Attachment 1 "Notes on the Meeting of a Committee To Consider the Feasibility and Conditions For a Preliminary Radiological Safety Shot for Operation 'Windsquall' [later named 'Jangle'] 5/21-5/22/51 SD - 9241 (Del) NOTES ON THE MEETING of a Committee To Consider the Feasibility and Conditions For a Preliminary Radiological Safety Shot for OPERATION "WINDSQUALL" Los Alamos, New Mexico 21 and 22 May 1951 This Document Consists of 55 Pages No.3 of 5 Copies, Series a LAB-J-2317 ATTENDANCE Advisory Committee S. Warren, Chairman W. Bleakney W. Claus R. Coiner G. Failla L. Hempelmann H. Hodge B. Holzman T. Nolan A. Spilhaus L. Thompson Others Present N.E. Bradbury J.C. Clark G. Felt G. Fowler G. Eraker R. Poole H. Schultz T. Shipman H.K. Stephenson W.R. Sturges K. Teller - 2 - FOREWORD This document represents a partial transcript of notes taken during the meetings of 21 and 22 May 1951. It is wished to emphasize that these notes do not comprise a complete, verbatim record of the discussion, nor are they intended to serve as anything more than an informal presentation of the material covered. For a summary of the results of the meeting, the reader is referred to the final report to be issued by the Committee. - 3 - NOTES ON THE MEETING OF A COMMITTEE TO CONSIDER THE FEASIBILITY AND CONDITIONS FOR A PRELIMINARY RADIOLOGICAL SAFETY SHOT FOR OPERATION "WINDSQUALL" Los Alamos, New Mexico 21 and 22 May 1951 I Afternoon Meeting - 21 May 1951 WARREN: The general outline of the problem is this: As you know, an underground type of weapon, one in which the explosion occurs underground, is of very great importance, and a series of tests had been planned under the general guidance of the Armed Forces and the Task Force formed for it, with Dr. Spilhaus in charge from the standpoint of the technical factors involved. The original plan was to hold this in the Aleutians; it then became desirable for a member of reasons to consider holding it in the continental United States. The job that the Division of Biology and Medicine has is that of considering general safety problems. This came into our lap to some extent and we felt that a very close look ought to be taken at the hazards which may or may not exist. One of the main purposes of this meeting is to determine these points. In the discussions between the Armed Services and the Commission, the Commission has agreed to the series of tests with the understanding that the first test would be one primarily focused on the questions of safety, and that in the light of the determinations made in that initial test, there would be further tests to determine the actual information required for the operational use of this particular type of weapon. The Commission has asked Captain Tyler to take direct over-all responsibility for the tests so far as the AEC is concerned; over-all responsibility for the tests so far as the AEC is concerned: I understand from his that Sandia will be concerned to a considerable degree in the tests, and that the portions of the tests in which the Commission is particularly interested and for which it is prepared to carry responsibility at the present time are, first, the determination of the radiological safety question, second, the question of blast, and third, the question of cratering. (Tyler confirms.) The problem which we have is focused almost entirely on the question of the radiological safety: how to do this first test, how to instrument it, what the details of it should be so far as site, micrometeorology, etc., are concerned, and to establish criteria so that just as soon as these results are obtained it will be possible to say that since it has come out in such a way, "OK, you can go on to the next test". - 4 - Notes on Mtg. 5/21 and 5/22/51 WARREN (cont.) In order to give each of us an understanding of the program as a whole as related to this problem of the safety aspects, it would perhaps be well if we went around the board more or less in line with agenda I've had a chance to discuss with most of you, in a series of fairly concise statements that will serve to set the framework of the problem and to move into a consideration or what to do in this test, which is concerned primarily with radiological safety and setting up a criteria which will allow a clear go-ahead. (Tyler was asked for his comments --he stated that Warren had covered the initial ground.) Then I will ask Dr. Spilhaus, who has had the responsibility for the planning of the initial series of tests, to give a general orientation of where we stand from the scientific and his organization standpoint at the moment. SPILHAUS: We stand about at this point, very briefly -- I have been working and trying to spearhead this change of site because the initial site selected very soon appeared completely unsatisfactory from three points of view: the meteorology, the geology of the island, and logistic picture in relation to the time scale. Now, actually, the planning that had been done on the scientific program has, up to the present time, progressed full steam and has not been affected in any large way by the talk of changing sites. When it was decided to abandon Amchitka, we were about at the point where construction would start for the instrumentation. So right now we're at about that point for a site in the United States; that is, as soon as a suitable site is picked, the various agencies and laboratories involved in the program are about ready to start in. Most of the people concerned in the agencies are assembled and working at their jobs, and we should be able to affect a smooth transition. So far as I think of it, this is a change of location which makes the whole job a great deal easier and, therefore, at this point we're ahead compared to the original schedule. There are three locations in mind: the north part of Yucca Flat, a spot north of Yucca Flat, and a site near Camp Irwin, California. From my point of view, any one of these three is satisfactory. WARREN: Dr. Claus had a chance to talk with the General Assembly Committee last week and, while their reply was quite noncommittal, it might be helpful if Dr. Claus summaries some of the points which the Division of Biology and Medicine is concerned about, and the reaction of the GAC. CLAUS: When Dr. Spilhaus first broached this subject to us several months ago, he made the plea that we take the positive approach, in other words, that they wanted to do this if at all possible. It is on this basis that we have approached the problem. Nevertheless, Biology and - 5 - Notes on Mtg. 5/21 and 5/22/51 CLAUS: (cont'd) Medicine has been put into the position of being the only group which is really dragging its heels a little bit in the attempt to use caution, look at the unfavorable aspects. There are some points which must be stressed. First, although we have been able to make some pretty good calculations in regard to particle size, etc., which make it appear safe, nevertheless, calculations are only as good as the premises upon which they are based and it is possible that these were not correct. Also, in practically every test there are some deviations from expectations (cites Trinity, Bikini. Greenhouse). So it might be well, if possible, to look pretty carefully at what might possibly happen unexpectedly. In addition to the health hazard, there are other things to consider. One of them is whether we want to mess up the Nevada site (which might well occur if you set off surface and subsurface explosions), and whether the radioactivity released might affect future test planning. It might be bad psychology to have to evacuate citizens from the surrounding territories once the good public relations have been established, as they have been. There are just points which must be considered. It has been calculated that an underground explosion of a 1-kt bomb buried ~ 17 ft. would toss up a cloud between 4,000 and 6,000 ft high. If conditions were chosen so that the wind was blowing about 10 mph and assuming a spread of the cloud of the order of 20o, it is possible to figure out that at distance where people might be, some 30 miles away, they could be exposed to the entire passage of the cloud without receiving a hazardous dose, either internal or external. Nevertheless, I'm afraid we can be sure the clouds won't behave that way--we saw that in Nevada, how the clouds hung over the valley the entire day. As it happened, the cloud contained very little radioactivity, but if it had consisted primarily of fission products, it might have been a fairly serious proposition. It is difficult, of course, to say how the dust will fall out. We might look at the Bikini test; we know the water vapor was thrown up and fell out over a distance of some miles, and at a distance of 3-1/2 miles. In one case, there was enough fall-out to produce an integrated dose of 100 r gamma dose, and there would be some 1000 r of beta dose associated with it. Of course, this is 1 kt compared to some 20, so that would give us a gamma dose of maybe 3 to 5 r, not a very serious proposition even with considerable more beta associated with it. At Greenhouse, as I understand it, there was a spot that got up to 35 r/hr, which produced an integrated dose of 175 r; if that were to occur in a populated area, if would be very serious. (Of course, again, that was a great deal more kilotonnage.) On the other hand, we can always say that if we have monitors set up and plans made, as in Nevada if something of this sort happened the people could be evacuated. It is hardly likely that it would occur as far away as Las Vegas, and the other sites are small enough that everyone could be evacuated - 6 - Notes on Mtg. 5/21 and 5/22/51 CLAUS: (cont'd) So I think from the point of view of external radiation, we don't need to worry very much. But the particle size problem is a great worry, primarily because we don't know much about the effect of small, hot particles in the lungs. On the basis of the possibilities of the kind of dose one might get from breathing particles which might become fixed in the lung, the boys at AFSWP and I have made calculating, particularly for 1u particles, the ones which are most likely to remain fixed in the lung, and the dose comes out around 800 rep to a small sphere of tissue in the immediate vicinity of the particle. Taken as an average value, even 800 rep is not apt to be hazardous, but one cannot take the average..... However, one can always say that there have been so many of these particles spewed about the country (from past tests), that so many people have already breathed pretty hot particles (why be concerned with it now). (We cannot, however, seriously consider that as an argument.) During the time of the Nevada tests, AFCAT collected particles over a great deal of the country, and they found all sizes of particles ranging from a few microns in diameter up to 10 or 12u in diameter. If we calculate from their results what the integrated dose would be, it comes out ~ 40 rep. Our calculations came out not quite 3 times that, ~ 100, so that the actual observations made by AFCAT and our calculations based on assumptions which we feel are justified, differ from each other by only a factor of 3. These calculations are based only on the mass of the bomb itself, the tamper and casing. Now if this is buried in soil it will be diluted by the dirt and soil, thus giving more particles which would be less dangerous because of less activity. Consequently, you would actually get, rather than ~ 100, the factor is somewhere between 10 and 100 times less--it is difficult to say because we don't know if you will get uniform dilution or not--than with the calculations based just on the bomb itself. The problem then becomes: what shall we test for in this first explosion? We must remember we probably have a period of time of about two weeks between making observations on the preliminary shot and deciding to go ahead on the next one. So we are going to have to develop apparatus and methods for taking and analyzing samples quickly. We want to know: (1) Spread of specific activity of cloud: (2) Particle size distribution; and (3) Gross behavior of the cloud (its heights, spread, etc.). (As for the GAC reaction): They admittedly felt that the calculations were based on solid enough assumptions, no question about that, but as to the biological effects, there was no one there who felt he was competent enough to decide whether it was safe or not. That's the sum and substance of their comment. - 7 - Notes on Mtg. 5/21 and 5/22/51 WARREN: Last week I went over it in a brief fashion with Biology and Medicine. They were all for going ahead with it--the safety standpoint--in this stepwise approach. (Introduces Hempelmann) HEMPELMANN: I can tell you in a rough way what happened at Alamogordo. This was a 20-kt shot set off from a 100-ft tower. The main body of the cloud rose to approximately 40,000 ft and the winds up to about 12,000 ft were toward the northwest; those over 12,000 ft were toward the northeast. The shot was set off here (draws diagram on board); there was an area of high activity, of course, immediately around zero point. The major part of the activity, as a matter of fact, all the activity, must have been carried up to the higher levels. . . . . there was a high spot out here about 15 miles or so where the radiation levels must have reached about 20 r/hr. (This was where the cows were which received the beta burns.) The major part of the activity apparently settled out in an area which showed the highest intensity at a point starting about 20 miles NE of zero point and the measured intensities were, the highest one was 20 r/hr, and then there were areas of lesser activity surrounding this hot strip which tapered off. We were still able to detect some activity a month after the shot in Colorado at a distance of 250 miles from zero point. There were no measurements made of particle size, but on the basis of previous tests on this type of fall-out pattern of dust particles of a fairly large size which had been made prior to the shot, it seemed to us that this was the result of the fall-out of the large dust particles of 100u or so, which were carried first of all by the upper winds to the NE and then were swept toward the NW by the lower winds. (Questioned as to whether this was all fall-out or some rain-out): So far as I know, although the atmospheric conditions, I understand, were quite unstable, there was no rain. In at least one point that I know of, the activity reached its peak after about an hour, remained high, and then fell very fast; there was no rain at this point. Greenhouse: There, the greatest radiation intensity measured on one of the inhabited islands as a results of the first shot was, I believe, 1.5 r/hr--on Japtan. I think, gamma radiation levels of 100 r/hr were measured. SHIPMAN: The fall-out following Dog shot was sufficiently unexpected that they weren't ready for it, there was no provision made for collecting dust particles and studying size distributions. It was generally thought, though, that the people on the inhabited islands--Parry, Kniwetok, Japtan--got an integrated dose of 1 r. It was pretty apparent that most of this came from large particles of 100u or larger, and there was absolutely no evidence of small particles. HEMPELMANN: There were about 75 or 100 active particles isolated from the ground and, as Tom says, all of them were ~ 100u or so in diameter. - 8 - Notes on Mtg. 5/21 and 5/22/51 SHIPMAN: A considerable number of dogs and cats were sacrificed and brought back here for study, and there was no indication at all of retention in the lungs of the particles. Going back to the tests in Nevada: the levels