CHAPTER 17 account for the low observed levels. ‘Thus, it is possible that at early times, radiation levels in the water around surface zero could add to the radiation field aboard a ship traversing the area. However, it is concluded that available data from surface bursts do not provide ea reasonable basis for predicting dose rates around surface zero at early times. The underwater-burst data indicate that within 2000 %%of surface zero and within the first 15 min after burst, doses of several hundred roentgens could be eccumilated from contact with the first few feet of surface water. However, after 1 hr after burst, activity in the water probably would be of no significance aboard ship, and by several hours after burst, activity levels in the water from either water-surface or underwater detonations would probably be lower than 1 r/hr. 17.7.4 Shipboard Dose~Rate Dato from Contaminated Water Shipboard dose and dose-rate data have been obtained at various weapons tests. In compartments below the water line, the recorded gemma doses and dose rates that were considered to be due only to contaminated water surrounding the ship were negligible in all cases; in fact, they contributed less than 1% of the levels measured at exposed C locations. Simultaneous measurements of dose rates in the water around a ship and dose rates aboard that ship are required for reliable esti- mates of the contribution of waterborne radiation. Such measurements are available for only a few shots. However, efforts have been made to distinguish the contribution of waterborne radioactivity from the con- tributions of other sources for several additional tests. 1. Water-Surface Bursts ration (YAG's 39 and GO) ulate portions of area on each ship Castle: For Operation Castle, two Liberty Ships were modified to have various parts of each ship sinNavy combatant ships. For instance, the recorder-room similated compartments below the waterline, adjacent to the shell, and was well-shielded from the weather surfaces by a le- inch concrete slab. Doses and dose rates measured in these rooms were attributed only to radiation penetrating the ships’ skins, and not to radiation from sources above, such as fallout. Dose rates in the recorder rooms after Shot 5 (Yankee) peaked at only 0.07 to 0.08 r/hr between 6 and 7 hr after burst, and the total doses measured to 12 hr were only about 0.5 r. During the same period, doses of over 100 r were recorded at unprotected topside stations on the same ships. C- ee ey er te ee ro 8 ee ee ee ee ee 17-99 ee ee ee eee ee -e ote ~ It