We Build Underground Bomb Shelters

Underground Bomb Shelter

Underground Bomb Shelter Planning Locations

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. You need to find the most optimal location. In doing so, you need to consider the terrain, water levels, and distance from other structures. This includes location of sewer and electrical lines.

Essentially, you want to have as much mass between your bomb shelter and the attack. After identifying potential nuclear bomb targets and where a likely blast wind will come from, determine a bomb shelter position that will serve the greatest protection. The lower edge of a hill, for example would be an excellent place for your bomb shelter if a prospected blast happens in the distance on the other side of the hill. The idea is use common sense in determining where an attack might occur. Then, build your bomb shelter in the best possible location.

In considering the fallout aspect, just know that its going to fall everywhere; no hill or mountain would reduce the amount of fallout since it falls straight to the ground like snow. So, you just need to make sure you put your underground bomb shelter deep enough - 36 inches or more below the surface.

Underground 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. Time and money are also significant factors. Essentially, you want an underground bomb shelter that is inexpensive and easy to build, yet strong enough to do the job of keeping you safe. When it comes to your safety (or better, survival), you may think money is no object. Clearly, money is an object - even in the bomb shelter business. Most Americans do not have an extra $80,000 just lying around to spend on a sophisticated bomb shelter system. Remember, with sophistication comes technology (electrical connections, water and air pumps, etc.) You will not be able to rely on such conveniences following a nuclear strike so why bother purchasing them? Frankly, you should rely on living for up to a month without these items.

You do not need a beautifully-shaped, convenience-packed bomb shelter so why spend $35,000 or more on one? Moreover, it wouldn't be wise to take out a second mortgage on your house to fund a bomb shelter. Think about it, you certainly aren't going to want to impress your neighbors with it. More importantly, you don't even want them to know about it! Though all of our bomb shelters and bomb shelter plans can withstand it, forget about surviving the blast wave - there will be no time for outrunning a 2,000 mph wind! And, there are no chemical elements produced during a nuclear explosion. What you need is an underground bomb shelter that offers certain, basic protection from radioactive fallout.

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. So, unless you know of an impending attack your chances for preparing for the blast will rely upon swift reaction to the super bright flash produced by the bomb.

If you see a bright flash, you should immediately duck and cover. After that, head for the bomb shelter. The fallout that will arrive in as little as a few minutes (distance-dependent) will be extremely hazardous. In fact, the radiation carried with the dust and dirt will very capable of penetrating several inches of steel, your house, your car, and most buildings.

An underground bomb shelter emplaced with its roof at least 36 inches below the surface will provide sufficient protection from radiation. If you are inside your bomb shelter within a few minutes following the attack, you will live. If you are outside, it's curtains. If you stand outside at a point of about 10 miles from the blast, you will likely survive the blast wave from any nuclear strike. But, within 30 minutes the first flakes of radioactive dust will begin to fall on your head. If you are exposed you will die an hour later from internal damage caused by the radiation found in the fall out particles. Those who move inside the underground bomb shelter will simply have to wait about 4 days before emerging unscathed.

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. When used by the general public, the word "radiation" commonly refers to ionizing radiation.

Alpha, beta, gamma radiation and what it penetrates.
PHOTO: Uranium Information Center

Dr. Frank Settle states on his web site, Chemcases.com:

The radiation produced by nuclear reactions interacts with living tissue in many ways depending on the type of radiation. This radiation includes high-energy, charged particles (alpha and beta), neutrons of various energies, and photons (gamma and x-rays). In addition to this primary radiation, fission also produces radioactive isotopes of many elements, which in turn can emit particles and photons, known as secondary radiation.

Many of these isotopes, such as strontium and iodine, can enter the body, where they replace non-radioactive elements and remain there emitting ionizing radiation. In many ways, the presence of these radioactive isotopes is more insidious than direct radiation from external sources that is more easily detected and reduced by proper shielding.

Dr. Settle also states:

The ability to penetrate matter differs greatly among the various types of nuclear radiation. A sheet of paper, a layer of clothing, or an inch of air can stop relatively slow moving, heavy alpha particles. Thus, it is easy to shield against alpha radiation, unless the alpha-emitting substance enters the body. Beta particles are lighter and travel faster than alpha particles. They can penetrate a fraction of an inch in solids and liquids and several feet in air.

Gamma rays and neutrons are electrically neutral and thus not slowed by collisions with the target materials. They do not interact strongly as the charged alpha and beta particles do and are therefore highly penetrating. Their ability to penetrate the target material depends upon their energy. High-energy gamma rays may require several feet of material for adequate shielding.

Note: For a more thorough understanding of nuclear radiation, please read Nuclear Weapon Radiation Effects.

Before Fallout Arrives at the Bomb Shelter

In some locations there may be detailed planning and preparation for protection in case of a crisis or emergency during which a nuclear attack might take place. In those localities, many of the tasks described here will already be done before the crisis happens. Even in those localities where as much has been done as possible before a crisis, there will still be some tasks that should be done soon after a crisis occurs.

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. Those tasks that require trips outside the bomb shelter will have to be postponed or forgotten if they are not completed by the time fallout begins to arrive, unless special circumstances of extreme urgency or very low risk make the trips worthwhile.

No one who is in a bomb shelter when fallout begins to arrive should leave the bomb shelter except under special circumstances of extreme urgency or very low risk.

If a crisis develops quickly, leading to a nuclear attack on short notice, pre-designated Cold War bomb shelters in the communities where people live would be used. In this case, there probably would not be time to do some tasks before fallout arrives, such as checking the dosimeters for leakage or improving the radiation safety of your bomb shelter.

On the other hand, you may know many of the people in the bomb shelter and may have an idea who might be able to help with radiation monitoring and other tasks. You may also know where useful and vital supplies are located. Furthermore, you may be familiar with the bomb shelter and will not need to spend much time checking it out.

If a crisis develops gradually, there may be time for people in high-risk areas, areas which might be targets, to relocate to areas of lower risk. In this case, people who relocate may set up housekeeping in or near the bomb shelter they would use if it became necessary.

There would probably be time to work out an organization of the bomb shelter population, check out the bomb shelter, get supplies for maintaining radiation records, stockpile materials for possible use as emergency shielding, and to leak-check the dosimeters.

Organization of Bomb Shelter Population

The bomb shelter Manager and assistants will supervise the organization of the bomb shelter population into small groups called bomb shelter units. 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. There may be between seven and 15 people in a bomb shelter unit.

There probably won’t be enough dosimeters for each person to have one. The bomb shelter Unit Leaders can help estimate the radiation exposure of those people in their units who don’t have dosimeters. The Unit Leaders can also see that someone fills out the radiation exposure record for those who are unable to do it themselves, such as small children.

Organization of the bomb shelter population into bomb shelter units will also be necessary in case people need to be moved to a different location in the bomb shelter where the exposure rates are lower. Unit Leaders can supervise the movement to see that their units move as a group and that no one accidentally moves into a hazardous area.

After the bomb shelter units have been organized and the Unit Leaders selected, the Unit Leaders should be shown how to fill out the radiation exposure records. If blank forms are available, these should be issued before fallout arrives. The Unit Leader should see that the top part of each form is filled out for everyone in the unit.

Radiation sensitivity categories are listed and described in the Table below. Identifying people according to these categories before fallout arrives may be useful if it should later become necessary to arrange for special shielding. The effect of a given whole-body exposure to radiation will vary somewhat among individuals, due partly to age, sex, body thickness, and general health.

TABLE - Radiation Sensitivity Categories

Category Description Cause for Immediate Concern*
PG Pregnant women Miscarriages, malformed babies, radiation sickness.
Child Infants, small children More susceptible to radiation injury than adults.
Y/A Youths and adults Radiation sickness

* In addition to radiation sickness, there may be radiation effects that occur many months or years after exposure such as cancer, leukemia, sterility, cataracts, and genetic injury. The probability of developing such late effects should not be a principal determinig factor in decision-making during a nuclear war or attack emergency, but such effects can and should be minimized by keeping controllable exposures as low as practicable.

The sick, aged, and very young are the most susceptible. Nevertheless, it is generally advisable for bomb shelter management to consider the entire bomb shelter population to be equally susceptible to the effects of radiation, with the possible exception that children and pregnant women should be treated as being more susceptible. If a women is pregnant, here radiation exposure record form should be marked “PG” on the line following “Rad. Sensitivity Category.”


Checking Out the Bomb Shelter

Many different kinds of bomb shelter will be used for protection against fallout in an emergency. Some bomb shelters may be in schools, churches, or banks. Others may be in factories, office buildings, large stores, underground garages, basements of apartments or houses, mines, or caves. 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.

Of course, if you have your own underground bomb shelter or fallout shelter, it may be minimal in size and people. You’ll most likely have your immediate family and a perhaps a friend or neighbor with you. In that case, you will be situated in an environment that’s far better than an overcrowded community fallout bomb shelter.

The Emergency Operating Center (EOC) should be consulted if special problems, not discussed here should arise. Finding a solution for some of these problems may mean the difference between life and death for some of the people in your bomb shelter. These solutions may depend on how good you are at inventing and putting together ideas on the spot and being able to do things in a difficult situation.

Here is a list of items to check out and do in your bomb shelter before fallout arrives. In the sections following the list, each item is discussed in greater detail. The most urgent items are included in Checklist ”A” at the front of this book. All items are included in Checklist “B”, the standard checklist for RM’s. You, the RM, will have to work in cooperation with the bomb shelter Manager and others on many of these items.

