Western. There are several people in the AEC who have commented on the report.

ACCURACY OF RADIATION MONITORING

Mr. ROBACK. One of the points in the report, I understand, has to do with the large margin of error in the kind of measuring instruments that might be available either to individuals or to monitoring agencies. The margin of error might be plus or minus 25, 35, or even 50 percent. Now, from a medical standpoint that might make quite a difference. Do you have any commentary on the state of the measuring instrument art, and on the findings of this national committee in that respect?

Dr. DUNHAM. I think that with most of the devices that would be available under these circumstances you would have to expect at least a 25 to 50 percent margin of error, because the individual is seldom in the same spot as the device is.

As far as the medical treatment of people goes, you don't treat by the measurements, you treat the symptoms as they appear, because people vary very greatly. One person receiving 200 roentgens will have no symptoms whatsoever, and the next person, if he is a person who, for reasons we don't understand, has an increased susceptibility, may go through the whole business of acute radiation body injury. So one must not rely on those readings except as very crude guides as to who is likely to have trouble and who isn't.

Mr. ROBACK. They are very crude guides, but from the standpoint of planning you have to look to the measurements rather than the symptoms, because you are trying to avoid the symptoms, or the things that cause symptoms.

Dr. DUNHAM. That is correct.

ALLOWING 200 ROENTGENS DOSE FOR CIVIL DEFENSE WORKERS

Mr. ROBACK. Now, in the light of the 200 roentgens standard which has been cited by the Office of Civil and Defense Mobilization as a kind of a top limit that one should be concerned about, if you had instruments with plus or minus 50 percent error, then 200 could become 400 for a sizable part of the population, and it runs you into trouble.

Dr. DUNHAM. That would run it up to 300, wouldn't it, rather than 400, plus or minus 50?

Mr. ROBACK. Or even 300?

Dr. DUNHAM. But that would be in the range of individuals variation, so I don't think you lose too much.

Mr. ROBACK. Do you think the 200 figure is a pretty good working figure?

Dr. DUNHAM. If you keep below that, you will have very few people who will be casualties from radiation.

Mr. ROBACK. There is a good deal of emphasis in civil defense exhortations to the public, and in some of their planning or guide documents, on immediate protection without trying to examine the different phases, you might say, of civil defense effort in terms of being in shelters, emerging, having specified rescue operations or recovery operations. Would it make any sense from a medical standpoint, to try to set up standards within that 200 roentgens limitation for different phases of civil defense, as, for example, in the acute or initial phase,

in some kind of an interim phase, perhaps, and then the recovery phase, should we try to assign roentgen's to each phase?

Dr. DUNHAM. I would like to comment this way. If you can spread your 200 roentgens exposure over a period of weeks, as Mr. Holifield pointed out earlier, then you are in a much safer ballpark than if you allow it to happen all of a sudden or in matter of 2 or 3 days.

This point that Mr. Corsbie touched on earlier, a factor of a hundred in terms of attenuation of fallout radiation in a shelter, really is a remarkably effective factor.

I believe some of the studies have indicated that in an ordinary brick house with a reasonable bit of shelter built in the basement you can get a protection factor somewhere between 100 and 200. This would require a 20,000 roentgens infite dose to 100 or 200 roentgens, which puts you right in the range where survival without any serious illness would be most likely.

Mr. ROBACK. But if you soak it all up when you are sitting under cover, you couldn't have much to go on if you are assigned to emerge for monitoring purposes or to obtain food or whatever the task is, assuming this is a group effort.

Dr. DUNHAM. I think we are going to have to take some casualties in the civil defense personnel, just like you always do with your firefighters in peacetime.

Some people are going to exceed the dose of radiation that will make them sick, there is bound to be some of that. You can't plan the dose precisely under an emergency situation. But with good emergency communications with people in the shelters and instrumentation indicating to them what the general levels are, then they can be given some guidance as to how long they can go out without accumulating another 10 to 15 roentgens. And this sort of thing can be extremely useful.

But, as far as going in and getting some supplies from some place that is very hot, I am afraid there will be some sacrifices. It is just the nature of war.

RADIATION DECAY RATE

Mr. ROBACK. Keeping in mind some technical controversy over the decay rates of radiation, will you comment on the longer term radiation hazards of nuclear attack?

Dr. DUNHAM. Well, the longer term hazards are the things I touched on in my testimony, which are essentially those beginning 4 or 5 years later. There is an increased incidence of leukemia among people who have had a hundred roentgens or more but it would be a relatively small fraction of those so exposed.

Mr. ROBACK. I am thinking, Dr. Dunham, from the standpoint of these differing formulas or relationships

Dr. DUNHAM. You mean the t-1.2 proposition?

Mr. ROBACK. Yes. Say after a year, between 1 and 10 years after the attack, what does the radiation environment look like?

In the t-1 -1.2 formula it looks a lot worse than others. So someone might be a lot concerned about the long-term hazard, depending on how they figured it.

Dr. DUNHAM. It is my understanding that this is primarily concerned with the exposure that would take place shortly after the deto

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-1.2 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.

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,

-0.9

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-12 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.