PLUTONIOM CONTAMINATION FOUND OFF-SITE FOLLOWING
ONE-POINT DETONATIONS
By M. W. Canter and 0. R. Pracax
U.S. Public Health Service, Las Vegas, Nevada
A series of four
during the winter
dental detonation
potential spread
experiments were conducted
of 1955 to determine if accicould occur and, if so, the
of contamination resulting
from accidental detonation of devices.
The off-site area includes all Lerritory within
an approximate 100-mile radius, but. excluding
the actual detonation area. A comprehensive
report of these activities has been prepared and
is available in the files of the Las Vegas Branch,
Test. Division, Albuquerque Operations Office,
U. 8. Atomic Energy Commission.
Estimation of alpha contamination over
many square miles of desert is not an established routine undertaking. The following
methods were used for monitoring purposes:
work-party conditions in areas where ground
contamination existed.
Pee Wee survey instruments are very useful
in the field for locating contamination and for
determining the order of magnitude of such
contamination,
Survey instrument readings
should be considered as indicative of the mini-
mum amountof alpha contamination present |
ata particular spot andnot as areprcseatative
value for an extended area of desert. Results
of alpha survey instrument. monitoring indicate
the extreme variability to be expected over a
relatively small area on the same type of
surface, For example, on a limited area of
concrete pad, Pee Wee readings varied from 500
counts per minute to 1,400 counts per minute.
portional alpha survey instruments (Pee
Wee).
(2) Fallout trays (80 square-inch sampling
There appears to be no strict correlation
between Pee Wee ground surface readings and
laboratory counts on fallout trays located at
the same spot. In order to have strict correla-
adhesive alkyd resin.
distribution over the entire trayarea in addition
(1) Surface monitoring with portable pro-
area) smeared with a relatively nondrying
These were placed in
rings around the detonation area to distances
of approximately 30 miles.
(3) Staplex air samplers using gless fibre
filter papers andan effective filtering area of
63 square inches.
Filter runs of 24 or 48
hours were accomplished without appreciable
loss of flow rate. Air samplers were located
in
11 populated communities surrounding
the Nevada Test Site and at 12 locations
on the site The maximum distance of air
sampler location was 95 miles.
(4) A mobile air sampler consisting of a
Staplex sampler shock mounted on a trailer
unit towed by a Jeep was used to simulate
tion it would be necessary to have uniform
to the same amountof dust overlay acting to
shield each uniformly distributed particle.
Fallout trays proved to be a simple convenient means of monitoring plutonium con-
tamination. They are easy to monitor in the
field and are easy to collect and transport to a
central laboratory for more detailed analysis.
Theyalso serve to differentiate new fallout from
residual alpha “contamination which may be
present in the same general area. Maximum
contamination found on a fallout tray was
100,000 disintegrations per minute per square
foot at a distance of approximately 5 miles.
185