clam shells and corals which were held at 600°C for thirty
minutes.
(5)
After cooling, the ash was slurried with
ethyl alcohol and a clean glass rod to distribute it evenly
on the plate.
var,
Following drying, a weightless amount of form-
ina s-percent solution of ethylene dichloride was added
to prevent ash from being blown off the plate.
After drying
under a heat lamp the plate was ready for counting.
3.3
Counting
The samples were counted in two Nucleometer internal
gas flow (pure methane) counting chambers.
Counting time.
counting time,
|
A compromise was made as to length of
since there were many plates to be counted,
only two counters were available and it was desirable to keep
the correction factor for decay to a minimum.
The counting
time for each plate was determined by its approximate counting rate,
including a 50 c/m background, in accordance with
the following schedule:
Counting Rate (c/n)
£500
500-1000
1000-2000
>2000
Counting time (minutes)
:
|
20
10
5
2
The counting period for practically all samples collected
after the Mike test (Nov. 1) was from November 24 to December 12.
Most of the samples from the pre-test collections were counted
-8-
Sp ary