Isegoria

The original plutonium-production piles in Hanford, Washington, General Groves explains in Now It Can Be Told: The Story of the Manhattan Project, we’re going to be helium cooled:

A major consideration in dropping the helium-cooled pile was the problem of designing and maintaining the necessary pressure-sustaining enclosure for the pile. Among other difficulties was that of loading and unloading such a unit under pressure. When it developed that the water-cooled pile would be easier and cheaper to design and build, all work on the helium method was stopped.

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Later, after we had decided on water-cooling, we discovered that not only was it necessary to have large quantities of cold water, but that its purity was of the utmost importance. We were just lucky that the Columbia River water did not contain dissolved chemicals in sufficient amounts to necessitate more than normal treatment.

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I was discussing the advisability of this with G. M. Read of du Pont, one night at Hanford, when Dr. Hilberry came into the room. I asked him for his views, and he replied that he did not think we would need the deionizing plant, but if we did, we could not do without it. I turned to Read and said, “Go ahead and build it.” Hilberry then asked what it would cost and I told him that it would be somewhere between six and ten million dollars. He replied, “I’m glad I didn’t know that when I gave my opinion.” Such quick decisions were not too frequent and they were always preceded by as much research, study and thought as could be devoted to them without delaying the completion of the project. Nevertheless, there were many decisions that had to be made when the unknown factors far outweighed the known. We built only the one deionizing plant and fortunately never found any need for it, for had it proved necessary, we would have had to build two more in a hurry, and would have lost considerable production while they were under construction.

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Shortly after the Hanford site was selected, I had talked to Robins, who had built the fish ladders and elevators at the Bonneville Dam, and outlined the measures we were taking to protect the salmon in the Columbia River. He made a lasting impression on me at that time when he said, “Whatever you may accomplish, you will incur the everlasting enmity of the entire Northwest if you harm a single scale on a single salmon.” As it turned out, we did not.

The concrete side walls of the retention basins were designed to extend high enough above the ground to prevent anyone within a critical distance from being exposed to radiation. To avoid any turbulence in the river, the discharge lines were brought into the main stream at an angle to provide for a converging flow, and, to prevent fish from swimming up the discharge pipe, a minimum velocity of over twenty miles per hour was planned. In addition, all effluent was monitored continuously by instruments to make certain that the radioactivity was at all times within entirely safe limits.

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Each pile unit was made of carefully machined, very pure graphite blocks with built-in aluminum tubes which were charged or loaded with uranium in the form of small cylinders or slugs. Since the piles were water-cooled, we were greatly concerned about the effects of corrosion, for it was estimated that the failure of only a small percentage of the tubes could cause the complete failure of the pile.

All design was governed by three rules: 1, safety first against both known and unknown hazards; 2, certainty of operation—every possible chance of failure was guarded against; and 3, the utmost saving of time in achieving full production. The complications were many, for many pieces of equipment weighing as much as 250,000 pounds each had to be assembled with tolerances more suitable for high-grade watchmaking. It was through the assistance and the strength of the industrial companies of America that du Pont was able to solve the hundreds of difficult design and material problems that had to be mastered.

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We also encountered an extremely difficult problem in the welding of the steel plates surrounding the piles. This work had to be almost perfect. An average superior job would not do. It took months to perfect the techniques required. We created a special super-classification of welders with premium pay. To hold this classification, a welder was required to take special training. He then had to take practical examinations at regular intervals to make certain that the quality of his work would remain up to what we needed.

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In order to insure an adequate water supply for each pile, completely independent water facilities were provided, each with duplicate lines. At the same time, all individual units were cross-connected. Arrangements were made for driving the water pumps by either electric motors or steam turbines, so that in case of a power failure from either source, a safe amount of water would still be provided. In addition, there were emergency elevated tanks with automatic cut-ins, in case the normal supply failed.

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The piles themselves were surrounded by heavy shields of steel, pressed wood and concrete, to protect the operators from the extreme radioactivity that accompanies the formation of plutonium. The energy of this radiation is equivalent to that of hundreds of tons of radium.

