Nuclear radiation does not affect most materials in
INITIAL NUCLEAR RADIATION
any visible manner. Thus ships, vehicles, electronic
Initial nuclear radiation is defined as the radiation
equipment (except transistors), and other equipment
(essentially neutrons and gamma rays) that is emitted
are not damaged by radiation. However, radioactive
by the fireball and the cloud during the first minute
contamination does pose a danger to operating
after detonation. All significant neutron radiation is
personnel. The term contamination is used to mean
emitted in less than 0.1 second and gamma radiation up
radioactive material that has been deposited where it is
to 20 or 30 seconds, depending on weapon yield. The
not wanted. All radioactive contamination presents a
l-minute limit is set, somewhat arbitrarily, as the
hazard to personnel.
maximum time for the nuclear cloud to rise beyond the
range in air at which gamma radiation is a significant
ATMOSPHERIC IONIZATION
hazard. Generally, initial nuclear radiation might not
produce significant material damages, but it will
Atmospheric ionization is an increase in the
incapacitate personnel.
density of electrons in the atmosphere around a nuclear
burst. These electrons affect radio and radar signals by
Transient radiation effects on electronics (TREE)
removing energy from the waves. This decreases the
is caused by initial gamma and neutron emissions from
a nuclear burst. These emissions result in the failure or
strength of the signals and refracts the wave front,
degraded operation of sophisticated solid-state
thereby changing the direction of transmission. For
circuits. Computers and other equipment having
detonations below 100,000 feet, this effect disappears
solid-state computers are particularly sensitive to
in a matter of seconds. At higher altitudes the effect can
TREE and also equipment with semiconductors. Some
last up to several hours. The effect can be of
effects are temporary but some are also permanent.
considerable importance where communications are
over a long range and where radar targets are in or
FALLOUT
above the ionized layer.
Fallout is a major effect of a surface, shallow
ELECTROMAGNETIC PULSE
underground, or underwater burst. It is the radioactive
material that falls from the nuclear cloud and is
An electromagnetic pulse (EMP) will be produced
deposited on exposed surfaces. The fallout consists
by high-altitude bursts, airbursts, and surface bursts.
primarily of fission products (gamma and beta
The initial nuclear ionizing radiation ionizes the
emitters) mixed with material that was vaporized by
atmosphere around the point of detonation. This action
the fireball and drawn up into the nuclear cloud.
produces an EMP, which will contain frequency
Fallout, whether airborne or deposited, is a major
components in the range from a few to several hundred
hazard because it emits gamma radiation. This
kilocycles per second. The EMP has magnetic and
radiation can penetrate ship structures, buildings, and
electric field components that exist for only a fraction
aircraft, to name a few. It can also reach personnel,
of a second. The magnetic field component is
causing radiation injury, incapacitation, and even
significant inside the radius of the ionized atmosphere.
death. Deposited fallout also presents a contamination
It can induce large currents in cables and long-lead
hazard to personnel. The militarily significant fallout,
wires. These large transient currents can burn out
often called early fallout, is usually deposited in less
electronic and electrical equipment. The electric field
than 24 hours in an area downwind of SZ.
component can also produce transient signal overloads
The wind directions up to the top of the cloud
and spurious signals on communication nets and in
determine the area contaminated by fallout. In a
computer-driven systems. At ranges where ships suffer
complete calm, the fallout pattern is roughly circular.
minor damage from other weapon effects, the major
A constant wind direction causes an elongation of the
effect of the EMP is expected to be the tripping of
pattern. Complicated wind patterns (wind shear), as
circuit breakers and blowing of fuses in protective
well as variations in wind speed and direction, cause
circuitry. At closer ranges, there is a high probability of
complicated ground patterns. The fallout pattern is
permanent damage to the electronic and electrical
difficult to predict accurately except under calm and
equipment.
very stable wind conditions.
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