va 2.01, Results of machine computations have been plotted graphically to permit evaluation of the ratios of Eq. 17-23 for a range of slab thicknessec and exposure point locations. These graphs are given in Ref.54 for the five (5) pseudospectrum energies, along with the ratios that permit conversion of circular to equivalent rectangular silsbe. To illustrate the results of ehielding calculations from airborne activity, Figs. 17-12 to 17-15 Ref.55) ere included. (reproductions of Figs. 7 to 10 of The shielding factor is plotted vs total deck- plating thickness for a number of locations within USS RANGER (CVA-61). The monoenergetic calculations have been weighted in accordance with the pseudospectra for unfractionated U-235 fission products at 70 sec and 1.12 hr after fission. Two sets of calculations wer» made for each time, one set using only the nominal plating thicknesses (t}) to give a minimal estimate of the shielding, and the other set using twice the plating thicknesses (2t) to give expected shielding factor values. As indicated in Ref.55, for airborne activity a considerable portion of the incident radiation penetrates through the side of the ship rather than through the weather deck. Therefore, the correlation of shielding factor with total plating thickness overhead is not an accurate measure of the radiation attenuation. However, it represents the best yardstick currently available. 17.5.6 Effect of Geometry at Unshielded Locations No data are available either from water-surface bursts or the earlier underwater bursts to establish experimentally the effect of the geometry of the ship or of the aerosol on transit-radiation levels at unshielded locations. However, analysis? of shipboard data from the Hardtack shots “indicates that the ship's superstructure has e detectable influence on the total gamma dose.... Because of the paucity of GITR data, the analysis was based on doses registered on film packs" (fixed at various locations in the ship). Furthermore, "the gamma records resulting from the passage of airborne radioactive material are sufficiently characteristic that records from shots Wahoo and Umbrella can usually be distinguished by inspection, particularly at downwind location.” ‘The differences in the records are due to differences in the geometries of the base surges resulting from the two shots. Film packs were located at various frame mumbers, on both sides of the ships (toward and away from surface zero). According to Ref. 32, plots of film-pack doses vs frame number, for both shots, show a fairly consistent difference between film pack doses on the opposite sides of the closer ships, a difference coneistent with the attitude of the ship. In general, film packs on the side of the ship toward surface zero registered significantly higher doses than those on the side away from surface zero. In addition, the same plots give a char- acteristic curve shape for each ship, regardless of the ship's attitude BEST AVAILABLE COPY 17-62 Ser erence me ee rn ones = ne mere ey ees ee eee ee eee ee ee ee ee +ee eee we ee eee