Chapter 4
CONCLUSIONS AND RECOMMENDATIONS
4.1- CONCLUSIONS
The project had only limited success in meeting its objectives for Shot Wahoo, but met most
of its objectives for Shot Umbrella. The conclusions are meant to apply only to the specific test
conditions and radiological environments encountered aboard the moored and washed target ships.
4.1.1 Total Gamma Radiation Aboard Target Ships. The gamma radiation data indicated
rapid rates of change with time after burst, and dependence upon distance from surface zero.
These characteristics are summarized in Table 4.1 for the washed weather-deck areas. After
Shot Wahoo, the weather-deck doses accumulated more slowly but eventually reached values
on the order of 300 r higher than for Shot Umbrella, even though the ships were from 1,000 to
2,000 feet farther from surface zero.
For nuclear-weapon-delivery situations simulated by the two closer-in ships, temporary
immobilization could result in lethal or near-lethal doses. After Shot Wahoo, the majority of
compartments received doses in excess of 500 r aboard DD 474 and in excess of 200 r aboard
DD 592. After Shot Umbrella, the two ships received doses in excess of 200 r in many compartments.
Ratios of dose or dase rate in compartments to dose or dose rate on the weather decks were
dependent upon changes in radiation-source geometries and upon the presence of contaminants
inside the ships. In one instance a dose-rate ratio changed by a factor of 1,000 within 28 minutes. The long-term dose ratios ranged between 0.36 and 0.63 for nonmachinery compartments
on or above the main deck, between 0.14 and 0.46 for other nonmachinery compartments, between 0.08 and 0.20 for machinery spaces above the waterline, and between 0.02 and 0.07 for
machinery spaces below the waterline.
4.1.2 Remote-Source Gamma Radiation.
For the washed weather-deck areas, the observed
total radiation can adequately represent the remote-source radiation during the first 10 minutes
after the shots. At least 95 and 98 percent of the total dose on the washed decks was attributed
to radiation from airborne radioactivity for Shots Umbrella and Wahoo, respectively.
On DD 474 and DD 592, a very-early radiation peak was observed between 0.5 and 6 seconds
after Shot Umbrella but the dose from this effect was negligible, i.e., less than 0.13 r.
No
data was available to indicate whether similar very-early radiation was received after Shot
Wahoo. There was apparently no correlation of dose-rate data with the size-versus-time relationship of the plume.
4.1.3 Total Gamma Radiation in Adjacent Water.
Determination of underwater gammaradi-
ation was not successful; data was obtained only for DD 593 after Shot Umbrella.
Contaminated water adjacent to the ship did not contribute significantly to the total radiation
observed aboardDD 593 after Shot Umbrella.
Indirect evidence suggests that, although radia-
tion from the water may have affected the compartment,deck dose-rate ratios to a considerable
degree at later times, the contribution of contaminated water to the total dose observed aboard
the target ships was probably of little significance.
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