  • Which locations appear to offer best bomb shelter protection against fallout? Sketch a bomb shelter floor plan and mark these locations.
  • Is there going to be enough room for all of the people in the bomb shelter location of best protection?
  • Can the radiation safety of the bomb shelter be improved with tools, materials, and manpower on hand?
  • Are there openings to be baffled or covered to reduce the amount of radiation coming into the bomb shelter?
  • Will these changes allow enough air to flow through to keep people in the bomb shelter from getting too hot when they are crowded?
  • Are materials and tools handy which could be used for putting up additional, improvised shielding inside the bomb shelter after fallout arrives?
  • Is there going to be a problem if a lot of people enter the bomb shelter while fallout is coming down?
  • Are brooms and dustpans on hand to sweep up fallout particles that will accumulate near the entrance of the bomb shelter?
  • Will trips for water or to restrooms increase radiation exposure?
  • Where could dosimeters be mounted or hung in the bomb shelter? Are needed materials available for mounting or hanging them?
  • Where can instruments, instrument supplies, flashlights, and batteries be stored securely in the bomb shelter?
  • Are there enough candles, lanterns, flashlights, and other light sources so you can move around and read instruments if the power goes out in the bomb shelter?
  • Are writing supplies available, including pens or pencils, and printed forms or paper, for keeping records of radiation exposure?
  • Do you have a notebook in which to keep a record (RM log) of events?

Best Bomb Shelter Protection

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

The best protection is provided by getting as much mass as possible between you and the fallout. Walk through the bomb shelter and get an idea where the best protected areas might be. Usually, but not always, the areas having the least amount of daylight reaching them will provide the best protection.

Basements provide good protection from the sides if they are well below ground and there is earth all around, but they may not always provide good protection from “skyshine” or from radiation from fallout that has settled above the basement or on neighboring rooftops.

If the floors above the bomb shelter are made of solid concrete, they will be much more massive than floors of wood and will provide much better protection from overhead gamma radiation. Similarly, walls of solid brick or concrete will provide better protection than walls of hollow concrete or cinder-block; these walls, in turn will provide better protection than walls of gypsum board (sheetrock) or plywood.

Tall buildings can provide good protection from gamma radiation in the inner rooms of floors that are at least four stories above the ground or surrounding rooftops. There should be at least three stories above the bomb shelter to provide protection from fallout on the roof. These locations do not provide blast protection and should not be used in areas less than 25 miles from a likely target for a nuclear weapon.

If we expect the gamma radiation from fallout to be reduced at a certain location by a factor of four from what the radiation level would be outside above a very large, flat, smooth, open area, covered with the same kind and amount of fallout, we say the Fallout Protection Factor (FPF) of the location is four. This factor is also called the Protection Factor (PF).

Some locations that are rated with a high protection factor, such as bomb shelters in upper levels of a skyscraper, may provide little protection against other nuclear weapons effects such as blast. A high FPF for a bomb shelter location only indicates good protection against gamma radiation from fallout.

Such a bomb shelter location may also, but not necessarily, provide protection against other nuclear weapons effects. The term FPF is used in this book instead of PF to indicate the protection provided by a bomb shelter location against gamma radiation from fallout.

Some FPF’s that might be possible in different locations in buildings are shown in the image above. Deep basements and buried bomb shelters have high FPF’s (1,000 and above). They provide good protection against gamma radiation from fallout in the locations indicated by dots in the drawing, but they provide little protection against blast. The FPF’s indicated above and below-ground bomb shelters that are surrounded or partly surrounded by buildings. The first floors of houses and partially buried basements have low FPF’s and provide little protection against gamma radiation from fallout.

The next image is an example of a sketch of a floor plan of an apartment building. Two kinds of interior wall construction are indicated in the sketch, concrete block and wallboard, probably gypsum. The rooms have been named with letters of the alphabet. Room “G” looks like it would provide the highest FPF’s because it is surrounded by outside rooms and has walls of concrete block.

Space in Your Bomb Shelter

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

After the locations have been found that appear to provide the best protection, you should talk with the bomb shelter Manager about the problem of having enough room. To answer this question you will need to know two things:

1. How many people are in or assigned to your bomb shelter.

2. How much space is available in the locations of best protection.

The bomb shelter Manager should be able to tell you how many people are already in the bomb shelter or are assigned to it. The bomb shelter Manager should have a list of names and radiation sensitivity categories of occupants, names of bomb shelter Unit Leaders, and a record of kinds of special skills that are available.

To answer the second question, you will need the sketch of the floor plan with the approximate dimensions of rooms. This sketch may not show what is in the rooms. You will need to look at the rooms that you have estimated to be the safest to see if there are furniture, equipment, and obstructions that can be moved to increase the space for people.

Bookcases, boxes, chests, desks, and file cabinets may be moved from the rooms expected to have the highest FPF’s into the rooms with lower FPF’s. Some kinds of tables should not be moved because people (especially children) may sit under them as well as on top, thus doubling the space. Wide, sturdy storage shelves can also be used for people to sit down or lie upon at more than one level.

If you aren’t sure which rooms have the highest FPF’s, the bomb shelter Manager may hold off having items moved until after fallout arrives and the radiation builds up to levels you can detect with the survey meter. Then the survey meter may be used to find the locations with the lowest radiation levels.

During the early hours after fallout arrives, it may become necessary to crowd people in the safest locations. After the radioactivity decays to a lower level, the occupants can spread out into rooms with relatively high radiation levels. You can get an idea of whether the bomb shelter Manager may need to crowd people by estimating the total available space in square feet of the safer locations.

Divide that number by 10, the number of square feet allowed per person. If the resulting number is larger than the number of bomb shelter occupants, you have plenty of space in the safer locations. If the number is smaller than the number of bomb shelter occupants, it may be necessary to crowd people temporarily in the safer locations. The number of people in the safer locations can be double if you crowd them temporarily by squeezing down the space per person from 10 square feet to five square feet.

In the floor-plan sketch above, the available floor space in Room G, including the toilet, is about 624 square feet. The hallway to the left of Room G adds about 132 square feet for a total of 756 square feet in the estimated safer locations. Divide 756 by 10, and round off to 76. If more than 76 people are assigned to the apartment building basement, they will need to be crowded in Room G and the hallway if the radiation builds up to hazardous levels after the fallout arrives.

With maximum crowding, they could squeeze about 152 people into Room G and the hallway during the most hazardous times. If more than 152 people were assigned to this bomb shelter, some of them would have to be bomb sheltered in the outer rooms, which are not as safe. In that case, they might work out a rotation scheme so people would share, as fairly as possible, the higher radiation exposures of the outer rooms.

If it is necessary to crowd people in the safer locations, it is very important that enough fresh air and light are provided so that people don’t pass out from heat prostration or get claustrophobia (fear of confined, crowded places) and run outside. Both the bomb shelter Manager and the RM will be involved in these problems.

Radiation Safety Improvement in Your Bomb Shelter

Can the radiation safety of the bomb shelter be improved with tools, materials, and manpower on hand?

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. Look for openings that can be covered up and for places where walls and ceilings can be thickened to cut down gamma penetration.

In the apartment floorplan sketch above, the radiation safety could be improved with a little effort. Earth could be piled up around the outside where the basement wall rises above ground level. All but two or three basement windows could be sealed with boards or with cardboard and plastic and then covered with earth. The remaining windows may be needed for ventilation and should be baffled rather than sealed. A way to construct a baffle over a basement window to reduce gamma penetration and prevent fallout from entering is shown in the following Figure.

About 40 - 50 man hours of labor would be needed for the improvements in the radiation safety of this bomb shelter. Shovels, picks, and some carpenter’s tools (hammers and saws) and supplies (nails, lumber, plywood, plastic sheeting and gloves) would be needed. People who are not accustomed to manual labor should wear gloves from the start when picking or shoveling earth. Blisters are painful and can develop into serious infections, especially if antibiotics aren’t available.

These efforts could improve the FPF’s of this bomb shelter by factors of four to 10. If the FPF of the safest location were about 25 before these improvements, the FPF could be 100 to 250 afterwards. If the fallout is heavy, this improvement could mean the difference between life and death for the occupants.

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?

Both the bomb shelter Manager and the RM will be involved with the problem of providing enough ventilation while maintaining the best radiation safety.

In the basement bomb shelter of the apartment floorplan sketch, all the windows except two or three should be sealed and covered with earth, as discussed previously. Two or three windows should be left uncovered to provide ventilation. These uncovered windows should be located on the side where fallout is least likely to pile up.

If the wind usually blows from the northwest, these uncovered windows should be located on the south or east side. In the floorplan sketch, if the top of the figure is north, the uncovered windows should be the two windows near the corner in Room F. If the local wind is blowing from the northwest when fallout is coming down, there may be less radiation buildup at the open windows on the southeast side.

These two uncovered windows should have a baffle or wall built around them with earth piled up on the outside to reduce the gamma radiation which shines directly into the bomb shelter from fallout on the ground. If the bottom of the window is at ground level, the inside of the baffle should be dug down several inches below the level of the window to provide a trap for fallout particles. If plastic or plywood sheeting is not available, a trough or a pipe from the inside of the enclosed trap to the outside ground level at a lower point is needed to provide drainage.

Materials for Shielding Your Bomb Shelter

Are materials and tools handy which could be used for putting up improvised shielding after the fallout arrives?

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.

You should know where and what materials are available to stack up against or cover a wall, doorway, window, or portion of a ceiling to reduce the gamma penetration. Such materials as books, bricks, earth, or wood may be used. Other materials and their shielding effectiveness are listed in Chapter 3. If some of these materials are located outside the bomb shelter, set up (or ask the bomb shelter Manager to set up) a work crew to move as much of it inside as possible before fallout arrives.

Bomb Shelter Entranceway Problems

Is there going to be a problem if a lot of people enter the bomb shelter while fallout is coming down?

One problem that could develop is that the bomb shelter entrance could be blocked by people who have stopped just inside the entrance. They may have stopped to brush off fallout particles or, if the bomb shelter is a large building, they may not know where to go.

