TABLE 5.2 - Experimental Field Decay Data
oe LL
Type of Decay
=
Ahrafter ABD)
2-10
Gamma Ionization
Time-Intensity
_{Recorder, How IslandShot 1
Gamma Ionization
Task Force Rad Safe
T1B Survey
5.1.2
—
‘Tsiope of Decay Curve over Period Indicated
10 - 48
48 - 480
0.815
1.52
-
1.50
‘
!
1.19
.
-
Exnerimental Laboratory Decay
Table 5.3 summarizes the slopes of the decay curves obtained
from samples measured in the laboratory on two instruments. Gamma decay
was measured with a 47 gamma ionization chamber and a gamma scintille-
tion counter. The average slope of the decay curves measured on 6 individual fallout particles with a gamma scintillation counter is -2,08
from 9 to 30 days and -1.50 from 30 to 60 days. Project 2.6a reportedl8/
an average slope of-2.11 for measurements with a similer gamma scintillation counter on the first four shots from total collector samples over
the period 0 + 7 to 0 + 22 days, The jJecay curve slones obtained from
meesurenents on the dr gamma ionization chamber are of more general |
interest since its response is close to that of the AN/PDR-T1B survey
meter. A comparison of Samples 1, 18, and 21 (Table 5.3) shows that the
decay curves of these fallout samples have comparable slopes; however,
the liquid fraction of Sample 18 has a slope of -1.22 while the solid
fraction has a slope -1.60. The ionization-counted gummed paper samples
from Shot 2 have ar average slope of -1.61 from 170 to 480 hr; for Shot
3 samples the slope was -1.73 from 200 to 600 hr. These slopes suggest
that the leaching of activity preferentially removed the longer lived
nuclides both in the case of Sample 18, Shot 3 and the rain- and sea~
washed gummed papers from Shots 2 and 3. It further suggests that the
gummed paper collectors lost a portion of their collected fallout from
leaching by sea spray and rain.
Tne date are consistent with little fractionation of activity
within the sampling area.
5.2
PARTICIE SIZE
Fallout particles from the differential fallout collector were
analyzed for size distribution with respect to both time and distance.
Data are presented primarily for Shot 1 with limited data on Shot 6.
The amount of visible particulate collected after Shots 2, 4, and 5 was
55.