attained.
However, a thick colloidal solution was formed; by us2 of continunt mixing, it colt?
pe assumed that uniform distribution of radioactive particles was obtained.
The sample for the decay tank was collected as soon after detonation as possible. A fairly
active sample was desired, so the collection was not made until the Horizon had reached a point
well inside the fallout pattern.
The water to be sampled was pumped into the tank by use of a
small! centrifugal pump from a depth of about 4 meters.
added as soon as practicable.
The sodium silicate and acid were
The final sample, as counted, contained approximately 500 gal-
ions of Sea-water sample, 110 gallons of commercial sodium silicate, and 25 gallons of hydro-
chloric acid.
The probe reading was recorded as soon as the tank was filled and at ¥,-hour intervals until
the end of the survey.
On occasion, it was impractical to add the chemicals until several hours after the sample was
drawn. This made it necessary to correct the first few readings of the decay curve for the effect
of dilution.
2.5.9
Penetration Recorder for Deep-Moored Stations.
For measuring early depth of fallout
penetration within 15 miles of ground zero, a special recorder was designed for use on the deepmoored skiffs. Figure 2.4 shows a block diagram of this penetration meter. The components,
and their function in the instrument, are listed below:
1. A battery power pack provided 700, 60, 30, and 6 volts of direct current for operation of
the unit.
2. Atwin-drum recorder unit, driven by a geared electric motor, provided linear speed of
approximately 2, in/hr for the waxed paper recording tape.
3.
Atrigger device, utilizing a gas triode vacuum tube, integrated the pulses from an Anton
315 G-M tube located in a collector assembly in the air above the skiff so that when a count
representing 15 mr/hr was received the balance of the recorder unit was put into operation.
4. A series of probes, placed at appropriate depths (1, 20, 40, 60, 80, and 100 meters) on
an electrically conducting cable powered by the 700-volt portion of the battery pack, were used
as the radiation-detecting devices, These probes were all Anton 315 G-M tubes and were enclosed in a cylindrical water-proof brass tube as a physical protective measure.
After connec-
tion to the proper electrical conductor in the cable, the splice and brass-covered G-M tube were
wrapped with several layers of rubber and plastic tape and then dipped in a rubber solution as
further water-proofing protection.
5. A weighted pressure-sensing device completed the underwater portion of the penetration
meter.
6. The counts from each of the above probes, including the pressure-sensing probe, were
Sequentially reported through contacts on a rotable multipoint wafer switch. This programming
Switch was rotated by a low-speed electric motor that made a full revolution every 12 minutes.
1. The pulse count from the G-M probe tubes was balanced by a simple vacuum-tube electronic circuit.
The current required to provide a balance was fed as a servo signal to a Hayden
pen-drive motor, which (by means of a rack and pinion) provided the lateral displacement to the
pen, making a trace on the waxed paper of the recorder unit.
8. A spring-driven 8-day clock, preset at 2400 and prevented from running by a stop interCepting the sweep-second hand, was started by the triggering device. The stop was removed by
an electrically operated solenoid. By recording the local time of recovery of the instrument,
the time of arrival of radiation that triggered the metering device could be calculated from the
Clock reading.
9. Miscellaneous electrical switching circuits for testing all or parts of the device were inCluded. Asa part of the sequence of readings, an index of the battery voltage was also impressed
On the Paper record.
2.6 RESULTS AND DISCUSSION
t
2.6.1 Nav-Rad Device. The Nav-rad device was mounted on the survey ships to safeguard
© personnel from the danger of hazardous radiation levels by detecting its approach and to
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