we found there were very much smaller than at Alamogordo, possibly because of the fact that this was an air drop, but we found the same thing that Louis mentioned, the rapid falling off of the activity. Air sampling done about the two hrs post-shot at least would give us levels that we could read, a few times background, but if we waited another two hrs we could not go back and find it again. That is, it seemed to be while the radiation was still airborne that the high radiation levels occurred. WARREN: One of the fundamental questions in this test--what kind of particles we'll get, what the dilution will be, whether most of them will be driven out to the sides of the dirt and never get into the cloud at all, what portion will get into the cloud--has a relation to the blast aspects. (Introduces Bleakney) BLEAKNEY: (Explains that he was not aware of the purpose of this meeting until his arrival is afraid he knows very little about recent developments and research in this field.) Most of my knowledge dates from a considerable time back; we had a number of underground explosions during the war, small-scale things. I think most of you are familiar with Lampson's reports on these. I know that a lot of work has been done since, but I just know of it, not the results. For example, we had a hand in planning some of the original tests at Dugway, but they were discontinued after the first year and I have not been in touch with that since it was started again. Likewise, Dr. Hartmann at NCL has done some very small-scale work with charges near the surface and I just know of that, do not know the results. There may be others, also. On the question of particle size, I can't help you at all. Everybody recognized that there is the chance here for a lot more stuff to get swept up into the air, and it seems to me there would be a lot more large particles and maybe a lot more small ones. You spoke of 1 kt buried deeper than the scaled depth, with the hope of minimizing the risk; I have a feeling that it will minimize the stuff getting out. I think a lot is driven into the walls of the crater and will stay there--judging this mainly on the character of these small explosions. For example, I think of a test of an 8-ton ILLEGIBLE explosion (I forget how deep) -- there was an awful lot of big stuff just tumbled around and of course a lot of smaller stuff would ooze up through the cracks. . . . . . One thing that surprised us--although possibly it should not have--we took shovels and dug some of this out; the crater looked something like this: - 9 - Notes on Mtg. 5/21 and 5/22/51 graphic Loose Dirt Original Cavity BLEAKNEY: (cont'd) As we dug it out with a shovel, we found that you could find the line of the original ball, a cavity which was very highly compacted, very hard (except that it would crumble, of course). One could find this very accurately and measure the size of it, could even see a coat of black (unburned carbon) on the top. It looked as though in the original explosion this stuff just got shoved out under high pressure and stayed there. I don't know, of course, if it will happen in a case like this, that all the material with particles of great size would get shoved into the cavity and stay there. But it was a close-packed surface, very well defined, very smooth, very nearly spherical in shape. Of course, here there will be high temperatures, vaporization, etc. . . . (Discussion of how deep the bomb should be buried. Spilhaus points that the problem is burying it deep enough for safety, not too deep to get the data needed.) (It was mentioned that if the optimal thing is to have a 2-wk interval between tests, then the conditions should not be too different from the first one, otherwise, there will have to be too much extrapolation between conditions. Bradbury also pointed out that the first shot did not have to be purely exploratory.) SPILHAUS: Yes, the first shot has considerable interest other than just the original purpose (of safety); it gives us three points; one deep, one at penetration point, and one at surface. THOMPSON: In view of the lack of information on this type of burst, that we just don't know anything about what might be expected, it occurs to me that if the time schedules permit, there might be some advantage in making some larger scale tests with explosives for which you need not have these hazards, and study particle size, etc. SPILHAUS: This is being done now at Dugway. The largest one is 320,000 lbs--that is being fired tomorrow, by the way--and this is in very similar, soft and sandy soil. - 10 - Notes on Mtg. 5/21 and 5/22/51 THOMPSON: Also from the standpoint of what appears to be the uncertainty as to actual hazards, I suppose the decision to make these tests in fairly inherited areas was made despite the advantage of not having this worry? I am just wondering if the possibilities of trouble might warrant thinking of locating these tests in uninhabited areas. SPILHAUS: You see, the Commission has said they will do these tests, and the military has rolled back Amchitka, it has been abandoned. It is a question now of finding how it can be done, stepwise, by exploratory measures. Obviously, one can bury the thing deep enough that it won't even rupture the surface--but we won't find out anything that way. (Question: What is the urgency of the time schedule? Is there a schedule very difficult to meet which requires this 2-wk period?) TILER: The operational procedure is somewhat complicated. We are attempting to tie these tests in with Los Alamos tests at Nevada, and the operational services --e.g., communications, AFCAT, etc.--are rather large for these. If you spread the tests out too widely it is difficult to hold the groups together. With a 2-wk interval between tests,this would be a month, just about as long as we could spread out these tests; this will involve a month of Los Alamos tests also, so it is two months altogether. We cannot hold this group from their normal activities any longer than this. If this turns out to be impractical, we might have to set up a series of tests separate from the Los Alamos ones. This is not impossible, it is less attractive operationally, but could be done. SPILHAUS: We considered the same thing, holding the interest concentrated and the people from their other jobs. (Question: How many explosions are being planned for the next six months or so?) TILER: It varies from month to month -- but I would say between not and next spring in this country, probably about a dozen, maybe less. WARREN: At lease in relation to that, fairly detailed calculations have been done as to how many bombs one can set off with general impunity, and the number is very large indeed. I don't think it needs to bother us except as the photographic industry is concerned, and they have made up their minds that they must go to other systems of water supply . . . . There probably is a limit (as to the number of bombs one could set off) for one community. HEMPELMANN: A measurement made at Eniwetok by Harry Schulte may be of interest, air sampling in the fall-out area within an hour. This was made in a region where the radiation level was 10 mr/hr, and he found 3 particles per square meter of air, which is about the amount of air which would - 11 - Notes on Mtg, 5/21 and 5/22/51 HEMPELMANN: be breathed by a person in that area. So I think (Cont'd) that when you get much below these easily measurable amounts of radiation, whether a person could or could not breathe a particle even if it should be the proper size to be retained by the lungs (does not matter). It is my impression that you can tie the two problems together. (The point is raised that by making quick-frozen sections of animal lungs and by radio-autography, one could determine the location of the particle quite readily.........) HOLZMAN: (Questioned about possibilities of rain vs cloud height): I think we can eliminate the rain problem from this risk problem; you just start off with a rule that you don't shoot when the possibility of rain exists within X miles. You might get rain at long distance (it always rains over Rochester!). (Asked whether there is any possibility of ionization of the cloud producing rain): The answer to that is a definite no--I'm so strong about that point, I think we can just discard it, there is no possibility. In fact, there is no moisture in these clouds. It is not ionization, but adiabatic cooling which you need (to produce rain)--it is this letter which causes the cloud chamber effect. WARREN: Our next point has to do with how the particles act, assuming they are in the lungs. (Introduces Hodge) HODGE: I will outline what we don't know about it, which is a very important part of the problem. You gentlemen perhaps know that since last March in Rochester, we have started a radioactive particulate study program. So far, we have the facilities, the philosophy, but no information to date. The fundamental question as to whether a single hot particle in the lung is capable of giving lasting damage is, as far as I know, simply unanswerable at the moment. But we do know a few things about how particles are handled in the respiratory tract. We know that large ones just don't get in, certainly down to 10u--maybe a few get into the nose but no further. From 5u on down, a large fraction of those that go in stay temporarily, but we have a good facility for getting them out of the lung: the cilia bring them back into the gastro-intestinal tract and they go right out. Particles of 1u have been stated as the happiest choice for retention. The curve for retention vs particle size looks something like this: - 12 - Notes on Mtg, 5/21 and 5/22/51 Retention 100 50 20 0.05 0.2 0.5 1 5 Particle Size (u) (Determined from a soluble, sub-micron material, UO2F2, the fumes formed when UF6 hits the atmosphere.) HODGE: (Cont'd) This curve raises the question that small particles may have a higher retention than the larger ones (i.e. larger than 0.5 but smaller than 1u). Taking a situation where 50% of the particles do not get into the lungs and 50% do, it is expected that of the 50% getting in, 50% of those would be retained in the lungs and 50% excreted through the urine. (Bradbury would like to see a curve including the whole picture--all the particles, not just those retained. Hodge says that he cannot draw such a curve. A few points are known, i.e., at 10u it is practically zero--and it goes up. With ordinary breathing through the nose, it would be pretty close at zero at 5u, also.) . . . . . . . . . . . (Questioned as to how small a bomb could be available for a test, Bradbury's answer was "one kiloton".) . . . . . . . . . . . BRADBURY: A few moments ago, Dr. Claus said that a man would be all right at 30 miles distance -- he must have assumed some particle size distribution. CLAUS: Yes, I think it is reasonable to expect in a test of this kind that a great deal of the particulate matter will be very large, and a lot will stay in the crater. On the other hand, we must remember that AFOAT in the Nevada tests picked up 10 - 12u particles clear to the east, quite a ways away. - 13 - Notes on Mtg, 5/21 and 5/22/51 SPILHAUS: I think one thing we should be able to get pretty shrewdly is what percentage of total activity goes up in the cloud, and, from a standpoint of a known and well-established wind velocity--and I'd like to see a certain amount of smoke studies in advance over somewhat comparable meteorological conditions to see what the cloud would amount to under these wind conditions--one should be able to get to a point where the air dilution is such that there is virtually an infinitesnal chance of breathing in these particles. I'd hope that we could wind up with something like this. WARREN: Since we have some general picture of how the particles get into the lung, what size and proportion of them stay there, I will ask Dr. Failla to tell us some of the relationships experimentally established in the past as to integrated dose and onset of cancer, and also take up the question of external hazard, which must also be thought of to some degree. FAILLA: I think we can dismiss the question of external hazard, because that is the simplest to calculate and one we can be fairly sure of what to expect, from past tests; it is not a serious hazard and can be controlled. The other question is again the particle problem, about which we know nothing very definite. If we assume that cancer is produced by a somatic mutation appearing in one cell, then we would predict that people having at least one or two particles in the lung would get cancer. On the other hand, I don't believe that this is the way cancer is produced, and while this is a speculation, I think we are all entitled to speculation today. But we have, for example, the instance of cancer of the skin, which occurs in farmers, particularly, because they are close to the sun and dust. Their skin become irritated, and then certain spots occur on the skin which are not normal in appearance or behavior and eventually in one of these spots cancer develops. If it had been a mutation then it would have been cancer from the very beginning, but it has not been, because observations have shown the transition from benign to malignant in the neoplasm. It is the same with radiation (causing cancers)--it takes several years. Again, histological observations show that there are these gradual changes between normal and abnormal tissues. It seems that conditions have been caused by some agent--in the struggle for existence of these cells, a somatic mutation does occur and you have cancer, but as far as I can see this does not occur in one cell alone but in a bunch of cells in their struggle for existence. WARREN: (Would, in general, agree with this), I think there are two pertinent animal experiments that might be cited. First, if one inoculates into a susceptible animal a suspension of healthy cancer cells, it takes pretty close to 40,000 of them to create a cancer in that animal. There have been a few very rare instances where in a disease such as leukemia, a single leukemic cell has produced cancer but in general - 14 - Notes on Mtg, 5/21 and 5/22/51 WARREN: (Cont'd) it takes 40,000 to persuade a cancer to take root. The second point of importance is the relation to the development of almost any type of cancer. It very rarely comes out of clear-sky, normal tissue. . .there is a period of abnormally before the cancer comes about. The most effective carcinogenic agent we have strikes a balance between rapid multiplication of cells, irritation, and the killing of cells. FAILLA: I think there is very little possibility, given a particle in mass tissue of 1 ILLEGIBLE diameter, one would get cancer, I think there would not be enough cells involved. When you come up to a matter of a 5 ILLEGIBLE sphere, however, I think you would have a very real possibility. (Shipman describes an experiment in progress at Los Alamos now, involving a fixed opening in a rabbit's ear. With a very small opening, they have given the rabbits as much as 25,000 r; with an opening of 1 cm or more, it is known that very profound damage can be caused. Just where the dividing line comes is not known--they are working on it now.) We assume that a 1 ILLEGIBLE sphere of cells that are damaged would not cause cancer, because the activity would not be large enough to give that much tissue serious damage. WARREN: I will ask Col. Holzman to speak on optimum meteorological conditions, and also, if he cares to, to comment on the variation of Stoke's law observed at Ranger. HOLZMAN: Those of you who know me know I have been an enthusiast and strong advocate of being able to do air drops in the US. You may be surprised when I say I don't think you can count on the meteorologists to do the forecasting here with any degree of reliability. . .