Methods and Conditions for the Determination of
Radioactivityin the Fish Samples:
| 1. Preparation of Samples:
One g of each sample was minced and placed in a
25 mm x 6mm, 5 cm@ stainless-steel planchet, then
dried thoroughly under a heat lamp.
,
2. Gross
fr-activity:
Detector: 1.4 mg/em2 end-window type, G-M counter;
Distance from the planchet to the window=
1.0 cm.
Efficiency of the counter=
20.2 % (against U30g
stand-rd).
ALOKA DC~5 with an automatic sample changer
and recorder.
Determination: Preliminary determination of the
f-activity of all samples was set at 200
Scaler:
counts.
When the counting rate of a sample
exceeded the background at the 95, con-
fidence level, re-dtermination of the
f-activity was ccaducted at a counting time
of 60 minutes.
pe Gross
r-activity:
Detector: 1" x 1" Nal crystal seintilletion counter,
we
with type ND-1O probe. Distance fromthe
planchet to the crystal = 1.0 em.
pete
~
Efficiency of the counter=7.0 % (against
vw
ee
‘ Scaler:
U30g standard).
An ALOKA DC-5 with an automatic sample
changer and recorder.
Determination: Preliminary measurements of the
1
r-activity of all samples was set at 1,000
counts.
t
When the counting rate of a sample
exceeded the background at the 95% confidence
level, redetermination of activity was
condueted at a total of 4,000 counts.
“Expression of results (average valu
es, Table
“Results are shown in cpm of the dried sample 3):
from 1 g
of the wet sample, at the 95% confidence
lovel.