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National Museum of Nuclear Science & History

David P. Rudolph’s Interview

Manhattan Project Locations:

David R. Rudolph was an administrator in charge of inventory at the Chicago Metallurgical Laboratory. In his interview, he discusses how he was one of the few individuals to be present at both the startup of Chicago Pile-1 and the Trinity test. Rudolph recalls the process of reactor construction, along with the disassembly of CP-1 for the construction of CP-2. He explains the importance of inventory control when it came to the uranium and graphite blocks used in CP-1, and how he helped discover that a section had not be stacked with enough blocks.

Date of Interview:
April 20, 1965
Location of the Interview:


Stephane Groueff: Recording Dr. Rudolph.

Dave Rudolph: As far as the organizational structure was concerned, when I reported to work, I reported to a man who had the administrative responsibilities for purchasing for the project and warehousing. You might say purchasing and supply functions – warehousing the stores, shipping to a small extent. No sooner did I report to work the very first day when I was introduced to Dr. [William] Jesse, who incidentally does live in this area. If you are staying in the area at all, you might see if you can contact him. He is at Saint Procopius College now, right near here.

Groueff: When was that?

Rudolph: This was in August of 1942.

Groueff: ’42.

Rudolph: Dr. Jesse was on the verge of being called away to a firm by the name of Metal Hydrides in Beverly, Massachusetts, who were attempting to produce massive uranium pellets or compacts by a sintering process. They were having some difficulties, and Dr. Jesse was required to go there to advise them or to review what they were producing to see if it fit the specifications that would be needed for the pile.

The first day I reported to work, I was told to report to Dr. Jesse. He took me into a room – something I would say 16 by 16 square – and he handed me a notebook. He said, “Now these are the high gadolinium oxides and these are the Columbia oxides.” At first, I was not sure why he was telling me all of this. Then when he closed the book, he said, “Well, I have to leave now. The material is all yours. You are responsible for the storage and distribution and accounting for all these materials.”

The materials, of course, were uranium oxide. There was a really conglomerate mess of material that had been brought over from the Columbia group, some of it in large metal cans and some of it in just in bulk containers. This was essentially the starting inventory. The work going down right at the moment was taking these oxide powders, and they were bulk uranium dioxide, which is a brown powder, and U3O8, which is a black powder, and pressing these into what they called “pseudo-spheres.” You may even have seen some on display.

Groueff: No.

Rudolph: If you have not already done so, you might want to go down to what has been called the Institute Laboratory, Building 25, where there is a structure made up of the original graphite and the original fuel from CP-1. There is a large batch of it. It is used as a zero power facility now, that is, as a subcritical reactor. But anyway, I felt there you could see that actual shape of these pseudo-spheres. They are really cylinders with conical ends. They look more or less like a sphere.

Anyway, the oxide that we had, such of it as met the purity specifications as then known, was being pressed into these pseudo-spheres and then turned. These were what were going into the reactor, into the cavities in the graphite blocks.

Right after this point, my entire job consisted of receiving, storing, and issuing these various powders. Simultaneously, some of the powders were then shipped to Mallinckrodt Chemical Works, where we were refining them and returning better quality. Subsequently, a lot of the oxide was then shipped to the Iowa State University, where Dr. [Frank] Spedding was converting it to metal. There was a constant flow. The same oxide was coming in, going out, and then coming back.

Groueff: But originally they were coming from where?

Rudolph: Well, our biggest supplier at first was Canadian Radium and Uranium, Great Bear Lake, but it was refined in Canada. We were getting it essentially as pure oxide, reasonably pure oxide.

Groueff: Where were you located?

Rudolph: We were at the West Stands, at Stagg Field.

Groueff: Stagg Field.

Rudolph: And we had this storeroom. It was in Stagg Field.

Groueff: Why and how were you recruited for this job? What was your background?

Rudolph: Oh, I had previously worked in a factory which produced springs for bedding and upholstery. My particular work in that organization, prior to the time that they cut down their operations, was inventory control.

