A fallout shelter is an enclosed space specially designed to protect occupants from radioactive debris or fallout

Nuclear fallout

Fallout is the residual radioactive material propelled into the upper atmosphere following a nuclear blast, so called because it "falls out" of the sky after the explosion and shock wave have passed. It commonly refers to the radioactive dust and ash created when a nuclear weapon explodes...

 resulting from a nuclear explosion

Nuclear explosion

A nuclear explosion occurs as a result of the rapid release of energy from an intentionally high-speed nuclear reaction. The driving reaction may be nuclear fission, nuclear fusion or a multistage cascading combination of the two, though to date all fusion based weapons have used a fission device...

. Many such shelters were constructed as civil defense

Civil defense

Civil defense, civil defence or civil protection is an effort to protect the citizens of a state from military attack. It uses the principles of emergency operations: prevention, mitigation, preparation, response, or emergency evacuation, and recovery...

 measures during the Cold War

Cold War

The Cold War was the continuing state from roughly 1946 to 1991 of political conflict, military tension, proxy wars, and economic competition between the Communist World—primarily the Soviet Union and its satellite states and allies—and the powers of the Western world, primarily the United States...

.

During 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 rain, it forms dust and light sandy materials that resembles ground pumice

Pumice

Pumice is a textural term for a volcanic rock that is a solidified frothy lava typically created when super-heated, highly pressurized rock is violently ejected from a volcano. It can be formed when lava and water are mixed. This unusual formation is due to the simultaneous actions of rapid...

. The fallout emits alpha

Alpha particle

Alpha particles consist of two protons and two neutrons bound together into a particle identical to a helium nucleus, which is classically produced in the process of alpha decay, but may be produced also in other ways and given the same name...

 and beta particle

Beta particle

Beta particles are high-energy, high-speed electrons or positrons emitted by certain types of radioactive nuclei such as potassium-40. The beta particles emitted are a form of ionizing radiation also known as beta rays. The production of beta particles is termed beta decay...

s, as well as gamma ray

Gamma ray

Gamma radiation, also known as gamma rays or hyphenated as gamma-rays and denoted as γ, is electromagnetic radiation of high frequency . Gamma rays are usually naturally produced on Earth by decay of high energy states in atomic nuclei...

s.

Much of this highly radioactive material then falls to earth, subjecting anything within the line of sight to radiation, a significant hazard

Radioactive contamination

Radioactive contamination, also called radiological contamination, is radioactive substances on surfaces, or within solids, liquids or gases , where their presence is unintended or undesirable, or the process giving rise to their presence in such places...

. A fallout shelter is designed to allow its occupants to minimize exposure to harmful fallout until radioactivity has decayed to a safer level.

Although many shelters still exist, many even being used as museum

Museum

A museum is an institution that cares for a collection of artifacts and other objects of scientific, artistic, cultural, or historical importance and makes them available for public viewing through exhibits that may be permanent or temporary. Most large museums are located in major cities...

s, virtually all fallout shelters have been decommissioned since the fall of the Soviet Union

Soviet Union

The Soviet Union , officially the Union of Soviet Socialist Republics , was a constitutionally socialist state that existed in Eurasia between 1922 and 1991....

 in 1991.

History

During the Cold War

Cold War

The Cold War was the continuing state from roughly 1946 to 1991 of political conflict, military tension, proxy wars, and economic competition between the Communist World—primarily the Soviet Union and its satellite states and allies—and the powers of the Western world, primarily the United States...

, 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 placard

Placard

A placard is a notice installed in a public place, like a small card, sign, or plaque. It can be attached to or hung from a vehicle or building to indicate information about the vehicle operator or contents of a vehicle or building.- Buildings :...

ed with the yellow and black trefoil

Trefoil

Trefoil is a graphic form composed of the outline of three overlapping rings used in architecture and Christian symbolism...

 sign.

The initial blast of a nuclear attack might well 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. The design of the individual shelter would have determined the ultimate result of such occurrences.

The National Emergency Alarm Repeater

National Emergency Alarm Repeater

The National Emergency Alarm Repeater was a civilian emergency warning device in the United States. It was a 2-3" square box designed to plug into a standard 110 volt power outlet to receive a special signal sent over the electric power transmission lines...

