Radioecology
Page 152
RESULTS
for gross beta
All of the samples were counted nucli
des.
ting
-emit
gamma
for
some
and
| Pactivity
ed value
limit
of
are
s
count
beta
gross
ily,
=
ve nor qualitaote they are neither quantitati
ate the
The results of gross beta counting are given
in Appendix Table A as average values. With few
exceptions the average is computed from the counts
of three samples, each from a different specimen.
The total number of samples counted was 825, but
in addition there were 495 recounts either to establish decay curves or to confirm the original
counts. The common and scientific names of the
to indic
Ftive but have been useful here
borne
Se arrival at the collecting areas of waterIn other instances beta counts
7 fallout nuclides.
can
ful for purposes of comparison when it
:
the
B be assumed that the isotopic composition of
same.
@ sanples being compared is approximately thebeta
™ In addition to the determination of gross
@ activity, specific nuclides were identified, quali-
specimens are listed in Appendix Table B.
Some of the data from Appendix Table A have
been selected for graphical presentation in Figure
2. Since all of the data could not be presented
in a limited number of samples by gamma
@ spectrum analysis.
conveniently in Figure 2, data representative of
The beta-counting system was composed of the
general results were selected.
#tollowing units: a thin-window 1 3/4-inch, pancaketype Geiger-Mueller detector, an automatic sample
¥changer with the lead shield modified to accommot date the detector, a decade scaler, and a printing
timer.
Seventy-two plankton samples, collected weekly,
were obtained from Palau in addition to six trimonthly samples from Guam and four trimonthly samples from the Gulf of Siam. The data for these
samples are presented in Appendix Table C and
.
Figure 3
The cups for the automatic sample changer
| were adapted to hold 14-inch stainless steel
; planchets.
The gamma-counting’ system was a model of a
The copper and
Gamma spectrum analyses were made of 17 samples to determine the presence of specific gamma-
F system described by Heath (1957).
| cadmium-lined shield weighed five tons and was
: built with lead bricks into the form of a cube,
emitting nuclides.
The samples were selected for
geographical location and high gross beta counts.
36
F inches on a side and four inches thick. The detector head consisted of a three-inch by three-inch
‘ sodium iodide crystal and a l2-stage, three-inch
photo cathode that was placed in the center of the
Results of analyses corrected to date of collection
are given in Table 1.
=
:
One of the limitations in the interpretation
shield, a minimum distance of 124 inches from the
; Sides.
The impulses from the detector head were
transmitted to a 256-channel analyzer.
h\
g
GROSS BETA ACTIVITY, MICROMICROCURIES PER GRAM OF WET WEIGHT
g
counts have not been corrected for decay during the
interval between times of collecting and of count-
KIDNEY
SPIDER SNAIL LIVER
ALGAE
FISH MUSCLE
FISH LIVER
HERMIT CRAB. SKELETON
SPINY LOBSTER LIVER
\
\
\
\
230
/
\
\
\
\
\
\
Ff
W....._..._
|
\
8
3
\
T
PL4 A ek,
of the results is the fact that the gross beta
0
i
Be SS
—
_]
a
Mies
ENMWETOK
OCT
wa
dA
APR.
oe
JY
Oct
eee
[_peemncnpy ———a Oharepu—000 thon 7]
ALY
oct
58
JAN.
APRA
1989
AY
OCT
[_r-—ong___—_lees then 7]
way
oct
ose
ia
00
APL.
GUAM
PALAU
G ULF OF SIAM
L200
L950
4.250
Figure 2. Average groas beta activity of marine organisms from Guam, Palau,
and the Gulf of Siam, 1958-1959. Average based on two to thirteen observations.
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