few rains. These seasonal effects have occurred each
summer and wintercycle.
Autoradiography”
of
part
of
a
sample
of
percolated rainwater taken in winter from the
chamber containing the large pieces of MHFT-12
revealed 0.05- to 0.8-um-diam plutonium oxide par-
ticles with a count median diameter (CMD) of0.095
um. These accounted for only 1 ppm of the total
plutonium in the sample, indicating that nearlyall
the plutonium particles carried through the soil by
water were less than 0.05 um in diameter.
Usually there is good agreement in measured
radioactivities among aliquots from the same per-
colated rainwater sample. Occasionally there is disagreement with one aliquot counting as much as
several hundred timesthe others. This indicates the
presenceofa significantly larger than average particle of PuO.. We estimated that the largest particle
foundin the high activity aliquots was equivalent to
a 4-um-diam sphere, five times the diameter of the
largest particle seen in the autoradiographic
during the first 5 min of rain, in contrast to the ex-
periment with the large pieces. Instead, airborne
plutonium decreased, and after the rain, the concen-
tration was an order of magnitude lower than before.
These lower concentrations probably indicate that
soll wetting inhibited resuspension of plutoniumbearing particles. The counting rates were so low
that we had to combinethefive filters used during
the rain to obtain meaningful statistics. The same
treatment was necessary forthe first five filters used
after the rain. There wasvery little seasonal effect on
the plutonium content of the rainwater that percolated through the soil; it averaged about 0.2 uCi
both winter and summer.
0
i
st
~
ed
|__|
Ps
0
:S ot
_-.-]
0
}|
isk
This concentration did not increase significantly
oo
TABLE V
CONCENTRATIONS OF AIRBORNE PLUTONIUM
DURING RAIN IN AN ENVIRONMENTAL CHAMBER
CONTAINING FINELY DIVIDED 238-PLUTONIUM DIOXIDE
Filter
No.
Collection
Time
__(nin)
Pu
Concentration
(pCi/m*)
1
103
1.9
2
5
2.1
60
1.9
2-7
Remarks
Before
Tain
First 5
min of
rain
Average
during
13
164
0.12
926
0.14
After
rain
3
63
| |
jo
493]
33
1B
8
| |
|
63
of4
tose}
7
7
I
t
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p——J
{
32
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ry
i;
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|
9,
t
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=
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0
95
}
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Tl
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o
6
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Tain
8-12
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of}
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=
in the chamber were also measured using an air
sampler. The results (Table V) show thatthe airborne plutonium concentration before the rain was
about the same as the prerain concentration in the
chambercontaining the larger pieces of MHFT-12.
0
—
0
analyses of a rainwater sample in which the count
rates of the aliquots agreed.
The fine particles of MHFT-12 interacted
differently with the simulated environment. These
particles were too small to have temperatures above
ambient, so spallation was negligible. Plutonium
concentrations in airborne particulates during a rain
!
066
69n0*
fotI
!
po
!
!
7
0
|
—
fb
po
67;
Jo
|
on
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r—
of
0
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9
a2
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ee
y
[oe
0
=
—y
—
W
bs
"4
23
132
35
088
—
als
027
06
|
|
on
Q
019
|
+
et
lowe
|
—
6
=
6
7
0089
7
f=
13
pos
[034
0}
Vi
FoF
oy
r—
desl
E+
LO
Lo
| bo) My|
10
40!
Total
a.Sampte to LFE Environmental
.
12
[ow
Lo
lots
71a
bad
eat
a XN
449s
|
ago
[ol
El
54
Core: positions:
as * 6
!
Pu
5
2
4:7
Fig. 2.
238Py in soil cores from chamber containing
fine material from MHFT-12 (ng).