If there is a possibility of problems at the entrances, one or two people should be selected to be receptionists at each entrance. The receptionists should see that people brush off fallout and shake outer garmets if they come to the bomb shelter after fallout begins to come down.

The receptionists should also show people where to put outer garments from which fallout particles can’t be shaken easily, show them where to go in the bomb shelter, sweep or vacuum fallout particles whenever they accumulate, and throw the swept-up particles outside (away from the entrance way).

The receptionists will need to wear dosimeters and must know how to read them. They should leave the entrance area and go back to the safest part of the bomb shelter as soon as their dosimeters read some preselected limit, such as 10 R. They may leave sooner if no one has arrived after fallout begins to come down.

The receptionists should set up places to store umbrellas, coats, and other outer garments if there are no convenient places to put these articles near the entrances. They should also have brooms and dustpans available.

It may be helpful to tape up sheets of paper near the entrances which show the way to the safest places in the bomb shelter. If there are no receptionists at the entrances, tape up a sheet of paper near the entrances with information on how to decontaminate oneself.

Restroom and Water Locations in Your Bomb Shelter

Are trips for water or to restrooms going to increase radiation exposure?

The RM should note where drinking fountains, water outlets, and restrooms are located throughout 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.

In nearly all public fallout bomb shelters, there will be plenty of water for drinking, cooking, and flushing toilets as long as there are no nuclear detonations close enough to break water lines, damage storage tanks, or cause an electric power failure. Remember, water arrives on pressure through gravity fed pipes in most places (the water tower on the hill in your part of town, for example).

If the electric power is knocked out by a distant nuclear explosion, there will still be water in the pipes and tanks, which flow by gravity. Water should be used as needed for drinking and sparingly for other purposes throughout the emergency.

In a nuclear war there is a possibility that the water supply might fail, so water should be stored in the bomb shelter before fallout arrives. If the bomb shelter runs out of water in a heavy fallout area, the RM may be faced with some difficult decisions and unpleasant situations.

About two weeks’ supply of water should be stored in areas where heavy fallout is expected. About two weeks after fallout has arrived, the radiation intensity even in the worst places will decay to levels where people can make emergency trips without the risk of radiation sickness or death. In areas where heavy fallout is expected and in the case of hot, crowded conditions int he fallout bomb shelters, a minimum of about seven gallons of water should be stored per person, just for drinking.

Dosimeter Locations

Where could dosimeters be mounted or hung? Are needed materials available for mounting or hanging them?

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 wil be located, to get an idea of what total exposures they are getting, if any. Tape, thumbtacks, nails, and string can be used to mount dosimeters.

In bomb shelters where the FPF may change as you move from one location to another, you will need to issue one or two dosimeters to each bomb shelter Unit Leader. The Unit Leader will then be responsible for estimating radiation exposure readings for the members of his or her unit. At certain times of the day or night, the Unit Leader may want to mount or hang one dosimeter in the vicinity of his or her unit and will then need materials for mounting or hanging it.

Bomb Shelter Instrument Storage

Where can instruments, instrument supplies, flashlights, and batteries be stored securely?

A central and secure location should be found for storing these items. In the apartment floorplan sketch (Figure above), the closet under the stairs in Room G can be used. If you can’t lock the door when you must leave, find someone to watch over the supplies. Don’t let children play with the radiological instruments.

Light Sources in Your Bomb Shelter

Are there enough candles, lanterns, flashlights, and other light sources to provide light so you can move around and read the instruments if the power goes out?

As mentioned before, 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. Some light must be provided so people won’t get hurt when they try to move around.

You will need a light of some kind to read the radiological instruments. You should have your own flashlight or lantern so you can move around freely and read your instruments whenever necessary.

Bomb Shelter Writing Supplies

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

The radiation exposure of each bomb shelter occupant should be recorded every day and for any special trip that increases the person’s exposure. A sample radiation exposure record is shown in the Appendix at the end of this book.

If enough printed forms for this record are not available, ordinary notebook paper or stationery may be used. If no paper is on hand in the bomb shelter and none is obtainable before fallout arrives, the records may be written on the walls or on whatever materials and surfaces are available.

Remember, the main purpose of the record is to help each person limit their radiation exposure and prevent radiation sickness. If people don’t know what they’ve been exposed to, they won’t know whether they are going to get radiation sickness if they make a trip out of the bomb shelter. Each person needs to know their own exposure so he or she can decide whether a trip outside can be safely made.

It will be useful to have a lot of paper to write and draw on in the bomb shelter, not only for radiation records but for bomb shelter sketches, messages, and bulletins. You will need a notebook, which we will cal the RM Log, to keep a record of events.

In this log you should enter such information as the tmie and date and a breif description whenever explosions are heard or detected, when falout arrives, when the peak radiation exposure rates are measured, when and where special measurements are made, and when there is trouble with instruments.

Getting and Checking Bomb Shelter Instruments

Each county may have a slightly different procedure for getting radiological instruments to the bomb shelters, if they are not there already. In some counties the instruments may be delivered, but in most counties the RM will be expected to pick up the instruments for the bomb shelter.

If you are selected to be an RM after you arrive at the bomb shelter, you may have to find out where the 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.

If the RM has not used the instruments recently and no instructions are given, the RM should read the Chapters, “Instruments for Detecting Nuclear Radiation”, and “How to Get Your Radiological Instruments Ready for Operation”.

If available, there should be at least one dosimeter for each bomb shelter unit and one dosimeter each for the bomb shelter Manager and the RM. It would be desirable to have one survey meter for approximately every 200 occupants in a bomb shelter and as many dosimeter chargers as there are survey meters.

You should get one extra D-cell battery for each survey meter and each charger. If extra batteries are not supplied with the instruments and if there is time, go to a store and buy them.

An operation check on the instruments should be made as soon as they are received, preferably at the place they are issued. Instructions for operational checks are given in the chapter “How to Get Your Radiological Instruments Ready for Operation”.

When you have the instruments at the bomb shelter, go through another operational check. Zero the dosimeters, if they haven’t been zeroed already (see the section, “Charging or Zeroing the Dosimeter” above). If there is time, start a leak check on all dosimeters (see the section, “Checking Dosimeters for Leaks”).

Let the bomb shelter Manager know that you have the instruments and their condition.

Keep the instruments in a secure place until they are put to use. If you can’t lock them up, find someone reliable to watch over them.

Informing the People in the Bomb Shelter about Radiation Exposure

Many people have a great fear of “invisible death” from nuclear radiation. There will be much anxiety among people in a bomb shelter when it is known that they are getting radiation from fallout. 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.

When the presence of fallout radiation first causes the needle to move up on the survey meter, the people in the bomb shelter should be informed. If there are several people watching the survey meter, the news of fallout radiation will travel very quickly through the bomb shelter.

In order to let people know the radiation levels, select at least one place in each small or medium-sized room where people are bomb sheltered (more places in large rooms) to mount a sheet of paper on which the survey-meter readings taken near the paper will be written periodically.

A sample sheet is shown below. It shows sample survey-meter readings at location 1 in the apartment floorplan sketch (above)

If there is time before fallout arrives, each bomb shelter Unit Leader should be shown how to read a dosimeter. Each Unit Leader should be encouraged to read Chapter Three, “Understanding Nuclear Radiation”, if they haven’t read it already. If there is only one copy, the fastest readers should be the first ones given the handbook to read.

Watching for Fallout to Arrive Near the Bomb Shelter

People may find that a nuclear attack is about to happen or is on its way by announcements on the radio or television, by sirens or other warning devices, or by word of mount. 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. No one should be outside or very far from a bomb shelter when fallout begins to come down.

A nuclear explosion several hundred miles away can cause an electromagnetic pulse (EMP) which may burn out the transmitting capability of some radio and television stations and knock out some telephone circuits. The EMP may also affect power lines, causing momentary blackout or flickering of lights. It may cause a lot of static similar to lightning static in AM radios, and may burn out FM radios or televisions with large antennas. Nuclear explosions near power lines or power stations may cause widespread power blackouts.

Nuclear explosions produce a brilliant flash and glow in the sky which may be seen 50 - 100 miles away in the daytime if the weather is clear, and much farther at night. Staring at the flash may cause eye damage even if the burst is far away. A shaking of the ground as in a mild earthquake may follow within a few minutes, depending on the distance from the burst.

The following procedure applies to bomb shelters that are located at least 25 miles away from a likely target for a nuclear weapon. After nuclear explosions have taken place with noticeable efects in or near the bomb shelter, or when notified by the EOC, the RM (for whom the following is written) should take the survey meter outside or by an outside window (on the windward side, if possible) and watch for the arrival of fallout.

If the FPF of the bomb shelter is high and the fallout is light in the area, the survey meter may not show that fallout has arrived if the meter is kept at the safest place in the bomb shelter. It is necessary to know when fallout has arrived, even if it is light, so that exposure control measures can be started.

If you, the RM must go outside, keep fallout particles from getting in your clothes and on your skin and hair. Carry an umbrella and wear a hat and an outer garmet if available. You should enclose your survey meter in a clear plastic bag, if available, to keep it from getting contaminated.

Carry a dosimeter in a breast pocket or on a chain or string around your neck. Take along a transistor radio or a two-way radio, if available, to keep informed of the situation around you. If it is nighttime, take a flashlight along even though the power may be on and the area may be brightly illuminated at the time you start your watch.

If fallout is expected to arrive within the hour, zero your survey meter and leave it on with the range-selector switch turned to “X0.1” If fallout is not expected to arrive for an hour or more, leave the survey meter turned off to save the batteries. You may want to turn it on every 10 or 15 minutes just to check the situation.