 (N.E.A.R.) program was developed in 1956 during the Cold War

Cold War

The Cold War was the continuing state from roughly 1946 to 1991 of political conflict, military tension, proxy wars, and economic competition between the Communist World—primarily the Soviet Union and its satellite states and allies—and the powers of the Western world, primarily the United States...

 to supplement the existing siren warning systems and radio broadcasts in the event of a nuclear attack. The N.E.A.R. civilian alarm device was engineered and tested but the program was not viable and went defunct about 1966. In the U.S. in September 1961, the federal government started the Community Fallout Shelter Program. (A letter from President Kennedy

John F. Kennedy

John Fitzgerald "Jack" Kennedy , often referred to by his initials JFK, was the 35th President of the United States, serving from 1961 until his assassination in 1963....

 advising the use of fallout shelters appeared in the September 1961 issue of Life

Life (magazine)

Life generally refers to three American magazines:*A humor and general interest magazine published from 1883 to 1936. Time founder Henry Luce bought the magazine in 1936 solely so that he could acquire the rights to its name....

magazine.)

In November 1961 in Fortune

Fortune (magazine)

Fortune is a global business magazine published by Time Inc. Founded by Henry Luce in 1930, the publishing business, consisting of Time, Life, Fortune, and Sports Illustrated, grew to become Time Warner. In turn, AOL grew as it acquired Time Warner in 2000 when Time Warner was the world's largest...

magazine, an article by Gilbert Burck appeared that outlined the plans of Nelson Rockefeller

Nelson Rockefeller

Nelson Aldrich Rockefeller was the 41st Vice President of the United States , serving under President Gerald Ford, and the 49th Governor of New York , as well as serving the Roosevelt, Truman and Eisenhower administrations in a variety of positions...

, Edward Teller

Edward Teller

Edward Teller was a Hungarian-American theoretical physicist, known colloquially as "the father of the hydrogen bomb," even though he did not care for the title. Teller made numerous contributions to nuclear and molecular physics, spectroscopy , and surface physics...

, Herman Kahn

Herman Kahn

Herman Kahn was one of the preeminent futurists of the latter third of the twentieth century. In the early 1970s he predicted the rise of Japan as a major world power. He was a founder of the Hudson Institute think tank and originally came to prominence as a military strategist and systems...

, and Chet Holifield for an enormous network of concrete lined underground fallout shelters throughout the United States

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

 sufficient to shelter millions of people to serve as a refuge in case of nuclear war.

American fallout shelters in the early 1960s were sometimes funded in conjunction with funding for other federal programs, such as urban renewal

Urban renewal

Urban renewal is a program of land redevelopment in areas of moderate to high density urban land use. Renewal has had both successes and failures. Its modern incarnation began in the late 19th century in developed nations and experienced an intense phase in the late 1940s – under the rubric of...

 projects of the Federal Housing Authority, examples being Barrington Plaza

Barrington Plaza

Barrington Plaza is an apartment complex in Los Angeles, California developed by Louis Lesser, which opened in 1962. At the time it was built, the New York Times called it the largest privately financed apartment project ever built west of Chicago and one of the largest projects insured by the...

, and other development projects of Los Angeles County Civil Defense and Disaster Commission

Los Angeles County Civil Defense and Disaster Commission

The Los Angeles County Civil Defense and Disaster Commission is a nine member panel originally set up to deal with the threat of nuclear war, in addition to perennial Los Angeles County concerns involving flooding, landslides, fires, and earthquakes.-History:...

er, Louis Lesser

Louis Lesser

Louis Lesser is an American business magnate. He received frequent press coverage in the 1950s and 1960s for his ability to earn money and for his various business operations. He sold the Taj Mahal to New York real estate developer Donald Trump...

, and were designed for large numbers of citizens.

Switzerland

Switzerland

Switzerland name of one of the Swiss cantons. ; ; ; or ), in its full name the Swiss Confederation , is a federal republic consisting of 26 cantons, with Bern as the seat of the federal authorities. The country is situated in Western Europe,Or Central Europe depending on the definition....

 built an extensive network of fallout shelters, not only through extra hardening of government buildings such as schools, but also through a building regulation that ensured that all residential building built after 1968 contained a nuclear shelter able to withstand a blast from a 50 megaton explosion at a distance of 700 metres. Coupled with this, there was the legal requirement for all supermarkets to store at least one year's supply of canned goods, etc., in blast-proof bunkers in the mountains, along with the requirement of one year's supply of oil; cilivians were required to store at least three weeks of food stuffs in their own shelter.