Groueff: In Chicago?

Rudolph: Yes, in Chicago. With the onset of the war and the control over steel use, the company had to go out of business or convert to another product. To prepare myself for wartime conversion, I entered a special brush-up production management program at the University of Chicago to get specialized training in production control. The Met Lab, which at that time was building up its staff, used all of the aspects of the university as a recruitment source. Since I had experience in inventory control, I was invited for an interview.

Groueff: But you knew nothing of physics or chemistry?

Rudolph: No, just administration.

Groueff: And you were quite young then?

Rudolph: Yes, let me see. In ’42 I was 23. Anyway, the job was primarily one of knowing where what was and knowing to whom it had been issued and keeping records.

Groueff: Keeping accounts?

Rudolph: Yes. The receiving end was, in fact, on a number of occasions, again because of the cover, shipments came into the customs house near the Pole Street railway station from Canada addressed to me personally. The customs brokers, all they knew that I as a person was importing all of this powder.

Groueff: Did they ask what it was?

Rudolph: Well, they did not. I do not remember them asking.

Groueff: The word “uranium” was not—

Rudolph: No. As a matter of fact, it had various cover names such as Tube Alloy was one of the most common. I think it is one that the British coined. This was a sort of relic, but evidently the Columbia group was calling it “molybdenum,” because first of all molybdenum was a rare metal and it was one that was hard to pronounce, so they figured people would not remember it. Of course, it has turned out subsequently now that molybdenum is important in some of the metallurgical processes. There are uranium molybdenum alloys being used in fuels today. But this just shows you how the fates will move to fulfill their own prophecies.

Groueff: So you would go to the customs, receive it, and how did the oxide arrive to Stagg Field? By trucks?

Rudolph: We used our own trucks. The University had a large van and some smaller trucks. The material from Canada ordinarily came in in fiber cartons about 75 pounds net or 100 pounds net as the case may be. There was a whole traffic in it. Some of it was going into the pile, some of it was going to Mallinckrodt and then coming back, and then going to Spedding at Ames and being cast into—

Groueff: Mallinckrodt would purify it?

Rudolph: Yes. Mallinckrodt Chemical Works is still, in fact – even today, they are still one of the principle refiners for the commission of—

Groueff: But it came back also oxide?

Rudolph: Yes.

Groueff: The purified one. Then you sent it to Spedding?

Rudolph: Some of it. At this point, Spedding was developing his reduction process, metal reduction process. As the process got to the point where he could go to production stage, there was a diversion. Some of it was being pressed into oxide blocks, but the rest of it – as much as available – was being shipped to Spedding to be converted into metal and then returned. But this was all a state of flux. I do not know what the true statistics are, but I think in the CP-1, as it was installed there, may have been just a token number of Spedding—

Groueff: Metal?

Rudolph: Spedding billets. There was a much larger amount of cubes that Westinghouse had produced, one-inch cubes.

Groueff: So Westinghouse production was bigger for the CP-1?

Rudolph: Yes, right. In fact, essentially all of the metal, such amount of metal that went into the first pile – this was in the core, the heart of the pile – was primarily all Westinghouse cubes.

Groueff: They were producing it by some rather primitive—

Rudolph: Yes. Now, they started out using a photochemical process, but I believe that they did maybe go to some other medium, because it started to come out in rather large quantities. So they may have achieved some sort of a casting reduction process. Others, I am sure, can speak to this point.

Anyway, my task primarily was just to keep close watch over how much we had and how much went into the pile and how much was left, and getting it shipped out and checking the returns. In fact, this function of accounting for and managing quantities and inventory of what we now call nuclear material is still a part of my responsibility. In my division, we have a nuclear materials branch, which supervises the accounting control over nuclear materials that are in the custody of our many contractors. Well, that was my introduction.

Groueff: You were responsible to whom in this job at CP-1?

Rudolph: Well, this again is where it gets diffused. Technically, I was employed in the purchasing and supply unit, which was headed by a Dr. McMahon, but as far as my work for CP-1, I worked directly under Dr. [Walter] Zinn. That is, I was supervising his material for him and keeping track of it for him.