If fallout arrives from a ground explosion 25 - 75 miles upwind, depending upon the yield of the weapon, you will probably notice its arrival by the sound of gritty particles striking the window or surfaces around you.

You may hear these gritty particles striking for many seconds before the needle on your survey meter begins to climb. When the needle reaches 0.1 R/hr, note the time; enter the bomb shelter; decontaminate yourself if you have been outside; record the reading, tmie, and date in your RM Log; and tell the bomb shelter Manager and occupants that fallout has arrived.

If fallout arrival is to be reported to your EOC, it should be done in accordance with your local plan.

Some people may be working outside the bomb shelter to improve its radiation safety, or they may be carrying shielding materials into the bomb shelter up to the last minute before fallout arrives. They may become aware of the arrival of fallout by noticing gritty particles striking their skin, by hearing them strike nearby surfaces, or by seeing the buildup of particles on surfaces.

These people should then go inside the bomb shelter and brush the fallout particles off their clothes and bodies. If they do not notice the arrival of fallout, you, the RM should tell them that the arrival of fallout has been detected by the survey meter.

If fallout comes to the bomb shelter from many large ground bursts 100 miles or more upwind, the fallout may not arrive for many hours. The fallout may be hazardous even though it arrives as late as 24 hours after the explosions. You may decide not to set up your own watch for fallout for that length of time if your bomb shelter has good two-way communication with the local EOC.

If the people in your bomb shelter feel they can rely on the local EOC, they may decide to depend on the announcements from the EOC to let you know how fast fallout is coming to your bomb shelter. These announcements should come at least every half-hour or hour from the EOC, depending on the situation.

When it appears that fallout might arrive at your bomb shelter in two or three hours, take the survey meter to a window or outside and begin to watch for fallout.

The people in the bomb shelter may want to have their own lookout for fallout, even though the EOC may seem to be reliable. If you expect the fallout to take a long time to arrive, arrange for people to take turns or shifts in watching for its arrival.

When fallout arrives from distant explosions, you may not notice it as much as you would notice the fallout from closer explosions. The particles may be so small that you may not feel them as they land on your skin. The climbing of the needle on the survey meter may be the only indication that fallout from distant explosions has arrived.

The fallout is carried most of the way to its destination by winds at high altitudes. On some days the wind at high altitudes may be blowing in a different direction from the wind on the ground. Under these conditions, you might thing fallout from a particular nuclear explosion will not come your way because the wind where you are is not coming from the direction of the explosion.

In this situation, the fallout might arrive at your bomb shelter contrary to your expectations. The direction that the particles are blown by the surface winds may make it seem that they are coming from the wrong direction. Unless you have positive information on the direction the fallout is being carried, do not make any assumptions about where it will come down.

While Fallout is Coming Down at the Bomb Shelter

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 (see section, “Symptoms of Radiation Injury”).

People who are caught outside in fallout should brush fallout particles off themselves and shake out their outer garments as soon as they get inside the bomb shelter. Some people may be carrying umbrellas and wearing raincoats to keep the fallout particles off their skin and hair.

If people have not taken such precautions, they should try to get the fallout particles off their skin and out of their hair and clothing as much as possible before going further into the bomb shelter. But, they should not block the entrance so others can’t get in.

It is more important that people get into the bomb shelter than it is to get every speck of fallout off every person before they go further into the bomb shelter. Fallout particles that are carried into the bomb shelter can be swept up and thrown outside.

If there is a possibility of blockage at the entrances because of a lot of people coming to the bomb shelter after fallout arrives, one or two receptionists should be assigned to each entrance to supervise the decontamination. Each receptionist should wear a dosimeter.

Arrangements should be made for them to be replaced so they can leave the entrance area as soon as their dosimeters show that they have been exposed to some pre-selected limit, such as 10 R, or radiation. If only one or two people come every few minutes to the bomb shelter, the receptionists should go back to the safer parts of the bomb shelter.

Instructions for decontamination and directions to the safest bomb shelter locations should be printed on sheets of paper and taped or tacked up in places where incoming people can easily see them.

Most fallout particles will be like grains of fine, dark sand and can be easily brushed off from dry surfaces. The particles can be removed from tightly woven fabrics and rainwear by lightly shaking them.

Loosely-woven outer garments such as knitted sweaters, shawls, and scarves may hold fallout particles even after a hard shaking. These garments should be stored in a special place set aside for them until they can be washed.

After they are washed, they will be suitable for normal use. The fallout particles will come out in the wash, and the fallout particles or the radiation will not damage the fabric or make it radioactive.

Fallout particles may stick to moist or oily surfaces, including sweaty or oily skin or hair. These surfaces should be carefully wiped or washed off. If contaminated hair cannot be washed, it should be thoroughly brushed or combed, with frequent shaking and wiping of the hair and alos of the brush or comb.

It is not necessary to get the last speck of fallout out of the clothing or hair or off the skin. A few grains of fallout carried by each person into the safest parts of the bomb shelter will produce no noticeable increase in the radiation hazard and will not be detectable by the radiological instruments. Daily sweeping of the bomb shelter for hygienic reasons will eliminate most fallout particles that may be carried into the bomb shelter even after decontamination procedures.

The reception area should be organized so people can shake out their outer garments without getting the particles on people around them. After they have shaken out their clothing and wiped off their exposed skin, they should move further into the bomb shelter and sweep the dust off their shoes with a brush or broom. If the shoes are caked with mud or dust, they should be left in the reception area.

Because the fallout particles will fall down to the floor, decontamination of a person should begin with the head and end with the feet. Brushing off or removing the shoes will be the last step of decontamination before a person enters the safer parts of a bomb shelter.

Finding the Places with the Lowest Radiation Levels in the Bomb Shelter

After the announcement is made to the people in the bomb shelter that fallout has begun to come down outside, you (the RM) should 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.

It should be explained to the people, or at least to the bomb shelter Unit Leaders, that these locations were chosen on the basis of estimates and that places with lower radiation levels might be found by taking readings with the survey meter.

Mark the sketch of the bomb shelter to show the locations where you plan to take readings of the radiation levels. Some of these readings should be taken near walls, posts, or columns upon which you can tape a form showing your readings.

A general survey of radiation levels with the survey meter should be made as soon as possible after the gamma radiation reaches levels that can be detected inside the bomb shelter. Write down the readings, the times the readings were made, and the exact location for each reading so you can find the same spot when you check later. You may wish to mark the floor where you make your measurements and assign a number to each location.

At this time, when you are trying to find the safest places in the bomb shelter as quickly as possible, you should take readings only in those locations where you estimate the lowest radiation levels will be. For example, if you are in a basement bomb shelter you should not take readings on the first floor at this time. If you are in a skyscraper bomb shelter, there is not need to take readings near an outside wall at this time.

The first survey should be spread out to get a general picture of the best bomb shelter areas. Follow-up surveys should then be made to get a detailed picture of radiation levels in the areas where people are finally bomb sheltered.

While fallout is coming down, the radiation levels may be climbing fast. Inside the bomb shelter at the location that you have estimated to be the safest, your survey meter needle may be climbing as fast as one to five smallest divisions on the “X0.1” scale each minute. If you plan to make a detailed comparison between the readings at several locations, the reading at the final location may be quite a lot higher by the time you get to it than it was when you began to take readings.

You will not be able to tell whether the higher reading results from a lower FPF or from an increase in radiation levels at all locations of the bomb shelter. The readings would have to be taken in both places at the same time to show which location had the lowest radiation level. You can only be at one place at one time!

If your bomb shelter has two or more survey meters (most will not) and two or more RM’s, you may work out a simpler method by making readings synchronized by timepieces showing seconds or by the use of two-way radio, telephone, or cell phone communication between the RM’s. The meters should be compared at one location (identical radiation levels) before and after the measurement (the instruments may drift) to make sure they read the same or to compensate for different readings.

You should not wait until the radiation levels stop climbing to make your detailed follow-up measurements, because it might be several hours before the fallout stops coming down. To get a proper comparison of the radiation safety between different locations while the radiation levels are climbing rapidly (due to the buildup of fallout), you will need to use a special method for taking measurements. One of the simplest methods for taking such measurements is the Time-Averaging method described in the following section.

Another method, to be used if no survey meter is available, is to place a dosimeter at each location to be checked. All the dosimeters to be used should be carefully zeroed at approximately the same time before positioning them. You may have to wait several hours before significant differences in the readings are observed, because the smallest division on the dosimeter is 10 R. With the survey meter, you will be able to compare the radiation levels at several locations within just a few minutes by using the time-averaging method.

The Time-Averaging Method

The time-averaging method is 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. If only two locations are to be compared and only a few second are needed to get from one location to another, the time-averaging method need not be used. The readings obtained at the two locations may be compared directly in that case.

The time-averaging method is a way to estimate what the approximate radiation levels WERE at several locations at ONE particular time. It consists of taking readings at different locations BEFORE and AFTER one particular time, then averaging those readings to get the reading at that particular time.

If only two locations are to be compared (locations 1 and 2), a reading is first taken at location 1. A short time later, a reading is taken at location 2. After another short period of time of EQUAL DURATION, whether 30 seconds or one or two minutes, a reading is taken at 1 again. The two readings taken at 1 are then averaged (add them and divide by two) and compared with the reading at 2.

If three locations are to be compared (locations 1, 2 and 3) with equal time intervals of say, one minute between readings, the readings are taken at locations 1, 2 and 3 and then at locations 2 and 1 again, IN THAT ORDER. The order of measurements, 1-2-3-2-1, must not be changed. The two measurements at 2 are taken ONE MINUTE BEFORE and ONE MINUTE AFTER the measurement at 3, the middle or CENTRAL measurement.

The two readings at 1 are averaged, and the two readings at 2 are averaged to give approximations of what the readings would have been at those locations at the same time that the reading at location 3 was taken.

