.ire
eek
channels of information were recorded on each tape; the equivalent of at least three decades of
radiation dose rates could be recorded linearly on each of two channels, and low-frequency
timing pulses were recorded on the third channel. The various recorders were Started either
manually or by the activation of a relay system connected to an Edgerton, Germeshausen and
Grier, Inc. (EG&G) radio timing-signal receiver installed on each ship. The recorder shut
itself off automatically when the end of the tape was reached.
The nominal dose-rate ranges of various GITR’s are presented in Table 2.1.
2.2.2 GITR Installations. Figure 2.3 presents the location and deSignation of GITR detector
stations used by Projects 2.1, 2.2, and 2.3 aboard the ships. Unshielded GITR detector units
were mounted on weather decks and in several compartments in order to obtain the total radi-
ation fields at these locations.
Each ship also had three specialized GITR stations: (1) Station
14 was directionally shielded against radiation sources aboard the ship, to permit estimation
of remote-source radiations; (2) Station 15 was suspended in the water to measure radiation in
the nearby water; and (3) Station 16 was modified to a higher dose-rate range to prevent loss of
data in case the standard GITR’s became saturated.
GITR Stations 1 through 16, on all three
ships, were of specific concern to this project, although data from other stations was utilized
as required.
With the exception of Stations 18 and 21 aboard DD 474 and DD 593 during Shot Umbrella and
Stations 15 aboard all three ships during both shots, the detector units were separated from the
recorder units. All detector units and all recorder units were spring-mounted to prevent dam-
age from shock. In compartments where temperatures exceeded 120 degrees F (Stations 9, 10,
1i, 12, and 13), the detector units were water cooled to prevent damage by heat. Approximately
0.1-inch-thick aluminum was used to: (1) cover each exposed weather-area station as a whole,
to provide protection, and (2) jacket the detector itself in the interior stations, to obtain similar
energy response characteristics. The centerpoint of each detector’s sensitive volume was located 3 feet above the deck on which the station was mounted, except in the specialized GITR
Stations 14, 15, and 16.
The modified detector in Station 16 was located 9 feet above the 02 deck to ensure a clear
view of all radiation sources, independent of ship orientation. The detector in Station 14 (3.3
feet above the main deck) was encased by 4-inch-thick lead, which shielded against radiation
from sources on the ship or in the nearby water but permitted a clear view of surface zero and
the sky overhead.
Figures 2.4 and 2.5 show general details of GITR mounting and cooling.
The underwater Station 15 was suspended from a boom extending over the ship’s fantail.
After the underwater shock waves had passed the ship, the instrument container was meant to
be submerged to a depth of 11 feet by means of a winch-release~and-braking mechanism,activated by a delayed relay-closure from the GITR starting circuit. The detector unit was mounted
inside the recorder unit case; the whole GITR unit, with detector facing upward, was firmly pad-
ded with expanded polystyrene and placed into the instrument container (Figure 2.6).
2.2.3 Gamma-lIonization Decay Unit. This unit consisted of a fallout-sample collector, an
acid-wash unit, a delivery tube, a polyethylene sample container, a GITR, and a 6-inch-thick
lead cave (Figure 2.7).
The sample collector was a polyethylene tray set inside a Project 2.3 open-close collector
(OCC) mounted on the unwashed platform on top of the gun director of DD 592 (Reference 7).
A perforated stainless-steel tube was attached to the inside edge of the tray to permit spraying
the tray with the acid wash. A 14-inch tygon tube, protected by flexible metal conduit, connected the tray’s drain hole with the sample container inside the lead cave, which was mounted on
the main deck of the ship.
The GITR detector was installed in the central cavity of the double-walled sample container
so that the fallout sample presented at least a 3-7 geometry to the detector. The detector and
the sample container were surrounded by foam rubber to prevent damage by shock, and the
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