132
LOCKHART, PATTERSON, AND SAUNDERS
A comparison of the overall distribution of the @ar
et
nuclides among the filters of a given collection2 discloses.susprisingly |
little evidence of fractionation; however, the comparison of‘the,nuclide
ratios of the extremes in the particle-size rdfiges showftigeTable a
gives definite indications of a
90g, as aa reference, at?
“t
in
thee
Table 5— COMPARISON OF ACTIVITY RATIOS
Sr FOR THE LARGEST AND THE SMALLEST-:Ss Fg.
PARTICLE-SIZE FRACTIONS
for initial filter vs. final filter
0.71
0.89
August 10 to 17
0.61
August 17 to
September 6
September 6to 13
October 24 to
November 8.
Average
oN
0.95
Sty
§13%Ccg
Ce
MIpm
1.19
0.65
1.01
0.99
et
1.85
1.23
ph
1.23
1.36
a |
0.28
0.71
7 wR.
0.53
BLE nedt*O87
“
.
awe
~ 6.88
0.49
0.86
- 0.83
Te ge
6.50".
76S
7
:
ie:
Bs
-
a,
87
0.41
$4
(0.23
0,52
a ae e-
Standard deviatiog--Sg
a
of themean
“#0.06 10:94:Boe:$0545 ae+0.10
at
of a single rat®o
nae x
+0. 16 6.119
ah
Standard deviation
ove&
-
sis ppleted in the largest
particles. The nuclides ‘8’cs, ‘4Ce, and te Disare rather variable in
their distribution, and *'Y appears to be fractiigeag ext. There was no
apparent, relation:Between the extent or dire
AVtionation and
the existgnce of gaseous or volatile precursors nthe,
sdecay chains of
the nuclifes. For example, there appeared to be no preferential as-
sociation of *ty, '“4Ce, and '’Pm with the larger particles, as might
be inferred from their lack of volatile ancestors. The observed association of 7!°Pb with smaller particles is to be expected on the basis
of its shorter average lifetime in the atmosphere since it is continually
being reintroduced through decay of the 3.8-day 72*Rn primarily in the
lower levels of the troposphere.
CONCLUSIONS
The results obtained in these studies of the distribution of radioactivity among filters in a pack indicate that the fission-product con-
glomerate encountered at ground level some months after a series of
nuclear detonations has the bulk of its radioactivity associated with
ie
88Sr
February 15 to 21
May 3 to 10
July 19 to
August 9
ee -
Ratio of activity ratios to Sr =~
Collection
dates, 1963
“tiers