The open-close total collector (OCC) 6,7 was designed to
collect and hold fallout material wnile reducing to a
minimum the amount of extraneous material deposited both
before and after the collecting period.
Wnen trigsered
either by an increase in radioactive backzround or by hand,
the cover of the device opens and a collecting tray rises
into the wind stream for the preset exposure time
in 15-minute increments between O and 81 hours).
(variable
The tray
has an effective collecting area of about 2.5 square feet
divided into numerous cells to reduce loss of material dupe
to wind.
Samples, other than cloud samples, were obtained»
from this type of collector mounted on converted liberty
ships (xAG's), barges (YFNB's) and “How Island.
After collection the fallout material was flown back
to the Laboratory and aliquotes by Chemical Technology
Division.
The aliquots sur2plicd
to this section for analy-
sis were placed in the polystyrene containers and prevented
from shifting,
in tne case of cranular or pulverized samples,
by tne addition of a small amount of paraffin.
The machine was calibrated so that on "standard" gain
the total absorption peak of a 100, 200, or 300, etc., kev
gamma ray would be centered on the 1/2-inch, l-inch, or 1-1/2inch, etc., line on the recordine paper.
This calibration
was accomplished first by careful zero-setting of the X-Y
8