Shot Wahoo eventually reached a value about four times that for Shot Umbreila even though the
dose was accumulated more slowly and the ship was 1,000 feet farther from surface zero.
For
example, DD 593 received 50 r within 150 seconds after Shot Umbrella compared to 50 r re-
ceived within 240 seconds after Shot Wahoo, whereas the dose eventually built up to 300 r for
Shot Wahoo compared to 67 r for Shot Umbrella. The maximum dose rates were approximately
9,100 r/hr for Shot Wahoo and 5,200 r/hr for Shot Umbrella.
The yery-early dose-rate peaks evident only on the DD 474 and DD 592 curves of Figure 3.2
(during the time period between 0.5 and 6 seconds after Shot Umbrella) occur at the same time
for both ships. This indicates the existence of Some radiation source which did not move horizontally; however, the shapes of the dose-rate curves do not appear to correlate with the sizeversus-time relationships of the plume at surface zero (References 8 and 9). The doses from
the above-mentioned very-early radiations were too low to be of any Significance; the values
observed on the weather decks were approximately 0.13 r on DD 474 and 0.03 r on DD 592. The
very-early radiation was not detected on DD 593 for either shot, and there is no data available
to indicate whether such radiation was received on DD 474 and DD 592 after Shot Wahoo.
The time sequences of the major dose-rate peaks which follow the very-early peak appear
to depend upon the distances of the ships from surface zero (Figure 3.2), thereby indicating that
radiation sources were moving horizontally during these later time periods. This is borne out
by Reference 7, which suggests that there is a correlation between the shapes of the dose-rate
curies and the movements of the visible base surge or cloud for both shots as determined from
timed aerial photographs. Sucha correlation would be consistent with the results of Section 3.2
uw. Which it is eStimated that more than 95 percent of the dose observed on the weather decks was
. on
wr
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TTR
" larity
-ate
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> 474
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arget
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ither-
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3.1.2 Compartment GITR Data.
are tabulated in Appendix D.
The dose-rate and dose data for the various compartments
Table 3.1 presents gamma doses accumulated within 24 hours after the shots.
the dose which was accumulated in the period later than 90 minutes after shot
(11 using the dose rates at 90 minutes after shot; (2) assuming that these dose
as indicated in Figure 3.42; and (3) integrating the resulting dose-rate curves
lime. As an estimate of how the average dose in a compartment is related to
That part of
was estimated by:
rates would decay
with respect to
the GITR dose
Gata, Table 3.1 also presents location-bias factors, which were obtained by averaging all availadie ratios of average film-badge dose in the compartment to film-badge dose at the GITR station. The locations of the various compartments and stations are shown in Figure 2.3.
The gross relationships, i.e., ratios, of the gamma dose or dose rate in various compart-
mcerts to the averaged dose or dose rate on the washed weather decks are presented as functions
ao ume in Figures 3.6 through 3.36. It is important to note that these ratios may not necessarLy be good measures of the penetrability of ship structures by radiation from exterior radiationsources for two reasons:
(1) the radiation inside some compartments may have been influenced
&: radiation sources that were inside the ship (Section 2.1, Table 3.2, and Reference 6); and (2)
Various weather-deck GITR stations may have been shielded by intervening structures whenever
remote radiation sources were not directly overhead.
This may explain why Figures 3.10, 3.17,
4.16, 3.26, 3.33, and 3.35 show radiation in some compartments to be higher than that on the
‘eather deck during periods preceding possible contaminant ingress. The principal reason for
Presenting the ratios was to show the variations in the relationship between the radiation inside
tte ships and the average radiation observed on the weather decks as functions of time.
. Tne ratios of dose in compartment to averaged dose on deck, presented in Figures 3.6 througii
“Af, Show some fairly consistent trends. There are relatively large variations in the ratios
t.r:ng the time period preceding the major-peak dose rate. This can be attributed principally
“: tse changing radiation-source geometries which probably altered the radiation fields at both
“érlor and exterior GITR stations to an extent depending upon the shielding afforded by structres
"
between the sources and the detectors.
For the time period following the major-peak dose
«<. by which time most of the dose has been accumulated, most of the dose ratios remain fairly
27