nuclear blast is an explosion with intense
light and heat, a damaging pressure
wave, and widespread radioactive material
that can contaminate the air, water, and
ground surfaces for miles around. A nuclear
device can range from a weapon carried
by an intercontinental missile launched
by a hostile nation or terrorist organization,
to a small portable nuclear devise transported
by an individual. All nuclear devices cause
deadly effects when exploded, including
blinding light, intense heat (thermal radiation),
initial nuclear radiation, blast, fires
started by the heat pulse, and secondary
fires caused by the destruction.
The extent, nature, and arrival time of
these hazards are difficult to predict.
The geographical dispersion of hazard effects
will be defined by the following:
- Size of the device. A more powerful
bomb will produce more distant effects.
- Height above the ground the device
was detonated. This will determine
the extent of blast effects.
- Nature of the surface beneath the
explosion. Some materials are more
likely to become radioactive and airborne than
others. Flat areas are more susceptible
to blast effects.
- Existing meteorological conditions.
Wind speed and direction will affect
arrival time of fallout; precipitation may wash
fallout from the atmosphere.
Even if individuals are not close enough
to the nuclear blast to be affected by
the direct impacts, they may be affected
by radioactive fallout. Any nuclear blast
results in some fallout. Blasts that
occur near the earth’s surface create much
greater amounts of fallout than blasts
that occur at higher altitudes. This is
because the tremendous heat produced from
a nuclear blast causes an up-draft of air
that forms the familiar mushroom cloud.
When a blast occurs near the earth’s
surface, millions of vaporized dirt particles
also are drawn into the cloud. As the
heat diminishes, radioactive materials
that have vaporized condense on the
particles and fall back to Earth. The
phenomenon is called radioactive fallout.
This fallout material decays over a long
period of time, and is the main source
of residual nuclear radiation.
Fallout from a nuclear explosion may
be carried by wind currents for hundreds
of miles if the right conditions exist.
Effects from even a small portable device
exploded at ground level can be potentially
Nuclear radiation cannot be seen, smelled,
or otherwise detected by normal senses.
Radiation can only be detected by radiation
monitoring devices. This makes radiological
emergencies different from other types
of emergencies, such as floods or hurricanes.
Monitoring can project the fallout arrival
times, which will be announced through
official warning channels. However, any
increase in surface build-up of gritty
dust and dirt should be a warning for
taking protective measures.
In addition to other effects, a nuclear
weapon detonated in or above the earth’s
atmosphere can create an electromagnetic
pulse (EMP), a high-density electrical
field. An EMP acts like a stroke of lightning
but is stronger, faster, and shorter. An
EMP can seriously damage electronic devices
connected to power sources or antennas.
This includes communication systems, computers,
electrical appliances, and automobile or
aircraft ignition systems. The damage could
from a minor interruption to actual burnout
of components. Most electronic equipment
within 1,000 miles of a high-altitude
nuclear detonation could be affected.
Battery-powered radios with short antennas
generally would not be affected. Although
an EMP is unlikely to harm most people,
it could harm those with pacemakers or
other implanted electronic devices.
The danger of a massive strategic nuclear
attack on the United States is predicted
by experts to be less likely today. However,
terrorism, by nature, is unpredictable.
If there were threat of an attack, people
living near potential targets could be
advised to evacuate or they could decide
on their own to evacuate to an area not
considered a likely target. Protection
from radioactive fallout would require
shelter in an underground area or in
the middle of a large building.
In general, potential targets include:
- Strategic missile sites and
- Centers of government such as Washington,
DC, and state capitals.
- Important transportation and communication
- Manufacturing, industrial, technology,
and financial centers.
- Petroleum refineries, electrical
power plants, and chemical plants.
- Major ports and airfields.
three factors for protecting oneself from
radiation and fallout are distance, shielding,
- Distance — the
more distance between you and the fallout
particles, the better.
An underground area such as a home or
office building basement offers
more protection than the first floor
of a building. A floor near the middle
a high-rise may be better, depending
on what is nearby at that level on which
significant fallout particles would collect.
Flat roofs collect fallout particles
the top floor is not a good choice, nor
is a floor adjacent to a neighboring
- Shielding — the
heavier and denser the materials—thick
walls, concrete, bricks, books and earth—between
you and the fallout particles, the
- Time — fallout
radiation loses its intensity fairly
rapidly. In time, you will be able to
leave the fallout shelter. Radioactive
fallout poses the greatest threat to
people during the first two weeks, by
which time it has declined to about
1 percent of its initial radiation level.
that any protection, however temporary,
is better than none at all, and
the more shielding, distance, and time
you can take advantage of, the better.
a Nuclear Blast
To prepare for a nuclear blast, you
should do the following:
- Find out from officials
if any public buildings in your
community have been designated
as fallout shelters. If none have
been designated, make your own
list of potential shelters near
your home, workplace, and school.
These places would include basements
or the windowless center area of
middle floors in high-rise buildings,
as well as subways and tunnels.
- If you live in an apartment
building or high-rise, talk to
the manager about the safest place
in the building for sheltering
and about providing for building
occupants until it is safe to go
- During periods of increased
threat increase your disaster supplies
to be adequate for up to two weeks.
During a Nuclear Blast
The following are guidelines for what to
do in the event of a nuclear explosion.
If an attack warning is issued:
- Take cover as quickly
as you can, below ground if possible,
and stay there until instructed
to do otherwise.
- Listen for official information
and follow instructions.
If you are caught outside and
unable to get inside immediately:
- Do not look at the flash
can blind you.
- Take cover behind anything
that might offer protection.
- Lie flat on the ground and cover your
head. If the explosion is some
distance away, it could take 30 seconds or more for the
blast wave to hit.
- Take shelter as soon as you can, even
if you are many miles from ground zero where
the attack occurred—radioactive
fallout can be carried by the
winds for hundreds of miles.
Remember the three protective
factors: Distance, shielding,
After a Nuclear Blast
Decay rates of the radioactive fallout
are the same for any size nuclear device.
However, the amount of fallout will vary
based on the size of the device and its
proximity to the ground. Therefore, it
might be necessary for those in the areas
with highest radiation levels to shelter
for up to a month.
heaviest fallout would be limited
to the area at or downwind from
and 80 percent of the fallout would occur
during the first 24 hours.
People in most of the areas that would
be affected could be allowed to come out
shelter within a few days and, if necessary,
evacuate to unaffected areas.
to Your Home
Remember the following:
- Keep listening to the
radio and television for news about
what to do, where to go, and places
- Stay away from damaged areas. Stay
away from areas marked “radiation hazard” or “HAZMAT.” Remember
that radiation cannot be seen, smelled,
or otherwise detected by human senses.