teristics of the various superstructure components; however, where a relatively thin section of the superStructure subtended more than 10 percent of the total unobstructed solid angle, an approximate shielding factor was estimated, using the ship’s plans and a gamma energy of 1 Mev. Plots of the approximate effective solid angle subtended by the radiating cloud are presented in Figures 3.213 and 3.214. A comparison of these plots with similar film pack plots demonstrates the effect of the ship’s superstructure conclusively. A more refined treatment af te.s problem would probably yield an even closer correspondence between film pack doses ang the tot.. solid angie subtended. 3.4.3 Conversion Factors. Although the effect of superstructure shielding has been demonstrated in the previous Section, the caiculation of conversion factors from isodoSe contours to stipboard exposures is subject to many errors. The variable nature of the radiological event at close ranges and the nonuniform distribution of radioactive material within the base surge are the principal sources of difficulty. These uncertainties can cause error even in the simple extension of a shipboard GITR measurement to another shipboard position where a film pack reading has been made. Because of these difficulties, the estimated conversion factors are restricted to total cumulative dose only. All factors should be used with caution. With the exception of the EC-2 during Wahoo and the DD-592 during Umbrella, the average total GITR dose and the average of the film pack doses from the exposed deck positions agree with the total dose estimated from the isedose contours to within +15 percent (see Tables 3.27 and 3.30, and Figures 3.103 and 3.109 for basic data). The film pack inside the pilot house on the EC~2 is omitted from these averages for obvious reasons, and the cumulative dose from the bow GITR on the DD-593 is also omitted for reasons discussed later. The average GITR dose is less than or equal to the total dose estimated from the isodose contours for Wahoo, whereas for Umbrella the average GITR dose is greater than the total dose estimated from the isodose contours. If only expesed shipboard positions are considered, the film pack data also shows some fairly consistent differences for the two detonations (Table 3.32). In general, the shipboard doses for Wahoo are approximately 10 percent lower than what would be expected from the isodose contours, whereas for Umbrella they are 10 percent higher. The data is, however, insufficient to make any further generalizations about the differences between Wahoo and Umbrella. The variations shown by the EC-2 during Wahco and the DD-592 during Umbrella are most probably due to errors in the isodose contours in the region of these ships, although another possible explanation is discussed later. Conversion factors that compensate for superstructure shielding can also be computed for each ship. Because of the paucity of GITR data, these conversion factors have been calculated from film pack data only. The average of all film pack doses aboard a given ship is low because of shielding effects, whereas that for the platform film packs and perhaps even for exposed positions on the superstructure decks is high because of the increased Solid angle subtended by elevated positions. The average of all exposed deck positions is, therefore, selected aS most representative of the free-field dose for a given ship, and all other shipboard FP doses have been normalized to these averages, to obtain the desired conversion factors (Table 3.33}. The pilots of film pack dose versus frame number (Figures 3.207 through 3.212) show a fairly consistent difference between film pack doses on the opposite sides of the closer ships. This difference is consisent with the artitude of the ship if allowance is made for movement after zero time (Figures 2.1 and 2.2). On the DD-593, the most distant ship, this difference is s0 smail as fo be somewhat arbitrary, On the closer destroyers for both shots and on the EC-2 for Wahoo, the starboard side was exposed either to surface zero or to the track of the base surge center (the hot line) and the starboard film packs; with the exception of a few ex- posed positions on the superstructure, the starboard film packs reflect this orientation by registering a Significantly higher dose than the port film packs. For Umbrella, the port side of the EC-2 was facing surface zero; however, neither the port or starboard film packs show a consistent pattern, although the port film packs generally tend to be higher. 311 /7@