Building an Underground Bomb Shelter
Bomb Shelter Planning
Frequently Asked Questions
Important Nuclear Bomb Facts

Understanding Radiation:

Types of Nuclear Explosions

The immediate phenomena associated with a nuclear explosion, as well as the effects of shock and blast and of thermal and nuclear radiations, vary with the location of the point of burst in relation to the surface of the earth. For descriptive purposes five types of burst are distinguished, although many variations and intermediate situations can arise in practice.

The main types, which will be defined below, are (1) air burst, (2) high-altitude burst, (3) underwater burst, (4) underground burst, and (5) surface burst.

Provided the nuclear explosion takes place at an altitude where there is still an appreciable atmosphere, e.g., below about 100,000 feet, the weapon residues almost immediately incorporate material from the surrounding medium and form an intensely hot and luminous mass, roughly spherical in shape, called the “fireball.”

An “air burst” is defined as one in which the weapon is exploded in the air at an attitude below 100,000 feet, but at such a height that the fireball (at roughly maximum brilliance in its later stages) does not touch the surface of the earth.

For example, in the explosion of a 1-megaton weapon the fireball may grow until it is nearly 5,700 feet (1.1 mile) across at maximum brilliance. This means that, in this particular case, the explosion must occur at least 2,850 feet above the earth’s surface if it is to be called an air burst.

The quantitative aspects of an air burst will be dependent upon its energy yield, but the general phenomena are much the same in all cases. Nearly all of the shock energy that leaves the fireball appears as air blast, although some is generally also transmitted into the ground. The thermal radiation will travel long distances through the air and may be of sufficient intensity to cause moderately severe burns of exposed skin as far away as 12 miles from a 1-megaton explosion, on a fairly clear day.

For air bursts of higher energy yields, the corresponding distances will, of course, be greater. The thermal radiation is largely stopped by ordinary opaque materials; hence, buildings and clothing can provide protection.

The initial nuclear radiation from an air burst will also penetrate a long way in air, although the intensity falls off fairly rapidly at increasing distances from the explosion. The interactions with matter that result in the absorption of energy from gamma rays and from neutrons are quite different.

Different materials are thus required for the most efficient removal of these radiations; but concrete, especially if it incorporates a heavy element, such as iron or barium, represents a reasonable practical compromise for reducing the intensities of both gamma rays and neutrons. A thickness of about 4 feet of ordinary concrete would probably provide adequate protection from the effects of the initial nuclear radiation for people at a distance of about 1 mile from an air burst of a 1-megaton nuclear weapon. However, at this distance the blast effect would be so great that only specially designed blast-resistant structures would survive.

In the event of a moderately high (or high) air burst, the fission products remaining after the nuclear explosion will be dispersed in the atmosphere. The residual nuclear radiation arising from these products will be of minor immediate consequence on the ground.

On the other hand, if the burst occurs nearer the earth’s surface, the fission products may fuse with particles of earth, part of which will soon fall to the ground at points close to the explosion. This dirt and other debris will be contaminated with radioactive material and will, consequently, represent a possible danger to living things.

A “high-altitude burst” is defined as one in which the explosion takes place at an altitude in excess of 100,000 feet. Above this level, the air density is so low that the interaction of the weapon energy with the surroundings is markedly different from that at lower altitudes and, moreover, varies with the altitude. The absence of relatively dense air causes the fireball characteristics in a high-altitude explosion to differ from those of an air burst.

For example, the fraction of the energy converted into blast and shock is less and decreases with increasing altitude. Two factors affect the thermal energy radiated at high altitude.

First, since a shock wave does not form so readily in the less dense air, the fireball is able to radiate thermal energy that would, at lower altitudes, have been used in the production of air blast.

Second, the less dense air allows energy from the exploding weapon to travel much farther than at lower altitudes. Some of this energy simply warms the air at a distance from the fireball and it does not contribute to the energy that can be radiated within a short time.

