The scintillation counter probe encloses a NaI crystal of 13
inches diameter and 13 inches in length, and a Dumont photo multiplier
tube in a steel pips 7.8 centimeters in diameter,
The probe was con-
nected to a count rate meter by a very long cable on a reel, and used
to take readings at varying depths below the surface.
During the voyage
from Japan, gamma background for the scintillation counter was reported
to us as 2400 cpm,
We were advised that 500 cpm was equivalent to 0.7
milliroentgens per week.
During the survey of the TAKUYO on 26 July, a rough check was made
to compare the background readings of the Japanese scintillation comter
with our MX-5.
The following results indicate a reasonable check:
Scintillation counter:
3315 cpm gamma (equivalent to 0.03 Hr/hr)
MX-5: 0,045 mr/hr gamma
The equipment on the SATUMA MARU consisted of one laboratory type
geiger counter similar to that on the TAKUYO, and one 0-200 milliroentgen
self-reading dosimeter and charger.
The dosimeter was of Japanese manu-
facture and similar to our Keleket 0-200 milliroentgen dosimeter,
During the voyage of the SATUMA, the dosimeter hung in a plastic bag
filled with a dessicant in a bulkhead doorway to the "Scientific Observation Room",
The door remained open at all times and the dosimeter was
therefore in an exposed position,
Readings teken daily by the scientific
personnel aboard are shown in Tab A, Appendix IV,
The readings show the
doses of 26 millircentgens from 8 to 15 July, and 24 milliroentgens from
15 July to 19 July.
There was no air sampling equipment aboard either ship.
The units
for the air data (cpm per cubic meter) listed on the ships course plots
DOE ARCEIIVES