To use the time-averaging method, you will need a wristwatch or clock that shows seconds as well as minutes. You should have an assistant to help you move quickly through crowds of people, watch the time, and help keep track of measurements.

Remember that the survey meter does not respond instantly to the radiation it is measuring when the range-selector switch is turned to “X0.1” You will need to allow a few seconds at each location for the needle on the meter to reach its final reading. Do not move, jiggle, or rotate the survey meter while the needle is settling down.

The survey meter should be held about three feet above the floor or at about waist level and about two feet away from the body when taking measurements. If you are taking measurements in a ground-level or below-ground bomb shelter full of people, it is important that all the people sit or lie on the floor while you take the measurement.

If people are standing, they will shield some of the gamma radiation from your instrument, and your survey meter will then show a lower reading than it would if people were sitting or lying down or if the room were empty. If you used this reading to compare with readings in other locations that are empty, you might conclude that the room with the people in it is safer, although it may actually be more hazardous.

If you plan to compare the readings at several locations, start the first reading where you think the reading should be the lowest, which should be where the people are located. Begin the readings 20 - 30 minutes after the needle reads about 0.1 R/hr in the safest location, after you have made your first rapid, spread-out survey.

If you start in another location, you may find that when you get to the estimated safest location, the radiation level may still not be high enough to read on the meter. You will then have to repeat the measurements later.

The 20- to 30-minute waiting period will allow time for enough fallout to settle on the ground so the readings will not be influenced much by radiation from falout particles still in the air.

You may wish to use this period to choose the exact locations where you will take measurements, mark these locations on your sketch and at the actual spot, and prepare a sheet of paper or a page in the RM log so your measurements can be written in the correct place when you take them.

You should have an assistant with you while you make these preparations so he or she will know what to do when you are taking the measurements. An example of the time-averaging method for comparing seven locations is shown in the Table below.

Table: An example of the use of the Time-Averaging Method

LOCATION
Room Location
Name Number MEASUREMENTS
Survey Meter
Time Reading (R/hr)
Before/After Before/After (Total) TIME-AVERAGE
Radiation Rate (R/hr)
(total divided by 2) COMMENTS
G 1 1040/1054 0.41/0.74 (1.15) 0.575 Lowest Rate
A 2 1041/1053 0.73/1.19 (1.92) 0.96 One-minute delay
B 3 1043/1051 0.69/0.95 (1.64) 0.82
C 4 1044/1050 1.01/1.29 (2.30) 1.15
F 5 1045/1049 1.32/1.55 (2.87) 1.435
E 6 1046/1048 0.79/0.86 (1.65) 0.825
D 7 1047 0.96 0.96 Central Measurement

* Table below shows where these locations are in the basement of the apartment floorplan sketch.

Note: This example results from an imaginary situation at the apartment floorplan sketch (earlier in this chapter) in which the time-averaging method is used to compare the radiation safety of various rooms when radiation levels are rising rapidly. The numbers are presented here as they might be entered by the RM in the RM log. The location numbers are entered on the sheet before starting. The columns marked “Before” under both the “Time” and the “Survey Meter Readings” are filled in from top to bottom as the measurements are made, and then the columns marked “After” are filled in from bottom to top. The numbers in parentheses in the column marked “Total” are obtained by adding the “Before” and “after” survey-meter readings at a location. The time-average radiation rate at a location, except for the central measurement, is obtained by dividing the total by two.

Figure: Locations of survey-meter readings (Plain View) for time-averaging in the basement of the apartment are shown by dots and are identified by numbers in circles.

The RM for the bomb shelter in the apartment, introduced in the discussion earlier, used the time-averaging method to compare the radiation safety of the seven rooms in the basement. The locations where the RM made the measurements are shown in the Locations Survey Measurement Figure above.

People were packed together in Room G, where the RM made the first and last readings. The choice of locations where readings were taken and the order in which they were taken was made before fallout arrived. In the example, fallout arrived at the apartment at 1009 hr.

Note: Twenty-four hour time is used to prevent confusion between AM and PM. This time notation is used by airlines and the military services. The first two digits indicate the hour of the day, starting with zero at midnight, and the second two digits indicate the minutes after the hour. The 24-hr time in the afternoon is obtained by adding 12 to the 12-hr time in the afternoon (hours past noon). Thus, 1:10 PM (ten minutes past one) becomes 1310 hr, 2:20 PM becomes 1420 hr, etc. See Appendix for a table to convert standard time to 24-hr time.

The first radiation reading inside the bomb shelter was made at location 1 at 1020 hr, as shown in the Figure. A rapid survey throughout the basement roughly confirmed that Room G provided the best radiation protection. It was decided the first series of detailed measurements for time-averaging would begin at 1040 hr.

The survey meter was brought to each designated location with enough time allowed to hold the meter in position for 10 - 15 seconds before the reading was taken. The first reading was taken at 1040 hr and the last at 1054 hr. Readings at location 1 were made seven minutes before and seven minutes after the central reading was taken at 1047 hr at location 7.

Readings at location 2 were made six minutes before and six minutes after the central reading at location 7, and so on. While moving from location 2 to location 3, the RM was delayed by a disturbance between some occupants of the bomb shelter, so the reading at location 8 was taken at 1043 hr instead of 1042 hr as initially planned.

In order to maintain the same time interval between the “before” and “after” readings at locations 1 and 2, the “after” readings at those locations were delayed a minute to 1054 hr and 1053 hr, respectively, instead of 1053 hr and 1052 hr as initially planned.

The two readings made at each location (except where the central reading was made) were added and divided by two to give an estimate of what the readings would have been at those locations at the same time the central reading was taken (1047 hr) at location 7. These time averages are listed at the bottom of the table (above).

From these readings, it was confirmed that Room G (location 1) provided the best radiation protection in the basement of the apartment.

Note: The readings at locations 1 and 2 almost doubled between the “before” and “after” readings.

Another series of measurements for time-averaging should be made as soon as practical, within 20 minutes after the first series, to confirm the results of the first series of measurements.

In the first series of measurements for time-averaging shows that there is an unoccupied area of the bomb shelter where the radiation levels are significantly lower, say 20 percent, than the area where the people are located, notify the bomb shelter Manager, and also inform him or her that you are going to make another series of measurements to check your results.

The bomb shelter Manager may wish to double-check your results. If your second series of measurements confirms the results of your first series, then the bomb shelter Manager will need to consider the possibility of moving bomb shelter occupants to this new location.

A number of factors should be taken into account before the decision is made to move or not to move. If the new location offers only a slight reduction (less than 20 percent) in radiation levels, a decision not to move may be made for several reasons, such as:

1. There may be less space, less desirable space, and/or not enough ventilation in the new location.

2. The location of the new space may result in higher radiation exposures to occupants while they walk to restrooms or to eating facilities.

3. Fire escape routes may not be as good.

If the new location offers substantially lower radiation levels, a decision to move may be made in spite of such shortcomings, especially if it appears that the radiation intensity may climb to such high levels that the accumulated exposure may result in radiation sickness.

Even if the current fallout is so light that radiation sickness is not likely, the bomb shelter Manager may decide that the occupants should move in order to be better prepared for the possibility of additional fallout from future attacks.

If a sudden squall or weather front with high winds and heavy rain strikes the bomb shelter while you are in the process of taking readings for time-averaging, you may need to disregard your measurements and wait until the weather settles down before you try the readings again. You may not be able to tell whether a decrease in reading from one room to another from the second room being safer or from a decrease in radiation level because fallout particles are temporarily being blown and washed away. The reading may change because of a combination of these two causes.

You should compare the radiation levels between the different areas at lest every 12 hours, or whenever anything takes place that might move the fallout particles around, such as a heavy rain or windstorm. After the fallout has stopped coming down and the rates are not changing rapidly, it won’t be necessary to use the time-averaging method for making these comparisons.

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.

During the first rapid, spread-out survey of the room, you may have noticed that your survey meter readings were higher in certain places within the room. This variance could be the result of:

1. Uneven piling-up of fallout around and above the bomb shelter.
2. The layout of rooms, walls, and stairways.
3. Openings in walls.
4. The use of lighter-weight construction materials in some places.

It may be possible to use the survey meter to locate a specific place where gamma radiation is entering or “leaking” into the bomb shelter to cause higher readings. When such an area is identified, any available materials should be used to cover it in order to reduce the level of radiation.

For the measurements you made to find the safest places in the bomb shelter, you held the survey meter out from your body about two feet, and, in crowded rooms, people were asked to sit or lie down, so their bodies would cause less interference with the reading. But for finding gamma leaks, you can make use of that interference.

The survey meter responds to gamma rays almost equally as well from all directions. If gamma rays come in greater intensity from one particular direction, you can’t detect the direction just by pointing the instrument toward it. But you may be able to use the shielding provided by your body and others to reduce the radiation coming from the direction where you and others are grouped together; the survey meter will then respond more to radiation coming from OTHER directions than from where you are standing.

For example, if a group of people crowd around a survey meter and leave an opening in only one direction, the reading on the instrument will be caused mostly by radiation coming through the opening, providing there isn’t a lot of radiation coming down through the ceiling or up from the floor. This method has not been tested in practice, and you may be able to improve it as you try it. Also, you may find that it does not work in your particular circumstances.

The measurements are made as follows:

1. Select a starting place somewhere along a wall, at a corner, at a door or window in the bomb shelter room.

2. Mark that location on the floor or on the wall with a piece of tape or by writing directly on the surface. Use a letter to designate the room and a number to designate the place where the measurement is taken in the room. For example, the first measurement in the apartment example mentioned earlier would be taken at a spot marked “G-1”, because the room marked “G” on the bomb shelter floorplan sketch is the room where the people are bomb sheltered.