Groueff: And Zinn was directly under [Enrico] Fermi?

Rudolph: Yes. Now again, “under” is perhaps a misnomer. Zinn’s responsibility was to get the pile built, and under him, there were shift groups so that in fact prominent physicists were acting as labor supervisors, you might say. For example, Dr. Alvin Graves was in charge of one shift. Dr. George Weil was in charge of another shift.

Groueff: They always worked physically, with their hands?

Rudolph: Yes, certainly at times they did. At others, there were labor crews that they supervised, but there were many times when everybody had to pitch in. As Dr. [Norman] Hilberry would probably point out, they all got on the trucks and pushed the graphite off.

Groueff: And very gladly?

Rudolph: Oh yeah.

Groueff: You were also in charge of the graphite procurement, graphite inventory?

Rudolph: Yes. That was all a part of the same. Although at that time, graphite was really a structural material, and it came in large truckloads. But all we tried to do is keep different grades separate so that if there was any special need for purity here versus less pure material there, it could be segregated. It was just like so much lumber, really.

Groueff: It was stored physically there in the Stagg Field court?

Rudolph: Yes.

Groueff: They used all this material for the different piles they built first?

Rudolph: Well, when you say different piles, actually it was really the same graphite that was reused.

Groueff: Reused about thirty times.

Rudolph: Again, if you visit the facility down in Building 25, you will see that there is a standard module of twenty-four inch – I think it was twenty-four inch by four inch square block – some with holes drilled and some solid. This was the module on which everything was built, so that there was a uniform distance between each cell, both in the lateral direction and horizontal and vertical also.

Groueff: After they built it and they successfully experimented the first pile, your remained on the same job for the other piles, no?

Rudolph: Yes. Now of course during that time, my participation with this group was interrupted to some extent. First thing after a brief period of operation, approximately the latter part of January of ’43, the whole pile was torn down and removed through Palos Park, where it was then re-erected and called CP-2. So I was responsible for supervising the transfer of the graphite and the uranium to Palos Park. Meanwhile, additional material was coming in, so that by the time CP-2 was erected, there was a great amount of Spedding metal that went in, and the oxide bricks were not put in.

Groueff: Because Spedding’s was much better?

Rudolph: Well, it was more compact. There was more uranium per unit of volume so that there could be a more efficient process, efficient multiplication. Then the next step was taking these blocks, these oxide spheres or compacts. These were then shipped back to Mallinckrodt or to Spedding for conversion into metal.

This occupied me for a time. In addition, we were responsible for a few other items, such as a rather sizable stock of beryllium metal, which is, as you know, an important nuclear metal. We had inherited a batch of beryllium from the National Bureau of Standards, which again I controlled the inventory of.

Then about a year later after I started, in August of ’43 I was whisked off into military service. But this was a brief encounter because as soon as the wheels could get adjusted, I was back on the job. I returned, I guess, approximately October, middle of October, I returned and resumed my same duties in civilian clothes but at a different rate of pay. I was now a member of the armed services.

Groueff: In your job, you were under the administration of the University and not the military?

Rudolph: Well, even when I returned as a soldier, I was a member of a detachment. In fact, the detachment was located in Oak Ridge. So officially, I was on the payroll of that Special Engineer Detachment, [SED] but for duty, I was assigned to the Metallurgical Laboratory. In fact, it was the same supervision that I had been under before. Subsequently, maybe six months later we started to receive large numbers of military personnel who were assigned in laboratory tasks. So although I was the first one to go through this metamorphosis, many more followed.

Groueff: You didn’t go to Hanford?

Rudolph: No. At the end of 1944, when the demonstrations that the Met Lab had supervised and coordinated were at the point of being ready to be exploited, then the military personnel in particular were just arbitrarily shipped to where they could do some good. Large number of the soldiers that were working in the laboratory were sent to Oak Ridge. A few were sent to Los Alamos, and I was one of those. So I was sent to Los Alamos and arrived there about the first of – well, sometime early in 1945.