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Each plant was a continuous concrete structure about eight hundred feet long, in which there were individual cells containing the various parts involved in the process equipment. To provide protection from the intense radioactivity, the cells were surrounded by concrete walls seven feet thick and were covered by six feet of concrete.

In use, the equipment would become highly radioactive and its maintenance and repair would be difficult, if not impossible, except by remote control. Consequently, periscopes and other special mechanisms were incorporated into the plant design; all operations could thus be carried out in complete safety from behind the heavy concrete walls. The need for shielding and the possibility of having to replace parts by indirect means required unusually close tolerances, both in fabrication and in installation. This was true even for such items as the special railroad cars that moved the irradiated uranium between the piles and the separation plants. The tracks over which these cars moved were built with extreme care so as to minimize the chances of an accident. Under no circumstances could we plan on human beings directly repairing highly radioactive equipment.

After being discharged from the reactors, the uranium slugs were kept under water continuously, then sent on the specially designed railroad cars to an isolated storage area. There they were immersed in water until their radioactivity had decreased enough to permit the separation of their plutonium content by chemical treatment.

Following the removal of the plutonium the residues were still highly radioactive. They still had to be handled by remote control.

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Experience gained at the Clinton laboratories indicated that the danger to anyone outside the immediate operating area would be much less than we had originally feared, but that the danger from the toxicity of the final product was considerably greater.

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Those body cells which multiply rapidly, such as bone marrow, are most easily affected by gamma radiation, while the slower-growing cells are relatively unaffected.

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The National Advisory Committee on X-Ray and Radium Protection had established a tolerance dose for gamma rays at one-tenth of one roentgen per day. Because this was not definitely known to be safe, the tolerance dose at Hanford was set at one-hundredth of a roentgen per day. This dose could be absorbed in a short period of time, or over an entire day, so long as it was not exceeded within a period of twenty-four hours. It was calculated that one foot of lead, seven feet of concrete or fifteen feet of water would provide adequate protection from the maximum radioactivity to be expected during the operation of one of our reactors.

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In addition to all the other precautions, du Pont designed a control system for the piles that we thought would be safe no matter what happened. It consisted of three distinct elements: first, the control rods could be moved either automatically or manually into the side of the pile; second, safety rods were suspended above the pile so that, in an emergency, they could be instantaneously released; and third, as a last resort, arrangements were made to flood the pile with moderating chemicals. This last device was designed for remote operation from a shielded control room. If this safety device had to be employed, the pile would no longer be usable.

Once Oppenheimer’s appointment was settled, General Groves explains in Now It Can Be Told: The Story of the Manhattan Project, they had to pick out a location for Project Y:

We needed good transportation, by air and rail, adequate water, a reasonable availability of labor, a temperate climate, to permit year-round construction and out-of-doors experimental work, and all the other things that make for an efficient operation. As before, we sought an isolated area so that near-by communities would not be adversely affected by any unforeseen results from our activities. Yet this installation would be different, because here we were faced with the necessity of importing a group of highly talented specialists, some of whom would be prima donnas, and of keeping them satisfied with their working and living conditions.

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One would lie somewhere along the Santa Fe Railroad, in New Mexico or Arizona, while the other would be in California. The Navy was already interested in the most promising California site, which did not have suitable living conditions from our point of view, and which would have been extremely expensive to develop adequately. While shielded by surrounding mountains against the chance of an accidental explosion, the teeming millions of Los Angeles County were too near for us to maintain the security we deemed necessary.

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I was also certain that it would be extremely difficult and unpleasant to try to keep our scientific personnel from mixing socially with the faculty of the California Institute of Technology. Inevitably, we would have had security breaches, and there would have been just too many people knowing what we were trying to do.

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After Oppenheimer and I had gone over the possibilities at some length, we agreed that there seemed to be nothing that suited our purposes as well as the general vicinity of Albuquerque. There was good rail service between that city and Chicago, Los Angeles, San Francisco and Washington, and all TWA flights to the Coast stopped there. Its climate was excellent, it was well isolated, and had the additional advantage of being far inland, which appealed to me because of the ever-present threat of Japanese interference along the Coast.

