Doves 7
samples were also collected in test compartments following Shot Umbrella, ©
and analysia of the samples indicated that 90% to 95% of the activity in
the samples was due to particles with radii of less than 1 micron. It
was demonstrated at previous tests that washdown is very effective with
small particles carried in an invisible mist, and washdown was opersting
on the test ships at both shots. Thus, it is possible that had wash-
down not been opereting, radioactive material might have been deposited
and remained on the weather decks of the test ships.
No data were
obtained at distances such as 10 to 20 miles from surface zero, to
permit "scaled" comparison with data from the barge shots of previous
operations.
ration Wi
: Tne YAC-39 encountered an invisible cloud of
airborne radioactive material between H + 16 and H + 19 min.
Residual
contamination wae left on the ship, but decay and the washdowm system
reduced the radiation levels quite rapidly, so that at H + 1 hr, the
average gamma dose rate on the weather deck was about 9 mr/hr.
The
YAG~LO avoided the "cloud," and made numerous traverses of the contaminated
area on D and D + 1 days, but encountered no fallout.
It was estimated
that very little residual activity remained on the hull of the ship. 2!
17.6.3 Weapons-Test Data for Shielded Locations
1.
Water-Surface Burste
Operation Castle:
A study was undertaken to obtain data on the
effectiveness of ships’ structures in shielding interior compartments
from gamma radiations during and after a contaminating event. Data for
this study were obtained from Shots 2, 4, and 5, and the recorded dose
and dose-rate values at exterior and interior locations on the test ships
are presented graphically in Chapter 2 of Ref. ©. Results of analysis
of the data, presented in Chapter 3 of Ref. 40, indicate that the shielding
factor (the dimensionless ratio of the dose rate or dose within a compartment to that measured above the weather deck) at locations between
the 2nd deck and weather deck were in the range from 0.1 to 0.2 on YAG 40,
and from 0.15 to 0.30 on the washdown-protected YAG 39.
In superstructure
compartments on both ships, the shielding factors generally were in the
range from 0.1 to 0.6.
It was pointed out that the shielding factor
actually represents shielding from all sources of radiation ~ transit,
deposit, and water-borne. However, it was concluded that “shielding
factors on the YAG-hO are believed to be a good approximation to the
shielding factors for activity deposited on the deck surfaces."
ration Redwing: Dose and dose-rate values recorded at exterior and interior shipboard locations for the Operation Redwing shots
indicate the extent to which the ships' structures attemated the gamma
radiations emitted by radioactive material surrounding am deposited on
the ships. The dose to 30 hr in the upper No. 2 hold of the YAG 39 was
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