(granted, the situation at Ranger was very good)--the real facts are that at Ranger we did not forecast the winds with any great degree of accuracy, we just didn't care what the winds were because we were so sure with air bursts that it would be all right. What I'm saying here is that you don't have to depend upon a prediction. You just beef your meteorology to the point where you're taking measurements, so that you're actually working with observations, not depending upon predictions. This is a must because of the uncertainties here. There are a number of awkward problems; not the measurements of winds because we can do this with reasonable accuracy, but we should be able to anticipate to what height the cloud will go, because when you say a 20o wind, a southerly wind, a wind with altitude--such a wind general veers or backs, it can take in a significant angle. The reason the cloud spread all over the sky at Ranger was the transport of the winds, it went so high. So you ought to know within reasonable limits the height to which the cloud will go and you can then plot accurately the points of expected fall-out. - 15 - Notes on Mtg. 5/21 and 5/22/51 HOLZMAN: (cont'd) There are some other points that have bothered me. I've started a bibliography, and have tried to draw some analogies to the popping off of a volcano--didn't get very far, but I get the feeling that you might have an aerosol develop where you get a rain of ash. There is a possibility, I'm not saying this would happen, but this would create a density current, something of a base surge phenomenon. I'm inclined to think, however, that this would be a rather local importance a great deal of the particles would fall out locally in this base surge. (Spilhaus says that such a surge was observed in the Dugway shots.) I'm inclined to think it might be even more than this. The point here is that what I would do here different from the other is that we would not depend upon a forecast but would depend upon measurements taken up to the time when we can say, okay, we'll have the shot within an hour. As for Stoke's law; no particular comments, but as you know, turbulence completely destroys the effect of this law. The size and shape of the particles also influence it. (Someone asks if one could say that Stoke's law will not apply in this case, for the particles that are important. Holzman would say this is true.) (Comment: It is particles 1u and under that we are worried about in this particular thing, and because the turbulence will maintain them in suspension--because Stoke's law does not hold in this at all. . . . then one wonders whether it is worse to about 1 kt in Nevada than 50 kt in Amchitka, because these particles could go twice around the earth in suspension!) What you run into here is the sort of thing that Rochester complains about--and it is true--it rains eventually and rains out. We could guarantee that it would not be rained out to within approximately 100 miles, or whatever you want to set up. HEMPELMANN: I think we may get some information from the further tests carried out at Kniwetok. As far as I know, and I am quoting early results, in each of the particles the average activity was about 1 mc/particle. And since these things are not additive, is., if you breathe 10 particles they'll go to 10 different parts of the lungs, it is a completely different problem from the external radiation hazard. If one of them will give you trouble, you cannot say that 10 of them will give you 10 times as much--I think it is a problem of the additional particles--and you cannot say that it is worse for one person to breathe 10 particles than for 10 persons to breathe one particle. It would seem, then, rather silly to worry about individual particles. Actually, it is the concentration of these particles that is important. It would appear that if the individual particles were going to cause trouble, it would have shown up in people here at Los Alamos who have worked with plutonium. - 16 - Notes on Mtg, 5/21 and 5/22/51 HOLZMAN: Have there been population and meteorological studies prepared for Camp Irwin and the other sites? SPILHAUS: The population studies have been carried out and some degree of wind direction studies on the Las Vegas site. Actually, one could roughly say that a B-SW wind direction is best both for Camp Irwin and Las Vegas, from the population standpoint. Such a wind looks to hit the minimum at both sites. This is crude but there will be plenty of opportunity at a suitable time for the climatology. (Nolan is introduced and asked from comments on site topography.) NOLAN: There are two requirements which limit the area of tests: (1) that it be a closed basin, and (2) that it be filled with an unconsolidated material to a considerable depth. Those conditions are more or less met only in the Great Basin Area, where there are fairly large closed basins, most of which, once you get away from Colorado drainage and the Mojave Desert, in general are floored by considerable thicknesses of unconsolidated material. (The sites under consideration are pointed out on the map.) SPILHAUS: (Reads a statement summarizing the geology of Camp Irwin.) This will hold for all of them, essentially. NOLAN: There is, however, a factor of amount and depth to ground water which has especially a local significance so far as contamination is concerned afterwards. Another factor, that of particle size--especially in the central portion of the closed basins where in general a required depth of unconsolidated material would be found, there is likely to be quite an effect of dust-sized particles which would have, at least in the northern part, a wide range of composition and might need some study in terms of the possible induced radiation in them. I would like to see whether the situation pictured on the board by Dr. Bleakney would apply here. I think the possibilities of incorporating quite a fraction of them in the dust cloud. . . .would have probably mostly local significance; that is a cattle and sheep country which would perhaps need some attention on that basis. I think there would be some need of studying the effect of ground water, because most of the stock wells are served by ground water and there is the possibility of contamination of future water supply by intake of ground water. (Depth to ground water is thought to be 500 - 700 ft, both at Yucca and Irwin. There are discontinuities in the water line, so that it might be closer to the surface in some places.) - 17 - Notes on Mtg, 5/21 and 5/22/51 NOLAN: (Cont'd) Another problem: clay fractions of the soil tend to absorb (the activity). On the other hand, in the plateau country there is good evidence that some active material is already being transported in ground water, from mining operations. (Comment: Doesn't this point out that probably one should insist the crater not be in a dry lake bed, to keep away from the clay!) SPILHAUS: (In explanation of the requirement for unconsolidated material); There is a lot of argument--the idea is to derive from these underground tests some basis for estimating effects on potential targets. These will obviously not be on homogeneous material, so one of the arguments is "why insist on homogeneous material?" However, I think that you would get so many reflections and refractions of earth shock wave in inhomogeneous material that the data would be almost uninterpretable. We know so little about earth shock even in homogenous media. To then go from that situation to an entirely different medium with totally different complexities seems impossible, but it does appear at least possible to go from a simple situation to at least a statistical interpretation of another. There should not be any vertical faults here. . .but mainly one wants fairly homogeneous seismic velocity, down and out for a certain distance (Asked about a test in hard rock), of course a test in hard rock of homogeneous seismic extent would be all right, but that is hard to get. TNT tests at Dugway are being done in unconsolidated material and we'd hoped we could get the relation between these and a nuclear shot and then study the effects in an inhomogeneous medium with TNT. (This means an ILLEGIBLE shot at the site is desirable, and this is planned--it is easy to do.) HOLZMAN: The principal meteorological factor is the fact that the wind varies with altitude. One can calculate, from a tremendous amount of Chemical Warfare information which is available, the actual eddy diffusion of the cloud. In general, it is about one in seven, i.e., for a cloud travel of seven miles, there would be a one-mile spread. Temperature stability of the atmosphere can change this, but the important thing is the actual wind backing and filling through the height at which the cloud will form. (Asked whether there is a correlation between size of shot and height of cloud)--Yes, we have some very good data on air bursts; in general, the bigger the bomb the higher the cloud goes. There is the effect of altitude and the height of burst, also the temperature stability of the atmosphere affects it, but in general one can say that correlation holds. That is why we are assuming a rather low cloud here. Bikini-Baker only went to 8,000 or 9,000 ft and tossed this tremendous column of water up -- normally, a 20-kt bomb will go to about 20,000 or 30,000 ft. - 18 - Notes on Mtg, 5/21 and 5/22/51 . . . . . . SPILHAUS: (Re the shock wave), there have been some peculiar effect from quarry explosions which make one want to avoid inhomogeneous media. CLARK: (Asked for his comments): I think Tyler made the points I would consider important--they are mainly operational. We are establishing in the Nevada area facilities for handling detonations up to about 25 kt, i.e., communications, weather, radsafe, etc., so about all I can say is that we hope due consideration is given to that area. TILER: Putting it in a slightly different way, I have a feeling that if this particular experiment turns out unsuccessfully, we have lost a continental site no matter where we put it. The Las Vegas site was chosen by a large group of people who studied this, as being the least hazardous and best of continental sites. If we are going to gamble on this (and it is a gamble, no matter what precautions we take), it might as well be done where it is operationally convenient. These operations are not simple. There is also the point of public relations to be considered. SPILHAUS: I would tend to agree, I don't think there is any advantage in building another Las Vegas. There is possibly a small advantage of railheads at Irwin-maybe not, and the advantage of having these tests together (with those of Los Alamos) may be tremendous. WARREN: There are a number of specific questions we're brought up against. The first one has already been answered: that is, presumably we want to use the smallest of the currently available types of detonations and that figures out to be 1 kt. as things are likely to exist. This presumably, from the general safety standpoint, in order to avoid kicking any more plutonium around the territory than we could help, ought to be of the U235 type. SPILHAUS: I am not concerned with what is in it, just the 1 kt bang . . . . (Bradbury says that it will be pure uranium.) WARREN: Then our next two questions are pretty closely allied to one another; how deep it ought to be placed and what sorts of instrumentation we want to give us the radiological safety information. I am not talking not about instrumentation from the blast or other standpoint, but simply from the radsafe standpoint. (This might include animals.) SPILHAUS: On the question of "how deep"; the second shot as we visualize it tentatively would be scaled to the penetration depth which one grabs out of the air at about 50 ft. This, scaled to 1 kt, is 17 ft. You can put your first shot at any depth below that. - 19 - Notes on Mtg, 5/21 and 5/22/51 SPILHAUS: (Cont'd) The Dugway series on a scaled basis go down to many hundreds of feet, that is, to the point where you get no rupture. (Asked why a 1-kt ILLEGIBLE shot cannot be fired); one thousand tons of TNT is so much volume, a huge sphere. When Dr. Warren's suggestion of a deeper shot came in, we welcomed it, thinking it would give us a further point so that in the event of deeper penetrations we would have some data. As rabbit out of a hat, a 40- or 50-ft depth has been thought of for the first one. (Question: What would be the computed depth of a 1-kt shot that just would not touch the surface? This can be easily computed from Lampson's data.) (As to criteria for cloud height): 2,000 and 3,000 ft would be pretty good as far as the cloud is concerned, unless Col. Holzman thinks that introduces too many variables from the weather standpoint. HOLZMAN: This makes it easier because you are less likely to get shear. (Comment: There are 4,000 or 5,000 ft. mountains around there, too.) CLAUS: It has also been suggested that rather than bury the thing completely, there be open shafts left. . . the advantage would be that you might get a better sample of the mixed fission products plus earth. (Comment: But it would not be a representative sample....and you might get a worse effect with a vent.) This suggestion is not original with me, I am just mentioning it--you leave a shaft to guarantee that something will get out. (Suggestions: What would happen if you had a shaft running out horizontally and a particle collector of some sort at the end of that? That would give you some idea of the particle size that would form.) SPILHOUS: As an example, we have computed the effects of 1 kt at 50 ft. In general, you can say that the difference between 50 ft and 17 ft is about as great as between 17 ft and the surface, in these studies, so that might work as a scaling point. It is order of magnitude; 50 ft isn't a bad first guess. (Question: What is the radius of the sphere of earth that would be vaporized at 1 kt?) These are the figures that we came up with: the fireball itself would be about 15 ft in radius, and the crater radius 200 ft; the volume of the fireball, 500 yd and the volume of the crater, yd3. This - 20 - Notes on Mtg, 5/21 and 5/22/51 SPILHAUS: (Cont'd) is based on Lampson's data and is for 17-ft. burial. (Question: Is it fair to assume there would be no appreciable difference in size of fireball between a 100-ft tower shot and a surface shot? Bradbury does not think so; there is quite different material to heat up, he thinks the fireball would be quite a different phenomenon) Dimensions of the crater, based on Lampoon's work and assumed soil constants, tabulated for surface, 17-ft and 50-ft burial, for 1 kt: Surface 17-ft 50-ft Crater radius 225 ft 250 ft 290 ft Crater depth 140 ft 165 ft Crater area 1.5 X 1055 ft2 up to 2.6 X 1055 ft2 (Comment: There are two advantages in deep burial: (1) the cloud will not go so high, and (2) more of the radioactivity will go into the ground. Also, more of the activity ought to fall out locally.) I've found some guesses here on the height of the cloud, don't know how they were computed. This is maximum height for 1 kt: Surface burst: 12,000 ft 17-ft burial: 6,000 ft 50-ft burial: 4,000 ft .............. (Discussion of particle size, and how much radioactivity will get out. Two calculations were made by AFSWP, one assuming it would all go up, the other assuming it all stayed in the ground. . . . Shipman believes the particles will be conglomerate things; they found this at Eniwetok. The dilution of the mass of the active material of the particle