Groueff: So you were there for the Trinity test?

Rudolph: Yes. In fact, no sooner did we arrive in Los Alamos than I was assigned to the Trinity site. I was assigned down there as an administrative assistant to the post engineer. At that point, we had just acquired the site. In fact, the Trinity site was really a part of an Air Corps reservation called the Alamogordo Bombing Range. Alamogordo was an Air Corps training center, and there was this large desert area that was used for bombing practice. They would drop dummy bombs all over the place.

We acquired a corner of that site, and that was the Trinity site. My duty there was to act as an aid to the post engineer. We started to build up a group of enlisted personal specialists in various engineering fields. We had tractor drivers and plumbers and electricians; all kinds of specialties were selected to come out there to install the service equipment and the monitoring and measurement equipment for the tests. I stayed at Trinity until after the test.

Groueff: You saw the test?

Rudolph: Oh, yes, until after the test was completed.

Groueff: So you saw the two historical—

Rudolph: Yes, I was there on both occasions.

Groueff: There are very few, very few people saw the two.

Rudolph: Well, Dr. [Samuel] Allison was also there.

Groueff: He was one of them, yeah.

Rudolph: He was at Los Alamos, and I think he was there for the test. Herbert Anderson also. I do not know if you have been to see Dr. Anderson at the university. He was also one of the—

Groueff: And Fermi.

Rudolph: Oh, yes, Fermi was at the test.

Groueff: So very few people saw the two.

Rudolph: That is right, I think that is true, so that is one thing I can pack away in my bag of memories.

Groueff: But on the first test in December 2 in 1942, from where did you see it? You were on the balcony?

Rudolph: No, I was actually in my storeroom getting my records up, because the first of the month was the normal time of getting a monthly inventory put together. So while the others were upstairs on the balcony watching the neutrons, I was working.

Groueff: You were in the same building?

Rudolph: Oh, yes. The physical layout, which you probably have seen—

Groueff: I saw a picture.

Rudolph: There was a sort of an empty room leading into the squash court. This was really a sort of a lobby. Originally it had been sort of a lobby for the entrance to the field. My storage room was one storage room right off of this lobby facing the west wall of the building – a small room, which was actually the ticket booth for the field, where I stored several of the items. That was sort of an inner storage room, because the entrance to that ticket booth was inside this other storage room. You have to go into one storage room to get into the ticket booth. I was in that area most of the day; I would pass by, occasionally, the milling throng up in the balcony. I did not have any work up with them. Of course, many of the people up there, too, were observers.

Groueff: Yeah.

Rudolph: Even though they did not want them, they were observers.

Groueff: Only actually Fermi was performing?

Rudolph: Well, there were a number of people working. There were various meters up there that the people were watching and reporting to Fermi on what the readings were.

Groueff: Also, some security measures for in case something went wrong?

Rudolph: Yes, there was the safety measures. There were jars of cadmium solution that could have been poured on top of the pile to quench the nuclear reaction.

Groueff: But there was no sense of extraordinary fear that something might go wrong?

Rudolph: Well, not that I could see. Most of the people, at least that I can reconstruct from talking afterwards – I think everybody in the back of his mind had the feeling that there may be some mysterious force that we would not know anything about. But all of the physical evidence that the experiment was built on made it clear that there was a great deal of safety. There was no likelihood of such wild speculations as igniting all the nitrogen in the atmosphere and so on. Those were conjectures.

Groueff: You can’t be completely sure.

Rudolph: That is right.

Groueff: There was no sort of expressed fear of the people?

Rudolph: No, the group had already had close enough contact with neutrons and radiation in general and, in fact, demonstrations of multiplication in the sub-criticals. I am sure that the consummate feeling was, “Will it work at all? Will we get over a threshold of where the escaped neutrons and the captured neutrons will be low enough so that the fission process can continue?” This was really the big question to be answered, because in theory – discounting the unknown processes that take away neutrons – it should have achieved bare criticality, and it did.

