RAIN SAMPLES, LRL BERKELEY
Collection
From the period April 5, 1958 through October 16, 1958, rain was collected in
ceramic enameled trays which were exposed outdoors for various lengths of time.
Between 8 to 9 a.m. after a rainfall, the sample was collected.
subsequently washed-out with tap water and reexposed outdoors.
The trays were
For the period October 18 through November 15,'a bag of 4 mil polyethylene was
inserted into a galvanized iron drum with the edge of the bag folded over the
lip of same.
This presents a collection area of 1.78 sq. ft.
After rainfall,
the bag containing the sample was removed and replaced with a new bag.
were changed daily during the rainy season.
Bags
Water Processing
The water sample is filtered through a Whatman 41H filter paper to remove the >
included dust and foreign debria.
the filter paper”.
About 50 ml. distilled. water is used to wash
A drop of conc. HNO3 is added to the filtrate and the sample
is then evaporated to dryness over a hot plate and/or a heat lamp.
to avoid bumping.
Bp
Care is taken
Counting
Counting is done with a 3 mg/cu* end window GM tube placed in a 13" lead pig.
Length of time for counting is random but varies from at least 4 hr. to several
hours.
Background of machine is taken prior to each days counting for a similar
time period.
cd
a
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Data Sheet
Colum headings of the table below are described as follows:
“Raw beta-ganma c/m net"--- The net counts per minute from the GM tube,
followed by the decay time in hours}
"a/m/1"--- 8% counter efficiency
95% material collection efficiency on the bottom of the beaker
90% conficence level
d/m/1 = aec/a
x 1.32 x 104
"ne fml"=~-- po/ml = d/m/l x 4.55 x 10710
“pe/aq.ft." --- total nceper sample
collection area (1.75 aq.ft.)
“inches of rain: --- total volume of collected sample
collection area
* an average of 18% is lost to this filter
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