PARTICLE ANALYSIS PROGRAM AT LRL
155
pendedin liquid. One 5% aliquot is mounted as a control sample. During
the aliquoting process, the suspension is vigorously mixed byair that
bubbles through the suspension.
3, Suitable sedimentation fluids are used. These fluids are moderately viscose, have densities that exceed the density of isobutyl alcohol
but are less than 2 g/cm’, and have no solvent effect on the particles.
n-Butyl alcohol, chlorobenzene, and carbon tetrachloride have been
used.
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Analysis
The four sets of particle samples produced by the sedimentation
are required for
r separate analytical programs. Set 1 fs. reserved
for permanent
rence and is used for nondestructive analysis,
principally gamma spectrometry and X-ray fluorescence. Set 2 is
committed to radiochemical analysis for those isotopic species whose
half-lives and abundances combine to make them of interest but which
cannot be determined by instrumental analysis. Set 3 is committed to
neutron-activation analysis, first to short-term activation and gammaspectral analysis and ultimately to long-term activation and chemical
Separation. Set 4 consists of particle samples suspended in an organic
medium andis allocated for optical and electron-microscopic examination and to X-ray diffraction and electron-microprobe analysis.
Existing LRL analytical facilities are used when possible. Analy-
ses such as those in sets 1 and 3, which constitute a continuing heavy
workload, are made using analytical facilities provided especially for
particle work.
PROGRAM STATUS
Since its inception in April 1964, the Particle Analysis Program
has been engaged in procedural development in connection with the
particle-separation problem and with equipment procurement in con-
nection with the analysis problem. The ashing and sedimentation pro-
cedures previously described were developed and tested with aerial
filter samples collected at other than the source. The first application
of these procedures to a prime sample was in October. A portion
of an aerial filter sample taken at zero + 8 min in the particulate
cloud resulting from the Sedan shot was ashed and separated into
sedimentation-rate fractions by using gravitational sedimentation in
n-butyl alcohol. The distribution of mass and gross gammaactivity
among the particle fractions is given in Table 1, These data in themSelves are insufficient to permit the calculation of the atmospheric
Sedimentation rate of the particle groups. They are presented only