Because a New Mexico National Guard regiment had been captured in the Philippines we could count on a population and a state government intensely interested in furthering the war effort. The support we received was superb.

Oppenheimer owned a ranch in the near-by Sangre de Cristo Range, so we could draw upon a firsthand source of information on the general character of the country in judging whether our scientific people might find working there to their liking.

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The only major problem left was whether the school’s owners would object to its being taken over. It was a private school with students from all over the country and, had they chosen to do so, its owners could have made considerable trouble for us, not so much by making us take the condemnation proceedings into court as by causing too many people to talk about what we were doing. When the initial overtures were made to them, I was most relieved to find that they were anxious to get rid of the school, for they had been experiencing great difficulty in obtaining suitable instructors since America had entered the war, and were very happy indeed to sell out to us and close down for the duration — and, as it turned out, forever.

In addition to his other work, General Groves explains in Now It Can Be Told: The Story of the Manhattan Project, Arthur Compton had been assigned over-all responsibility for the physics of bomb development:

As a first step in June, 1942, he had appointed Dr. J. Robert Oppenheimer to take charge of this particular phase of the project. Oppenheimer was then at the University of California at Berkeley. He began work on the problem with a small group of theoretical physicists.

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Adding to my cause for doubt, no one with whom I talked showed any great enthusiasm about Oppenheimer as a possible director of the project.

My own feeling was that he was well qualified to handle the theoretical aspects of the work, but how he would do on the practical experimentation, or how he would handle the administrative responsibilities, I had no idea.

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Of the men within our organization I had no doubt that Ernest Lawrence could handle it. He was an outstanding experimental physicist, and this was a job for an experimental physicist. However, he could not be spared from his work on the electromagnetic process; in fact, without him we would have had to drop it, for it was far too difficult and complex for anyone else. I knew of no one then and I know of no one now, besides Ernest Lawrence, who could unquestionably have carried that development through to a successful conclusion.

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Oppenheimer had two major disadvantages — he had had almost no administrative experience of any kind, and he was not a Nobel Prize winner. Because of the latter lack, he did not then have the prestige among his fellow scientists that I would have liked the project leader to possess. The heads of our three major laboratories — Lawrence at Berkeley, Urey at Columbia, and Compton at Chicago — were all Nobel Prize winners, and Compton had several Nobel Prize winners working under him. There was a strong feeling among most of the scientific people with whom I discussed this matter that the head of Project Y should also be one.

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His background included much that was not to our liking by any means. The security organization, which was not yet under my complete control, was unwilling to clear him because of certain of his associations, particularly in the past. I was thoroughly familiar with everything that had been reported about Oppenheimer. As always in security matters of such importance, I had read all the available original evidence; I did not depend upon the conclusions of the security officers.

Finally, because I felt that his potential value outweighed any security risk, and to remove the matter from further discussion, I personally wrote and signed the following instructions to the District Engineer on July 20, 1943:

In accordance with my verbal directions of July 15, it is desired that clearance be issued for the employment of Julius Robert Oppenheimer without delay, irrespective of the information which you have concerning Mr. Oppenheimer. He is absolutely essential to the project.

It was understood that all du Pont’s work would be based on technical information to be furnished by the Metallurgical Laboratory, General Groves explains in Now It Can Be Told: The Story of the Manhattan Project, and that the government assumed all responsibility for the results of the endeavor, as well as for any damages that might be incurred in the course of the work:

This last provision was necessary because of the nature of the entirely unpredictable and unprecedented hazards involved.

Normal insurance coverage was impossible because of the need to maintain security. While we could have disclosed the normal risks involved to a single insurance representative, there would have been little point in it, for reinsurance on large risks requires that adequate knowledge be in the hands of many groups, which would seriously have endangered our security. Moreover, the unusual hazards were such that no group of insurance companies could possibly have written the coverage, even after complete disclosure. First, no one had any reasonable idea of what the hazards might be or the likelihood of their occurring. Second, no one could predict the duration of the effects of the hazard, or, in many instances, even when the effects might first appear. Third, no one could possibly predict the extent of the damage if a major catastrophe occurred.

