nation. And Mr. Corsbie has a statement here which I would be happy to have him read to you—it is very brief-on this point.

Mr. ROBACK. Will you enlighten the committee on this point with your statement, Mr. Corsbie?

Dr. DUNHAM. I think it covers the matter very nicely.

Mr. CORSBIE. Here is a statement on the application and limitations of the t-12 decay rule by Dr. Samuel Glasstone, editor, "Effects of Nuclear Weapons."

Fallout is a very complex and variable mixture of many radioactive species and so the rate of decay cannot be represented precisely in a simple manner. Nevertheless, for planning purposes some formula or rule is essential for predicting the rate of decay and the radiation doses which might be received from fallout. Without such a formula, planning would be impossible. It appears from actual measurements and theoretical studies that the t-12 rule provides a simple but good working representation of the radioactive decay of fallout under average conditions. It is believed to provide the best approximation available for short-range planning purposes during the period between 30 minutes and 200 days after a nuclear explosion. It is emphasized that the t-12 rule can be used only provided there is no change in the quantity of fallout during the time interval under which the rule is used. If the fallout is still descending or any is removed by weathering, etc., or added by winds or additional explosions, the rule is invalid.

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Measurements made on actual fallout from weapons tests indicate that, although the t-1.2 decay represents a reasonable average, there have been instances where explonents in the ranges of to -2.0, rather than -1.2, are required to represent the rate of decay. In fact, different exponents are sometimes needed for different times after the explosion. These anomalies apparently arise from the particular circumstances of the explosion and are very difficult to predict, except in cases where a large quantity of neutron-induced activity is known to have been produced. Furthermore, fallout from two or more explosions occurring at different times will completely change the observed decay rate. For measurements made over a long period of time after the burst, weathering will tend to alter the dose rates in an unpredictable manner. Consequently, in an actual situation following a nuclear detonation, estimates based on the t-1.2 decay rule must be used with caution and should be verified by actual measurements as frequently as possible.

In summary, the t-2 rule is the best formula available for short-range planning purposes. It could not predict exactly what the situation would be after 1 month from a measurement made at the end of the first day, for example, because of inevitable changes in the intervening period. Consequently, estimates based on the t-1.2 rule must be verified by actual measurements with instruments as frequently as possible.

Mr. ROBACK. That will be reflected in the revised handbook?

There are several references in Dr. Glasstone's statement to the effects of weathering. I think we ought to understand more precisely that weathering does not affect the decay rate; it affects the presence of radioactive material in any given place. Is that correct? Dr. DUNHAM. It affects the amount that is on the surface. Mr. HOLIFIELD. It affects the exposure of dosage, but it doesn't affect the decay rate as such?

Dr. DUNHAM. No.

REVISION OF "EFFECTS OF NUCLEAR WEAPONS"

Mr. ROBACK. Mr. Corsbie, do you have any information in addition to what was said yesterday about the nuclear weapons handbook, "Effects of Nuclear Weapons"?

Let me preface that inquiry by saying that from some points of view it is taking a long time to revise this book; and from other points

of view, perhaps among scientists, it has been a tight schedule proposition, and a lot of important information perhaps is not reflected in it. Now, the importance of having an authoritative manual is obvious, because this is probably the most widely quoted and the most important document for civil defense information at a reasonably high technical level that there is.

Have you any commentary?

Mr. CORSBIE. I would like to add this to the testimony of yesterday. During the hearings before the Special Subcommittee on Radiation of the Joint Committee on Atomic Energy on "Biological and Environmental Effects of Nuclear War," June 1959, there was testimony on the need for revising the AEC-DOD handbook on "Effects of Nuclear Weapons." Subsequent to the hearings the AEC and DOD staff members discussed the testimony with Chairman Holifield and exchanged views on the significance of the effects information developed since issuance of the 1957 book. Arrangements were worked out between DOD and the Atomic Energy Commission to undertake the revision, and the services of Dr. Glasstone were obtained as the editor. The scope and format of the book, it was decided, would remain unchanged. The objectives were and are to bring it up to date, to make appropriate corrections, and to add new items of information.

While the revisions are not expected to increase greatly the size of the book, they will include important data in the areas of blast, fallout, and electromagnetic effects on communications. Some changes will result from use of material declassified since the preparation of the 1957 book.