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

Biological warfare

Biological warfare is the use of biological toxins or infectious agents such as bacteria, viruses, and fungi with intent to kill or incapacitate humans, animals or plants as an act of war...

 or chemical

Chemical warfare

Chemical warfare involves using the toxic properties of chemical substances as weapons. This type of warfare is distinct from Nuclear warfare and Biological warfare, which together make up NBC, the military acronym for Nuclear, Biological, and Chemical...

 (NBC) attacks. The largest buildings usually have dedicated shelters tunneled into solid rock. Similar projects have been undertaken in Finland

Finland

Finland , officially the Republic of Finland, is a Nordic country situated in the Fennoscandian region of Northern Europe. It is bordered by Sweden in the west, Norway in the north and Russia in the east, while Estonia lies to its south across the Gulf of Finland.Around 5.4 million people reside...

, which requires all buildings with area over 600 m² to have an NBC shelter, and Norway

Norway

Norway , officially the Kingdom of Norway, is a Nordic unitary constitutional monarchy whose territory comprises the western portion of the Scandinavian Peninsula, Jan Mayen, and the Arctic archipelago of Svalbard and Bouvet Island. Norway has a total area of and a population of about 4.9 million...

, which requires all buildings with an area over 1000 m² to have a shelter.

The former Soviet Union

Soviet Union

The Soviet Union , officially the Union of Soviet Socialist Republics , was a constitutionally socialist state that existed in Eurasia between 1922 and 1991....

 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

Cold War

The Cold War was the continuing state from roughly 1946 to 1991 of political conflict, military tension, proxy wars, and economic competition between the Communist World—primarily the Soviet Union and its satellite states and allies—and the powers of the Western world, primarily the United States...

. In Switzerland

Switzerland

Switzerland name of one of the Swiss cantons. ; ; ; or ), in its full name the Swiss Confederation , is a federal republic consisting of 26 cantons, with Bern as the seat of the federal authorities. The country is situated in Western Europe,Or Central Europe depending on the definition....

, 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 (e.g., wine cellar

Wine cellar

A wine cellar is a storage room for wine in bottles or barrels, or more rarely in carboys, amphorae or plastic containers. In an active wine cellar, important factors such as temperature and humidity are maintained by a climate control system. In contrast, passive wine cellars are not...

s, ski rooms, gyms). However, there has been renewed interest seen since 2001. These shelters also provide a haven from natural disasters such as tornadoes and hurricanes, although Switzerland

Switzerland

Switzerland name of one of the Swiss cantons. ; ; ; or ), in its full name the Swiss Confederation , is a federal republic consisting of 26 cantons, with Bern as the seat of the federal authorities. The country is situated in Western Europe,Or Central Europe depending on the definition....

 is rarely 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, reducing gamma rays by 1024 times (2¹⁰).

Usually, an expedient purpose-built fallout shelter is a trench, with a strong roof buried by c. 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 cannot 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 swing 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

Kearny Air Pump

The Kearny Air Pump is an expedient air pump used to ventilate a shelter. The design is such that a person with normal mechanical skills can construct and operate one. It is usually human powered and employed during a time of crisis...

, 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.

Collective NBC protection system

Usually blast protection valves are installed at the air-inlet and air outlet to prevent the penetration of blast waves caused by explosions outside of the shelter.
A positive pressure (overpressure) is created in the shelter by pulling filtered air into the protected area. The air is filtered by the means of NBC-filters (NBC = Nuclear, Biological and Chemical filters)

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 is closer than 1.5 km (1 mi). One of Switzerland's solutions is to utilise road tunnels passing through the mountains; with some of these shelters being able to protect tens of thousands.

Contents

A battery-powered radio is very helpful to get reports of fallout patterns and clearance. In many countries (such as the U.S.) civilian radio stations have emergency generators with enough fuel to operate for extended periods without commercial electricity (also made inert in blast EMP).

