5 A.1
Soot 1
Fourteen difce--rcinl fallout collectcrs were recovered frem
the lend ard lagoon sta*ione after Shot 21. Of these, eieht ficd sa anled
proverly end the data therefrom ere presentec in Anpendix C (Firs. C-°
throuch C-14).
Of the 40 sarrlinr increments, Samples 10 and 1}, 20
and 21, and 30 and 31 were collected over the same time interval (see
ooints A,B, ard C of Figs, C-° through C-16.)
"ith perfect sampling
these increments would collect icentie:1] amounts of fallout and the
reduced data could then be used +9 determine not only the period of
fallout sut also the rate of errivsl, However, cs indicated from
inererent groups A,B, and C, the levels of activity varied by as much aan order of mernitude, This varietion was undoubtedly the result of
:
NN
No.
sampling small amounts of meterial over a small area ror short time
‘ntervalc,
This deficiency does not affect the usefulness of the 1i..-
trument in perforzing its primery function of determining the time of
arrivel fut it does explain the crratic nature of the curves, Relative
counts of each increment were mede “ith a gamma scintillation counter
uncer fixed geometry.
The level 2f activity es indicated in Figs. C-9
through C-16 should not be construed as indicative of the rate of arrival
of falleut material.
Several differential fallout collectors that failed to trigger
were analyzed to determine the “leld backerc und of the collecting inecrements. Firure C-17 shows the genersl level of contamination found in
a non-orerating sampler located at station 251.09 that was exposed to
fallout.
Table 5.6 tabuletes time of errivul period and time of cessation of fallout within the Bikini Atoll area. Date collected from Project 2.2 and Project 2.5a time-intensity recorder traces are also presented,
c-:
|
~
Station
| 250.05
» 250.06
,
TALE5.6-Time of Arrival olof
Fallout
aeenSnanenneiaenttieneettieeee
=
Tp
_
Time of
Arrival
Sampler
= Period
(rin)
(min)
Differential Collector | 0 + 20
Differential Collector: OQ +25
=
Differential Collector
0+ 35
§
251.04
251.05
Differential Collector
Differential Collector
O + 30
0 + 35
;
251.10
251.03
Differential Collector
Fime Intensity Recorder,
0 + 40
0 +15
250.22
| 250.24
251.06
' Dog
j Oboe
Differential Collector | 0+ 25
Differential Collector
(a Proj. 2.2
0+ 25
<O4+15
<0 +15
Proj. 2.2
‘|
|
125
115
60
8&0
125
90
{
|
70
50
-
~
~
(a) See Xeference 2 for an account of this project
69
Coda.
Time of
| Cessation
(min)
--
’
7
L
O+ 145
O + 140
O¢*
95
O+ 95
O + 155
O + 126
0+
0+
-
-
95
90
;