will be a good factor here.) NOLAN: (Be induced radiation in the particles): Most of the induced radiation presumably would be in short-lived isotopes, but those based on a calcium chloride environment (as at Eniwetok) might be quite different from here, where you have aluminum silicates, etc., they might be longer-lived. WARREN: As I recall, the iron would be one of the more troublesome contaminants. Is there much iron involved in this particular region! NOLAN: As an offhand guess, I would say it would not run more than 3 to 5% at the worst. However, it would certainly be worthwhile to look into this. - 21 - Notes on Mtg, 5/21 and 5/22/51 WARREN: The induced activity in silicon, as I remember, isn't a very important thing. SPILHAUS: I have a figure here--a best guest--they estimate that 50% of the fission products remain in the crater from a 17-ft depth, 75% for a 50-ft depth. (Question: Isn't it an important point that the mountains are about the height of the cloud?) HOLZMAN: You'd expect a lot of catching effect. The tendency of air currents to ooze over the mountains is a function of the stability of the air. If it is stable, it tends to go around rather than over; if not, it tends to go over. In other words, you can choose a set-up whereby very little would go over. I have also been thinking about what time to shoot, in what light to get good photography, good weather, etc. I had thought of early morning... SPILHAUS: Yes, you would choose a time somewhere in the morning hours, but not just at sunrise... HOLZMAN: Yes, wait until the sun is up, so there won't be drainage winds, but before the inversion busts up. You want a fairly good wind, say 10 mph, because with such a wind velocity you'll get a good wind direction. (Comment: The fluidizing effect of the dust...giving rise to a base surge phenomenon--this would be hopeful. Holzman thinks it is a good certainty, as does Spilhaus.) (Clark gives the population figures for the Las Vegas site and points out on the map the areas of population location.) WARREN: (To summarize briefly): We have no choice but a 1 kt U235 bomb. We think that the Las Vegas area looks reasonably good. We think there is some feasibility to a 50-ft depth for the first shot, which would give us a pretty reasonable cloud height, a pretty fair radiological safety determination with probably more than half of the stuff held back, and would still give Dr. Spilhaus some incidental information on what he wants finally to learn. FAILLA: One minor objection: I think it would be undesirable to entirely rule out the Civil Defense aspects for the other site, they have not been mentioned. I believe Camp Irwin is better from that standpoint. CLARK: Civil Defense has said they cannot get ready by the time we are ready (for this fall.) - 22 - Notes on Mtg, 5/21 and 5/22/51 WARREN: Yes, the Federal Civil Defense Administration (FCDA) has notified the chairman, orally at any rate, that they cannot possibly participate in any tests as soon as this one is. TILER: So far as the area is concerned, if I'm asked to conduct Civil Defense tests it will probably be in Las Vegas. I'll have some more information on this when I go to Washington. SPILHAUS: Just for the record, on Camp Irwin--in the event it might be needed, we did ask the Department of the Army whether it would be available. If it is needed for any purpose in connection with tests it will be available. FAILLA: (Re Civil Defense participation): It is a question of giving a lot of people some training in actually coming into contact with radioactivity. CLARK: Oh, this will be done. It is anticipated that our radiological safety group will bring in a limited number of people for training. We can do this in the Los Alamos tests and also on this. (Spilhaus suggests these underground tests be called "Windsquall" now.) WARREN: I think this is a good point to have in the record, that the interests of the FCDA have been weighed in this and that (1) they will not be ready for full-scale participation, (2) selected individuals from their organization will have an opportunity to tie in with the general monitoring work of the test. TILER: Let us say, "A limited training program will be conducted during these tests". (The discussion turns again to the question of depth for the first shot.) SPILHAUS: (Explaining the scaling considerations): Let us say that a reasonable, practical penetration is 50 ft. If you scale 20 kt at 50 kt down to 1 kt, the scaled depth is 17 ft. Now if you put the first 1-kt bomb at 50 ft, this would mean a penetration to about 150 ft, and this is a very good thing to have because may be developed to penetrate between 100 and 150 ft. And the 50 ft. for this first shot is also for other considerations, safety and the like. HOLZMAN: Why not put it another way: that you want a depth such that your cloud height will be kept to 2000 - 4000 ft? (Questions: If it went higher, would you still feel safe? Answer: This is a thing we have already determined. The most pessimistic calculations indicate that beyond 30 miles with a certain wind flow you can't exceed a certain amount of radiation.) - 23 - Notes on Mtg, 5/21 and 5/22/51 CLARK: I have some figures which Scoville worked up (puts on blackboard). This is gamma radiation from airborne, zero-sized particles, based on 8 to 10 mile wind, spread laterally but not up and down, no vertical shear. The calculation assumes no fall-out, that the particles remain in the cloud; and is for one hour after burst: Distance from Zero 1 Mile 2 Miles 4 Miles 10 Miles Surface Burst 5 r/hr 1 0.25 0.05 Underground 10 2.5 0.1 -- (Question: At what height can you count on not having a reversal of wind direction?) HOLZMAN: That is the point I made at the outset: you would not rely on predictions, but take measurements an hour or so before shot time, shoot wherever it is operationally feasible. This area is not at all like the Eniwetok area; you don't get a reversal until you get up to 50,000 or 60,000 ft as a rule, in the stratosphere. So from that point of view the height is not important, because you can pick a day when there's no chance of reversal. You can also pick a day when local fall-out will be great and get rid of as much as possible of it in the neighborhood. CLARK: On the basis of figures such as these, one would expect to have to evacuate the mining activities within a maximum of 20 miles radius. There are mines 15 miles away, and there's also a tungsten mine around 40 miles away. BRADBURY: Do I gather the committee feels that if you do evacuate people to within 20 miles downwind, this is adequate safety? CLARK: And also do you approve of evacuating people this way? Does this raise a public relations question? WARREN: I raised this with the Division of Biology and Medicine. They felt that if this were a small group and skillfully done for a short time not to exceed, say, a week's time, there would be no question involved. It would be fairly important to make clear to them this was not going to be a continuously recurring event, but for one, two, or three times it would be a feasible thing to do if it were adequately handled from the standpoint of advance publicity, selling, etc. (Hempelmann questions the figures on the board. Bradbury asks again if evacuation within 20 miles downwind would absolve the AEC.) - 24 - Notes on Mtg, 5/21 and 5/22/51 WARREN: (Cont'd) I think the answer to that hinges not only on the distance--we have not only a distance factor, but an actual wind rather than a calculated wind to deal with, and we have the advantage of intervening mountains, being able to choose a time when there is no appreciable spillover of the wind over mountains.... (Holzman would not say completely no spillover, but a great diminution) ....and with this I am not clear whether it is a 20-mile or 30-mile evacuation. CLARK: Twenty miles will include the mining activities. If you get over to 35 - 40 miles (depending on the site) then you start to get into the Hicko Valley. I would not recommend evacuating that valley unless it is absolutely necessary; there are a lot of people, and it is a nice valley to control from a radsafe standpoint--quite a narrow canyon, normal to the winds. Also if you get to 40 miles, there is more than one mountain range in between, a whole series of ranges. HOLZMAN: Isn't the way to answer this question to say that we will not shoot under conditions which require evacuation beyond 20 miles? BRADBURY: You must have some criteria -- that if the shot is fired at this depth, this material, this yield, the wind in a given sector of directions up to x thousand ft, it will be sufficient to evacuate out to a certain radius, to give the AEC all the assurance it needs that it has taken every precaution. . . . (Suggestion for wind criterion: say the wind must be 5 - 10 mph and separately that it must be a steady wind.) HOLZMAN: Actually a higher velocity might be all right, but if you have steadiness and direction...you don't want to tie yourself down too much either (as to steadiness), because if you get a velocity shear this gives greater dilution. What you really want is, you don't want the cloud to go over an area which is apt to cause some possible hazard. TILER: Why not pick a typical spot and say that 20 miles is adequate for these conditions; use this as a typical condition and work around that accordingly. I would want to sit down with Holzman at the time and discuss the shear, etc., with him, in any event. WARREN: Assuming that we have a reasonably steady wind of a surface-to-1000-ft velocity of 5-10 mph or thereabouts, is a 20-mile evacuation downwind adequate? HEMPELMANN: In case a condition develops of abnormal fall-out, is there any question of the time of return? It's clear that spotty fall-out can occur to 15 to 20 miles. - 25 - Notes on Mtg, 5/21 and 5/22/51 WARREN: I think that would hinge upon the monitoring at the time...Unless someone objects very seriously, I would suggest that we consider a radius of 20 miles downwind. That seems very reasonable. TILER: We might use our own judgement, actually wait until the fall-out occurs. CLARK: But the people in the Groom mine area are trapped in there, they are isolated (because of bad roads). We would have to get them out beforehand. We can get to the Hicko Valley any time, there are good blacktop roads. SHIPMAN: I would hate to think of a post-shot evacuation, would rather do it beforehand. It is bad public relations and we could expose them more than if they buttoned themselves up in the house. (Someone questions the effect of blast on the mine. Spilhaus says this would be 0.005 g's at 10 miles -- people inside would be safe.) (Suggestions: Why not leave this evacuation thing in fairly broad terms: removal from an exposed area, and just how it is carried out the people who have that responsibility can settle best?) WARREN: (Be a suggestion as to using gas masks): I don't think so -- it is psychologically bad and also almost impossible to enforce. SHIPMAN: From our experience with the fall-out after the first shot on Eniwetok, we found most of the people had fall-out in their hair. I think we could gain more by urging the people to take baths. (Again, bad public relations.) HEMPELMANN: One point makes my unhappy; all the discussion of particle size indicated that we had absolutely no idea whether breathing these things in was serious or not. I think we should at least have some philosophy or basis for saying that we think people 20 miles downwind would be safe. I would like to propose this: we can certainly never guarantee that there particles aren't going to be breathed, and I would think if we could say that at 20 miles on the basis of the measurements made at Eniwetok, where the external radiation levels were extremely low, that it is quite improbable that any given person would breathe a particle, so far as I am concerned that would be safe. (Comment: If you evacuate to 20 miles, the next person is essentially at 40 miles.) I would say on the basis of the preliminary work I quoted, that if the radiation levels of 1 mr/hr obtain, it is quite improbable that anyone would breathe a particle. (However, we actually have no facts.) If you can predict what the fall-out and the local spread will be, if you say that it is not higher that 1 mr/hr, I think you can say that no one is going to breathe a particle. With these data, and add another - 26 - Notes on Mtg, 5/21 and 5/22/51 TILER: We will take measurements in Las Vegas as we did before -- we get more ground shock from a truck going by then from the blast. WARREN: (Suggests adjournment for the afternoon.) We must still take up the questions of suggestions as to instrumentation from radiological safety standpoint, and what the criteria are that we will apply to the data obtained from this first shot to enable us to move promptly, so as to be able to keep the prompt sequence of test operations that are essential. (Tyler says that a two-week interval is not the minimum -- he would like to make it ten days if this is possible.) The time it takes for data collecting and analysis will control this. From what was done at Eniwetok, we may be able to speed it up. As for the two sites under consideration at Las Vegas, I would suggest it could be left to operational detail to determine the feasibility between the two. As a general preamble to our discussion, everything we have said is on the basis of calculation and speculation, and it applies only to the first shot. (Meeting adjourned until the following morning.) - 28 - II Morning Meeting - 22 May 1951 HEMPELMANN: No consideration was given to fall-out of particle size. Stoke's law is based on a ground dose under ideal conditions. Ground dose probably will not follow that model. I would like to see more careful calculations done by persons more qualified to consider the problem. Our calculations are probably based on a figure which is subject to change later on. Any figure which we accept now will probably influence future planning, and I would much rather see it done based on opinion of what we consider safe as far as particle size and distribution. I would like to see the whole problem reexamined by phenomenologists and leave the exact distributions up to their best opinion. I would like to use our assumed figure of 20 miles and base everything on that, only to revise it later. FAILLA: Twenty miles is the worst possible figure -- the worst that could occur. HEMPELMANN: If you look at Alamogordo, it was spread out over a quarter of the state of New Mexico, even though the amount of fission products was 1/20 of that. On the basis of what we discussed yesterday, your safe region would be in an area where there would be a certain number of particles/m3 of air, probably in the region of 1 mr/hr. Our safe region is based on how many particles this committee is willing to let another person breathe. WARREN: Let persons breathe one particle, because chances of that happening anywhere in the northern hemisphere is a good possibility. One very useful point is that the Reactor Safeguard Committee has been making a somewhat similar type of calculation and later in the morning I hope that we can arrange for Teller to give us the data based on their calculations. How would it be if we examine what I think is the most fundamental premise here, namely that if external level is 1 mr/hr, the chance of particle inhalation is very slim and not exceeding one. HEMPELMANN: I would be perfectly willing on that basis and then leave it up to persons who are qualified to consider this cloud to say where this would be. I am probably completely wrong, but I don't have much confidence in that calculation. WARREN: I