3. Hold the survey meter against your waist and face the wall with the survey meter against the wall or a few inches from it. Have an assistant write down the location designation, the time, and the survey meter reading in the RM log or on a sheet of paper.

4. Move three or four feet to your right or left (it doesn’t matter which direction you go as long as you keep going in the same direction) along the wall and mark the location with the same letter as before, but with the number “2” (“G-2” in the apartment, for example).

5. Hold the survey meter as before, read the dial, and again record the location, time, and reading.

6. Continue the measurements until you have gone completely around the room and have reached your starting point.

It is important that you take readings in the middle of doorways, windows, other openings or irregularities in construction. You may have to break your pattern of equal spacing between measuring locations in order to obtain these special measurements.

You will very likely be taking these measurements while fallout is still coming down. As you go around the room, the readings will become higher and higher in a fairly regular pattern unless you find a place that appears to be a “leaky” area.

As you approach such a place, the readings will increase more between readings than before, and as you go beyond the area, there will not be as much of an increase in the readings; in fact, there may be a decrease in the reading. Because the radiation levels will be increasing at a fairly regular rate under most conditions, you should try to maintain an equal time interval between measurements as you go around the room.

A time interval of 20 or 30 seconds may be about right. Don’t try to go too fast or you might not be able to keep up with the schedule. If you notice an area that appears to be “leaky”, don’t slow down. Continue with your measurement schedule around the room. You may need to ask the bomb shelter Manager to give you some assistance to make sure that nothing will interfere with your schedule of measurements.

After you have completed your measurements around the room, examine the numbers your assistant wrote down for indications of “leaky” areas. If you find any indication of such areas, tell the bomb shelter Manager. You should also tell him or her that you will need the assistance of several people to help you decide whether there is an actual leak of gamma radiation at the locations or whether the readings are a result of the way the scattered gamma radiation happens to be focusing at that location.

You will need to repeat your measurements in the vicinity of the suspected area, starting at the location just before the increased numbers were recorded, and make measurements, again at regular time intervals, until you have passed the suspected area; but this time the people in the vicinity of the area should be asked (possibly by the bomb shelter Manager, depending on the situation) to stand and press fairly close to you while you make each measurement.

The shielding that is provided by their bodies will block out scattered gamma radiation that comes from different directions inside the room. If the readings still show an increase as you approach the area and a decrease as you go past it, there is a “leak” of gamma radiation in the area you are surveying. This leak could come from the area in front of you, or it could come from above (or below, if you are in an underground bomb shelter). If the readings no longer show an increase as you approach the area and a decrease as you go past it, the previous reading (without the people standing closely behind you) was caused by the pattern of scattered gamma radiation in the room, not by a gamma leak.

If you are trying to find gamma leaks in an empty room, you may use the “front-to-back” method. In this method, your own body is used as a shield to try to find from what direction the gamma radiation is coming. Again, this method has not been tested in practice, and you may be able to improve it as you try it, or you may find that it won’t work in your particular circumstances.

To try to find a gamma leak, hold the survey meter tightly against your stomach and face the area where you expect extra gamma radiation to be coming from. If you are working with the range-selector switch turned to “X0.1”, wait a few seconds before taking a reading. This reading will be called a “front” reading. Turn around so your back faces the suspected leak, and with the survey meter still held tightly against your stomach, take another reading.

This reading will be called a “back” reading. If there is more radiation coming from the direction you faced for the first reading than from the opposite direction, the front reading will be higher than the back reading. As you slowly turn around, you may notice that the meter needle goes through the lowest reading when you are facing a particular direction. The radiation leak is then at your back.

Repeat these “front-to-back” readings at different places and directions until you have a fairly good idea of where the extra radiation is coming from. The difference between the front and back readings may be made greater, if the radiation is actually coming from one direction more than another, by having several others stand alongside and behind you when you make the measurements. The extra shielding provided by their bodies will take out more of the radiation from the rearward direction, which is what you want to do while making this type of measurement.

When you are fairly certain you have found a radiation leak, tell the bomb shelter Manager. A work party should be organized to build a gamma barrier to cover up the leak. If you had the time and opportunity, you should have gathered materials for this purpose before fallout arrived, as discussed earlier. Work on construction of this barrier should begin as soon as possible, before the radiation climbs to higher levels.

The barrier can be improvised from any materials on hand. If you have lumber, nails, and carpenter’s tools available and have hauled the piles of earth or sand into the bomb shelter before fallout arrived, you may be able to construct a very good barrier. Stacks of bricks will also make good barriers. If these materials aren’t available, items such as furniture, books, magazines, newspapers, and water containers may be used.

While the barrier is being constructed, do not forget to take the regular readings which tell whether the radiation levels are rising or falling. Write these readings on a piece of paper or on the survey meter readings form. Then, tape or tack it to a wall or post near the place where the reading was made.

After the barrier is constructed, take several measurements of the kind you took to find the leak, to see if the radiation leak has been covered up. If you found the leak by taking a series of measurements from one side of the area to the other, with several people standing closely behind you, you should repeat that kind of measurement. You should be able to tell by these measurements if the barrier has improved the shielding in the leak area, or if more work is required on the barrier.

If there is no change in these readings from your earlier readings, there is a possibility that the barrier may have missed the area through wich the extra gamma radiation is passing. In this case, more work should be done to locate the leak and construct the barrier.

Again, let us look at the apartment floorplan example. The bomb shelter sketch is show earlier in this chapter. In making a detailed survey of room G, the RM found readings in two places which were 15 - 30 percent higher than at other places in Room G. One location was by the closet under the stairs and the other location was by the open door to Room F.

The reading by the stair closet was about 15 percent higher than elsewhere. The radiation was assumed to be coming from above, through the stairways. The bomb shelter Manager, RM, and Unit Leaders decided not to pile material on the stairs because the occupants would then have trouble getting out if there were a fire.

Instead, they blocked off an area by the closet and planned to rotate people in and out of that area so the radiation dose would be evenly spread out among people in radiation sensitivity category Y/A (see Table near front of this Chapter).

The reading by the door to Room F was about 30 percent higher than elsewhere. in the time-averaging readings, Room F (location 5) was found to have a higher reading than the other rooms, as shown in the Time-Averaging Table above. This higher reading was expected, because in improving the radiation shielding of the bomb shelter, all windows around the basement had been covered except two in Room F.

Materials were not available to construct baffles around these windows, such as shown in the Figure in the section, “Openings and Ventilation” earlier in this Chapter. Instead, a wall of earth was piled up a few feet away from the window to shield the window against gamma radiation coming from fallout on the ground beyond the earth barrier.

It was considered absolutely essential to leave these windows open to provide cooling for the people packed in Room G. Fresh air was coming in from those windows, passing through the open door to Room G, and flowing out the door by the stairs.

After examining the sketch of the floor plan, it was decided that a hole could be knocked in the wallboard partition to allow air to fow between Rooms C and F and the door between Rooms C and G could be left open. The door between Rooms G and F could then be closed and covered with a barrier.

The hole between Rooms C and F was made on the far side from the door by the outside wall, so the gamma rays from the two open corner windows would not have a direct open path to the door between Rooms C and G. The door between rooms F and G was closed, and a stack of bricks was built in front of it.

These measures reduced the radiation in Room G near the door to Room F to levels that were about the same as elsewhere in the room (except by the stairway closet). Ventilation became much better for the people along the north half of the room, but the people in the hall leading to Room F soon complained about lack of ventilation.

The bricks in front of the door to Room F were restacked so there were one- to two-inch gaps between the bricks on the bottom four layers. The door was propped open a few inches so air could flow through the gaps left between the bricks. Another wall of bricks, only six layers high, was constructed about six inches back from the door-high stack of bricks, to block off gamma rays coming through the gaps.

Gamma Shielding by People in the Bomb Shelter

The table in Chapter 3 shows the human body has a density of 0.4 relative to concrete. 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.

If the estimated or projected radiation exposures look as if they may become high enough to cause radiation sickness and other ways to decrease or avoid radiation exposure are not possible, this shielding method could be used. It would be expected that this extreme measure of providing shielding would be used only during the first 24 hours after fallout arrives, when the radiation hazard is by far the most severe.

Ordinarily, people in most bomb shelters will be sitting or reclining on the floor most of the time. More gamma radiation will be blocked if the people are standing up, because their bodies will then absorb some of the gamma rays coming from the ceiling as well as those coming from the walls.

This shielding, provided by people who are standing, could provide an extra measure of protection for children, mothers with infants, and pregnant women. By forming a two-or three-person-deep circle around the more radiation-sensitive occupants of a bomb shelter, these individuals can possibly be spared high radiation exposures that would be especially detrimental to them. The survey meter should be used to find the arrangement of people that provides the best shielding.

Children and infants may be provided additional protection from overhead radiation by placing them underneath beds, desks, tables, or other suitable items. People with less radiation sensitivity may then sit or lie on top to provide additional shielding.

The RM may verify the shielding effect provided by people by reading the survey enter at different levels in the middle of a room full of people who are standing up. In basement bomb shelters, where no gamma radiation comes up through the floor, the survey meter reading at the floor might be as much as ten times lower than the reading at waist height at the wall. The radiation may even be undetectable at the floor. In high-rise bomb shelters where much of the gamma radiation comes in horizontally through the walls and some comes up at different angles through the floors, this effect won’t be as dramatic.

Keeping Track of Everyone’s Radiation Exposure (Group Dosimetry) in the Bomb Shelter

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.

In most bomb shelters the radiation levels will be different as you move from one place to another. In these bomb shelters each Unit Leader should have a dosimeter. The readings on the Unit Leader’s dosimeter will be used to fill out the radiation exposure record of each member of the unit. For this reason, every member of the unit should stay close to the leader, especially during the first 24 hours after fallout arrives. This method of estimating individual exposures is called Group Dosimetry.

