close attention to the hairy parts of your body,
body creases, and fingernails, where dirt tends to
gather.
NUCLEAR RADIATION
Nuclear radiation presents a threat to our
naval forces. The effects of this threat can be
controlled if the basic facts of nuclear radiation
are understood. The following paragraphs
describe the phenomena of initial radiation,
radioactive fallout, and types of radiation emitted
by contamination.
Initial Radiation
Initial nuclear radiation consists of gamma
rays and neutrons and is emitted at the time of
a nuclear detonation. This radiation is emitted in
the first minute after burst; however, most of it
is emitted in the first few seconds. This radiation
causes no damage to material, but it can be very
injurious to ship’s personnel and produce many
casualties. The casualty range of initial radiation
of a normal kiloton burst is over 1 mile. Initial
radiation can readily penetrate the surface layers
of targets. However, dense material, such as steel,
can appreciably reduce radiation.
Radioactive Fallout
Radioactive fallout is a delayed phenomenon
of a nuclear detonation. Most of the fallout
occurs minutes to hours after the burst. Surface
and subsurface (underwater and underground)
nuclear bursts deposit large amounts of fallout
in localized areas. An airbursr in which the fireball
does not contact the surface usually does not result
in fallout of military significance. This is because
there is less radioactive material, and it is dispersed
over a great area before reaching the surface.
Within a few seconds after the burst, the
radioactive products primarily are in the atomic
cloud (fig. 7-6) along with a much larger amount
of nonradioactive material, such as seawater or
surface material. Radioactive elements mixed
with nonradioactive material form the total
contaminant produced by the burst. This radio-
active mixture falls back to the earth’s surface as
radioactive fallout.
Heavier particles in the cloud fall out around
surface zero soon after the burst. The prevailing
winds carry finer and lighter particles over a large
area many miles from surface zero. A megaton
burst carries significant amounts of fallout several
hundred miles and disperses it over thousands of
square miles. The time when fallout reaches a
given location may be from a fraction of a minute
to as much as 24 hours.
Types of Radiation
Emitted by Contamination
Radioactive contamination can emit three
types of ionizing nuclear radiation: alpha, beta,
and gamma. A single particle of contaminant may
be the source of one or more of these types. These
radiations are not detectable by the human senses;
however, electronic instruments (radiacs) can
detect the presence of radiation, differentiate
among the three types, and measure their
respective amounts and intensities. The following
paragraphs discuss the three types of radiation.
ALPHA. —You can stop alpha radiation by
almost any barrier, including 1 to 2 inches of air.
7-23
Figure 7-6.—Relative sizes and altitudes of radioactive fallout clouds.
