of 100 miles per hour, which is about 25 miles per hour higher than an officially defined hurricane wind. We know how hurricane winds can move things and people. An incident overpressure of 5 pounds per square inch will be accompanied by 160-miles-per-hour winds and 10 pounds per square inch will have 290-miles-per-hour winds in a clean wave form. Although the concept of blast pressure is unfamiliar to many people, it becomes easier to understand when put in terms of the accompanying high-velocity winds.

BLAST PROTECTION IN BURIED FALLOUT SHELTER

Mr. HOLIFIELD. Could I stop you there for a moment, and ask you to give the committee the general feeling of how many pounds per square inch pressure would be needed to collapse a quonset-huttype shelter buried 3 feet underground; that is, where the top center of the quonset curve was 3 feet underground? Have we any information on that?

Mr. CORSBIE. Yes, sir. I would estimate more than 50 pounds per square inch, and maybe a hundred.

Mr. HOLIFIELD. Šo there is a great deal of protection from blast, even in a so-called fallout shelter of that type?

Mr. CORSBIE. Yes, sir.

Mr. HOLIFIELD. That would not ordinarily be termed a "blast shelter" in the sense of the blast protection that we associate with underground missile bases. But ground pressures of 50 pounds per square inch, if spread over a wide area of the earth, would still leave in safety the people in a very ordinary type of so-called radiation shelter, would it not?

Mr. CORSBIE. Yes, sir. There would be a very high degree of protection against blast.

Mr. HOLIFIELD. Now, how much radiation would it take-how many roentgens of radiation would it take to penetrate 3 feet of earth? Mr. CORSBIE. You are talking about prompt radiation, sir?

Mr. HOLIFIELD. Prompt radiation.

Mr. CORSBIE. You would need less than 3 feet of earth to protect against the bomb radiation, or the radiation which occurred within a minute, impinging on the crown of the shelter arch except for very close bursts.

Mr. HOLIFIELD. Within the sphere of the immediate bomb, yes, I understand that.

But getting out on the perimeter, say a mile or two from the lip of the crater, would a person have enough protection with 3 feet of ground over him from the type of radiation that would occur?

EFFECTS AT 1 MILE FROM MEGATON BURST

Mr. CORSBIE. Let me try to answer it this way. A mile from, say, a megaton burst, you have a pressure of the order of 30 pounds per square inch.

Mr. HOLIFIELD. So you are safe from blast a mile away?

Mr. CORSBIE. Yes, sir.

Mr. HOLIFIELD. All right.

Mr. CORSBIE. And you have a prompt radiation dose of about 10,000 rem. About 35 inches of concrete or 48 to 56 inches of earth would give you a protection factor of 100 against the prompt radiation, possibly more than 1,000. You would also have a thermal radiation dose of about 1,000 calories per square centimeter.

Mr. HOLIFIELD. That is based on an hour's exposure at that rate? Mr. CORSBIE. No, this is based on what you would get in a minute, that is your prompt radiation dose.

So you would have at a distance of 1 mile from 1 megaton about 30 pounds per square inch pressure, you would have about 10,000 rem prompt radiation dose, and you would have about 1,000 calories. per square centimeter thermal radiation.

Mr. HOLIFIELD. And you would be free from the thermal, you would be safe underground from the thermal?

Mr. CORSBIE. Yes, sir.

Mr. HOLIFIELD. But what would your reaction be from 10,000 roentgens in, say, a 3- or 4-foot underground structure?

Mr. CORSBIE. You would have a protection factor of more than 1,000, against prompt radiation which should be enough to protect against prompt radiation and later fallout. You might need to increase it for very close bursts. In this particular situation the principal design criterion could be the prompt radiation dose.

EFFECTS AT 2 MILES FROM MEGATON BURST

Mr. HOLIFIELD. Now, let's move another mile, which would be 2 miles from the limits of the crater.

What happens then as far as prompt radiation is concerned? Mr. CORSBIE. At 2 miles the prompt radiation would not be much of a problem, 16 to 20 roentgens, you would be essentially beyond its effective range.

