information regarding the distribution of activity among
same size.
Such an approach was employed by Project 2.63%
particles of the
in experimen-
tal studies at Operation REDWING. During these investigations the activity-size relationships of individual coral fallout particles from two
shots, designated as A and B, were studied.*
EXPERIMENTAL PROCEDURE
Experimental design was based on the collection and analysis of single discrete particles; consequently, preservation of individual character-
istics was a fundamental collection requirement. Fallout particles were
collected on a special sampling surface and the determinations of individual size, shape and gamma activity were undertaken. Procedures were also
included to obtain some particle size distribution information, although
another project? featured this as its primary objective.
ling
Technique
Fallout particles were sampled by incremental collectors (IC), which
are fully described in Reference 8 The collectors sequentially exposed
h x 4-in. plastic sampling trays, each containing a cellulose acetate disc
coated with a heavy layer of special grease; the actual sampling area was
8.2 cm in diameter.
For each IC, the exposure period of its trays were
identical and preset at either 3, 15 or 36 min, depending on the number of
Ic's at a station and the expected rates of fallout.
The particles studied were collected at major project sampling stations located on several vessels. For Shot A, only the collection from
the YAG-40 was studied. For Shot B, the samples investigated were from
YAG-hO, YAG-39, LST~-611, YFNB-13, and YFNB-29 (two stations). At all stations, project collectors - of which the IC was one type - were located
on an elevated wind-shielded platform, designated as a standard platform.
Detailed descriptions of the vessels, platforms and their instrumentation
may be found in Reference 8.
Except for the YAG-hO collections from both
shots, the particles investigated were sampled by platform-mounted IC's
and shipped back to HRDL for analysis.
In addition to its platform collectors, the YAG-4O had special collect-
ing equipment and a shielded laboratory with facilities to take early-time
measurements. Particles for the present study were collected by two adjacent, independently operated, modified IC's designated as special incremen-
tal collectors (SIC).
*
hese instruments were in a 6 x 3-1/2 x 6-ft housing
Shot A is the first of the shots in which USNRDL participated during
Project 2.63; Shot B is the fourth.
2