It is possible to construct an electrometer-type radiation meter called the Kearny Fallout Meter

Kearny Fallout Meter

The Kearny Fallout Meter or KFM is an expedient radiation meter designed to be able to be constructed immediately before or during a nuclear attack by someone with a normal mechanical ability and from common household items. It also is a science project demonstrating the effect of ionizing...

 from plans with just a coffee can or pail, gypsum board, monofilament fishing line

Monofilament line

Monofilament fishing line is fishing line made from a single fiber of plastic. Most fishing lines are now monofilament because monofilament fibers are cheap to produce and are produced in a range of diameters which have different tensile strengths...

, and aluminum foil. Plans are in the reference "Nuclear War Survival Skills" by Cresson Kearny

Cresson Kearny

Cresson Henry Kearny wrote several survival related books based primarily on research performed at Oak Ridge National Laboratory.-Career:Kearny attended Texas Military Institute in the 1930s, where he became the commanding officer of the cadet corps, a champion runner and rifle shot, and...

.

Usage

Inhabitants should plan to remain sheltered for at least two weeks (with an hour out at the end of the first week - see Swiss Civil Defence guidelines (which was once part of Swiss Zivilschutz)), 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

Potassium iodide

Potassium iodide is an inorganic compound with the chemical formula KI. This white salt is the most commercially significant iodide compound, with approximately 37,000 tons produced in 1985. It is less hygroscopic than sodium iodide, making it easier to work with...

 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 information, including storage, and use of an inexpensive saturated solution, see potassium iodide

Potassium iodide

Potassium iodide is an inorganic compound with the chemical formula KI. This white salt is the most commercially significant iodide compound, with approximately 37,000 tons produced in 1985. It is less hygroscopic than sodium iodide, making it easier to work with...

.)

Protection offered by the solid walls and roof of a structure

>

The fallout from either a weapon or an accident is a complex mixture of many radioisotopes. For weapons fallout the photon energy is assumed to be the same as the gamma rays from ⁶⁰Co

Cobalt

Cobalt is a chemical element with symbol Co and atomic number 27. It is found naturally only in chemically combined form. The free element, produced by reductive smelting, is a hard, lustrous, silver-gray metal....

. Data collected after the Chernobyl disaster

Chernobyl disaster

The Chernobyl disaster was a nuclear accident that occurred on 26 April 1986 at the Chernobyl Nuclear Power Plant in Ukraine , which was under the direct jurisdiction of the central authorities in Moscow...

 can serve in a simulation of fallout shelter efficacy, reconstructing the contribution of different radioisotopes to the radiation dose over time. The simulation detailed below assumes that no chemical separation occurred during the transport of radioactivity to the site where the fallout fell (this in real life is not true), and that no decontamination or removal of fallout (e.g. weathering) occurs.

No shielding

Using the data for the source term (radioactive release) from Chernobyl, and other literature data it is possible to estimate how much protection a wall of concrete will offer in the event of a Chernobyl like accident. These calculations are for a room with no windows or doors. The radioactive dust on the roof, and the windows and doors will make the estimation of the protection factor more difficult.

10 cm concrete shielding

These graphs show that thicker walls increase the protection factor. The protection factor is the ratio of the dose rate suffered by a person inside the shelter divided by the dose rate in the open. The protection factor changes as a function of time. This is because some of the short-lived isotopes such as ⁹⁵Zr and ⁹⁵Nb generate very high energy gamma photons, while the longer lived ¹³⁷Cs have a lower photon energy.

As the wall is made thicker the average gamma photon energy for those photons which pass through the wall becomes higher. So each additional layer of concrete has a smaller effect on the dose rate.

20 and 30 cm concrete shielding

(Refer to charts, at right) As the shield becomes thicker the very high photon energy emitters such as ¹⁴⁰Ba/¹⁴⁰La and ⁹⁵Zr/⁹⁵Nb become more and more important.

Other matters and simple improvements

In the long term it is important to consider the protection which is offered by a person's home in the months and years after an event such as the Chernobyl accident. While the person's home may not be a purpose-made shelter, it can be thought of as a shelter if any action is taken to improve the degree of protection. It is also notable that most bomb shelters have a limited amount of oxygen, and should not be inhabited by one person for more than two weeks.

