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

Understanding Radiation:

Distribution of Energy in Nuclear Explosions

It has been mentioned that one important difference between nuclear and conventional (or chemical) explosions is the appearance of an appreciable proportion of the energy as thermal radiation in the former case. 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.

Consequently, the temperatures reached in the former case are very much higher than in the latter, namely, tens of millions of degrees in a nuclear explosion compared with a few thousands in a conventional explosion. As a result of this great difference in temperature, the distribution of the explosion energy is quite different in the two cases.

Broadly speaking, the energy may be divided into three categories kinetic (or external) energy, i.e. , energy of motion of electrons, atoms, and molecules as a whole; internal energy of these particles and thermal radiation energy. The proportion of thermal radiation energy increases rapidly with increasing temperature.

At the moderate temperatures attained in a chemical explosion, the amount of thermal radiation is comparatively small, and so essentially all the energy released at the time of the explosion appears as kinetic and internal energy. This is almost entirely converted into blast and shock, in the manner described earlier. Because of the very much higher temperatures in a nuclear explosion, however, a considerable proportion of the energy is re leased as thermal radiation. The manner in which this takes place is described later.

The fraction of the explosion energy received at a distance from the burst point in each of the forms depicted in Figure 6-2 depends on the nature and yield of the weapon and particularly on the environment of the explosion.

For a nuclear detonation in the atmosphere below an altitude of about 100,000 feet, from 35 to 45 percent of the explosion energy is received as thermal energy in the visible and infrared portions of the spectrum.

In addition, below an altitude of about 40,000 feet, about 50 percent of the explosive energy is used in the production of air shock. At somewhat higher altitudes, where there is less air with which the energy of the exploding, nuclear weapon can interact, the proportion of energy converted into shock is decreased whereas that emitted as thermal radiation is correspondingly increased.

The expect distribution of energy between air shock and thermal radiation is related in a complex manner to the explosive energy yield, the burst altitude, and, to some extent, to the weapon design, as will be seen in this and later chapters.

However, an approximate rule of thumb for a fission weapon exploded in the air at an altitude of less than about 40,000 feet is that 35 percent of the explosion energy is in the form of thermal radiation and 50 percent produces air shock. Thus, for a burst at moderately low altitudes, the air shock energy from a fission weapon will be about half of that from a conventional high explosive with the same total energy release; in the latter, essentially all of the explosive energy is in the form of air blast.

This means that if a 20-kiloton fission weapon, for example, is exploded in the air below 40,000 feet or so, the energy used in the production of blast would be roughly equivalent to that from 10 kilotons of TNT.

Regardless of the height of burst, approximately 85 percent of the explosive energy of a nuclear fission weapon produces air blast (and shock), thermal radiation, and heat. The remaining 15 percent of the energy is released as various nuclear radiations. Of this, 5 percent constitutes the initial nuclear radiation, defined as that produced within a minute or so of the explosion.

The final 10 percent of the total fission energy represents that of the residual (or delayed) nuclear radiation which is emitted over a period of time. This is largely due to the radioactivity of the fission products present in the weapon residues (or debris) after the explosion. In a thermonuclear device, in which only about half of the total energy a rises from fission, the residual nuclear radiation carries only 5 percent of the energy released in the explosion.

It should be noted that there are no nuclear radiations from a conventional explosion since the nuclei are unaffected in the chemical reactions which take place.

Because about 10 percent of the total fission energy is released in the form of residual nuclear radiation some time after the detonation, this is not included when the energy yield of a nuclear explosion is stated, e.g., in terms of the TNT equivalent.

Hence, in a pure fission weapon the explosion energy is about 90 percent of the total fission energy, and in a thermonuclear device it is, on the average, about 95 percent of the total energy of the fission and fusion reactions. This common convention will be adhered to in subsequent chapters.

For example, when the yield of a nuclear weapon is quoted or used in equations, figures, etc., it will represent that portion of the energy delivered within a minute or so, and will exclude the contribution of the residual nuclear radiation.

The initial nuclear radiation consists mainly of “gamma rays,” which are electromagnetic radiations of high energy originating in atomic nuclei, and neutrons. These radiations, especially gamma rays, can travel great distances through air and can penetrate considerable thicknesses of material.

Although they can neither be seen nor felt by human beings, except at very high intensities which cause a tingling sensation, gamma rays and neutrons can produce harmful effects even at a distance from their source. Consequently, the initial nuclear radiation is an important aspect of nuclear explosions.

The delayed nuclear radiation arises mainly front the fission products which, in the course of their radioactive decay, emit gamma rays and another type of nuclear radiation called “beta particles.” The latter are electrons, i.e., particles carrying a negative electric charge, moving with high speed; they are formed by a change (neutron proton + electron) within the nuclei of the radioactive atoms. Beta particles, which are also invisible, are much less penetrating than gamma rays, but like the latter they represent a potential hazard.

The spontaneous emission of beta particles and gamma rays from radioactive substances, i.e., a radioactive nuclide (or radionuclide), such as the fission products, is a gradual process. It takes place over a period of time, at a rate depending upon the nature of the material and upon the amount present.

Because of the continuous decay, the quantity of the radionuclide and the rate of emission of radiation decrease steadily. This means that the residual nuclear radiation, due mainly to the fission products, is most intense soon after the explosion but diminishes in the course of time.

	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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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:

Distribution of Energy in Nuclear Explosions

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