Mr. HOLIFIELD. So without going into the refined calculation, you would say that with what we would call the ordinary shelters from radioactivity—and I am designating this as an underground quonset type hut, with from 3 to 4 feet of ground over it-you would immediately start saving a tremendous number of lives, 2 miles from the lip of a 1-megaton explosion.

Mr. CORSBIE. Yes, sir.

Mr. HOLIFIELD. Now, if that same type of shelter had a foot of concrete over it as well as 3 feet of earth, you would step up your protection from prompt radiation, would you not?

Mr. CORSBIE. Yes, sir.

Mr. HOLIFIELD. Álso it would make it impervious to blast or to heat at a distance of possibly 1 mile, wouldn't you say?

Mr. CORSBIE. Yes, sir.

Mr. HOLIFIELD. You have 1 foot of concrete and 3 feet of earth over a shelter?

Mr. CORSBIE. I would like to check that figure, but it is in the right direction.

You would achieve a very large protection factor against the radiation. At that particular distance the design and materials of the shelter would be most important in protection against prompt radiation.

PROTECTION OUT TO 10 MILES

Mr. HOLIFIELD. Could you furnish to the committee a graduated scale showing the protective value of quonset-type hut shelters buried 3 feet underground, at the top part of the arch; also the same type of a scale showing the additional protection that 1 foot of concrete would give over that type of a structure, and graduate that on the basis of 10 miles from the ground zero of a ground burst. Will you furnish us a table along that line?

Mr. CORSBIE. Yes, sir.

Mr. HOLIFIELD. You have data which will allow you to do that, do you not?

Mr. CORSBIE. I think we have, sir.

Mr. HOLIFIELD. Thank you.

And give us the pounds per square inch of pressure, the amount of thermal exposure, and the amount of radiation exposure which people would have in a graduated range from zero out to 10 miles in the event of a megaton burst.

Mr. CORSBIE. Yes, sir.

(The following information subsequently was received:)

PROTECTION AGAINST NUCLEAR EFFECTS AFFORDED BY AN UNDERGROUND
CORRUGATED METAL ARCH SHELTER

The protection afforded by an underground, corrugated metal arch shelter under two coverings is considered. In case I the cover consists of a minimum of 3 feet of earth; in case II the cover consists of a minimum of 3 feet of earth plus a 1-foot-thick slab of standard concrete. In estimating the protection afforded by such shelters, it is assumed that the entrances, exits, vents and other openings provide protection against ionizing radiation, thermal radiation and blast consistent with the basic structure.

A metal arch shelter designed to withstand 35 pounds per square inch overpressure is described in reference 1. A report on field tests in which the shielding afforded by a minimum of 3 feet of earth was determined is contained in reference 2.

Radiation attenuation factors for the shelter with a minimum of 3 feet of earth over the crown of the arch are of the order of 1,250 for initial ionizing radiation and 10,000 for fallout radiation. Attenuation factors for the same shelter with a minimum of 3 feet of earth over the crown of the arch plus 1 foot of standard concrete are of the order of 4,000 for initial ionizing radiation and greater than 200,000 for fallout radiation.

Assuming that a war emergency radiation dose of 100 roentgens may be accepted as a nondisabling injury, outside doses of initial radiation of 125,000 roentgens and 400,000 roentgens would not cause disabling injury inside of the two shelters having attenuation factors of 1,250 and 4,000, respectively. Initial ionizing radiation doses of 100,000 roentgens and higher will be observed in regions where blast pressures will destroy all but especially constructed buildings.

A fallout radiation attenuation factor of 10,000 will provide excellent protection against fallout radiation. An early time dose rate such as 10,000 r/hr at H+1 hour would be reduced to 1.0 r/hr. During a 2-week period the accumulated dose would be less than 5 roentgens. Attenuation factors greater than 10,000, as seen in case II, would result in much lower inside dose rates and lower accumulated doses.

The shelter described in reference 1 was designed to withstand a blast pressure of 35 pounds per square inch. The protection against radiation afforded by both the earth and the earth plus concrete coverings is satisfactory at the 35p.s.i. range from surface burst weapons having yields from 1 to 10 megatons.

