In August 1959 the prototype shelter was completed, and simulated occupancy tests were begun. I will describe this program in some detail in a moment. These simulated occupancy tests were tests that used 100 simulated shelterees to establish the ventilation adequacy.

In November 1959 we conducted a 2-day preliminary human occupany test in which 18 people lived 2 days in the shelter to check out the equipment and our experimental plans for larger tests of this type. In December 1959 we held our first full-scale occupancy experiment, and this test was one in which 100 male volunteers lived 14 days in the shelter.

In April 1960 we conducted a firestorm experiment in which 300 tons of fuel on 4 acres around the shelter were burned to find the protection needs under mass-fire conditions.

During May and June of 1960 there was a continuation of the simulated occupancy tests which added data on the ventilation needs. In July 1960 we held our second full-scale occupancy tests in which 100 male volunteers lived in the shelter 5 days during hot weather. In September 1960 we accomplished a radiation shielding experiment in which a radiation source was used to check the shielding afforded by the newly designed entrance and exhaust ventilator.

In November 1960 we held a mixed population shelter test in which 100 men, women and children lived 2 days in the shelter.

Since January of this year we have been working on a fallout ingress experiment which is designed to see if filters are necessary in the ventilation system, and this experiment is still in progress.

PERFORMANCE CRITERIA AND DESIGN CHARACTERISTICS

I feel it is important to reiterate the characteristics that we were trying to incorporate in this shelter.

We have considered shelter performance criteria as consisting of two categories: protective criteria and operational criteria.

The requirements initially established in this program were, as far as protective criteria, radiation protection: a reduction factor of 1,000 for gamma radiation from fallout. Necessity for filtration of air supply was uncertain.

Mr. HOLIFIELD. In other words, there is some doubt that it is necessary?

Mr. STROPE. Yes. I will cover this in a moment in greater detail, Mr. Chairman.

For mass fire protection, we assumed a closure to the outside atmosphere would be required for a period of 24 hours.

For blast protection we assumed a closure during a red alert period with the boundaries proof against either 10 or 35 pounds per square inch blast overpressure. We also required that an emergency exit be provided in addition to the normal entrance.

The operational criteria we used were as follows: The time to load the shelter to rated capacity was not to exceed 5 minutes.

The space allotted per person was to be 12 square feet gross floor

area.

The period of occupany for which the shelter was to be stocked was 14 days maximum.

The environmental limits were for normal occupancy, that is, while one was in the shelter under fallout conditions but not expecting

an attack itself; ventilation sufficient to maintain normal oxygen and carbon dioxide concentrations, and an effective temperature of not more than 85°; for emergency closure conditions, that is, under attack, blast, or mass fires, facilities to maintain oxygen concentration not less 14 percent; carbon dioxide concentration not more than 3 percent; and the effective temperature not more than 90°.

We were to provide food at 2,000 calories per person per day for 14 days. We were to provide water at a minimum of one-half gallon per person per day, and we also looked at the situation where we provided 1 gallon per person per day.

As far as accommodations go, we set a requirement for sleeping accommodations, eating accommodations, and sanitary facilities; lighting was to be sufficient to permit movement of persons, with some areas having sufficient illumination to permit reading, and similar tasks.

Emergency equipment was to consist of a first aid kit, emergency lights, simple tools, radiation detection devices, and a battery-powered AM radio receiver for monitoring the conelrad broadcasts; auxiliary power generators, two-way radios, and periscope were considered desirable but optional.

SHIELDING FACTOR OF SHELTER

The radiation protection requirement of a factor of 1,000 reduction was based on two considerations:

First, that the radiation exposure in the shelter should be limited to a nominal amount to allow allocation of most of the allowable exposure to the postshelter phase. This is a consistent position that the Naval Radiological Defense Laboratory has adopted: that the problems that will be faced in the recuperative phases are sufficiently grave that, if you are going to build shelters, you should build them so that people come from the shelters to the postshelter activities without a legacy of radiation exposure of any significance.

Secondly, we felt that a high-performance requirement would minimize possible future obsolescence of the shelters as weapons changed and improved.

The mass fire protection requirement of 24-hour closure was based on the best available information as to the time period during which outside air would be hazardous as the result of mass fires near the shelter.

BLAST PROTECTION

The blast protection criteria were selected as reasonable protection levels outside the close-in region where high initial radiation levels would defeat the radiation protection afforded by the shelter. I would like to expand for a moment on this matter.

Mr. Chairman, you have mentioned a number of times that the problem of blast protection is a relative one, and I would like to second this as being absolutely true.

In this case, where we are studying fallout shelters, the least shelter we are considering is a 10-pounds-per-square-inch blast shelter.

It is a fact that any fallout shelter provides some blast protection, and while it is true that by going out of your way you could make this blast protection very minimal; on the other hand, even by considering

it in a very modest way you could afford quite appreciable blast protection.