In general, the first of these factors is effective between 100,000 and 140,000 feet, and a larger proportion of the explosion energy is released in the form of thermal radiation than at lower altitudes. For explosions above about 140,000 feet, the second factor becomes the more important, and the fraction of the energy that appears as thermal radiation at the time of the explosion becomes smaller.

The fraction of the explosion energy emitted from a weapon as nuclear radiations is independent of the height of burst. However, the partition of that energy between gamma rays and neutrons received at a distance will vary since a significant fraction of the gamma rays result from interactions of neutrons with nitrogen atoms in the air at low altitudes.

Furthermore, the attenuation of the initial nuclear radiation with increasing distance from the explosion is determined by the total amount of air through which the radiation travels. This means that, for a given explosion energy yield, more initial nuclear radiation will be received at the same slant range on the earth’s surface from a high-altitude detonation than from a moderately high air burst. In both cases the residual radiation from the fission products and other weapon residues will not be significant on the ground.

Both the initial and the residual nuclear radiations from high-altitude bursts will interact with the constituents of the atmosphere to expel electrons from the atoms and molecules. Since the electron carries a negative electrical charge, the residual part of the atom (or molecule) is positively charged, i.e., it is a positive ion. This process is referred to as “ionization,” and the separated electrons and positive ions are called “ion pairs.”

The existence of large numbers of electrons and ions at high altitudes may have seriously degrading effects on the propagation of radio and radar signals. The free electrons resulting from gamma-ray ionization of the air in a high-altitude explosion may also interact with the earth’s magnetic field to generate strong electromagnetic fields capable of causing damage to unprotected electrical or electronic equipment located in an extensive area below the burst.

The phenomenon known as the “electromagnetic pulse” (or EMP) is described elsewhere in this book. The EMP can also be produced in surface and low air bursts, but a much smaller area around the detonation point is affected.

If a nuclear explosion occurs under such conditions that its center is beneath the ground or under the surface of water, the situation is described as an “underground burst” or an “underwater burst,” respectively. Since some of the effects of these two types of explosions are similar, they will be considered here together as subsurface bursts.

In a subsurface burst, most of the shock energy of the explosion appears as underground or underwater shock, but a certain proportion, which is less the greater the depth of the burst, escapes and produces air blast. Much of the thermal radiation and of the initial nuclear radiation will he absorbed within a short distance of the explosion. The energy of the absorbed radiations will merely contribute to the heating of the ground or body of water.

Depending upon the depth of the explosion, some of the thermal and nuclear radiations will escape, but the intensities will generally be less than for an air burst. However, the residual nuclear radiation, i.e., the radiation emitted after the first minute, now becomes of considerable significance, since large quantities of earth or water in the vicinity of the explosion will be contaminated with radioactive fission products.

A “surface burst” is regarded as one which occurs either at or slightly above the actual surface of the land or water. Provided the distance above the surface is not great, the phenomena are essentially the same as for a burst occurring on the surface. As the height of burst increases up to a point where the fireball (at maximum brilliance in its later stages) no longer touches the land or water, there is a transition zone in which the behavior is intermediate between that of a true surface burst and of an air burst.

In surface bursts, the air blast and ground (or water) shock are produced in varying proportions depending on the energy of the explosion and the height of burst.

Although the five types of burst have been considered as being fairly distinct, there is actually no clear line of demarcation between them. It will be apparent that, as the height of the explosion is decreased, a high-altitude burst will become in air burst, and an air burst will become a surface burst.

Similarly, a surface burst merges into a subsurface explosion at a shallow depth, when part of the fireball actually breaks through the surface of the land or water. It is nevertheless a matter of convenience, as will be seen in later chapters, to divide nuclear explosions into the five general types defined above.