For all these hazards the government assumed full responsibility. To facilitate the handling of claims not resulting from a major catastrophe a special fund was established. This fund was placed under the control of du Pont so that it could continue to be available for many years. All claims were to be approved by the government before payment.

Ever-present in our thinking was the sad example of the luminous watch-dial painters of World War I. Here the effects did not become apparent for many years. The delayed reaction to excessive radiation also hit many of the original researchers and users of X-rays. How could we be certain that radiation exposure in our installations might not have similar effects despite all our efforts to prevent them?

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Mr. Carpenter said that du Pont did not want any fee or profit of any kind for this work, and wanted furthermore to be certain that the company would receive no patent rights. A new letter of intent incorporating provisions to this effect was prepared and was immediately accepted.

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At du Pont’s request, Dr. Bush forwarded a letter to the President outlining the circumstances surrounding the assumption by the United States of all responsibility for the unusual hazards involved in this work. Mr. Roosevelt initialed his approval on the letter and a photostatic copy of it was given du Pont.

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We encountered one other snag in making sure that, though du Pont was doing the job without profit, it would not be subject to any direct financial losses. For purely legal reasons, provision was made for a fee of one dollar.

Although the expected duration of the contract was stated, as is usual, soon after V-J Day du Pont was paid the entire fee of one dollar. This resulted in a disallowance by government auditors, since the entire time of the contract had not run out. Consequently, du Pont was asked to return thirty-three cents to the United States. Fortunately, the officers of du Pont had retained their sense of humor throughout their many years of association with the government, and were able to derive considerable amusement from this ruling.

The original plan for the first experimental test pile had been to place it in the Argonne Forest, General Groves explains in Now It Can Be Told: The Story of the Manhattan Project, some fifteen miles out of Chicago, where special facilities were being built to accommodate the pile and its accompanying laboratories:

The already insufficient time available for this construction was cut even further by some labor difficulties which, while not particularly serious, led to delays.

In the meantime, work had begun on a small pile under the West Stands of Stagg Field at the University of Chicago. This pile was to be used to perform exponential experiments to determine the feasibility of the larger test pile. An exponential experiment, as its name indicates, is one from which, using measurements of the results obtained under varying conditions, the results to be expected under vastly different conditions can be calculated. When the supply of pure graphite necessary for the construction of a self-sustaining pile became available somewhat sooner than had been anticipated, Compton raised the question: “Why wait for Argonne?”

There was no reason to wait, except for our uncertainty about whether the planned experiment might not prove hazardous to the surrounding community. If the pile should explode, no one knew just how far the danger would extend. Stagg Field lies in the heart of a populous area, while the Argonne site was well isolated. Because of this, I had serious misgivings about the wisdom of Compton’s suggestion. I went over the situation with him, and told him of my feelings, but I did not interfere with his plans, nor did I display outwardly my concern by being present during the initial test. I learned then that nothing is harder for the man carrying the ultimate responsibility, in this case myself, than to sit back and appear calm and confident while all his hopes can easily be destroyed in a moment by some unexpected event over which he has no direct control.

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Although the committee was in the Chicago laboratories on December 2, 1942, when the Fermi experimental atomic pile was first placed in operation, the only committee member to witness the actual demonstration was Greenewalt. He was invited by Compton on the ground that he was the youngest and would be able to talk about it for the most years.

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“The Italian navigator [Fermi] has just landed in the new world. The natives are friendly.”

The December 2 test proved that a controlled chain reaction could be achieved, but it gave no assurance that it could be used to produce plutonium on a large scale. Neither did it give us any assurance that a bomb using plutonium or U-235 would explode. In the reactor the chain reaction was based on slow neutrons, i.e., ones slowed down by graphite or other means. In the bomb, the neutrons would be fast, for because of technical limitations there could be no moderators. Nevertheless, the committee, basing its opinion on what it had seen and heard during its inspections, reported favorably on the plutonium process.