A 35-p.s.i. shelter at a distance of 2 miles from the point of detonation will withstand the initial ionizing radiation, thermal radiation, and the blast from surface bursts from 1 to 8 megatons. At 2 miles from a 9-megaton surface burst (40 p.s.i.) and 2 miles from a 10-megaton surface burst (44 p.s.i.) some damage may occur to the shelter.

The 35-p.s.i. shelter will withstand the effects 1 mile from a 1-megaton surface burst. Some structural damage is expected at 1 mile from a 2-megaton surface burst where the overpressure will be about 64 p.s.i. At 1 mile from a 3megaton surface burst where the overpressure will be about 90 p.s.i. structural damage to the shelter is expected.

At 1 mile from surface bursts of 4 to 10 megatons the overpressures will be greater than 100 p.s.i.

It is anticipated that there will be no appreciable damage from ground shock to a well-constructed underground shelter beyond 21⁄2 apparent crater radii from surface zero. For a 1-megaton surface burst, 21⁄2 apparent crater radii equal about one-half; for a 10-megaton surface burst, 21⁄2 apparent crater radii equal about 1.1 miles. (Both examples are for wet soil in which the largest apparent craters are produced.) At 21⁄2 crater radii from 1- to 10-megaton surface burst weapons, overpressures would exceed 100 p.s.i., which exceeds the design resistance of the 35-p.s.i. shelter. Inasmuch as the 35-p.s.i. is well beyond the range of 21⁄2 apparent crater radii, structural damage from ground shock should not be expected, although ground shock would be felt by the occupants of a 35-p.s.i. shelter at the 35-p.s.i. range. At such ranges and pressures slight to moderate accelerations and ground roll may occur. Depending on soil characteristics, some attention should be given to protection of shock-sensitive equipment and possible hazards to personnel from displacement and overturning of shelter fittings and furnishings.

The use of the 35-p.s.i. shelter for illustrative purposes should not be construed as advocating such a shelter in preference to those which would protect in regions of higher or lower overpressures. For example, a good case may be made for a shelter resistant to all effects at the 10-p.s.i. range and beyond. For a 10megaton surface burst there are about 265 square miles in the ring whose inner boundary is the 10-p.s.i. line (4.1 miles radius) and whose outer boundary is the 2-p.s.i line (10.1 miles radius).

Practical design information for shelters and other structures will be found in reference 3.

1. CEX 58.7, AEC Group Shelters.

REFERENCES

2. WT 1464, Operation Plumbbob Project 32.3, "Evaluation of Countermeasure System Components and Operational Procedures."

3. ASCE Manual of Engineering Practice No. 42, "Design of Structures to Resist the Effects of Nuclear Weapons," American Society of Civil Engi neers, 33 West 39th St., New York City, 1961.

Thermal dose at 1 to 10 miles from 1 to 10 megaton surface bursts in calories per square centimeter

Initial radiation doses in rem at ranges of 1 to 10 miles from 1 to 10 megaton explosions

1 At ranges of 3 to 3.5 miles and greater initial radiation is not significant.

NOTE.-Values are probably valid within a factor of 10.

Overpressures in pounds per square inch at ranges of 1 to 10 miles from 1 to 10 megaton surface bursts

[Values rounded off to nearest pound per square inch]

1 Maximum fireball radius is greater than 1 miles and less than 2 miles for explosions from 2.5 to 10

megatons.

Mr. HOLIFIELD. Proceed.

RADIATION DOSES

Mr. CORSBIE. The ionizing radiations which accompany and may persist following nuclear explosions are well known for the ability to injure living things. For acute doses of penetrating radiation a report of the National Academy of Sciences-National Research Council has this to say:

* * * it can be stated with some confidence that total doses up to 150 to 200 roentgens delivered acutely or over days or months, would result in no apparent acute effects and serious late effects in only a small percent of those exposed.

When the dose gets larger the clinical symptoms increase. A small percentage of the people receiving doses between 200 and 300 roentgens might need hospitalization; most of those receiving doses between 300 and 400 roentgens would need hospitalization; and all of those receiving doses over 400 roentgens would need hospitalization. The LD-50-that is the lethal dose for 50 percent-is often given as 450 roentgens; that is, 50 percent of the people receiving that much of a dose would not be expected to recover.