	Bomb Shelter Planning Location, Underground Bomb Shelter Plans, Blast/Fallout, Radiation
	Build Your Bomb Shelter First Steps, Materials Required, Costs
	Stocking Your Bomb Shelter Nuclear Emergency Kit (NEK), Emergency Supply Kit, Food, Water, Medical, Etc.
	Bomb Shelter FAQ's Complete List of Essential Nuclear Blast and Underground Bomb Shelter FAQs
	Understanding Radiation Overview of Radioactive Fallout and How to Protect Yourself From It
	Nuclear Bomb Facts Kiloton, Blast Wave, Damage

BOMB SHELTER ARTICLES

North Korea Says it will Restart its Nuclear Facility
North Korea announced Thursday that it is preparing to restart the facility that produced its atomic bomb.

Security Specialists Say US More Vulnerable to Nuclear Attack
The U.S. is now more vulnerable to a catastrophic terrorist attack than it was seven years ago - in part because the government has dragged its feet in defending against the threat.

Iran Signals No Plans to Stop Nuclear Regime
Iran's nuclear program remains unchanged, a government spokesman Saturday, indicating that Tehran has no plans to meet a key Western demand that it stop enriching uranium.

U.S. Unprepared for Dirty Bomb
The U.S. has a shortage of laboratories to test the thousands of people who might be exposed to radiation if a “dirty bomb” detonated in a major city, according to a congressional report released Thursday.

Radioactive Fallout Will be the Killer
Like the more than 160 million Americans who live within the danger zones, your greatest concern following a nuclear attack comes from radioactive fallout. That's the main reason you will need a well-constructed, underground bomb shelter.

Bomb Shelter Writing Supplies
Are writing supplies available, including pens or pencils and printed forms or paper, for keeping records of radiation exposure?

Watching for Fallout to Arrive Near the Bomb Shelter
When a nuclear weapon explodes anywhere within several hundred miles, there will be many signs to indicate it. By that time, people should be on the way to, or already at, their bomb shelter.

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How a Nuclear Bomb Works

Bomb Shelter Writing Supplies
Are writing supplies available, including pens or pencils and printed forms or paper, for keeping records of radiation exposure?

Use of the Penalty Table as a Guide for Bomb Shelter Operations
The Penalty Table was developed to provide a simple guide when decisions must be made that will involve some risk.

Group Dosimetry: Keeping Track of Radiation Exposure
The radiation hazard will be worst throughout the first 24 hours after each fallout cloud arrives. It is important to start keeping track of everyone’s radiation exposure right away, as soon as fallout begins to arrive.

Time-Averaging Method
Used to compare the radiation levels between two or more locations in a bomb shelter when the radiation levels are climbing rapidly and when you have only one survey meter.

Space in the Bomb Shelter
Is there going to be enough room for all of the people at this bomb shelter in the locations of best protection?

Restroom and Water Locations in the Bomb Shelter
After fallout has arrived, he or she should check the radiation levels at these locations. Some of them may have to be blocked off until the radiation decays to a safer level.

Radiation Safety Improvement in Bomb Shelters
As you go through your bomb shelter looking for the places that appear to provide the best shielding from gamma radiation, you should also look for ways to improve the shielding.

Organization of the Bomb Shelter Population
Organization of the bomb shelter population into bomb shelter units, each with its own Unit Leader, is necessary not only for good management but also for keeping a radiation exposure record for each person in the bomb shelter.

Materials for Shielding the Bomb Shelter
You may have improved the radiation safety of the bomb shelter to the best of your judgment and capability, as discussed earlier. But after fallout arrives, you may find with the use of your survey meter that gamma radiation is shining through at some unexpected location.

Light Sources in the Bomb Shelter
Electricity may fail in many locations due to a wide-scale nuclear attack. Most of the bomb shelters with the highest FPF’s will also have the least daylight reaching them. If the power goes out, these bomb shelters may be pitch black.

Informing the People in the Bomb Shelter about Radiation Exposure
Even if people are frightened, it is better not to hold back information. The policy of “what they don’t know won’t hurt them” has never worked with the American public.

Getting and Checking the Bomb Shelter Instruments
If you are selected to be an RM after you arrive at the bomb shelter, you may have to find out where the radiation instruments are, and you may have to make a special trip to get them. Instructions on how to use the instruments may be given at the place where they are issued.

