CHAPTER 17 reliable. Experiments were carried out using a distributed C090 source on the flight deck of the COWPENS to simlate deck-deposited activity, and shielding factors at below-decks locations were measured. Results indicated that the ship's structure attemated radiations to less than 1% of the level on the weather deck. Shielding factors fo. the same energy and the same locations were computed, using twice the deckplating thickness above each location. A correlation between some of the measurements and the computational method indicated that twice the plating thickness should be used in computing the factors.” Comparison of the two sets of values (listed in Table 17-5) showe that in the B section of the ship (where the compartments were larger), the majority of the computed values were lese than 204% different from the experimental values, an agreement considered very good. In the A section of the ship, where there were many small compartments, the majority of computed values were more than 50% larger than the experimental values, and thus did not indicate as mich attemation of the radiations as the experimentally obtained factors revealed. The most divergent results occurred for the location on the main deck (22 ft from the centerline) where the computed factor was about 2.6 times larger than the experimental one. The divergence in values for the B section of the ship may indicate that use of twice the deck-plating thickness ie not sufficient to account for all the shielding in certain portions of the ship. Shielding factors computed by the method described probably will overestimate the dose or dose rate at a given location; hence they pro- vide a safety factor. No Gata are available to indicate whether radiations from deposited activity will affect shipboard equipment. However, high doses (thou- sands of roentgens) or high dose rates (hundreds of thousands of r/hr) generally are required for such effects. SEST AVAILABLE Co at Nee py 17-89 ee een -otwe