think there is one important thing that we have to consider here in relation to the Alamogordo shot. We are putting certain limitations on cloud height and wind velocity and steadiness that I think would have some bearing on reducing the spotty type of fall-out that was characteristic at Alamogordo and was not of the other air bursts. Suppose we lay this on the table until we have a chance to see what Dr. Teller has to say. - 29 - Notes on Mtg, 5/21 and 5/22/51 HEMPELMANN: Are these calculations based on the cloud as a constantly expanding sphere? FAILLA: They took the cloud to consist of something of this sort: (drew diagram on board) Vertical section of cloud Horizontal section spreads out like this HEMPELMANN: This is 4000 feet high, then? SPILHAUS: That is the thickness of the cloud at 1/4 hr, 1/5 mile. This is a conservative figure. FAILLA: If the cloud won't be vapor, it will solidify into particles. You can figure out the mass of one particle and divide it into the total particles. If they remain suspended, you can figure out what the concentration will be at any distance. When you figure it like this, you get a larger concentration than you can possibly get. You will get a maximum value which is certainly not realistic. THOMPSON: Is there a possibility that Dr. Hempelmann's calculations are related to a channel which might make these calculations void? FAILLA: The cloud fans out within a certain angle of 20o and the height does not change very much. How many particles will fall out at various distances? That is a speculation. If you get a low level at a distance of 10 miles then you don't have to worry how many will fall out. How many particles can conceivably go to a distance of 10 miles? That is the question. SHIPMAN: It has been stated that these calculations have been based on the worst conditions that could be produced. In situations so far where fall-out has occurred, namely, following Trinity and Dog shot at Eniwetok, it was spotty and quite intense in certain areas and at a minimum in other areas quite close to that, and so excepting these calculations for a homogeneous cloud I think that conditions rather worse might be encountered at some point within the triangle. FAILLA: It is based largely on speculations as to what air currents will be at that moment. The cloud has come a considerable distance in the air -- 20,000 ft for the small shots and considerably more for larger ones. The majority of the activity and certainly most of the fission products have apparently gone up in the height of the cloud. The small particles have been mostly in the height of the cloud. The small particles have been mostly in the head of the cloud and have had a great distance for dispersal. Now the height of the cloud will go only three or four thousand feet up into the air and particles, instead of coming down at Rochester, will come closer to us. In mountainous areas in tests last winter we saw the lower part of the cloud just envelop Charleston peak like a blanket. The greater amount - 30 - Notes on Mtg, 5/21 and 5/22/51 FAILLA: (Cont'd) of activity seemed to be on the back of the mountain where there was a certain amount of turbulence. We will be rather intimately connected with the upper part of the cloud, which we have not had to contend with before. . . . . . . . . . . HOLZMAN: We do have data at Trinity and at Greenhouse. Has anyone used this to try to explain away fall-out? Has anyone made calculations using height of cloud there and same way here and seen whether the radiation level here fits the theory? If they are greater, it seems we ought to explain them and see if the model is still all right. HEMPELMANN: If you look at a map of the fall-out at Trinity, its zero point is down here (pointing to map), but I think the distance to the maximum fall-out is about 20 or 25 miles. If you will notice the red streak, it is 15 r/hr, and next dose is 3 r/hr. This line is 1 r/hr, measured at 4 hrs after the shot, which is the time of maximum build-up. it certainly does bear out the point Tom mentioned, that when particles do come down there may be a concentrating effect. Within an hour you can get from 1 to 15 r. On the far said of hills the intensity was apt to be higher. These highest measurements were recorded in a valley 800 - 1000 ft deep. They were apparently large particles. SPEAKER (?): Gamma radiation there to the cows presented a beta ray hazard because it nestled down in their hair and into the skin and didn't give them enough gamma radiation to kill them. SPILHAUS: If we can get conditions under which measurements were made -- If you get set a number of milliroentgens on the ground the number in the air is less. How long were particles in air when measurements were made, and was it after they were settled or not? HEMPELMANN: If you consider the activity of 1uc 4 to 6 hrs after the shot ..... 100 ILLEGIBLE/hr, which is the level which we are concerned with. One particle per square centimeter on the ground. If you assume the cloud is passing over the area 1200' high and assume particles were distributed in that column, Brennan indicated 3 parts per cubic meter -- actual measurements were smaller by about 10 -- in 100 mr by 8 mr sucking air at the place indicated that in one meter there were three particles. SHIPMAN: Radiation levels-as shown on map are approximately 4 hours post shot--four hours later, at H + 8, levels had dropped very much lower than one would expect from the half-life of material. We got significantly high levels at Ranger. HEMPELMANN: 19.5 miles from zero at Alamogordo, radiation started at 1-1/4 hours after explosion, rose at 2-1/2 hours to 2 r/hr. It was maintained - 31 - Notes on Mtg, 5/21 and 5/22/51 HEMPELMANN: (Cont'd) at that level for one hour and fell rapidly, and 4 hours after was 1 r/hr and then the decay rate followed the 1/t law. It was apparently some geometric dose. SHIPMAN: Because of that, at Ranger we steeled ourselves not to get worried about early reports of high intensity. We knew essentially the set level would fall again. HEMPELMANN: I can give you an estimate of what the area which measured 15 r/hr was. I think it was 15 miles by 3 miles. At Alamogordo the highest area was about 25 miles from Alamogordo. I can find out -- this map doesn't give the scale. FAILLA: If fall-out of that magnitude has occurred, one might expect it again. SHIPMAN: It seems to me at Greenhouse one thing was forgotten. 100 - 200 mr would go up into the cloud and particles of that size are bound to come down. The meteorologists said that if they had been told the particles were that large, they could have told us that it would come down! We would be able to predict how particles come down if we assume ideal conditions. SPILHAUS: We want to eliminate Ranger as much as possible, because those shots were air bursts, whereas Trinity, Greenhouse and Sandstone come closer to what we were talking about -- surface bursts. SPEAKER (?): Try and assume a cloud that wouldn't be greatly higher than its uppermost part. How much distance do we have here? Thirty five miles to the center of population. If we stick with the SW wind that has been spoken of, I think it is about 40 miles before we got to the valley. HEMPELMANN: The area I was looking for was 12 miles by 1 mile, and the nearest point was 22 miles from zero point. HOLZMAN: The weather was very bad at the time of shot and so the data here were actually taken pre-shot time -- and this time the weather cleared up and we shot about one or two hours and winds could have changed significantly from these, but I think this is a good guess. Lowest winds were SW below 10,000 ft, ran from 10 to 15 knots at 10,000 to 15,000 ft, 10 to 30 knots about 15,000 ft. It was what we would call a non-steady wind situation. SPEAKER (?): The figures Clark has dug out on the distances are 15 miles to the mine, and assuming evacuation, it is 44 miles before any further evacuation. - 32 - Notes on Mtg. 5/21 and 5/22/51 CLARK: Ten degrees N of E is high population center. It is 44 miles up to that populated valley. SHIPMAN: You fly over that valley and you wonder whether it is populated or not. Little tiny ranches and small villages. Collections of two or three or four houses. Certainly any post-shot attempt at evacuation would be very difficult because you wouldn't have people in groups. You would have to pick up a few here and a few there, etc. The next valley running from Pilosh, Caliente, is a good 75 miles wide at its closet point. The total population is 2600. Caliente is a railroad junction. Between Hicko and Mowapa that is no telephone. The monitors on that road were a little put to get their reports in. CLARK: We are putting in an ideal radio station, on Charleston. SPILHAUS: If you had a S-SE wind, there would be no possibility of hitting this population. CLARK: A S-SE wind at the first 10,000 ft. The mine is to the east. We plan to evacuate the mine. There is a maximum of fifteen people. There were 15 geophysicists there ten days ago. We visited the mine and found they were very cooperative. The reason for evacuating them is that there is a bad road out. It is better to get them out so that there is not a hot cloud above them. HEMPELMANN: At Trinity the hottest area was about a mile wide. It is impossible to survey all that area. Geiger counters in those days weren't very good. HOLZMAN: I had assumed that this was not a fall-out but a rain-out. Rain-bearing clouds were 50 or 60 miles away so there would be a question as to whether it was a fall-out or a rain-out. Isn't this somewhat inconsistent? SHIPMAN: As to whatever caused rain-out or fall-out at Ranger, I can't see how particles can drop from 8 miles up and hit areas 1 mile wide. SPILHAUS: How do you know it wasn't rain-out? SPEAKER (?): People in surrounding areas observed no rain. There was no mention of it from people who lived in the hot canyon. Perhaps the rain didn't reach the ground. And these levels are consistent with those at Greenhouse, 35 r/hr. SPILHAUS: You would get 1/20 of the total radiation if a hot spot occurred again. HEMPELMANN: This doesn't seem to set with the picture of 4 miles from zero established yesterday. - 33 - Notes on Mtg, 5/21 and 5/22/51 SPEAKER (?): At four miles, it was 1/10, yesterday. FAILLA: Is there any definite size of particles? HEMPELMANN: Guessed at particles of 100 microns. The reading was on the lee side of hills. It must have been 15 r/hr, but we just couldn't find it. It must have been though, since the cows were burned. Some were burned at a distance of thirty miles. But the cows in these areas travel many miles each day, so we have no exact idea where they were. SPEAKER (?): As far as I can see, making calculations similar to those made are not helpful to us unless we introduce some new factors. Some might come out of these recent tests> The fact that there was a fall-out on one of these tests at a considerable distance from the site of explosion cannot be discounted. There was one case in which there was a fall-out and in which cows had been injured. So there might be activity and we must estimate at what distances that could occur. At Eniwetok it was 30 miles. WARREN: There is 1/20 the activity involved, and there is also the expectation that a fair amount of the activity will be held in the region of the crater while we based our assumption on all the material's getting up into the cloud. The actual possibility is that a fair amount will be retained in the walls of the crater and the material that falls into the crater after the burst. CLARK: At Eniwetok in Dog shot, total activity was 1/90 -- 90 kt burst. Tom has in mind to procure a large number of air-sampling devices to be placed wherever seems the best place. SHIPMAN: We just can't send people around trying to catch something. Air sampling equipment has to be planned in prodigal fashion in the hope that we can get a good cross-section. SPEAKER (?): (drew a diagram on board) The radiation activity was around 40,000 ft, so even if there was a fall-out chances were small. Now we have a cloud at 4,000 ft and chances are much greater. There might be a higher percentage of activity in this cloud since it is so low. CLARK: This is an underground test, and not a surface or air burst. - 34 - Notes on Mtg, 5/21 and 5/22/51 . . . . . . . . (A discussion of foreign sites ensued. It was agreed that while such might be desirable in some respects, it was unrealistic from a political standpoint at this time..) HODGE: Following Hempelmann's general approach, I would suggest our trying to agree on conditions which we know are safe. Isn't there some r/hr that we would unhesitatingly say to be completely safe even if it all fell out? WARREN: I think that this is a feasible thing to shoot for. I am quite sure that the level already mentioned--I believe Dr. Hempelmann brought it out--of 1 mr/hr is absolutely safe, beyond question in such an area. The question is how far above the one could move with safety. There I think the tie that we need is the proper number of particles per square meter of air as we move up from that point. Have any of your calculations taken that into consideration? SPILHAUS: I don't believe so, not in relation to the activity. But this could be done, except that the number of particles--one would have to assume different particle sizes. WARREN: We are speaking now of internal radiation; as far as the over-all amount of radiation is concerned, it is external, but we're trying to figure the relationship of internal hazard to the reading of external radiation. FAILLA: The total number of 1u particles is 1020 in the fireball -- assuming they're all 1u particles -- and in the crater it is 3 x 1022. Total activity . . . .is 1.3 x 1013 curies . . . for 10u particles the activity will be 103 greater. (This for 1 kt.) (There is some doubt that we can relate the number of particles in the air to the activity on the ground.) WARREN: On the other hand, would not a reading of a meter in the area give you an approximation of the number of particles present, both still suspended passing through the cloud and on the surface? FAILLA: Yes, you can get a reading on the meter that will indicate the total activity in the cloud. There is a certain concentration in the cloud, making certain assumptions--you can get that. HEMPELMANN: We have this one measurement of the number of particles that fell out. SPILHAUS: You can get the number of particles if you know the volume of the cloud. Taking a distance of 20 miles--let us take the 3-hr figure--for 1u particles (assume they are all 1u particles)--I get 3 X 108 particles/meter. - 35 - Notes on Mtg, 5/21 and 5/22/51 . . . . . . . (Schulte come into the meeting and is introduced. He will describe the situation at Eniwetok.) SCHULTE: After the experience on the first shot at Eniwetok, of course, there was a great deal of interest in this matter of fall-out, and one of the first things done was an attempt to determine the particle size. Of course, this was done after the shot had occurred and the information obtained was to a certain extent circumstantial, but it appeared that the material that fell out was all of the order of 100 to 500u in diameter. This, as I say, is somewhat circumstantial because samples were not collected at the time of the fall-out. The manner in which it was done was that the ground was surveyed for spots of activity, and I think this is also significant, that the activity was not uniform but gathered in certain spots. These spots were localized as much as possible, the soil gathered up and halved, analyzed for activity and halved again--until eventually the activity was found to be confined to one or