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In his letter, Compton was quite positive. He stated that the production of plutonium following the procedure then in hand was feasible; that there was a 99 per cent probability that it would be successful; that the probability of a successful bomb was 90 per cent; and that the time schedule, assuming continued full support, would see delivery of the first bomb in 1944 and a production rate of one bomb per month in 1945. This was by far the most optimistic estimate that I ever received prior to the explosion of the first bomb some thirty months later; and it was not at all justified by the existing knowledge.

After he had studied all the possibilities, General Groves explains in Now It Can Be Told: The Story of the Manhattan Project, he concluded that only one firm was capable of handling all three phases of the plutonium effort, and that firm was du Pont:

When I broached the subject to Arthur Compton, he agreed at once, saying that he knew Stone and Webster were overburdened and were way out of their field of experience, and that it would be a great relief to have du Pont in the picture. However, he warned me that we would encounter opposition, some of it quite strong and quite influential, from some of the people in his laboratory.

He told me that in the previous June he had assembled his staff and proposed bringing in an industrial firm to take over responsibility for the production phase of the plutonium project. The suggestion had resulted in a near rebellion, particularly among those whose entire experience had been in academic institutions. They simply did not comprehend the immensity of the engineering, construction and operating problems that had to be overcome. Whenever attempts were made to explain them, they brushed them aside as inconsequential. After the furor had subsided, Compton announced that he expected to go ahead with his idea.

He said that while his position had been accepted then, he had no doubt that there would be many objections, voiced and unvoiced, and that the selection of du Pont — the very symbol of large industry — would be particularly opposed. He went on to assure me that personally he was very much in favor of my proposal and, moreover, that he felt that du Pont was by far the best choice that could be made.

On the other hand, a number of his scientific people, particularly those who had been trained in Europe, where scientific and engineering education were more closely linked than in this country, had the idea that all design and engineering for the project should be accomplished under their personal direction. Some even went so far as to say that they could also supervise the construction.

When I visited the laboratory on October 5 and again on October 15, I was told by several different persons that if I would provide them with from fifty to one hundred junior engineers and draftsmen, they would then themselves design and construct the plutonium plant, rapidly and without delay. They added that the plant could then be turned over to a private company for operation, or possibly be run under the Civil Service.

The absurdity of such a proposal is apparent when it is remembered that this was the plant where our construction forces reached a peak of forty-five thousand and was so difficult an undertaking as to strain even the great resources of du Pont, with the full power of, and considerable aid from, the government and much of America’s industry behind it.

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The urgency of the project did not allow time for us to conduct any detailed security checks in advance of negotiations; instead, we relied upon the discretion and patriotism of American industry. We considered this a good risk and we were never disappointed.

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I said that there were three basic military considerations involved in our work. First, the Axis Powers could very easily soon be in a position to produce either plutonium or U-235, or both. There was no evidence to indicate that they were not striving to do so; therefore we had to assume that they were. To have concluded otherwise would have been foolhardy. Second, there was no known defense against the military use of nuclear weapons except the fear of their counter-employment. Third, if we were successful in time, we would shorten the war and thus save tens of thousands of American casualties. (I have always believed it was for these reasons, and particularly the last, that Carpenter and his colleagues on the du Pont Executive Committee agreed to undertake the work in spite of all the hazards it entailed for their company.)

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They pointed out that even in one of their own fields of specialization they would not attempt to design a large-scale plant without the necessary data that could be accumulated only by a long period of laboratory research, followed by semi-works operation: for example, it had taken them many years to get nylon into mass production; yet the nylon process was simple compared to what we were asking of them.

