Fallout shelter Totally Explained

Everything about Fallout Shelter totally explained

A fallout shelter is an enclosed space specially designed to protect occupants from radioactive debris or fallout resulting from a nuclear explosion. Many such shelters were constructed as civil defense measures during the Cold War.
After a nuclear explosion, matter vaporized in the resulting fireball is exposed to neutrons from the explosion, absorbs them, and becomes radioactive. When this material condenses in the cloud, it forms dust and light sandy material that resembles ground pumice. The fallout emits both beta particles and gamma rays. Much of this highly radioactive material then falls to earth, subjectting anything within the line of sight to radiation, a significant hazard. A fallout shelter is designed to allow its occupants to minimize exposure to harmful fallout until radioactivity has decayed to a safer level.

History

During the Cold War many countries built fallout shelters for high-ranking government officials and crucial military facilities. Plans were made, however, to use existing buildings with sturdy below-ground-level basements as makeshift fallout shelters. These buildings were usually placarded with the yellow and black trefoil sign as shown in the top of this article. The initial blast of a nuclear attack might have rendered these basements either buried under many tons of rubble and thus impossible to leave, or removed their upper framework, thus leaving the basements unprotected. Switzerland built an extensive network of fallout shelters (mainly through extra hardening of government buildings such as schools) of a scale to protect and feed the entire population for two years after a nuclear attack. This nation has the highest ratio of shelter space to national population of any country. All these shelters are capable of withstanding nuclear fallout and biological or chemical (NBC) attacks but the blast-proof requirement varies depending on the size of the building. The largest buildings usually have dedicated shelters tunneled into solid rock. Similar projects have been undertaken in Finland, which requires all buildings with area over 600 m² to have an NBC shelter, and Norway, which requires all buildings with an area over 1000 m² to have a shelter(External Link

).
The former Soviet Union and other Eastern Bloc countries often designed their underground mass-transit and subway tunnels to serve as bomb and fallout shelters in the event of an attack.
Interest in fallout shelters has largely dropped, as the perceived threat of global nuclear war reduced after the end of the Cold War. In Switzerland, most residential shelters are no longer stocked with the food and water required for prolonged habitation and a large number have been converted by the owners to other uses (for example wine cellars, ski rooms, gyms). However, a renewed interest has been seen since 2001. These shelters also provide a safe haven from natural disasters such as tornadoes and hurricanes, although Switzerland isn't subject to such natural phenomena.

Details of shelter construction

Shielding

A basic fallout shelter consists of shields that reduce gamma ray exposure by a factor of 1000. The required shielding can be accomplished with 10 times the amount of any quantity of material capable of cutting gamma ray effects in half. Shields that reduce gamma ray intensity by 50% (1/2) include 1 cm (0.4 inch) of lead, 6 cm (2.4 inches) of concrete, 9 cm (3.6 inches) of packed dirt or 150 m (500 ft) of air. When multiple thicknesses are built, the shielding multiplies. Thus, a practical fallout shield is ten halving-thicknesses of packed dirt. This reduces gamma rays by a factor of 1024, which is 2 multiplied by itself ten times. This multiplies out to 90 cm (3 ft) of dirt.
Usually, an expedient purpose-built fallout shelter is a trench, with a strong roof buried by ~1 m (3 ft) of dirt. The two ends of the trench have ramps or entrances at right angles to the trench, so that gamma rays can't enter (they can travel only in straight lines). To make the overburden waterproof (in case of rain), a plastic sheet should be buried a few inches below the surface and held down with rocks or bricks.

Climate control

Dry earth is a reasonably good thermal insulator, and over several weeks of habitation, a shelter will become too hot for comfort. The simplest form of effective fan to cool a shelter is a wide, heavy frame with flaps that swings in the shelter's doorway and can be swung from hinges on the ceiling. The flaps open in one direction and close in the other, pumping air. Attach a rope, and take turns swinging it. (This is a Kearny Air Pump, or KAP, named after the inventor.)
Unfiltered air is safe, since the most dangerous fallout has the consistency of sand or finely ground pumice. Such large particles are not easily ingested into the soft tissues of the body, so extensive filters are not required. Any exposure to fine dust is far less hazardous than exposure to the gamma from the fallout outside the shelter. Dust fine enough to pass the entrance will probably pass through the shelter.

Locations

Effective public shelters can be the middle floors of some tall buildings or parking structures, or below ground level in most buildings with more than 10 floors. The thickness of the upper floors must form an effective shield, and the windows of the sheltered area must not view fallout-covered ground that's closer than 1.5 km (1 mi).

A battery-powered radio is very helpful to get reports of fallout patterns and clearance. In many countries (including the U.S.) civilian radio stations have emergency generators with enough fuel to operate for extended periods without commercial electricity.
It is possible to construct an electrometer-type radiation meter called the Kearny Fallout Meter from plans with just a coffee can or pail, gypsum board, monofilament fishing line, and aluminum foil. Plans are in the reference "Nuclear War Survival Skills"

by Cresson Kearny.

Usage

Inhabitants should plan to remain sheltered for at least two weeks, then work outside for gradually increasing amounts of time, to four hours a day at three weeks. The normal work is to sweep or wash fallout into shallow trenches to decontaminate the area. They should sleep in a shelter for several months. Evacuation at three weeks is recommended by official authorities.
If available, inhabitants should take potassium iodide at the rate of 130 mg/day per adult (65 mg/day per child) as an additional measure to protect the human thyroid gland from the uptake of dangerous radioactive iodine, a component of most fallout and reactor waste. (For more info, including storage, and use of an inexpensive saturated solution, see potassium iodide).

Protection offered by the solid walls and roof of a structure

Further Information

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