If any member of the unit needs to make an urgent trip to some area where the radiation level is higher and for a length of time such tat the person’s radiation exposure might be a few roentgens higher than the rest of the unit, special arrangements should be made. The bomb shelter Manager and RM should be consulted if the trip is unusual. An extra entry should be made on the individual’s radiation exposure record for such trips.

Trips to restrooms and drinking fountains in areas of higher radiation levels should be limited in number and length. The Unit Leader should make about the same number of trips as other unit members at about the same times for the same length of time. The dosimeter should be worn by the Unit Leader on these trips to get an idea of how much exposure is received during these trips. If some members need to make additional trips, the extra exposure should be estimated by the Unit Leader, with help from the RM if necessary, and entered on the members’ radiation exposure records.

You, the RM, should very carefully monitor your own exposure and make forecasts on your future exposures so you will not exceed the limit of exposure set in Row A of the Penalty Table (below). Your experience and training make you very valuable to the occupants of the bomb shelter.

A dosimeter hung on the wall or a post at eye level or higher will show a higher radiation exposure than a dosimeter carried on a person in the same area. The person’s body shields the dosimeter from some of the gamma radiation. If the person wearing the dosimeter is surrounded by many people who are standing up, the reading on that person’s dosimeter will be even lower because of the gamma shielding provided by the people’s bodies.

During the first 24 hours after fallout begins to come down, entries should be made every 4 hours in each person’s radiation exposure record. The Unit Leader should check each entry on each record kept in his unit. The RM should spot-check records throughout the bomb shelter and look for entries which seem too high or too low. Such entries may be due to faulty instruments or to shielding conditions which the RM should know about. It is important that these situations be corrected as soon as possible.

Sample radiation exposure records from the apartment example (earlier) are shown in the Figures below. The radiation exposure record in the the first Figure shows what a dosimeter would read if it were mounted at location 1, where survey meter readings were taken earlier. The radiation exposure record taken from dosimeters clipped to the clothing of adults on the edges of Room G would have entries which may be less than 75 percent of the entries in the first figure, due to the shielding effect of their own bodies and others. The entries on records of those in the interior of the room would be even lower.

In the second Figure the radiation exposure record is shown for John Doe, an infant. His radiation sensitivity category is “Child”, as listed in the Radiation Sensitivity Category Table near the beginning of this Chapter.

This record was maintained by his father, James Doe, who was made the leader of the bomb shelter unit in which the Doe family was placed. The radiation levels in the apartment started to climb a second time at 1645 hr on July 5, 1989, as shown by the survey meter readings in the first Figure, indicating the arrival of another cloud of fallout.

By 1745 hr the radiation level had reached 5 R/hr at location 1 and was still climbing. It was decided that human body shielding would be used to protect those in the first two radiation sensitivity categories. This special shielding, involving all the people in the bomb shelter, began at 1800 hr, as shown on the radiation exposure records in the second Figure, and reduced John Doe’s exposure to less than half of what it would have been without this special shielding.

On the second day, 24 hours after fallout arrived, special shielding was terminated, but partial shielding for John Doe was provided by the members of his bomb shelter unit. The next 13 entries were made on a daily basis instead of every four hours. On July 18, the occupants of the apartment were relocated to a bomb shelter in an area with much lighter fallout.

After Fallout Has Stopped Coming Down near the Bomb Shelter

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.

The highest radiation exposure at a given place in a bomb shelter will accumulate during the first 24 hours after fallout arrives. After these first 24 hours have passed, there are two general rules which can be used to forecast the radiation exposure, as follows:

Rule 1: The radiation exposure at a given place during the entire week following the arrival of fallout is unlikely to be more than 2 1/2 times the exposure during the first 24 hours.

Rule 2: The radiation exposure at a given place during the entire month following the arrival of fallout is unlikely to be more than 3 3/4 times the exposure during the first 24 hours.

If the fallout comes from distant ground bursts and doesn’t arrive at your bomb shelter until 24 hours or more after the explosions, the numbers in Rules 1 and 2 may be slightly greater. For example, if the fallout takes about 36 hours to get to your bomb shelter, the number 2 1/2 in Rule 1 will be increased to 3.0 and the number 3 3/4 in Rule 2 will be increased to 4.5.

If the fallout takes about 48 hours to get to your bomb shelter, the corresponding numbers will be increased to about 3 1/3 and 5 1/3, respectively. When the fallout takes a long time to arrive, the radioactivity will have decayed a great deal. If the fallout comes from a large number of ground bursts of large-yield weapons, as might take place on military targets, the fallout may still be hazardous even though it may take 48 hours to arrive at your bomb shelter.

If the fallout comes from closer ground bursts and arrives at your bomb shelter in 12 hours or less after the explosions, the numbers in Rules 1 and 2 will be less. More than half of the total exposure in a week will accumulate in the first 24 hours after fallout arrives. The number 2 1/2 in Rule 1 will be decreased to between 1 1/2 and 1 3/4, and the number 3 3/4 in Rule 2 will be decreased to between 1 3/4 and 2 /12.

Exposure forecasts can be made using the seven-ten rule described earlier when all the fallout is the same age, when the time of the explosion is known fairly well, and when there are no weathering effects. These circumstances are unlikely in a modern, full-scale nuclear war. The Radiological Defense Officer in the local Emergency Operating Center (EOC) may be able to provide further guidance on estimated radiation exposure.

The general rules given above can be used to make forecasts for the possibility of radiation sickness among a group of people in a given bomb shelter. If the radiation exposure of an average adult is 60 R or less at the end of the 24 hours after fallout arrives and that person remains in the same place, that person’s accumulated radiation exposures will be expected to be less than 150 R in one week and less than 225 R in one month, providing no additional fallout arrives.

According to the Penalty Table (below), that person should require no medical care in the first week, but the exposure in a month would exceed the limits set in the Penalty Table for not requiring medical care.

If it appears that the radiation exposure of average adults will be more than a pre-selected value, such as 60 R, at the end of the first 24 hours after fallout arrives at the bomb shelter, the local EOC should be notified. Some emergency action may be possible which will reduce the accumulated radiation exposure and thus prevent radiation sickness among these people.

Again, let us look at the made-up example provided by the apartment bomb shelter. The radiation exposure record for a dosimeter mounted at location 1 is shown in the first Radiation Exposure Record (above), and the survey meter readings for that location are shown in the Survey Meter Readings Figure. The first detection of fallout was made outside the bomb shelter at 1009 hr on July 5. It was estimated that this fallout resulted from many large-yield ground bursts on military targets about 250 km (150 miles) upwind during the night before, at around 2100 hr on July 4.

The radiation level from this fallout reached a maximum value at around 1330 hr on July 5, indicating that most of the fallout destined for the apartment bomb shelter from these explosions had reached the ground by this time. The fallout took 13 hours to reach the apartment bomb shelter. It kept coming down for about 3 1/2 hours.

A distant explosion was heard at 1400 hr on July 5, in the direction of a city located about 50 km (30 miles) upwind. The fallout from this explosion began to arrive at the apartment bomb shelter at about 1645 hr, an hour and 45 minutes after the explosion was heard. This fallout was more radioactive than the older fallout from the distant explosions. Being fresher, it would decay faster. This fallout kept coming down for about 2 1/2 hours and added to the radiation levels which were already there from the older fallout.

At the end of the first 24 hours after fallout arrived, at 1000 hr on July 6, the accumulated radiation exposure by the dosimeter at location 1 was 81 R, as shown in the Radiation Exposure Record (above). After one week, the accumulated radiation exposure was 174 R, 2.15 times the exposure during the first 24 hours. After one month, it was 226 R, 2.79 times the exposure during the first 24 hours.

The Penalty Table

Medical Care Will Be Needed By:

Accumulated Radiation Exposure (R) in Any Period of: a b c
One Week One Month Four Months
A None 150 200 300
B Some 250 350 500
C Most 450 600 ----

Note: The Penalty Table here is taken from Radiological Factors Affecting Decision-Making in a Nuclear Attack, National Council on Radiation Protection and Measurements, Report No. 42.

An adult will not normally need medical care when the whole body is exposed to the quantities of radiation listed in Row A of the Penalty Table if the exposure is spread out over the listed periods of time. Rows B and C are intended to be used for making decisions on performing urgent missions which may involve the risk of increased radiation exposure.

Each person can tolerate a certain amount of sunshine on bare skin in an afternoon without getting a painful sunburn. Similarly, each person can be exposed to a certain amount of whole-body gamma radiation within a certain period of time without getting sick. The Penalty Table shows in Row A what exposures might be received by an average adult without requiring medical care, when the exposure is spread out over different periods of time.

Infants, small children, and pregnant women should be given special consideration when possible, because they are more likely to have radiation sickness at lower levels of radiation exposure than other individuals of the general population.

For most bomb shelter occupants, the exposures in Row A should not be exceeded. If the radiation levels reach 10 R/hr in the bomb shelter and continue to climb, it is possible that the accumulated exposure in one week will be greater than 150 R. In this case, the local EOC should be notified. Some emergency action may be possible which will reduce the accumulated radiation exposure and thus prevent radiation sickness in the bomb shelter.

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. The choice of the numbers was based on judgment derived from extensive clinical radiotherapy experience, pathological studies of radiation-accident victims, and laboratory experience with numerous large and small animals. There is no directly applicable disaster or laboratory experience involving humans that clearly supports the choice of all of the numbers in the Penalty Table.

There is also no satisfactory biological model or mathematical formula relating radiation effects (of the type considered here) to exposure rates and durations that provides a satisfactory basis for deriving the amounts of exposure indicated in the table for time periods greater than one day. These are the best numbers available at the present time for this purpose.