two particles for these hot spots. Just by the laborious job of dividing each sample in half, seeing which was hot, and finally working under the microscope. . . these particles measured from 100 to 500u in diameter. Now this work was to a certain extent prejudicial--the method finding the original spot would be prejudiced to some extent by large particles. On the final shot, provisions were made for air sampling. A destroyer was utilized that was on patrol; the weather people were able to predict to a good degree of accuracy where fall-out would occur, the destroyer was sent out, and we sampled out of the air. The samples gave no appreciable activity until 5 hrs after the shot. Samples were collected with a cascade impactor. In this case, when it was counted it was found that all the activity was on the first two stages of the cascade impactor. We examined these two slides by blocking off portions of the slide and found here that again the activity was localized on a certain portion of the slide. We put this under the microscope in this particular area we searched there was a particle similar to what had been located previously and we found that more than 99% of the activity was on this particle. There were two particles on stage 1 of the cascade impactor and one particle on stage 2. One particle measured 80u, one 100u, and one 200u. These three particles constituted practically the entire activity of the sample ILLEGIBLE collected. This ties in with the other data, indicating that the material isolated on the first shot was actually the material that was airborne... The destroyer was cruising from 10 - 15 miles offshore from practically due east of the explosion. - 36 - Notes on Mtg, 5/21 and 5/22/51 WARREN: I think that it is significant that the activity is contained in particles of this size, because these particle would have no significance insofar as internal hazards is concerned. BRADBURY: Remember this is for a very specialized operation, totally different from the one we are discussing. SHIPMAN: The character of the soil out there seems to affect it greatly. At Ranger, more than 90% of the activity was on the final stage of the cascade impactor. There we had a medium particle size in case of 0.6 and in one case of 0.3u. One of these samples was taken very close to Indian Springs, the other about 9,000 ft up Charleston Peak. (Bradbury stated that the situation at Eniwetok seemed to be that gross particles of coral were carried up essentially by the updraft, had picked up some of the activity and fallen down. There is also the vaporization of large amounts of coral and subsequent recondensation to consider. He pointed out that the height of burst of the Ranger shots makes that situation inapplicable to our considerations here; the ball of fire did not touch the ground except for the F shot, so that again there would just be gross particles carried up. He feels that the only thing which has bearing on this is the Trinity case, where the ball of fire did touch the ground and the kind of ground we are discussing here.) (Schulte believes one of the significant things is the accuracy with which the weather people were able to predict where fall-out would be found. Holzman is afraid this is not very impressive: at Fitzwilliam he predicted the fall-out and they found it where he said it would be; however, they also looked in places which he had not specified and found good samples there.) (Schulte confirmed the fact that at Kniwetok the concentration of particles was about 3 per cubic meter at an 8 mr/hr level for gamma radiation. This was determined by the fact that they isolated 3 active particles for each cubic meter of air sampled, the samples taken at the time when the background on the ship was increasing. They sampled during the entire time of fall-out and the peak was about 8 mr/hr. It was very constant for 5 hours after the shot at about 1/10 mr/hr, rose very sharply and then fell off. Samples were taken with the opening of the impactor facing into the wind.) WARREN: Would it be worthwhile now, with these added facts in hand, to try to make a certain number of assumptions and see where we come out? One of the first things I think would be helpful would be an approximation of how much of the initial material we might expect to be in the cloud. We start out with 1/20, roughly, of the Trinity amount. We assume that - 37 - Notes on Mtg, 5/21 and 5/22/51 WARREN: (Cont'd) all of Trinity plus the number of tons of steel in the tower could contribute to the activity of the airborne material there. Now, in the light of the crater shape and characteristics, it is obvious that a certain proportion at least of the activity is going to stay in the crater itself. Would you dare hazard a guess, Dr. Bleakney, as to what proportion might stay both in the walls of the crater and the loose material that falls back into the crater, for a 50-ft burial depth? BLEAKNEY: I don't think I can make any better guess than has already been made in some of these preliminary calculations--I think it was about 1/2. SPILHAUS: One-half is probably conservative for 50-ft burial, it may even be 75%. One-half is on the safe side. FAILLA: I should like to suggest that the uncertainty involved in the final calculation is much greater than a factor of 2. WARREN: Well, I think we have a factor of safety in that 1/2. Second, at this depth there is a pretty fair indication that there will be some type of base surge phenomenon which is going to keep an appreciable amount of activity fairly close in. Third, the two fall-out cases which we have cited here, one that of Trinity and the other Eniwetok, are 20 odd miles from zero. The energy with which we are dealing here is 1/20 to 1/90. The measurement of the particles that we have at Eniwetok shows them to have a size that would not be an internal hazard. I think also with the cloud height less we can assume that the distance of travel of the particles will be appreciably less. Is that fair? HOLZMAN: For the size of the particles that will fall out. WARREN: ...and that we will have an appreciable degree of dilution from the mass of earth that is vaporized. (Question: Won't there be another element of dilution in the mass that is carried up in the cloud--the dust-sized particles--which will be a much larger amount then?) It is my impression that the fall-out patterns that have been observed are so erratic that making an attempt at a model fall-out would be pretty impractical. Is this within the range of possibility? SPILHAUS: I don't think we have a mechanism to explain this peculiar Trinity fall-out nor the one at Eniwetok, and if you don't understand the mechanism of the one observed.... NOLAN: Fall-out seems to be related to the particles that were physically brought up in the blast...... - 38 - Notes on Mtg, 5/21 and 5/22/51 SPILHAUS: This plating effect--you blow out a lot of earth and then the vaporized earth sublimes around these. This would tend to make the particles of a larger size. SHIPMAN: Those samples from Ranger were collected from what was essentially a visible dust cloud. It was just like the stem of a water spout--the cloud itself went on up and moved away, the stem flattened out and it was very easy to differentiate between them. Most of this had no contact with the ball of fire itself, it just came up like a finger and moved off. FAILLA: Is there evidence that a fall-out has occurred at a greater distance than 25 miles? HEMPELMANN: Not at Alamogordo. The only think I know is rain-out that occurred, this is not what we are thinking of here. (It is suggested that the assumption can then be made that the main worry is within 25 miles, and that this assumption is perfectly safe because here we have 40 miles to play with. Thompson believes this is a risky assumption; it is a plausible basis for faith but not a good basis.) HEMPELMANN: I don't think you can be too excited about these Trinity data, because they were obtained from roads. The actual amount of surface covered in this survey is small compared to the total area. HODGE: I believe, by whatever mechanism, I believe we are going to find a great deal more of this aggregate business in which large particles are carried up--so that instead of having most of the activity in a very highly disseminated form we may find a larger part of the activity in the larger particles. This makes it safer, might even make it full out faster. WARREN: Suppose we line up these various thinks mentioned and begin to shape them up something as follows: With the low cloud height, with the probability of large particles, with the strong possibility of an appreciable amount of activity being involved in the base surge, with a steady wind of low velocity, with intervening mountain ranges, with the observed instances of fall-out (even though they are open to question as to their completeness of pattern) with the fact that we are stepping down the amount of source material by a factor of roughly 20 to 100 --it would look as though this 20-odd-mile ILLEGIBLE might be entirely safe, or if not entirely safe, at least reasonably safe. (Suggestion: could you compare it with the state of information pertaining at the time of the first test? Could you say that relatively the uncertainties are not more serious than they were - 39 - Notes on Mtg, 5/21 and 5/22/51 WARREN: (Cont'd) at the time? The trouble with this is that the first test was conducted in wartime, this in peacetime. Theoretically, the time to do research and development is in peacetime, but in actuality we always wait until wartime. It is a question of calculated risk, and Failla believes that the time has come when we should take some risk and get some information for the future situation. In other words, we are faced with a war in which atomic weapons will undoubtedly be used, and we have to have some information about these things. With a lot of monitoring, the end instrumentation will give us the information we want; if we look for perfect safety, we will never make these tests.) I think our frame of operation is not in the political sphere but to do the best we can so far as the radiological safety angle is concerned. The face that both the Armed Forces and the Commission have decided such a test is desirable ought to be enough from the standpoint of politics. Our problem is the feasibility and conditions under which it can be carried out with the maximal safety and, if it cannot be carried out with complete safety, to state as we see it what the particular hazards involved are. (At this point, Warren read the draft of his summary of yesterday afternoon's meeting. For a complete record of the agreements reached, the reader is referred to the final committee report. Some of the discussion is presented below.) SPILHAUS: I think the feasibility of carrying out an underground shot in the US, if depth is not specified, can be accepted right not--it is feasible if you bury it deep enough, so it boils down to the question of depth. BRADBURY: I still with it could be stated more plainly here that on the basis of present information one really believes the next shot can be done safely. One has said nothing about what you will do with the data and how much less safe the next shot at 17 ft or at the surface will be. I believe it is necessary to state the criteria on which we will move to the next shot on the basis of evidence obtained in this test. In other words, if one made at this time with this document (the final committee report) the best possible guess for the fall-out pattern for this test, and for the 17-ft and surface bursts (it would be possible to proceed to the next tests with more certainty). (There followed a discussion of the matter of external radiation hazard, which is tied in with the fall-out pattern and half-life of the material. Schulte stated that at Eniwetok the activity decay followed reasonably well the exponential minus 1/t relationship -- it appeared to be between t-1 and t-1.2. Shipman said that at Ranger a fair amount of 8-hr activity was observed.) - 40 - Notes on Mtg. 5/21 and 5/22/51 WARREN: I would almost say from the discussion thus far that in the light of the size and activity of some of these particles, their unpredictability of fall-out, the possibility of external beta burns is quite real. I think we could say there would not be an external hazard so far as gammas are concerned, but are we safe in ruling out the betas? FAILLA: How about saying "a fall-out which may present a beta or gamma hazard will occur within the confines of this reservation", and then we would have to go into a certain number of r/hr. (The question of whether a 25-mile radius downwind of evacuation was sufficient was debated at length. It was suggested that it be extended to 45 miles. Hempelmann felt that any statement should emphasize that the matter should receive further detailed study. Schulte pointed out that there will be more data available from Eniwetok, but Bradbury does not believe this will apply to the case at hand-he feels it will be completely irrelevant, that the only data even vaguely applicable are those from Trinity. Thompson expressed the opinion that this debate is focusing attention on the question of whether enough evidence exists to base doing the tests within the continental limits, or whether they must be done outside the country.) HEMPELMANN: I would like to say that we propose certain biological limits and then use the best possible calculations to arrive at the distances. One mr/hr means that a person will probably not be harmed, but I think this should be checked because it is a preliminary calculation. On the basis of fall-out from Trinity, saying that came from over 12,000 ft (and it must have done so), the average particle size should be on the order of 80u. . . . (Question: Can one say that the average particle size would be approximately 80u and there would be none of 1u? Can one make any statement that very probably the particle size distribution from a subsurface burst would not differ markedly from the Trinity particle size? The group did not feel the data warrant such a statement. Bradbury suggested a calculation by which the number of particles in a subsurface shot might be at least naively related to the number of Trinity particles.) CLAUS: Can we arrive at some figure that seems to be a reasonably safe radiological condition, then attempt to determine the probability that this might occur? We might find that the probability would be so low there would be no point in even thinking about it. That is, can we go at the problem the other way--say how much radiation we will tolerate and what conditions are necessary to produce it. (It was suggested that the accepted international permissible dose level of 300 mr/wk be used. Shipman thinks this is unduly restrictive, having been set up for laboratory workers dealing with -41 - Notes on Mtg, 5/21 and 5/22/51 CLAUS: (Cont'd) such radiation all their lifetime. Failla pointed out that the permissible internal dose level will be even more restrictive. Another suggestion was to set up the condition that people would not be exposed to more than one particle at a level of 1 mr/hr. There was not general agreement on this criterion.) WARREN: What we're attempting to do is to set up a test that outline the safest method of operation we can figure out. I think when we come to some of our latest criteria, the chance of any portion of the cloud getting into any concentrated form 40 miles away will be extremely slight. . . We are taking this one free-floating point which is not at all firm as the only point we can pin this to at all. And what we must say for the next point is that