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of the geometry of the ship on transit radiation doses at unshielded
locations is discussed in 17.5.6, and the effects of transit radiation
on electronic equipment are indicated in 17.5.7.
17.5.2 Weapons-Test Data for Unshielded Shipboard Locations
1.
Water-Surface Bursts
All the test shots classified as surface bursts (Table 17-2 )
were over relatively shallow water, considering the high yields involved,
and the proximity of the sea bottom and the motion of bottom material
probably influenced the subsequent radiation effects. Thus, these shots
probably did not produce the same effects that would have occurred had
they been water-surface bursts at sea (over deep water).
However,
radiological data from these tests can be useful in estimating radiation
effects from water-surface bursts at sea.
Operation Castie: According to Ref. 40, no separate measurements
of transit radiation were recorded for either Shot 4 (Union) or Shot 5
(Yankee).
However, crude estimates indicated that on the YAG 39 target
ship with the washdown system operating, doses at least greater than
0.8 r accumilated between 1 and 3 hr after Shot Union, and doses greater
than 23 r accumlated between 1 and 12 hr after Shot Yankee. In neither
case was the target ship directly downwind in the peth of fallout.
Taking estimated differences in geometry into account, these figures
led to an estimate that, at the end of fallout, as mch as half the
dose accumilated on the weather decks of a washdown-protected ship was
due to transit radiation.
On a ship not protected by washdown the
transit dose was estimated to be of minor significance relative to the
deposit dose.
Operation Redwing: For the two water-surface bursts and one
shot partly on land and partly over water (Shot Tewa), various records
of dose rate and dose with and without washdown are available.4!, 4
Reference 41 concluded that “the air contributions to the ganma-rad-
lation fields aboard ship were highly significant during the period of
fallout.” The only separate transit-radiation records for Shot Tewa
are “estimated” (i.e., adjusted for instrumentation) 2x free-field
dose rates and doses.
The highest such readings were a dose rate of
3.5 r/hr at 4 hr after burst and a total dose of 9 r accumlated by
25 hr after burst, after the YAG-39 had completed maneuvers in an area
north of surface zero while the wind direction was at 105°.
For Shots
Navajo and Flathead, gamna radiation was recorded in washed and unwashed weather-deck areas aboard the YAG's starting at several hours
after burst, but no estimates of transit radiation alone are available.
Incremental-collector and GITR (gamma intensity time recorder) records #¢
are available, and transit radiation doses and dose rates have been
calculated® from the records by estimating fallout arrival times and,
17-35
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