The reason why we have not considered higher blast protection than 35 pounds per square inch is because shelters of higher protection would survive very close to the fireball of the weapon, where initial radiation effects would be very great. This would force the shelter deeper for protection, and at that point types of shelters other than this cut-and-fill-type shelter that we are dealing with-in which you dig a hole in the ground and put in the shelter and cover it over again-would become competitive and probably preferrable, and I am speaking of tunnel-type structures.

So we limit ourselves in these considerations to what we regarded as a minimum fallout shelter, which allowed 10-pounds-per-squareinch blast protection, which is still quite significant, and an alternative at 35 pounds per square inch.

The operational criteria were developed on the basis of an extensive literature search for pertinent requirements for an effective and habitable shelter, yet of minimal nature. In other words, we are not trying to maintain the present standard of living under thermonuclear attack.

Mr. HOLIFIELD. Getting back to the partial blast protection, in order that the committee might understand the meaning of 5 pounds per square inch and 10 pounds per square inch and so forth, would it be possible for you to give us a table of the effects of 5 and 10 and other relative amounts on ordinary structures?

What would happen, in other words, if a house had a 10-poundsper-square-inch pressure put against it, in a shock wave; what would happen if it were 5? Would it collapse the walls? Would the doors be blown in? Of course, the windows would be. Give us some kind of a feeling for that amount of protection.

Mr. STROPE. Yes, I can do this, Mr. Chairman, extract this information from the "Effects of Nuclear Weapons."

I recall that complete destruction of houses occurs at the order of 5 pounds per square inch; that 10 pounds per square inch obtains from a 1-megaton weapon at the order of 2 miles from the detonation, and 35 pounds per square inch at the order of 1 mile, and this is very close to the maximum fireball radius, which, as I recall, is of the order of seven-tenths of a mile.

So there is a marked decrease in the radius of destruction by incorporating these measures of blast protection in what is primarily otherwise a fallout shelter.

Mr. HOLIFIELD. What kind of pressure would a steel quonset hut type of structure, with the apex 3 feet underground-what kind of pressure on the surface of the ground above it could it withstand? Mr. STROPE. This particular structure that we have dealt withMr. HOLIFIELD. Yes.

Mr. STROPE (Continuing). Has been tested successfully at pressures above 50 pounds per square inch.

We rate this one at 35 pounds per square inch because the conditions of the tests in Nevada are not those with which we are concerned; namely, high-yield weapons.

Mr. HOLIFIELD. So the development of backyard shelters buried 3 feet underground, which we oridinarily term "radioactive fallout shelters", would indeed give a great deal of blast protection?

Mr. STROPE. There is an extensive history of testing of these types against blast, which is in the literature, and if attention is given to the proper design of these types of structure, your statement is entirely

correct.

Mrs. GRIFFITHS. Mr. Chairman, if I may ask how far away from the blast would you have to be for a basement, for the ordinary basement, to protect you?

Mr. STROPE. That is a difficult question to answer. I think that for the ordinary home, the problem of fires is more serious than blast, and this occurs at very long range. The fire problem of a shelter in the basement of a burning building is very serious.

I would have to consult the data to answer that question directly. I do not recall it. Mrs. GRIFFITHS. And from blast, fire, and fallout.

Mr. STROPE. Yes, I will give you that information.
Mrs. GRIFFITHS. Thank you.

(The information referred to follows:)

BASEMENT SHELTER PROTECTION

According to "The Effects of Nuclear Weapons," a normal well-built basement offers a considerable amount of protection against the effects of thermal radiation, blast, and fallout. Protection against the initial thermal radiation is of course complete, outside the fireball. However, should a fire storm occur, or should the house itself be ignited by thermal radiation, such a retreat would have to be evacuated immediately. (Newly painted white framehouses with no incendiary litter have withstood thermal exposures of up to 25 cal/cm3. Such exposures would occur from a 1-megaton airburst at ranges up to 5 miles, and from a 1-megaton surface burst at ranges up to 3 miles. If homes are not wellkept or if incendiary litter such as newspapers, and other trash are exposed, fires may be expected 5 or more miles away from a 1-megaton surface detonation.) For single-family houses of light construction, a well-built basement is likely to remain unpenetrated, even if the house is completely destroyed. For buildings of heavier construction (e.g., steel and concrete), the basement of a building lying beyond the crater radius offers very nearly complete protection against blast, even in regions where the building itself may be destroyed. The basement of a framehouse will attenuate fallout radiation by about a factor of 10 (and the initial radiation somewhat less than this). In summary, a normal basement provides good protection against the immediate effects of a 1-megaton surface burst beyond about 5 miles. The protection afforded against fallout, however, is not sufficient if the basement is in the heavy fallout area downwind of the detonation.

Mr. STROPE. Both protective and operational criteria were developed as a basis for design and costing, and were considered as subject to test and possible modification upon availability of the prototype, and this is exactly what happened.

That is, we tested whether this 24-hour closure against fire was necessary, and I will recount the results in a moment, but these were our considerations at the beginning of the program.

BASIC NRDL SHELTER DESIGN

The design study evolved a shelter that is, I think, familiar to this committee from previous testimony, but I have included in the document a sketch of the shelter. (See fig. S-1.)