if in the actual test the number of particles exceeds such and such, we would start evacuating the population and we would say that another test could not be carried out. (After further discussion, the meeting was adjourned for lunch.) - 42 - III Afternoon Meeting - 22 May 1951 (Warren read a set of weather criteria written up by Holzman. It was accepted, with the actual number of miles within which rain-out should not occur still to be determined.) (It was agreed that the actual depth of burial for the first shot should be set specifically, but should be chosen to give an estimated height of cloud of 4,000 ft for the maximum. Lampson and others will be asked to make a calculation of the depth this will entail.) (The criteria for the site from the standpoint of topography were agreed upon, and are as set forth in the final report of the committee.) CLAUS: I have a calculation here of the number of particles which come out, a very conservative number, on the basis of the bomb alone: ~ 30,000 particles/m3. Now if you include 500 yd3 of fireball, that would be increased by a tremendous number, something over 100 times, to, say, 300,000. This is based on the assumption that everything came out of the bomb, converted into an infinite cloud, converted into 1u particles, the cloud passes over and the people are in the middle of it, and that the radiation level reaches 2 mr/hr (computed from the 300 mr/wk tolerance figure). In order to produce such a level, the number of particles would have to be 30,000 (or 100 times that if you include the earth).. . . So that, I think, eliminates the need of any idea of calculating permissible particulate matter in terms of r/hr -- we can pretty well throw that out and take that quantity in the air on some other criterion. (Comment: Another way of putting Claus's calculation is that to get that concentration, one would have to inhale 5 kg of earth.) FAILLA: Perhaps, as Dr. Warren suggested, if we take the accepted concentration of Sr90, and figure particles /m3 of air, or per liter--that turns out to be 40,000 particles/liter, which is 2 x 10-10 uc/cc . . . . .This permissible concentration in air is based on the material being soluble so that it can go to the bones. So this may not help us. WARREN: I think we will have to have some sort of number to use in order to get some measure by which we can decide whether the data in test 1 permit us to move to test 2. FAILLA: We have to decide someway or other how many particles/m3 of air you would say are satisfactory from the standpoint of hazard. The air breathed by a man is 20 m3/day. . . . (Ways and means of making such a calculation were discussed. Applying the figure for activity of 1 u c/particle to the 40,000 particles mentioned earlier was agreed to be unrealistic, since most of the material in the particles will be earth.) - 43 - Notes on Mtg, 5/21 and 5/22/51 FAILLA: (Cont'd) In the past we have dodged this issue, and I'm afraid we'll have to dodge it this time. Could we say that the number of particles/m3 should be as low as possible? What is reasonable for the number of particles/person/lifetime? (Hempelmann thinks the ideal thing would be to say that nobody would get any of these particles. It was suggested that if the 40-45 mile range were evacuated, there would not be anybody to inhale the particles, and beyond that range the hazard from particles would not be appreciable.) WARREN: I can foresee unless we do grab some particular figure and put it down, sitting down with just the same puzzlement after the first test, and wondering whether to go to the second test. While I hate to pick a useless number, I think we can figure roughly what the chance of getting an aggregation of these things in the lungs would be. HEMPELMANN: Isn't the whole picture changed by the fact that we think now we may be dealing with many particles, each of which has low activity? Can't we worry about it on the basis of the total activity absorbed? FAILLA: (Would tend to disagree.) Let us say we figure out now many particles a man would inhale in the next 20 years and may for this test that would be satisfactory. WARREN: Again, that would be a pretty astronomical number. I don't have the figure but it would something like 10o particles. CLAUS: If we run down the list of permissible exposures, we find in almost all cases 10 x 10-11 uc/cc as a reasonable average value for permissible air concentration. Now out of this bomb something like 108 curies of beta. (He makes a calculation.) These are beta particles rather than gamma, the worst kind you can possibly collect. Figured on the basis of the over-all accepted dose, based on an average value of 10-11 cu/m--calculated on the bases of the total number of beta particles we might get out of the explosion, it comes out 10 particles/ILLEGIBLE as the permissible number. There is still a favorable factor of maybe 1000 times because this is figured on the basis that everything gets out. WARREN: Could you say if there proved to be at the 40-mile distance, 10 or less beta particles/m3 to go ahead--if more, to not go ahead? In there any serious objection to this number or less as safe for a green light to go ahead; that if it's exceeded beyond the 45-mile limit, experimental data obtained would be submitted to the committee for further consideration? - 44 - Notes on Mtg, 5/21 and 5/22/51 SCHULTE: It seems to me you must specify some activity in these particles, because we could shut down Los Alamos on this criterion. HEMPELMANN: How about saying the total activity should not exceed a certain value per cubic meter in particles smaller than a certain diameter? I should think that if you took two criteria: (1) the overall value per cubic meter, and (2) the specification that there should be no more than 10 active particles of a size to be retained in the lung, this would cover it. (Comment: The total activity of these particles we are talking about, ~ 1u, is about 1.3 x 10-7 curies.) How about thinking of it as so much activity per cubic meter of air as measured on the third or fourth stage of the cascade impactor? Say 1uc/m3 of air on particles less than 5u in diameter, on the third or fourth stages of the cascade impactor. This you could measure directly, it would be an easy thing to do? (Suggested phraseology: "The beta activity due to particles less than 5u in diameter shall not exceed one microcurie per cubic meter at 40 miles distance at the time of fall-out. If this figure is exceeded, then reconsideration of the problem by the Committee is indicated before the next test.") CLAUS: How does this figure compare with 10-11 cu/m3? Tolerance values are based on retention in the lung, they are based on absorption of soluble fission products and also for a lifetime. That is using a value of 100 times less than tolerance and using it for insoluble rather than soluble matter. (Thompson thinks it's an interesting figure, at any rate.) WARREN: This brings us to the point of recommendation of the types of instrumentation (using that in a broad sense to include animals as well as instruments) from the radiological safety viewpoint. I think it would be unwise for us to attempt to be too detailed or explicit, rather, to state the sort of data we hope will be obtained at the tests. It is obvious that in the first place there must be very detailed following of the cloud with all the meteorological frills that can be of value in this. I think you would want a good deal of information as to the presence or absence or height of inversion, and the local variation in wind currents due to mountain ranges, and a pretty detailed micrometeorological picture all the way through. As to the area to be covered, I would say that we would want our micrometeorology at least out to 50 miles to give us an overlap beyond our evacuation area. Is that reasonable or possible, Col. Holzman? - 45 - Notes on Mtg. 5/21 and 5/22/51 HOLZMAN: It depends on what you define as micrometeorology. You need some wind data to check up to there, would not want to rely just on the command post, but this would not require a host of stations surrounding the area. WARREN: Then if we were to recommend that the cloud be followed in detail with wind data up to 50-mile radius, would that cover it from your standpoint? HOLZMAN: I think so. (Sturges asked how many tracker planes that would imply--he has tentatively asked for two low-altitude cloud trackers. Clark stated that at Ranger the clouds were followed out to 300 miles with two trackers; there almost have to be two in the air, in case the cloud splits. He would recommends C-47s for these low altitude clouds.) WARREN: The second point would have to do with the measurement of external radiation hazard, the gamma rays. How far, Dr. Failla, do you think that should be checked? FAILLA: I suppose as far as instruments would permit. I would say to the permissible limit, which would be -- 2 mr/hr? WARREN: If we were consistent, it would be. SHIPMAN: From the operator's standpoint, he would need it in miles. CLARK: What we would try to do is protect people, would put the monitors in the inhabited areas and then furnish monitors and collecting devices for the target area. (Question: Do we want to plot the fall-out pattern, as Dr. Hempelmann drew it on the board for Trinity? Hempelmann stated that there is no hurry on this, it was done later for Trinity.) WARREN: There are two parts to this: (1) to protect people, and (2) to measure the intensity in the immediate neighborhood of ground zero. This is considered to be one of the important military effects. CLARK: We would like to have this specified: how much monitoring you would want in the vicinity of zero, plus off-site monitoring sufficient to protect personnel, plus monitoring where fall-out would occur. (Shipman mentions that part of the country is completely inaccessible, and the monitoring must be limited to existing - 46 - Notes on Mtg, 5/21 and 5/22/51 roads. Fortunately, these are strategically located, he thinks a representative cross-section can be obtained. Failla believes it is very important to get a plot of the contamination because this sort of information is needed for civil defense. Spilhaus stated that one of the really urgent reasons for abandoning ILLEGIBLE as a test site was that because of the limited extent of the island, it was felt a complete fall-out picture could not be obtained, and it would be very bad if this were omitted. Clark suggested this be submitted in the test proposals.) FAILLA: Another thing needed very badly for Civil Defense is the ratio of beta activity to gamma activity at different times, because the beta-ray instruments are not very good for the military and Civil Defense; they are not rugged enough, have to have a thin window, cannot be made water-tight. The conviction is that if you know the gamma-ray level you can estimate the beta-ray level; however, a good many health physicist don't believe this can be done, they are very upset about it. We think this is a good opportunity to find out, I believe a determined effort should be made to establish this. CLARK: My only comment on that is that if it isn't retained in these criteria, it should be submitted as part of the test program. (Spilhaus states that it is in the program at the present time.) WARREN: Now in this list of desired data for our purposes from the test, in addition to this ratio ILLEGIBLE/y (which really ties more directly into the conduct of the test), we've got the following of the cloud with the wind data, measurement of external gamma, detailed plot of fall-out. This brings us to the studies of the particles, their distribution, their constitution, including the plating effect, their concentration in air and their size and specific activity. CLARK: This you will get from the cascade impactors or regular filter studies. CLAUS: Yes, we propose a variation of these. WARREN: I think we will want, in addition, their distribution in the lungs of test animals. I'm thinking of the number of particles of that one size, lodged in the lungs of test animals that have breathed for a unit time. (Asked for a proposed method), I think one can, on the one hand, distribute animals close in, and in addition, you could have with the monitoring teams a cage of mice which could be dropped off and left for a specific time at a specific point. - 47 - Notes on Mtg, 5/21 and 5/22/51 BRADBURY: Could this be recommended, not as a policy requirement but as something for which consideration should be given?--because I foresee complications. WARREN: Yes, we might say, "If practical. . ." (At this point, Warren asks Teller, who has just come into the meeting, to give the group some of the conclusions to which the Reactor Safeguard Committee has come with regard to continental sites, and some of their general impressions in relation to the over-all general hazard, the particle size question, etc.) TELLER: I'm afraid I cannot help you on particle size at all, but I would very much like to say a few simple things about the problem as it relates to the size of the explosion. In the early discussions about Tonopah, to be more precise, in a meeting of the Reactor Safeguard Committee in September in New York, the question was brought up whether a 1- 2-kt explosion at the Tonopah site would be acceptable. Now we do not, of course, know anything about the particle size to be expected, but we don't know, either, anything about the particle size to be expected if a pile should be exploded, and therefore (in order to get an idea of the relative hazards), we try to equate this kind of explosion to the explosion of a pile. I will briefly summarize for you the conclusions and make it more specific, insofar as I believe that the shot now contemplated for Tonopah is the A shot, which is 1.25-kt yield, and there is, of course, another advantage of this kind of shot, no plutonium but only relatively harmless 25. Now we may assume that the activity from such a 1.25-kt explosion will vary as the time to the minus 1.2 power, whereas the activity from the most dangerous pile, the accumulative activity, varies as the time to the minus 0.2 power. It is clear the activity from the bomb becomes relatively less harmful than from the pile. Also, one can assume one is not going to fire this shot in a very high wind, and in order to make a complete estimate, we said that we hoped for sufficiently low wind velocity. . .one need not consider the position, these distances ensure that the first danger will not arise. It may actually this time be longer or shorter, depending on wind conditions, but the comparison activities will be inversely proportional to the pile, so let us say that in one hour the level of activity will correspond to a pile that is three times as big--in nine hours it will correspond to a pile that is three times less powerful. . .Also, the comparison is overcautious in that the bomb will not be as dangerous as the comparison pile because we normalize to equal activities, but from there on the activity from the bomb will decay considerably faster than the activity from the pile will decay. - 48 - Notes on Mtg, 5/21 and 5/22/51 TELLER: (Cont'd) The 1.25-kt bomb may be compared to a pile of 100 megawatts (or 105 kw). I can best illustrate it by writing on the board. We have as a general principle of guidance and without very detailed argument accepted the following criterion: that in the neighborhood of 105 kw, we have as a very crude criterion for the location of the pile accepted this, that there shall be an exclusion distance from every pile of 0.01 times the square root of the kilowattage, and the answer comes out in miles. For this case, 0.01 square root 