Gamma Shielding by using People in the Bomb Shelter
The shielding effect of human bodies can be used to provide extra protection. This protection would be of particular benefit to those people with the greatest sensitivity to radiation, namely, children and pregnant women.

Forecasting Radiation Exposure
When the survey meter readings level off and then continue to decrease, the arrival of fallout from that particular cloud at your location has almost ended. If no more fallout clouds arrive, the radiation levels will continue to decrease rapidly.

Finding the Places with the Lowest Radiation Levels in the Bomb Shelter
Use the survey meter to find the places that have the lowest radiation levels. The people in the bomb shelter should be gathered at the locations that are estimated to have the lowest radiation levels.

Finding and Covering up Leaks in Bomb Shelter Gamma Shielding
After the safest locations have been found in the bomb shelter and the people have moved there (if they weren’t there already), use the survey meter to make detailed measurements of the radiation levels in and around the area where the people are located.

Dosimeter Locations: Where to Place Dosimeters
In some bomb shelters where the FPF is high and about the same everywhere, as in deep underground bomb shelters, caves, and mines, only a few dosimeters need to be mounted or hung where people will be located, to get an idea of what total exposures they are getting, if any.

Decontamination of People Caught in Radioactive Fallout
Fallout arriving within a few hours after a nuclear explosion is highly radioactive. If it collects on the skin in large enough quantities it can cause beta burns

Checking Radiation Levels Outside the Bomb Shelter Area
Sometime no later than 24 - 30 hours after fallout has begun to come down, you (the RM) should take the survey meter and check the radiation levels in rooms next to the bomb shelter area and on the way to the outside.

Checking Out the Bomb Shelter
Some bomb shelters may have many rooms, some of them on different levels, and others may have just one large room. The problems of providing the best radiation safety will be a little different in each bomb shelter.

Best Bomb Shelter Protection
Which locations within the bomb shelter appear to offer the best protection against fallout? Sketch a bomb shelter floor plan and mark these locations.

Bomb Shelter Openings and Ventilation
Are there openings to be baffled or covered to reduce the amount of radiation coming through them? Will these changes allow enough air to flow through to keep people from getting too hot when they are crowded?

Bomb Shelter Location
The location you choose for your bomb shelter should be one which gives you the greatest protection possible. Just placing an underground bomb shelter in your back yard is not enough.

Bomb Shelter Design
What should your underground bomb shelter look like? What materials should it consist of? How should it be designed? These are all important considerations when planning the construction of an underground bomb shelter.

Blast and Fallout Concerns
The blast wind produced by a nuclear bomb will reach 2,000 mph within the first half mile from ground zero, drop to about 1,000 mph at 2 miles, and will still be at hurricane force (200 mph) several miles out.

Get an Underground Bomb Shelter, Hop in, Now What?
You are going to need a complete underground bomb shelter plan, and you want to make sure such a plan has been scrutinized thoroughly.

Before Fallout Arrives
It may not be possible to do all these tasks before fallout arrives at the bomb shelter or fallout shelter, and in that case, those tasks that can be done inside the bomb shelter can be done later while fallout is arriving.

Types of Nuclear Explosions
The immediate phenomena associated with a nuclear explosion, as well as the effects of shock and blast and of thermal and nuclear radiations, vary with the location of the point of burst in relation to the surface of the earth. For descriptive purposes five types of burst are distinguished, although many variations and intermediate situations can arise in practice.

Sources of Radiation
Blast and thermal effects occur to some extent in all types of explosions, whether conventional or nuclear. The release of ionizing radiation, however, is a phenomenon unique to nuclear explosions and is an additional casualty producing mechanism superimposed on blast and thermal effects.

Time Scale of a Fission Explosion
An interesting insight into the rate at which the energy is released in a fission explosion can be obtained by treating the fission chain as a series of “generations.” Suppose that a certain number of neutrons are present initially and that these are captured by fissionable nuclei; then, in the fission process other neutrons are released.