As stated earlier, we expect to publish it before the end of the year. One additional item which may be of interest is this. Over the years we in the Commission have been concerned with putting information at hand in such shape that lends itself to simple practical applications. Certain data from the current "Effects of Nuclear Weapons" was put on a circular sliderule some time ago, and it resulted in such popularity as a timesaver, not only for the layman but to the scientific and technical people, that we now have underway a revision of the nuclear bomb effects computer sliderule to bring it into agreement with the revised effects of nuclear weapons. Each copy of the revised effects book will have an envelope inside the back cover with a notice telling of the sliderule computer and its availability.

Mr. ROBACK. We received some of those from your office. Are those the revised or the unrevised slide rules?

Mr. CORSBIE. The ones you have agree with the current 1957 edition. There will be some additional information put in the new design; however, the data on the present sliderule will probably remain 90 to 95 percent accurate. It is not a precise instrument; it gives rather gross information as answers, but it has been very helpful to us.

RESEARCH ON RADIATION EFFECTS

Mr. ROBACK. Mr. Corsbie. I would ask you to comment on two things from the standpoint of interest in civil defense:

No. 1, new weapon potentials, and No. 2, the opportunities and limits for testing in a radiated environment without nuclear explosions.

Mr. CORSBIE. We now have underway a program at the Nevada test site which uses a bare reactor on a 1,500-foot tower.

Mr. ROBACK. By "bare" you mean unprotected?

Mr. CORSBIE. I mean bare, unshielded, unmoderated. It will give a radiation flux comparable to that given by a nuclear weapon, that is, gamma and neutron radiations.

The principal objective of the experiment is to assist in improving our knowledge of radiation doses received by survivors in Japan in 1945. It is closely related to the Atomic Bomb Casualty Commission program. We will be able to place this reactor at distances from the ground to the top of the tower. We will study the attenuation or shielding characteristics of materials and combinations of materials at such distances as to stimulate situations that prevailed under the bursts in 1945.

This is basic data.

Although we will be working at very low radiation levels, since the reactor will operate at about 1,000 watts for periods of 6 to 8 hours a day several days a week, it does permit us to use laboratory-type instrumentation where we can work in tenths of millirads to obtain the information we seek.

It appears to me that there could be a number of applications serving basic nonmilitary defense needs on the shielding characteristics of materials or combinations of materials, shelters, and houses that could use this sort of approach.

In this reactor application we have simulated a radiation field that permits us to conduct experiments safely, during normal working hours, 5 days a week; and, unlike weapons tests, if the experiment is not successful it is very simple to do it again the next day.

Mr. ROBACK. Will you identify for the record, give us a little more information about the reactor, that is, who makes it?

Mr. CORSBIE. The reactor we propose to use is a health physics research reactor which has been designed for permanent installation in the facility at Oak Ridge. It is part of the Division of Biology and Medicine research program.

Mr. HOLIFIELD. Is this reactor already in existence?

Mr. CORSBIE. The reactor has been designed, built, and is now at Oak Ridge undergoing its final tests before being shipped to Nevada for use in these experiments, which we expect to begin about December. It will be returned to Oak Ridge around April to be installed in the permanent facility.

Mr. HOLIFIELD. This is what is called the fast burst reactor?

Mr. CORSBIE. Yes, sir; it is the fast burst reactor. We call it the health physics research reactor.

Mr. HOLIFIELD. And what power of fission will it produce?

Mr. CORSBIE. Up to 10 to the 17th fission within 35 microseconds. Mr. HOLIFIELD. Which would be equivalent to what size weapon? Mr. CORSBIE. I will try to develop figures on such equivalence and give them to you later, Mr. Chairman.

Dr. DUNHAM. It really isn't equivalent to a weapon, except in the sense that the radiation and the relative neutron and gamma fluxes are the same. If you get very close to it you can simulate something like a quarter of a mile from a 20-kiloton weapon, or if you get even closer you can get something like you get out of a megaton weapon.

But what we are interested in here is the relative neutron gamma components, and then using the reactor against structures and structural material to study shielding.

Mr. HOLIFIELD. As a matter of fact, by moving your shielding or your animals that would be exposed to it from far out to close in to the reactor, why you could almost simulate the radiation effect of any sized weapon, couldn't you?

Dr. DUNHAM. That is correct. And this is what will be done when the reactor goes back to Oak Ridge.

Mr. HOLIFIELD. Of course, you couldn't get blast or thermal.

Dr. DUNHAM. We are completely free from blast or thermal, which makes your experiments simple.