Measures to lower the beta dose

The main threat from beta emitters is from hot particle

Hot particle

A hot particle is a small, highly radioactive object, with significant content of radionuclides. Because radioactivity can be inherent to a substance or induced, and there are many initial sources of radioactivity, hot particles can originate from a multitude of sources.- Attributes :Hot particles...

s which are in contact or close to the skin of the person. Also a swallowed or inhaled hot particle could cause beta burns. As it is important to avoid bringing hot particles into the shelter, one option is to remove one's outer clothing on entry.

Measures to lower the gamma dose rate

The gamma dose rate due to the contamination brought into the shelter on the clothing of a person is likely to be small compared to gamma radiation that penetrates through the walls of the shelter. The following measures can be taken to reduce the amount of gamma radiation entering the shelter:

• Roofs and gutters should be cleaned to lower the dose rate in the house.
• The top inch of soil in the area near the house should be either removed or dug up and mixed with the deeper layers of soil. This reduces the dose rate as the gamma photons have to pass through the soil before they can irradiate a person.
• Nearby roads can be rinsed and washed down to remove dust and debris; the contaminated materials would collect in the sewers and gutters for easier disposal. In Kiev
  Kiev
  Kiev or Kyiv is the capital and the largest city of Ukraine, located in the north central part of the country on the Dnieper River. The population as of the 2001 census was 2,611,300. However, higher numbers have been cited in the press....
  
   after the Chernobyl accident a program of road washing was used to control the spread of radioactivity.
• Windows can be bricked up, or the sill raised to reduce the hole in the shielding formed by the wall.
• Gaps in the shielding can be blocked using water cans, such as bottles of water. While water only has a density which is one tenth that of lead, it is still able to absorb some gamma rays.
• Earth can be heaped up against the exposed walls of the building, this forces the gamma rays to pass through a thicker layer of shielding before entering the house.
• Nearby trees can be removed to reduce the dose due to fallout which is on the branches and leaves. It has been suggested by the US government that a fallout shelter should not be dug close to trees for this reason.

Alpha

In the vast majority of accidents and in all atomic bombs the threat due to beta and gamma emitters is far greater than that posed by the small amount of alpha emitters in the fallout. Alpha radiation can be very harmful, but only if radioactive materials are ingested or inhaled. Alpha particles can be blocked easily by a sheet of paper.

Beta

It is likely that even a light structure will give good protection against most beta emitters, but small particles of fallout can cause localised radiation injuries known as beta burns. It is thought that if a person entering a fallout shelter was to change their footwear and leave their outer clothing outside the main area then the persons inside will be protected from these beta burns. Beta rays are more penetrating than alpha rays, but internal exposure will tend to do less damage because the LET

Linear energy transfer

Linear energy transfer is a measure of the energy transferred to material as an ionizing particle travels through it. Typically, this measure is used to quantify the effects of ionizing radiation on biological specimens or electronic devices....

 is lower.

Three centimeters of aluminum can block the beta emissions from even a high energy beta emitter such as ⁹⁰Sr, while a lower energy beta emitter such as tritium

Tritium

Tritium is a radioactive isotope of hydrogen. The nucleus of tritium contains one proton and two neutrons, whereas the nucleus of protium contains one proton and no neutrons...

 or ¹⁴C will be stopped by thinner objects.

Gamma

These are not charged particles but electromagnetic rays, and are thus more able to pass through objects and may pose a great threat to a person in a fallout shelter. Most of the design of a fallout shelter is intended to protect against gamma rays. The rays' intensity can be reduced by dense materials such as lead

Lead

Lead is a main-group element in the carbon group with the symbol Pb and atomic number 82. Lead is a soft, malleable poor metal. It is also counted as one of the heavy metals. Metallic lead has a bluish-white color after being freshly cut, but it soon tarnishes to a dull grayish color when exposed...

, steel

Steel

Steel is an alloy that consists mostly of iron and has a carbon content between 0.2% and 2.1% by weight, depending on the grade. Carbon is the most common alloying material for iron, but various other alloying elements are used, such as manganese, chromium, vanadium, and tungsten...

, concrete

Concrete

Concrete is a composite construction material, composed of cement and other cementitious materials such as fly ash and slag cement, aggregate , water and chemical admixtures.The word concrete comes from the Latin word...

 or packed earth

Soil

Soil is a natural body consisting of layers of mineral constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics...