105 kw ~ 3.16 miles. This exclusion distance has come about from an estimate that if a pile blows up and dispenses its activity into the air, then there will exist in this radius a danger. . . . for persona to get lethal dose, that at this distance in case of a blow-out it is surely dangerous. We have generally accepted the statement that if we go to a distance of 10 times this, there is still a danger (in perhaps unusual, isolated instances) but it is not appreciable. This is why, with Las Vegas 70 miles away, we felt this explosion was not dangerous. Another point to consider is that ILLEGIBLE may not choose the right meteorological conditions when they go up. The Brookhaven pile has 1/5 that activity but is 70 miles from New York. There are other piles where, however, the activities which one is considering (for instance, in Utah) are perhaps 4 times the big amount, 105 kw. A factor of 4 in activity should correspond roughly to a factor of 2 in distance. . . . With the right weather conditions, one can be sure that only vary sparsely populated areas are affected. . . .it was for these reasons that the Reactor Safeguard Committee, in a purely informal discussion, concluded that an explosion like this should be acceptable if the right weather conditions are observed and if one is very careful, as you are, in trying to find out where the activity would go. (Holzman, who was also present at the meeting cited, mentions that these deliberations were for an airburst.) TELLER: Yes, we did not mention underground burst. All our discussions left out particle size. We were worried that an airburst might produce particle sizes of unknown magnitude; it now seems that an airburst indeed gives quite a small fall-out or no fall-out, so the worry of particle size is nonexistent. No matter what assumptions we make about the particle size, the activity is, with the proper weather conditions, such that it can be accepted as safe. - 49 - Notes on Mtg, 5/21 and 5/22/51 TELLER: (Cont'd) (The lethal dose referred to above would be ~ 500 r. Question: then you say that if you take 10 times that distance there would be some danger but not appreciable?) Yes, just when the cloud arrives, by some chance the lethal dose might still occur. There was, however, a general feeling in a number of discussions based on several different lines of argument that the dose will decrease roughly as one over the distance squared. So it would 5 r rather than 500, by this inverse square law, with, however, the recognition that precipitation and inhalation of particles might produce worse conditions. BRADBURY: There is a fact to consider that one is fairly sure a pile will not blow up, where for the purposes of public relations, we have a bomb we know will blow up! TELLER: Yes, but there is also the fact that when a pile might blow up we could not control the weather conditions. Also, I am comparing giving New York 5 r against giving a mining town of perhaps 100 people 5 r. BRADBURY: Yes, but this is an Act of God versus what you do yourself. TELLER: We are not quite sure we'll give these 100 people 5 r, it is only if the cloud should do so and so, and furthermore, we will follow this cloud and if people are exposed to a danger of this order, then 100 people can be moved. In one part in a hundred, one has seriously to inconvenience a small number of people, but one can still be quite certain one is not hurting them. Whereas, in the other case--the Act of God--you just can't do anything because probably you will kill more people in traffic accidents than you will save by evacuating them. In other words, I should think that an underground test might give a dose to people that you wouldn't want to; I think that chance is small but I think it exists, but if you follow the cloud there is no reason why you should injure anybody. WARREN: The people here had almost agreed that from this shot the external radiation hazard was neglible at 40 - 50 miles, but that the particle size. . . TELLER: I should think that an underground test is likely to result in large particles which will fall out at near distances and at, say, 70 miles you would get practically nothing. CLAUS: The intensity you indicated on the board at 3.16 miles--what is that due to? - 50 - Notes on Mtg, 5/21 and 5/22/51 TELLER: We have assumed it is entirely due to the cloud not rising, but passing over in a body with as much dispersion as you would expect at that distance. Remember, we are talking about a pile, which may be just a slow burn. . . (Teller leaves the meeting. Bradbury points out that the criterion he outlined is actually a very much less generous one than this group has been assuming if it were accepted, the distance would have to be twice as far. The Reactor Safeguard Committee is notoriously conservative. However, he points out that the first time we have to evacuate people, because of actual fall-out on them, is the last time we test in the continental limits. It is agreed that there is no actual worry about killing people--we won't--but about losing the test site.) BLEAKNEY: I would like to ask a question about measuring the number of particles per cubic meter--is it proposed to do that just on the ground or near the ground, or in the air, too! CLARK: They can have planes instrumented completely with filter collecting devices. (Asked whether these determine particle size in flight), I think they have to come down and assemble their equipment, but you can collect the sample in the air. HOLZMAN: This gives a particle count; you get some rough idea of concentration because you know the volume of the air you have sampled. There are some which give counts directly. WARREN: I would think this would be worthwhile. In addition, we want it on the ground. HEMPELMANN: Norris, there was a time when nitrous oxide being formed in the cloud was worried about, but since the cloud was so high, we stopped worrying. Will this be a factor here? BRADBURY: I think you're rather less likely to be perturbed about it this time, there is a lot less energy, more ground. However, it's a nice point, might bear looking into. SCHULTE: We can sample for oxides for nitrogen, too, can do it in a plane for that matter. WARREN: We have met a fair number of things we had lined up, how well the Lord only knows, but apparently as well as can be within the limitations of our collective knowledge or absence of knowledge. (Thompson would like to include a statement in the final report to the effect that this is all based on conjecture and incomplete data.) - 51 - Notes on Mtg, 5/21 and 5/22/51 WARREN: (Cont'd) One thing I'm afraid of is that in stating our scientific caution here, we overdo it from the standpoint of lay and political feeling. Although in our final wording we have to give due regard to our gaps in knowledge, we must not make these overly prominent so as to mislead those who are not used to scientific caution. We have considered the following points: the scale, the depth in general terms, the place, the weather, the data to be obtained by instrumentation, and the criteria to apply to these data in determining whether one goes on the second test without reconvening this group for another opinion or to reconvene in light of a certain set of events occurring and determine whether or not to go on in the light of the data obtained. Are there holes that need to be filled beyond those that we are all too painfully aware of? NOLAN: Am I correct in assuming that the data suggested to be obtained are those needed to evaluate the health problem? WARREN: We are concerned only with the health problem, it is up to the operators to consider the effects of blast, cratering, etc. I don't think our particular group is qualified to consider that. FAILLA: One of the things I had in mind was to see what kind of problems we encounter in contamination and decontamination that would be applicable to civil defense, in case of an atomic attack on a city. SPILHAUS: That is in the present program. It is essentially part of the tests. FAILLA: I went to be sure they are incorporated into the tests. WARREN: If it will be helpful to mention certain ones that we hope will be retained from our field of interest, we might do so. SPILHAUS: I don't think it would be particularly helpful at this particular time, because right now we are operating on the assumption that the whole program will go forward. Unless someone goes over the whole thing and cuts it--I might call on that committee if they tend to cut out things like decontamination. BRADBURY: I might make a remark here; I think the Commission, in taking over from the Armed Forces, did not agree to take everything lock, stock and barrel, but only to take limited responsibility. SPILHAUS: The reason the test was moved from the island to a continental sit was because on the island we thought we could do only a fraction of the program. This the Commission recognized, and it would seem peculiar now if in making the shift they cut out a lot. - 52 - Notes on Mtg, 5/21 and 5/22/51 COINER: I believe that the intent, at least, of the Commission was that AEC would carry out those things, blast, cratering, radiological safety measurements, but that the remainder of the program would be done by the remnants of ILLEGIBLE-131. (There is a difference of opinion on this matter. Clark points out that if the whole program is to be done, it may not be possible to do it in the fall.) CLARK: I would like to say this, Dr. Failla, that the Civil Defense has requested the AEC to make a detonation for them; that is currently on the books and with a very large program. They are not figuring on doing it this year at all; the FCDA has said that they are not ready. I think this is the time to take care of your requests, when they do a test for Civil Defense. FAILLA: My question is when that will be done--time is rather important! SPILHAUS: Dr. Clark just said we could not do this whole program on the time scale in Las Vegas. It is part of this group's function to determine the site. I think the site must be determined in relation to the time scale. Then perhaps it might be well to reconsider whether it should be done at Irwin, where I'm sure it can be done in three months. HOLZMAN: Gen Wilson told me that the remnants of the original group would be taken over by the Air Forces which would then do only what the AEC told them to. (It was agreed to drop this subject until the matter could be settled with finality.) WARREN: As far as our specific responsibility is concerned, are there any obvious holes that you see here? It now amounts to an additional group of more technical people who know the particle problem pretty well to come up with a group of instruments and techniques of analysis. This is part of the operational detail, we set down the criteria that we feel we need, then it is up to the operational group to decide how to obtain that. CLARK: The operational group will be glad to receive suggestions from the experts. WARREN: I believe they should come from those competent on the committee rather than the committee itself. Now I think there are two pretty important things that we have to settle here prior to getting our minutes drawn up in thoroughly formal style. But I think, because of the urgency of the time scale involved, we ought to have a specific statement of the committee now that in line with these criteria as laid down in the minutes, - 53 - Notes on Mtg, 5/21 and 5/22/51 WARREN: (Cont'd) this is or is not a feasible test. Is there anyone who feels that we need further discussion before voting a specific recommendation for or again this? If not, I would be glad to entertain a motion as to the feasibility of carrying on this initial underground test, with an eye chiefly to obtaining essential data with regard to the radiological safety problems. (The committee adopted the following statement: "It is unanimous opinion of the committee that a test involving the explosion of a 1-kt, B235 bomb, under the conditions stated in the body of the report, can be carried out without undue hazard." It was suggested, and agreed, that the body of the report include a definition of "undue hazard", and also motion that this consideration includes both humans and livestock. The motion relating to the next test was also agreed upon, as follows: "The committee recommends that subsequent tests follow. . .on schedule unless some adverse occurrence is evident.") COINER: Does this first statement mean at Las Vegas? WARREN: The criteria we have laid down do not name a specific site, they refer to either Las Vegas or Camp Irwin. They specify (1) the general topography, (2) the meteorology, (3) the distance to which population shall be evacuated, and (4) radiological safety criteria. These I think would be just as applicable to Camp Irwin--the only difference I recall is that there might be a few more or less people involved. SPILHAUS: Population measurements have been made for Camp Irwin and population of a similar order is involved. I think we should make sure in the body of the report that we clarify the fact that these criteria could apparently be met by Irwin as well. FAILLA: I think some re-evaluation will be necessary before subsequent tests anyway-- BLEAKNEY: If the limitations on safety were just about met by this first test, than we would have to reconvene? (Warren answers in the affirmative. It is suggested that a statement to that effect be incorporated into the body of the report.) BLEAKNEY: Will an attempt be made to measure the radioactivity in the crater? - 54 - Notes on Mtg, 5/21 and 5/22/51 SPILHAUS: I'm afraid I can't answer this right now because I am a little confused as to the status of the test program. In the original test program, there is considerable effort with remote-controlled weasels to get samples from the crater. To answer the question: yes, this is in the test program and some considerable effort is planned. The instrumentation to obtain these samples is almost completed. My worry is that I do not know if these features will retained in this shift of responsibility. BLEAKNEY: It is certainly a part of the determination--if the cavity caves in we may not know how much radioactivity stayed in. This is important, should be left in the program. WARREN: I think if there is any question, we should put it down in our program here. Assuming that there is any question at all, I would want to reconvene the committee. If, on the other hand, the values are all well below the point of concern, I don't think it would be necessary to take your time. (As for the recommendation for the next shot), I do not feel competent to make this on my own, would certainly turn to individual members of the committee--and if we are crowding the limitations at all, I would want to reconvene the whole committee. (Asked how the limitation will be checked), we will be able to check the specification of 1ęc for betas; we will have data as to the behavior of the cloud which I think is of major importance, data as to the fall-out pattern, particle size distribution and concentration, etc. I think we have spelled out fairly clearly what we want. For example, if we found that everything fall out within 5 miles of the center, I would not feel it necessary to call all of you together again. If we found a hot spot at 25 miles, I would. HEMPELMANN: For the sake of completeness, you may want to mention this nitrous oxide hazard. I called Edward (Teller) about it--he says that as he remembers it, it is about the same as the fission product hazard; in view of the dust it may be no hazard at all, but it is probably something that should be considered. (Warren agrees.) (The meeting is adjourned.) - 55 -