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I should make it clear that reactor theory at this time did not overlook the possibility that once a chain reaction was started, it could, under some conditions, get out of control and increase progressively to the point where the reactor would explode. If highly radioactive materials were blown into the atmosphere and spread by winds over a wide area, the results could be catastrophic. We knew, too, that in the separation of the plutonium we might release into the atmosphere radioactive and other highly toxic fumes which would constitute a distinct hazard for operating personnel. It was not surprising, therefore, that du Pont should entertain grave doubts about the desirability of joining us in our work.

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As the directors entered the room at their next Board meeting, they were asked not to look at the faced-down papers on the table in front of them. Carpenter explained that the Executive Committee was recommending that du Pont accept a contract from the government for a project in a previously unexplored field so large and so difficult that it would strain the capacity of the company to the utmost. He added that there were elements of hazard in it that under certain conditions could very well seriously damage if not well-nigh destroy du Pont. He said that the highest officials in the government, as well as those who knew the most about it, considered it to be of the highest military importance. Even its purpose was held in extreme secrecy, although if any Board member wished to he was free to read the faced-down papers before voting. Not a single man, and they were all heavy stockholders, turned them over before voting approval — or afterwards — a true display of real patriotism.

On October 5, 1942, General Groves paid his first visit to the Metallurgical Laboratory at the University of Chicago, as he explains in Now It Can Be Told: The Story of the Manhattan Project, where he met with Arthur Compton and “about fifteen of his senior men”:

Among them were two other Nobel Prize winners, Enrico Fermi and James Franck, together with the brilliant Hungarian physicists Eugene Wigner and Leo Szilard, and Dr. Norman Hilberry, Compton’s assistant.

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With respect to the amount of fissionable material needed for each bomb, how accurate did they think their estimate was? I expected a reply of “within twenty-five or fifty per cent,” and would not have been greatly surprised at an even greater percentage, but I was horrified when they quite blandly replied that they thought it was correct within a factor of ten.

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My position could well be compared with that of a caterer who is told he must be prepared to serve anywhere between ten and a thousand guests. But after extensive discussion of this point, I concluded that it simply was not possible then to arrive at a more precise answer.

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This uncertainty surrounding the amount of material needed for a bomb plagued us continuously until shortly before the explosion of the Alamogordo test bomb on July 16, 1945. Even after that we could not be sure that Uranium-235 (used in the Hiroshima bomb) would have the same characteristics as plutonium (used in the test and later against Nagasaki), although we knew of no reason why it should be greatly different.

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After the meeting, Compton and I resumed a discussion we had begun earlier with Szilard on how to reduce the number of approaches which were being explored for cooling the pile. Four methods—using helium, air, water and heavy water—were under active study. It was essential that we concentrate on the most promising and more or less abandon work on the others. By the end of the afternoon we settled on helium cooling. But within three months this decision was changed. The design problems early encountered in the comparatively small air-cooled reactor at Clinton indicated that the handling of any gaseous coolant in the much larger Hanford reactors would be very difficult. And as the operation of the Fermi test pite in December had proved that in a properly designed uranium pile water could be used as a coolant, it was adopted for the plutonium reactors we built at Hanford.

I left Chicago feeling that the plutonium process seemed to offer us the greatest chances for success in producing bomb material. Every other process then under consideration depended upon the physical separation of materials having almost infinitesimal differences in their physical properties. Under such circumstances, the design and operation of any industrial processes to accomplish this separation would involve unprecedented difficulties. It was true that the transmutation of uranium by spontaneous chain reaction into usable quantities of plutonium fell entirely outside of existing technical knowledge; yet the rest of the process—the chemical separation of the plutonium from the rest of the material—while extremely difficult and completely unprecedented, did not seem to be impossible.

Up until this time, only infinitesimal quantities of plutonium had been produced, and these by means of the cyclotron, a laboratory method not suitable for production in quantity. And by quantity production of plutonium, I do not mean tons per hour, but rather a few thimblefuls per day. Even by December, 1943, only two milligrams had been produced.

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This was in accord with the general philosophy I had followed throughout the military construction program and to which we adhered consistently in this project; namely, that nothing would be more fatal to success than to try to arrive at a perfect plan before taking any important step.