G.5-Mt yield to be approximately 4 x 10 r, whereas
(2) particle and drop-size ranges of fallout and airborne materials at ground level, (3) amount and
distribution of radioactive materials in fallout and
airborne matcrials, and (4) gross gammaand beta-
measurements for Shot 4 Indicated that only 1.55 =
10 r were received. At approximately 4,500-yard
range, this handbook shows a prediction of about
800 r; measurements showed that only about 84 r
were received.
It would appear that the initial~gamma radiation
is of negligible mgnificance, since the blast and thermai effects in the same range of distances are so
great that personnel could only survive if they were
disposcd inside blast- and thermal-proof bunkers.
gamma decay rates of radioactive materials (some
gammafield measurements were also made for correlation purposes).
The distribution and intensity of fallout from all
shots was investigated. The residual gamma pattern
and some dau: on gamma decay and particle-size
distribution was established for Shot 1. The fallout
from Shot 1 was a dr. white particulate, irregular
in shape; many particles were flaky in nature.
Project 2.3 “Neutron Flux Measurements”
(WT-914), Naval Research Laboratory; T. D. Hans-
Gamma levels of military significance were found to
exist at downwind distances to at least 280 nautical
miles. The fallout from Shot 2 was more nearly
characteristic of an aerosol with no evidence of large
particulate. The fragmentary data on the residual
gammafield show the level of activity 5 hours after
detonation to be 145 r/hr at a downwind distance of
45 nautical miles.
coms, Project Officer.
This project was assigned the problem of measuring tne neutron flux enrountered in the detonation
of the nuclear devices at Castle, using the same
techniques as used at Snapper and Upshot-Knothole.
Gold, sulfur, and tantalum were used to measure
the flux in the thermal region and the region above
3 Mev. The fission detectors were used to measure
the 1-Mev region of the neutron spectrum and to give
an iaea of the shape of the spectrum above that point.
Project 2.5b ‘Fallout Studies” (WT-916), Chemi-
cal Warfare Laboratories, Army Chemical Center;
E. F. Wilscy, Project Officer.
.
The objectives of this project were to determine
(1) the characteristics of fallout from land-surface
Because of the short half ives of some of the in-
cuced activities, it was necessary to provide counting
facilities in the field: two trailers were installed on
F'mec Island for this purpose, and were equipped
tc handle the counting of gold,!
and water-surface bursts, (2) the evaluation of the
hazards associated with the residual contamination
from such bursts, (3) the evaluation of the contam-
and pluto-
ium. The remaining samples were sent to the Naval
Research Latoratcry for counting.
The plutonium samples were included to provide
data in the region above 200 ev; the Oak Ridge National Laboratory supplicd these samples and the person-
nel to handle them.
Because of the unanticipated delays and shotschedule revisions after the firing of Shot 1, the participation of Project 2.3 was considerably modified.
Samples were exposed on the first two shots only,
and because of shifts in shot sites and the modification of the Shot 5 device, further participation was
curtailed.
inating characteristics of fallout debris from such
bursts, and (4) information for the evaluation of mech-
anisms of particle formation and distribution. Intermittent fallout collectors located at Bikini and Eniwetok Atolls were used to sample and collect the
fallout.
Mostof the data, except the survey data, were
obtained from Shot 1. Shot 1 activities which were
sampled ranged up to 290 millicuries for areas of
0.6 in? at the downwind stations. The greatest amount
:
The data acquired from Shots 1 and 2 indicated
that the neutron flux is relatively small outside the
radius of extreme damage caused by blast and thermal radiation.
Project 2.5a ‘Distribution and Intensity of Fallout”
(WT-915), U. S. Naval Radiological Defense Laboratory; R. L. Steton, Project Officer.
‘The gathering of fallout data at Castle was a logical
extension of previous fallout documentation. The
variation in yields as well as the opportunity to document surface water detonations for the first time
made this study of fallout extremely important.
The specific objectives were to sample and analyze
fallout material to determine: (1) time and rate of
arrival of the fallout and its final distribution patterns,
109
of radioactive fallout reached the downwind station
east and southeast of ground zero at H + 5 to H + 15
minutes. The main downwind stations received a
second wave from H + 25 to H + 60 minutes, and one
station sampled a third and smaller wave from H + 4
toH +5 hours. Fallout continued to occur in very
small quantities up to H + 12 hours.
The average Shot 1 decay slopes were —1.69 for
the period from H + 210 to H + 450 hours, and —1.37
from H + 400 to H + 1,700 hours.
The Shot 1 fallout consisted primarily of particles
that appeared to be coral and salt.
Most of the ac-
tivity associated with the larger particles was located
near the particle surfaces, while for smaller particles
the activity appeared to be distributed regularly or
irregularly throughout the particle.
Project 2.6a “Chemical, Physical, and Radio-
chemical Characteristics of the Contaminant”
(WT-917), U. S. Naval Radiological Defense Labora-