.

Weapons fallout

The bulk of the radioactivity in nuclear accident fallout is more long-lived than that in weapons fallout. A good table of the nuclide

Nuclide

A nuclide is an atomic species characterized by the specific constitution of its nucleus, i.e., by its number of protons Z, its number of neutrons N, and its nuclear energy state....

s such as that provided by the Korean Atomic Energy Research Institute

KAERI

The Korea Atomic Energy Research Institute in Daejeon, South Korea was established in 1959 as the sole professional research-oriented institute for nuclear power in South Korea, and has rapidly built a reputation for research and development in various fields...

 includes the fission

Nuclear fission

In nuclear physics and nuclear chemistry, nuclear fission is a nuclear reaction in which the nucleus of an atom splits into smaller parts , often producing free neutrons and photons , and releasing a tremendous amount of energy...

 yields of the different nuclides. From this data it is possible to calculate the isotopic mixture in the fallout (due to fission products in bomb fallout).

The mixture of radioisotopes present in used power reactor fuel can be more complex because neutron activation of fission products is possible, a good example of this is the caesium

Caesium

Caesium or cesium is the chemical element with the symbol Cs and atomic number 55. It is a soft, silvery-gold alkali metal with a melting point of 28 °C , which makes it one of only five elemental metals that are liquid at room temperature...

 isotopic signature

Isotopic signature

An isotopic signature is a ratio of stable or unstable isotopes of particular elements found in an investigated material...

. In terms of activity (becquerel

Becquerel

The becquerel is the SI-derived unit of radioactivity. One Bq is defined as the activity of a quantity of radioactive material in which one nucleus decays per second. The Bq unit is therefore equivalent to an inverse second, s−1...

s or curie

Curie

The curie is a unit of radioactivity, defined asThis is roughly the activity of 1 gram of the radium isotope 226Ra, a substance studied by the pioneers of radiology, Marie and Pierre Curie, for whom the unit was named. In addition to the curie, activity can be measured using an SI derived unit,...

s), the activity in a power reactor fuel one hour after shutdown tends to be more long lived because the majority of the short lived fission products will have had time to decay.

For example, some fissile

Fissile

In nuclear engineering, a fissile material is one that is capable of sustaining a chain reaction of nuclear fission. By definition, fissile materials can sustain a chain reaction with neutrons of any energy. The predominant neutron energy may be typified by either slow neutrons or fast neutrons...

 material is used in a bomb

Bomb

A bomb is any of a range of explosive weapons that only rely on the exothermic reaction of an explosive material to provide an extremely sudden and violent release of energy...

, and in 10¹² fissions an equal number of ¹³¹I and ¹³⁷Cs atoms are formed. Because the ¹³¹I has such a short half-life when compared with the ¹³⁷Cs, the activity ratio of ¹³¹I to ¹³⁷Cs will be very much in favour of the ¹³¹I one hour after the fission event.

If, on the other hand, a lump of fuel in a power reactor undergoes 10¹² fissions, which will generate a given amount of ¹³¹I, if the reactor was run at a constant power for one year then the majority of the ¹³¹I will have had time to decay. However the vast majority of the ¹³⁷Cs atoms will not have had time to decay. So the ¹³¹I to ¹³⁷Cs ratio is more in favour of ¹³⁷Cs than the mixture formed.

Fallout shelters in popular culture

Fallout shelters feature prominently in the Robert A. Heinlein

Robert A. Heinlein

Robert Anson Heinlein was an American science fiction writer. Often called the "dean of science fiction writers", he was one of the most influential and controversial authors of the genre. He set a standard for science and engineering plausibility and helped to raise the genre's standards of...

 novel Farnham's Freehold

Farnham's Freehold

Farnham's Freehold is a science fiction novel set in the near future by Robert A. Heinlein. A serialised version, edited by Frederik Pohl, appeared in Worlds of If magazine . The complete version was published in novel form by G.P...