Three examples of the Penalty Table are given here:

Example 1 - It would be best if everyone’s radiation exposure could be kept as low as possible, but due to wartime conditions, some individuals may have to spend some time in areas of higher radiation levels. Suppose you are trying to limit their radiation exposures to levels resulting in low risk. The numbers in Row A of the Penalty Table above apply in this case. According to these numbers, it would be necessary to limit the total radiation exposure of individuals to less than 150 R in any one week (column a), 200 % in any one month (column b), and 300 R in any four-month period (column c).

For example, if individuals were exposed to the one-week limit of 150 R (column a) within the first week, then the limit for additional exposure during the following three weeks of the first month, to keep within the one-month limit (column b) would be 200 R - 150 R = 50 R.

This additional exposure of 50 R could be received at any rate (for example, by going outside the bomb shelter into areas of higher radioactivity) during the following three weeks of the first month, without exceeding the one-week or one-month limits in the Penalty Table.

However, if this additional exposure of 50 R were received, for example, within the second week, then the individuals would have to be kept completely free of further exposure (which may not be possible) during the remainder of the first month to keep within the one-month limit for Row A (200 R). Similarly, if the individuals were exposed to the limit of 200 R in the first month, without exceeding 150 R in any one week of that month, the limit of additional exposure for the following three months of the first four months (colum c) would be 100 R, for a total of 300 R (200 R + 100 R) in four months.

Example 2 - Suppose you need to conduct operations at the intermediate level of radiation exposure, involving significant medical risk (Row B), justified by highly critical emergency situations. The decision to conduct such operations must involve the bomb shelter Manager.

In this case, the decision-maker may find it necessary to allow greater exposure than one or another of the limits indicated in Row A but would be constrained whenever possible by other limits in Row A and always by limits in Row B of the Penalty Table.

For example, if individuals who have been exposed to 150 R within the first week are required in some emergency to be exposed to an additional 200 R during the remainder of the first month (for a total of 350 R in the first month), it is desirable, if possible, that the one-week constraint for Row A (column a) be observed by allowing no more than 150 R of this additional exposure during any one week within that month, even though the one-month limit (200 R) and four-month limit (300 R) for Row A will have been exceeded and the one-month limit (350 R) for Row B will have been reached.

If it is not possible to keep within any of the constraints for Row A, then the Row B constraints have to be applied. In other words, you try to keep exposure in any one week as far as possible below 250 R and to limit the exposure during the first month to 350 R. Any additional exposure after this first month must be kept as far as possible below the additional 150 R which would attain the four-month limit of 500 R (Row B).

As in example 1, the decision-maker could schedule exposures in a variety of ways within the constraining limits to meet the work required by the problem at hand.

Example 3. Suppose you need to conduct operations at the high levels of medical risk (Row C), justified only by extremely critical emergency situations. Again the decision to conduct such operations must involve the bomb shelter Manager. Those activities that could result in saving a significant number of lives may call for the deliberate exposure of some persons at the highest constraint levels, where radiation sickness and a 50 percent probability of death are expected (Row C). If such situations arise, the decision-makers would use for guidance Row C of the table in a manner similar to that discussed for the low- and intermediate-risk rows (A and B) in examples 1 and 2.

After a time of no more than two weeks, it should be possible to move people from areas of high radiation levels to areas of lower radiation levels. In the areas of lower radiation levels, people should be able to get outside and work for different lengths of time as long as their radiation exposures stay within the limits of Row A of the Penalty Table.

The “one-month” and “four-month” columns of the Penalty Table are intended primarily for these situations. No one should have to stay totally confined inside the bomb shelters for more than two weeks, although people may have to live in them in some locations for longer periods.

Checking Radiation Levels Beyond the Immediate 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. The purpose of this exploration is to:

1. Get an idea how dangerous the levels are outside the immediate bomb shelter area.
2. Estimate the risks in emergency operations.
3. Forecast when people could leave the bomb shelter for short periods and when they could move to safer areas if needed.

Your experience and training make you very valuable to the occupants of the bomb shelter. You should very carefully monitor your own exposure and make forecasts on future exposures so you will not exceed the limit of exposure set in Row A of the Penalty Table.

If you used the time-averaging method to find the safest location in the bomb shelter and the fallout pattern hasn’t been shifted by wind or rain, you may use the results of those measurements to estimate the radiation levels in the other rooms which you checked, by using the Ratio Method.

Suppose you stayed near location 1, your “home base”, during the first 24 hours after fallout arrived. Now you want to find out how high the radiation level is at location 5. Suppose you included location 5 in your time-average comparison. Then you can estimate the present reading at location 5 by first finding the ratio of the time-average reading at location 5 to the time-average reading at location 1. Then multiply this ratio times the current reading at location 1 to get the current reading at location 5. In other words,

Current read = (Time-avg reading at location # 5) x Current reading at location # 5 (Time-avg reading at location # 1) at location # 1

The measurements at the apartment bomb shelter will be used as an example. Suppose we would like to know what the survey meter reading wuold be at location 5 in the apartment bomb shelter at 2000 hr on July 5, without actually taking the survey meter to the location. We have been making measurements regularly at location 1, as shown in Radiation Exposure Record (above). We have the set of time-average measurements that were made earlier for seven locations, including locations 1 and 5, as listed in the Time-Averaging Table (above).

To get the current reading (at 2000 hr) at location 5 without taking a survey meter to that location, the following steps are taken:

1. The current reading (at 2000 hr) at location 1 is found to be 6.0 R/hr.
2. The time-average reading at location 5 was 1.435 R/hr.
3. The time-average reading at location 1 was 0.575 R/hr.
4. The ratio of the time-average reading at location 5 to the time-average reading at location 1 is 1.435/0.575 = 2.5.


5. The current reading at location 5 is estimated by multiplying the ratio obtained in setp 4 times the current reading at location 1, which yields 2.5 x 6.0 = 15 R/hr.

If more than one set of time-averaging measurements has been made, be sure to calculate the ratio with readings that were made in the same set of measurements.

Once the ratio of the time-average readings has been caluclated, that same ratio can be used to estimate the reading at the remote location at any other time, assuming that the fallout pattern hasn’t been shifted by rain or wind.

For example, the estimated reading at location 5 in the apartment bomb shelter at 2100 hr would be 2.5 times the reading at location 1 at that time, which is 5.5. The estimated reading at location 5 at 2100 hr would be 2.5 x 5.5 = 13.75 R/hr.

You may use the ratio method to estimate the radiation levels; first, at various strategic locations inside your bomb shelter building and, later, at various locations outside your building. First take a reading at your home-base location. Then take the survey meter (wear a dosimeter) to the strategic location and take a reading there. You will not need to use the time-average method after 24 hours after the last particles of fallout have arrived because the radiation levels will be decreasing slower than 1 percent per minute. The ratio of the reading at the strategic location to the reading at the home base can be used to estimate readings at the strategic location by multiplying that ratio times the home-base readings.

As an example, the RM at the apartment bomb shelter measured 2.1 R/hr at location 1, the home base, at 1000 hr on July 6. The Rm took the survey meter up the stairs and made a quick trip into the lobby of the apartment bomb shelter, where the survey meter reading was 85 R/hr. The ratio of the lobby to home-base reading was 40. By 1000 hr on July 7, the home-base reading was 1 R/hr. The ratio of 40 was used to estimate that the radiation level in the lobby at that time was 40 R/hr.

At that time the RM took the survey meter upstairs and out to the street in front of the apartment bomb shelter, where he measured a radiation level of 105 R/hr. His dosimeter showed an increase of 2 R for this trip, which he made as quickly as possible. The street to home-base ratio of readings was thus determined to be 105.

Leaving the Bomb Shelter

When the exposure rates outside the bomb shelter are known, use the Permissible Activities Table (below) as a general guide for permissible activities.

Table - General Guide for Permissible Activities Outside the bomb shelter

If the outside exposure rate (R/hr) is: Permissible Activities: More than 100 Outdoor activity may result in sickness or death. Occasions which might call for outside activity are (1) risk of death or serious injury in present bomb shelter from fire, collapse, thirst, etc., and (2) present bomb shelter is greatly inadequate - might result in fatalities - and better bomb shelter, available for occupancy, is known to be only a few minutes away.

10 - 100 Time outside of the bomb shelter should be held to a few minutes and limited to those few activities that cannot be postponed. All people should remain in the best available bomb shelter no matter how uncomfortable.

2 - 10 Periods of less than an hour per day of outdoor activity are acceptable for the most essential purposes. bomb shelter occupants should rotate outdoor tasks to distribute exposures. Outdoor activities of children should be limited to no more than 10 to 15 minutes per day. Activities such as repair or exercise may take place in less than optimum bomb shelter.

0.5 - 2 Outdoor activity (up to a few hours per day) is acceptable for essential purposes such as fire fighting, police action, rescue, repair, securing necessary food, water, medicine, and blankets, important communication, disposal of waste, exercise, and obtaining fresh air. Eat, sleep, and carry on all other activities in the best available bomb shelter.

Less than 0.5 No special precautions are necessary for operational activities. Keep fallout from contaminating people. Sleep in bomb shelter. Always avoid unnecessary exposure to radiation.

Decisions on how much exposure may be allowed should be based strictly on the Penalty Table. Unit Leaders should continue to keep close track of the radiation exposure of each member until the bomb shelter is no longer required. If the bomb shelter is vacated and people are moved to other bomb shelters, it would be preferable if units remained together. Exposure records must go with the individuals to whom they belong.

If the fallout is relatively young (two or three hours since fallout stopped coming down) and the radiation levels are decaying rapidly, greater relaxation of bomb shelter control can be tolerated than indicated in the Permissible Activites Table. Conversely, if the fallout is relatively old (several days or weeks), more rigid control would be required.