Mr. ROBACK. While we are on this particular subject, may I inquire what information you have about simulated fallout situations? Do you have laboratory situations for simulating fallout?

Mr. CORSBIE. Since 1957 and 1958, largely under the encouragement and early direction of Dr. Libby, who has appeared before the chairman many times, we have developed a capability to simulate fallout radiation by pumping a point source of radiation through up to a mile or more of plastic hose which is arrayed around a structure or over a structure in such way as to simulate a radiation field in terms of curies per square mile or roentgens per hour.

Mr. ROBACK. Is there actual deposition of material?

Mr. CORSBIE. No, this is a point source that is moved under hydraulic pressure. By placing many instruments inside a structure and running the pump for long periods, up to several hours, depending upon the massiveness of the structure, we can obtain readings that give the attenuation factor, or the protection factor of the structure itself. Depending on where it is performed, we can use sources from a fraction of a curie up to 300 curies. We have done considerable work with the system, or a prototype, including measuring the protection factors in the AEC headquarters building, and extensive work at the Nevada test site. We surveyed one shelter structure at the request of the Office of Civil Defense and Mobilization at Thomasville, Ga.

Mr. ROBACK. Mr. Corsbie, referring to what has been called in public statements the neutron bomb, will you please comment on the civil defense implications of that?

Mr. CORSBIE. Mr. Counsel, I spend most of my time on effects, and I am really not qualified to talk about a neutron bomb or its implications for civil defense or otherwise.

CRITERIA FOR IDENTIFYING SHELTERS

Mr. HOLIFIELD. Gentlemen, you have had a lot of experience in this field of testing out at Nevada. I have been out to Nevada on occasions when you were present. And I know you have been deeply interested in this matter. We have had quite a bit of discussion the last few days in regard to surveying of shelters all over the United States. And there has been a proposal that some $93 million be set aside for the survey and marking of shelters. I am wondering if it isn't possible to set up criteria which would make a relatively unskilled person able to identify a shelter?

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In other words, is it necessary to have a long-drawn-out educational program in order to equip a man to go into the basement, for instance, and by consulting certain criteria in regard to the compositions of the walls and overhead beams and so forth, to be able to estimate the degree of protection that you would get from radiation.

Dr. DUNHAM. That is absolutely true, Mr. Chairman.

Mr. HOLIFIELD. Hasn't all of the exploratory work been done in this field?

Dr. DUNHAM. The criteria are available. The problem of education and the national program is to get people to do something about it, as I see it, because the criteria are already laid out-and Mr. Corsbie may want to add a point--to protect yourself against 5 pounds per square inch, against an infinite dose of 20,000 roentgens, or 15,000 roentgens, whatever you want to pick.

This sort of information is available.

Mr. HOLIFIELD. I see no reason for replowing a great deal of ground. We have been doing nothing else but accumulating data on radiation and on structures through all of our tests out in the Nevada flats and our tests in the South Pacific. And it would seem to me that we have plenty of data available.

Now, the next problem would be to convert that data into common, usable criteria, or standards which could be used as a guide rule to people who do not necessarily have all this background of experience. Would it not be possible to develop that kind of criteria?

Mr. DUNHAM. I will let Mr. Corsbie answer that.

Mr. CORSBIE. First, Mr. Chairman, we haven't done a very good job in taking the data which is available from the Department of Defense, the Federal Civil Defense Administration, the OCDM, and the AEC, and putting it in practical form so that a person who works as a designer or draftsman or architect could use it in the same way that he uses other handbook information. I think that we know enough about radiation to develop such guides.

I think there is still a need for additional experimental work on certain types of structures to permit a final refinement of it by category or classification of structure at some future time.

I say that principally because in the work that we have done in making experimental measurements of the protection provided by a variety of structures from homes to more complicated buildings, we have found invariably that there is more protection in the structure than we would have estimated on theory alone. And if you multiply this bonus of protection across the whole Nation, it becomes quite an important figure, whether in terms of concrete, steel, life, medical supplies, or people. We have gone a long way with this work, but whether we have gone far enough to proceed immediately with a national program I cannot say.

Mr. HOLIFIELD. It would seem to me that the sensible thing for us to do now is to let those people who have had years of experience in this field bend their efforts toward establishing as simple a criterion as possible, rather than the Defense Department embarking upon a program of letting contracts to architects and engineers who have to learn, you might say, all over.

Of course they know the stresses and strains of building materials, but there is a little different problem involved here, And I am just