CHAPTER 17
17.6.6 Simulant Experiments
An experiment was conducted on a Naval ship to evaluate shielding
effectiveness of the ship's structure against gamma radiation from an
external source.
Results are reported tn Refs. 71,72,73,74 and 75.
In the experiment, to approximate a condition of uniform contamination,
a 145-curie Co™
source (1.25 Mev gamma energy) was pumped through
plastic tubing laid out on the flight deck of the COWPENS (AVT 1), a
light aircraft carrier. Two dosimeters were placed at each of various
locations on the flight deck and in below-decks spaces. Numerous
dosimeter readings were averaged and then divided by exposure time to
provide dose rate as a function of time from the centerline of the ship.
The measured flight-deck dose rates were corrected for the size of the
“contaminated” area, since experimental data and computations indicated
that the observed dose rate on deck would be increased by 4.5% if the
entire deck were contaminated. Adjusted readings were used to determine
the shielding factors. Two portions of the ship, designated A and B,
were investigated. The A section had more and smaller compartments than
the B section.
Figure 17-16 illustrates echematic cross-sections of the COWPENS
at the frames where the measurements were obtained.
Measurements on
the Gallery Deck, the Forecastle, and the Main Deck were made about
frame 35 (the A Section), while measurements on the Hangar Deck and
the 2nd and 3rd Decks were made about frame 85 (the B section). Dos-
imeter arrays at each location were supported 3.5 ft above the various
decks.
The shielding factors obtained experimentally are listed in
Table 17-5.
Also listed in the Table, for the same locations and
source energy, are shielding factors calculated by the theoretical
method described in 17.65,
above each location.
using twice the total deck-plating thickness
The factor of 2 was derived from measurements
made in the B section. ©
Experimental results indicated that on large ships, such es eair-
craft carriers, at locations on the 2nd and 3rd Decke and below, the
ship's structure attemated radiations to less than 1% of the level
on the weather deck.
17.6.7 Summary
A eurvey has been made of available information on the interaction
of surface ships with deposit radiation resulting from water-surface
or underwater bursts. Results of the survey, which included weapons
test data, experimental data using similants, and theoretical calculations,
are mimmarized in the following paragraphs.
BEST AVAILASLE COPY,
17-85
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