One incident that I was heartened by, and that I believe may have convinced others that my job had some consequence: for the night shift, it was my responsibility to keep record of what was issued through the pile group, so we would have some record of where the material went and how much we had left and so on. For the night shift, since I was not going to be around, I would check in in particular to Westinghouse cubes, and stack them in ready and pre-counted containers. In other words, this box contained so many cubes. I would leave a supply as suggested by the night shift supervisor.

I believe in this particular case, Dr. Graves was the night shift supervisor in question. I left a number of boxes of Westinghouse cubes for him to use in stacking the layers they were approaching, and then he would sign a receipt for the number that he used when the shift quit.

The next morning when I came to work, I checked his receipt against the remaining unused parts of the batch I had assigned to him and they did not agree. By my record, he had not used as many as he had said he did. I had more left than I should have had. So I reported this to Dr. Zinn immediately, and the suspicion was that there were a number of holes in that layer, which were empty instead of being full of uranium blocks.

Now the way the reactor was built, there were alternate layers where there were interspersed cavities and then the next layer was all solid graphite. The next layer would be interspersed holes. So they had already gone up a couple of layers while Zinn ordered them to tear down the few layers up from where they had filled. Sure enough, they found there were a number of holes that had not been filled, bore out my evidence that they had not filled the holes. Now there was really no way of conjecturing what this would have done to pervert the data or the measurements, but it was near the middle of the reactor, probably in a reasonably critical zone.

Groueff: Could have changed the—

Rudolph: It might have made a difference. They might have had to go higher to get criticality, let us say. They may have had some anomalies. But at least the reaction that Dr. Zinn expressed was that this demonstrates that it pays to keep records. This is one of the few highlights I can recall.

One other one, which is somewhat amusing, was – as I recall this was December 31st of 1942, which was New Year’s Eve, the day of New Year’s Eve. Naturally, everybody was trying to get through at work and get home for the festivities. It just so happened at the very moment, that afternoon, we had scheduled a shipment to Mallinckrodt of a large number. I guess we already knew that we did not need any more oxide. All of the oxide that had been flowing in was just accumulating. We did not need any more oxide for this experiment.

So arrangements had been proceeding through many channels to get the stuff shipped back to where it would go into production. Low and behold, that morning I had a call from Dr. [Richard L.] Doan, who was then the director of the laboratory, saying, “You get the oxide shipped to Mallinckrodt by express today!”

I arranged with the Railroad Express Company. They sent a truck over, and we loaded our truck. We filled both of these with the 75-pound drums of oxide to be shipped to Mallinckrodt. This was a real sizeable amount of material, probably three tons over weight, and we just loaded it up and got the express rate and shipped it away.

When I returned to the Met Lab about two years later, the auditors were still trying to investigate, why did we ship that express? That is so expensive, to ship by express. You pay per pound rather than by the truckload. I do not know if they ever were satisfied, but all I know was that when I remarked to Dr. Doan that it would be very expensive, he said, “Well it has to be there, ship it express.”

Groueff: The scientists are usually not very inclined to go into the inventory details.

Rudolph: Or are concerned about money. That is very true; that is still true. Even at present in our supervision of nuclear materials, where small samples are assigned to scientists, they apparently think nothing of loaning the sample to someone else without a record being made of it. The first thing you know, control has been lost.

Groueff: Usually that is sort of against what they call—

Rudolph: I think so. He is more inclined to think of this material in terms of, “What I am getting out of it? Or what it will do for me? Or what it might do for him if I loan it to him?” Rather than the fact that back in the other building there is somebody who has a card that says, “This is now here.” This is still true.

Groueff: Probably has presented sometimes troubles in bookkeeping.

Rudolph: Oh, yes indeed. I said even today, it is hard to get away from these attitudes.

Copyright 1965 Stephane Groueff. From the Stephane Groueff Collection, Howard Gotlieb Archival Research Center at Boston University. Exclusive rights granted to the Atomic Heritage Foundation.