(Heinlein built a fairly extensive shelter near his home in Colorado Springs in 1963), Pulling Through by Dean Ing, A Canticle for Leibowitz

A Canticle for Leibowitz

A Canticle for Leibowitz is a post-apocalyptic science fiction novel by American writer Walter M. Miller, Jr., first published in 1960. Set in a Roman Catholic monastery in the desert of the southwestern United States after a devastating nuclear war, the story spans thousands of years as...

by Walter M. Miller and Earth

Earth (novel)

Earth is a 1990 science fiction novel written by David Brin. The book was nominated for the Hugo and Locus Awards in 1991.-Plot introduction:...

by David Brin

David Brin

Glen David Brin, Ph.D. is an American scientist and award-winning author of science fiction. He has received the Hugo, Locus, Campbell and Nebula Awards.-Biography:...

.

The Twilight Zone

Twilight zone

-Television series and spinoffs:*The Twilight Zone, the anthology television series and its franchise:**The Twilight Zone , the 1959–1964 original television series***Twilight Zone: The Movie, a 1983 film based on the original series...

 episode The Shelter

The Shelter (The Twilight Zone)

"The Shelter" is an episode of the American television anthology series The Twilight Zone.-Synopsis:It is a typical evening in a typical suburban community. At the residence of physician Bill Stockton, he enjoys a birthday party being thrown for him by his wife Grace and their son Paul...

, from a Rod Serling

Rod Serling

Rodman Edward "Rod" Serling was an American screenwriter, novelist, television producer, and narrator best known for his live television dramas of the 1950s and his science fiction anthology TV series, The Twilight Zone. Serling was active in politics, both on and off the screen and helped form...

 script, deals with the consequences of actually using a shelter.

In 1999 the film

Film

A film, also called a movie or motion picture, is a series of still or moving images. It is produced by recording photographic images with cameras, or by creating images using animation techniques or visual effects...

 Blast from the Past

Blast From the Past (film)

Blast from the Past is a 1999 romantic comedy film based on a story and directed by Hugh Wilson and starring Brendan Fraser, Alicia Silverstone, Christopher Walken, Sissy Spacek, and Dave Foley.-Plot:...

was released. It is a romantic comedy film

Romantic comedy film

Romantic comedy films are films with light-hearted, humorous plotlines, centered on romantic ideals such as that true love is able to surmount most obstacles. One dictionary definition is "a funny movie, play, or television program about a love story that ends happily"...

 about a nuclear physicist, his wife, and son that enter a well-equipped spacious fallout shelter during the 1962 Cuban Missile Crisis

Cuban Missile Crisis

The Cuban Missile Crisis was a confrontation among the Soviet Union, Cuba and the United States in October 1962, during the Cold War...

. They do not emerge until 35 years later, in 1997. The film shows their reaction to contemporary society.

In book 11 of the Cirque Du Freak book series, Darren and Harkat must go into an alternate world. They then find a fallout shelter with post cards on the refrigerator from the late 1940s and realized that they had gone forward in time.

The Fallout series

Fallout series

Fallout is a series of post-apocalyptic role-playing games published by Interplay Entertainment and later by Bethesda Softworks. Although the series is set during the 22nd and 23rd centuries, its retrofuturistic story and artwork are influenced by the post-war culture of 1950s America, and its...

 of computer games depicts the remains of human civilization after an immensely destructive nuclear war, thus, the United States of America built underground vaults to protect itself against a nuclear attack.

The Metro 2033

Metro 2033 (book)

Metro 2033 is a novel written by Russian author Dmitry Glukhovsky.-History:Some twenty years after a nuclear war, only a few thousands of people survive in the metro...

 book series by Russian author Dmitry Glukhovsky

Dmitry Glukhovsky

Dmitry A. Glukhovsky is a professional Russian author and journalist. Glukhovsky started in 2002 by publishing his first novel, Metro 2033, on his own website to be viewed for free. The novel has later become an interactive experiment, drawing in many readers, and has since been made into a video...

depicts survivors' life in the subway systems below Moscow and Saint-Petersburg.

Cormac McCarthy

Cormac McCarthy

Cormac McCarthy is an American novelist and playwright. He has written ten novels, spanning the Southern Gothic, Western, and modernist genres. He received the Pulitzer Prize and the James Tait Black Memorial Prize for Fiction for The Road...

's book The Road and the accompanying movie has its main characters finding a shelter (bomb

Bomb shelter

A bomb shelter is any kind of a civil defense structure designed to provide protection against the effects of a bomb.-Types of shelter:Different kinds of bomb shelters are configured to protect against different kinds of attack and strengths of hostile explosives. For example, an Air-raid shelter...

 or fallout) with uneaten rations.

