——
4
r pertinent question reusinaunsettled is the variation
in fallout
apart.
And .38 d/min/gn
from place to place in a given locality. A satisfactory progrim of
replication has not been possible up to the present time. Howtver, at
iogan, Utah, we did collect replicates from two pastures abouticne mile
The total radiostrontium assay of these soils was .22
Retention by Gummed Films of Particulates in
Similated Rain
An experiment was designed to measure the rention by gam d films
of radioactive particulates suspended in raindrops.
When we first began
to use gummed sampling media in our fallout studies, field
that the activity collected by gummed paper was comparable
ducible than the reaulta obtained using traye designed for
of the rain water. However, reliable controlled data have
previously,
The following procedure was adopteds
tasks danondgrated
to,land gore reprotothl
coirection
motibeen available
Normal radioactive debris was simulated by finely divided pilelirradiated
iron having a massa median diameter of 3m. To suspend the irom powder,
a few milligrams were added to two liters of distilled water
aid agitated.
Particle size control over the suspended particulates was obtained by
elutriation of the original suspension. At a given time, 700 sillizeters
at the top of the cylinder was decanted into a sprinkling arrsdgenent
(Figure 5) which provides for contimed agitation of the suspegsion until
the sample enters a capillary tube from which droplets are pergitted to
fall to the gummed file. Under the conditions reported here,
of "rainfall" was 1" per hour.
fhe rate
The retention of the gumed fijn was
expressed as the percentage of suspended activity recovered byithe film,
A cumulative frequency curve of particle size versus time was dalculated,
using Stokes Law (with Cunningham's correction as necessary).
curve, and the data on retention at various times, Figure 6 wag
[From this
developed.
The retention of the gummed films in these tests was not as high
as was
Similar tests at lower rainfall rates are being planned but have
not as
expected,
This may be because of the heavy rate of simulated
yet gotten under way.
gainfall.
Experiments to determine the effect of 2 hours of temperature konditions
of the gummed papers are given in Table 3. Conditioning at 5° and at
85°C do not appear to significantly influence the retentivity af
the filus.
In order to determine if the iron was going into solution, sacples ef
Suspensions of various ages were passed through @ Millipore filker.
Essentially 100% of the activity was recovered on the filters, indicating
that solubility is not a factor in the above procedures.
00131986 018
—_—
LOS 704)