Thermonuclear Fusion Reactions
From experiments made in laboratories with charged-particle accelerators, it was concluded that the fusion of isotopes of hydrogen was possible.

Thermal Radiation
The observed phenomena associated with a nuclear explosion and the effects on people and materials are largely determined by the thermal radiation and its interaction with the surroundings. It is desirable, therefore, to consider the nature of these radiations somewhat further.

Fission Products
Many different initial fission product nuclei, i.e., fission fragments, are formed when uranium or plutonium nuclei capture neutrons and suffer fission. There are 40 or so different ways in which the nuclei can split up when fission occurs; hence about 80 different fragments are produced.

Fission Energy
The significant point about the fission of a uranium (or plutonium) nucleus by means of a neutron, in addition to the release of a large quantity of energy, is that the process is accompanied by the instantaneous emission of two or more neutrons.

Critical Mass for a Fission Chain
Although two to three neutrons are produced in the fission reaction for every nucleus that undergoes fission, not all of these neutrons are available for causing further fissions. Some of the fission neutrons are lost by escape, whereas others are lost in various nonfission reactions.

Attainment of Critical Mass in a Nuclear Explosion
In order to produce an explosion, the material must then be made “supercritical,” i.e., larger than the critical mass, in a time so short as to preclude a sub-explosive change in the configuration, such as by melting.

Residual Radiation
The residual radiation hazard from a nuclear explosion is in the form of radioactive fallout and neutron-induced activity.

Radiation and Fallout
Radioactive fallout will fall in a manner similar to that following a volcanic eruption. It will be flaky in appearance and its size may reduce to dust particles or smaller. Expect it to be thicker near the detonation site and thinner as it travels down wind.

Initial Radiation
About 5% of the energy released in a nuclear air burst is transmitted in the form of initial neutron and gamma radiation. The neutrons result almost exclusively from the energy producing fission and fusion reactions, while the initial gamma radiation includes that arising from these reactions as well as that resulting from the decay of short-lived fission products.

General Principles of Nuclear Explosions
An explosion, in general, results from the very rapid release of a large amount of energy within a limited space. This is true for a conventional “high explosive,” such as TNT, as well as for a nuclear (or atomic) explosion, although the energy is produced in quite different ways.

Worldwide and Local Fallout
The radiobiological hazard of worldwide fallout is essentially a long-term one due to the potential accumulation of long-lived radioisotopes, such as strontium-90 and cesium-137, in the body as a result of ingestion of foods which had incorporated these radioactive materials.

Energy Yield of Nuclear Explosions
The “yield” of a nuclear weapon is a measure of the amount of explosive energy it can produce. It is the usual practice to state the yield in terms of the quantity of TNT that would generate the same amount of energy when it explodes.

Distribution of Energy in Nuclear Explosions
The basic reason for this difference is that, weight for weight, the energy produced by a nuclear explosive is millions of times as great as that produced by a chemical explosive.

Atomic Structure and Isotopes
A less familiar element, which has attained prominence in recent years because of its use as a source of nuclear energy, is uranium, normally a solid metal.

Understanding Radiation
What is radiation, you ask? Radiation in physics is the process of emitting energy in the form of waves or particles. Various types of radiation may be distinguished, depending on the properties of the emitted energy/matter, the type of the emission source, properties and purposes of the emission, etc.

Bomb Shelter Entranceway Problems
One problem that could develop is that the bomb shelter entrance could be blocked by people who have stopped just inside the entrance.

Minimizing Exposure to Radiation
It's people like you and me (hopefully) that will survive the initial blast. Our greatest concern is radioactive fallout. Fallout will kill as many, if not much more than the blast itself. And how long you have before fallout arrives depends on three things.

Building an Underground Bomb Shelter Bomb Shelter Planning Frequently Asked Questions Important Nuclear Bomb Facts

Understanding Radiation:

Types of Nuclear Explosions

Building an Underground Bomb Shelter
Bomb Shelter Planning
Frequently Asked Questions
Important Nuclear Bomb Facts