See also

• Blast shelter
  Blast shelter
  A blast shelter is a place where people can go to protect themselves from bomb blasts. It differs from a fallout shelter, in that its main purpose is to protect from shock waves and overpressure, instead of from radioactive precipitation, as a fallout shelter does...
  
  
• Bomb shelter
  Bomb shelter
  A bomb shelter is any kind of a civil defense structure designed to provide protection against the effects of a bomb.-Types of shelter:Different kinds of bomb shelters are configured to protect against different kinds of attack and strengths of hostile explosives. For example, an Air-raid shelter...
  
  
• Bunker
  Bunker
  A military bunker is a hardened shelter, often buried partly or fully underground, designed to protect the inhabitants from falling bombs or other attacks...
  
  
• Collective protection
  Collective protection
  Collective protection is used for group protection of personnel in a nuclear, biological or chemical event, .Collective protection is an important aspect of fixed site defense....
  
  
• Command center
  Command center
  A command center is any place that is used to provide centralized command for some purpose.While frequently considered to be a military facility, these can be used in many other cases by governments or businesses...
  
  
• Continuity of government
  Continuity of government
  Continuity of government is the principle of establishing defined procedures that allow a government to continue its essential operations in case of nuclear war or other catastrophic event....
  
  

Nation specific:

• Diefenbunker
  Diefenbunker
  Emergency Government Headquarters are nuclear fallout bunkers built by the Government of Canada at the height of the Cold War during the infancy of the ICBM threat...
  
  
• HANDEL
  HANDEL
  HANDEL was the code-name for the UK's National Attack Warning System in the Cold War. It consisted of a small console consisting of two microphones, lights and gauges. The reason behind this was to provide a back-up if anything failed....
  
  , UK's national attack warning system
• Sonnenberg Tunnel
  Sonnenberg Tunnel
  The Sonnenberg Tunnel is a 1,550m long motorway tunnel, constructed between 1971 and 1976 and located near Lucerne, Switzerland. At its completion it was also the world's largest civilian nuclear fallout shelter, designed to protect 20,000 civilians in the eventuality of war or disaster.-Motorway...
  
  

General:

• Fission product
  Fission product
  Nuclear fission products are the atomic fragments left after a large atomic nucleus fissions. Typically, a large nucleus like that of uranium fissions by splitting into two smaller nuclei, along with a few neutrons and a large release of energy in the form of heat , gamma rays and neutrinos. The...
  
  
• Retreat (survivalism)
  Retreat (survivalism)
  A retreat is a place of refuge for those in the survivalist subculture or movement. Retreats are also sometimes called Bug-Out Locations...
  
  
• Survivalism
  Survivalism
  Survivalism is a movement of individuals or groups who are actively preparing for future possible disruptions in local, regional, national, or international social or political order...
  
  

Publications:

• Fallout Protection
  Fallout Protection
  Fallout Protection: What To Know And Do About Nuclear Attack, was an official United States federal government booklet released in December 1961 by the United States Department of Defense and The Office of Civil Defense....
  
  
• Survival Under Atomic Attack
  Survival Under Atomic Attack
  Survival Under Atomic Attack was the title of an official United States government booklet released by the Executive Office of the President, the National Security Resources Board , and the Civil Defense Office...
  
  

External links

• History of the design of the Fallout Shelter Sign
• Nuclear fallout decontamination device. (www.greeneyetech.com)
• Fallout exposure based on size of bomb and distance from explosion. (www.bomb-shelter.net)
• Bomb Shelter Questions and Answers (www.undergroundbombshelter.com)
• Oregon Institute of Science and Medicine This website offers the entire online version of Nuclear War Survival Skills with full graphics and web navigation, created with the permission of the author Cresson Kearny. This manual has proven technical info on expedient fallout shelter, shelter habitation, and assorted shelter system needs that can be created from common household items. OISM also offers free downloads of other civil defense and shelter information as well.
• SurvivalRing Hosts hundreds of freely downloadable PDF files including dozens of authentic fallout shelter plans, fallout shelter regulations, fallout technological data, and cold war related fallout shelter defense data.