installed on the "flight" deck, which was situated on the ship's bow
approximately 8 ft above the main deck. The SIC's were so mounted that
their sampling ports were located together and exposed flush with the
roof of the structure. To reduce wind bias effects, a horizontal steel
plate was placed on top of the SIC housing to give an 18-in. overhang on
the forward and lateral sides. The opening in the plate for the sampling
ports was located forward of the plate center and the plate was greased
to prevent those particles falling on the plate from blowing or rolling
into the sampling port. Investigators located in the shielded laboratory
below controlled the SIC sampling intervals and, immediately after exposure,
the trays were lowered by an elevator into this laboratory where analytical procedures were begun.
Particle Selection
Analytical procedures generally were the same at the field laboratory and at NRDL, with minor differences as noted.
Some of the sampling trays exposed during the heavier fallout were
examined with a low-power binocular stereomicroscope to determine the
size and shape of the particles. Each particle was typed according to
shape and sized in situ. Only Shot B particle collections were studied
for size distribution. Circular areas were randomly marked on each tray
and in these areas, particles larger than 10 p in diameter were studied.
On the YAG-40 trays, a circle 1.2 cm in diameter was used, while « cir-
cle 0.6 cm in diameter was used on all other Shot B trays (analyzed at
NRDL).
No attempt was made to obtain size distribution information from
the YAG-40-Shot A particles; these were selected to obtain a sufficient
number of particles from all size groups present to provide reliable data.
Immediately after being sized, each particle was carefully scooped
up with ea hypodermic needle and suspended in a small glass vial for subsequent gamma counting.
Particle Shape and Size Determination
Particles were classified in three general categories on the basis
of physical appearance:* spheroidal if spherical in character, irregular
if irregular or angular, and dendrite-like when distinguished by an inter-
lacing branching network structure of extreme delicacy (Fig. 1).
* The color of YAG-40 particles (both shots) was also determined; however, this parameter was not utilized in the present study.