Nuclear Blast
A
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.
Hazards of Nuclear Devices
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.
Radioactive Fallout
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
deadly.
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.
Radioactive Fallout
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 range 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.
How can I protect myself from a nuclear blast?
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Protection from a Nuclear Blast
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 taking shelter in an underground area
or in the middle of a large building.
In general, potential targets include:
- Strategic missile sites and military bases.
- Centers of government such as Washington, DC, and state capitals.
- Important transportation and communication centers.
- Manufacturing, industrial, technology, and financial centers.
- Petroleum refineries, electrical power plants, and chemical plants.
- Major ports and airfields.
The three factors for protecting oneself from radiation and fallout are distance, shielding, and time.
- 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 of 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 so the
top floor is not a good choice, nor is a floor adjacent to a
neighboring flat roof.
- Shielding - the heavier and denser the materials -
thick walls, concrete, bricks, books and earth - between you and the
fallout particles, the better.
- 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.
Remember 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.
Before 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 out.
- During periods of increased threat increase your disaster supplies to be adequate for up to two weeks.
Taking shelter during a nuclear blast is absolutely necessary. There
are two kinds of shelters - blast and fallout. The following describes
the two kinds of shelters:
If you are caught outside and unable to get inside immediately:
- Do not look at the flash or fireball - it 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, and time.
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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.
The heaviest fallout would be limited to the area at or downwind
from the explosion, 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 of shelter within a few days and, if necessary, evacuate to
unaffected areas.
Remember the following when returning home:
- Keep listening to the radio and television for news about what to do, where to go, and places to avoid.
- 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.
