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.
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