DNA 1240H-2
2.
Underwater Bursts
" Operation Hardtack: At Operation Hardtack, three destroyers
utilized as target ships during the two underwater shots were instrumented
with film badges and GITR's in many compartments. In addition, ea CITR
waa suspended from a boom over each ship's fantail, and was to drop into
the water after the passage of the underwater shock wave. After Shot
Umbrella, GITR and film-badge data were obtaired on all 3 ships, although
not all GITR's operated. From gamma dose-histories tabulated in Appendix
D of Ref. 33, it is possible to compare doses recorded by the GITR‘'s at
several shipboard stations located 3 to 6 ft below the waterline of the
DD-593 with the doses recorded by the GITR suspended in the water over
the fantail at station 15. Stations 11 and 18 were at the lower level
in the forward and aft firerooms, respectively, and station 8 was located
in the magazine. At station 15, doses measured were 0.0) r by 18 min,
0.03 r by 81 min, and 0.367 r by 8.5 hr. At stations 1) and 18, doses
measured about 2.8 r by 9 min. They were about 3.24 r at station 11 by
93 min and 2.91 r at station 18 by 92 min. At station 8, doses were 13.2
r by 9 min and 13.4 r by 90 min. These doses are listed in Table 17-7.
Table 17-7.
Station
15
Dose data from DD-593 for Shot Umbrella.
Location
Dose
In water
0.0lr
0.03 r
0.367 r|
ll
18
8
Lower level,
fwd fireroom
Lower level,
aft fireroom
Magazine
2.8r
3.24 r
2.85 r
2.91 r
13.2 r
ar
Time
18 min
81 min
8.5 hr
9 min
93 min
9 min
{91 min
9 min
90 min
Comparison of the doses recorded in the water with the doses recorded
aboard ship indicates that the former were only about 1% of the latter
even at shipboard locations only partially shielded from airborne activity.
Thus the contribution of waterborne contamination to shipboard doses must
have been very small. Although shipboard doses were recorded at Shot Wahoo,
17-102