little dose was accumlated after the first few minutes. However, of the samples collected in the AFI (air filtration instrument) in 2- and 10-minute intervals,>2 the first samples in both series from Umbrella were heavily loaded with visible residue resembling pulverized coral. There was also evidence that heavy liquid deposition associated with radioactive material occurred during the first few minutes.2* BEST AVAILASLE COPY 17-74 Air