Stephane Groueff: Okay, now it’s recording. Dr. Foote, you started telling me from the beginning—
Frank G. Foote: Knowing nothing about the uranium, and this was supposed to be my new business; I’d go over to the library to find out what was known.
Groueff: In 1942?
Foote: In 1942, August. Ordinarily, you'd expect this to be some weeks work, grinding through the literature. It turned out you could do the whole thing in a half an hour or so, because that’s about all that was known. About the metallurgy, there was practically nothing that was known. I looked in the ASM Metals Handbook, the melting point was given as about—what was it Jim? 17—?
James F. Schumar: Yeah, about 1700.
Foote: Turns out the actual melting point is only about 1130. It makes a tremendous difference in the technology, this difference in melting point between 1750 and 1150. But that just illustrates the lack of known information. If you went and looked for the chemistry of uranium, you would find huge masses of information on a big variety of chemical compounds.
Right then and there, it gave me a very good illustration of a difference in approach between metallurgists and the chemists. The chemist would study the material simply because it’s interesting, and the chemist then, when this material became useful, had a large amount of background information available. The metallurgist, on the other hand, will study a material only if it is useful. When a material suddenly becomes useful, you have no background information. You have to essentially start right from the beginning. I think the chemists had a much better approach to their problems than the metallurgists had.
It occurred to me also in 1930, when I was looking around for a thesis problem, I was looking for something that wasn’t awfully useful since I had been a physicist prior to that time. So I chose to work on magnesium, which wasn’t a particularly useful material at the time. If I just had been clever enough to have worked on uranium instead of magnesium, ten years later I had been a damned hero. [Laughing]
Groueff: But, how were you brought in to this project? You were probably at University of Chicago?
Foote: No. I was at Columbia at the time. I knew most of the people who were working very early in the business, particularly [Walter] Zinn and [John] Dunning. It was Zinn who got me into the business, basically.
Groueff: Your specialty was metallurgy?
Groueff: They called you and then said, “Here is this metal that we don't know very much about. You have to do this and that with uranium.” And you had to start from scratch, no?
Foote: Yes. At the time, practically nothing was known about uranium. It wasn’t even known that it had two solid state transformations. This was found out after the Project started. The melting point wasn’t known.
Schumar: It has three distinct, crystalline—
Foote: But the fact that it had two other solid forms was not known at that time. It meant that one had to start essentially from the beginning to work up both the knowledge of the properties, the ways of preparing the material, and the whole technology that’s involved in understanding and producing the material.
Groueff: You received the raw material in what form and from where?
Foote: Well, let’s see. They came here— in August ’42, I stayed for five days and then I went to Boston. I was working at the Metal Hydrides plant up in Beverly [MA]. They received the material in the form of a purified oxide, which I believe they got from Mallinckrodt [Chemical Company]. The problem there was to reduce this oxide to metal.
Groueff: That was your job?
Foote: Well, I was helping. It wasn’t really my job. I was sent out from Chicago to sort of do whatever I could to help this company, who had a process for making uranium.
Foote: No. This was the Metal Hydrides Corporation. This was a small company that was set up to do specialty reductions of one kind or another. They were making a great variety of things. Among other things, they had made uranium powder by their process, which involved calcium hydride reductions. They had published this process and made a few alloys of uranium. When it was necessary that one produce metallic uranium, of course people looked through the literature and they found out that this man [Peter P.] Alexander, who was operating this small company, had made uranium powder. So the whole project descended upon him. [Laughing]
Schumar: He stopped doing everything else and started making uranium. [Laughing]
Foote: Somewhat reluctantly, I might add.
Schumar: Yeah, he fought it. Here’s a guy that reaped nothing. Out of this whole new industry that has been created, you never hear of Metal Hydrides. You hear of United Nuclear. You hear of Davison Chemical. You hear of Mallinckrodt. You hear of Kerr-McGee. You hear of a lot of other companies. Poor Alexander never had nothing.
Groueff: I know, but he was one of the first?
Foote: Yes. Some of the first metal that was made was made by Metal Hydrides. But their material was not very good, as good as it should have been.
Groueff: In what quantities did you receive it? Very small quantities?
Foote: No. The oxide was shipped to us in, oh, I don't know. It must have been 100 pounds.
Schumar: It was pound quantities.
Foote: In total, we received many tons of this stuff.
Groueff: The first year, ’42, you were receiving pound quantities. Arrived in your laboratory in Chicago—or, where did you work?
Foote: I was working in Beverly, Massachusetts at the time.
Groueff: I see.
Foote: I had been sent out from Chicago to help with this process that was being carried out in this Beverly factory. But the powder that we got was somewhat impure. Of course, very high purity was another requirement, and there were having trouble with contamination by titanium, of all things. We finally found out where the contamination was coming from. But in addition, the powder that was produced was finally divided and quite pyrophoric. We lost a fair amount of product by simply burning.
Some of it we consolidated by metallurgical methods, just by pressing and cindering. This didn't work very well. We developed also a method for melting this powder and casting it into bars. This work was carried out at MIT. It was rather early in ’43 that this process was essentially abandoned. In the meantime, people at Iowa State College studied—Wilhelm had developed another, superior reduction method. So the Metal Hydrides process was abandoned, rather early in ’43.
Groueff: Until ’43, you personally worked in Massachusetts and not in Chicago?
Foote: Yeah. I came here long enough to get on the payroll and then I left.
Groueff: Was there a metallurgical group organized here in the Chicago group? Or the same group where [Arthur] Compton, [Enrico] Fermi?
Foote: Yes. Creutz, Ed [ward C.] Creutz organized a metallurgy group, didn't he, Jim?
Schumar: Yeah, working on the metal. Working on melting, and casting, alloy.
Groueff: But was it also working on the—
Schumar: They were making a powder.
Groueff: A powder, at the beginning.
Foote: Well, they were melting their powders too. Westinghouse had gotten into this job on the basis of this erroneous melting point determination. With a melting point this high, there was some hope that it might be useful as [inaudible]. So they set up a somewhat intricate process for making the metal. That process was again somewhat difficult to carry out, and again was abandoned or superseded by the Ames [Iowa State] process, which became, and still is, the standard.
Groueff: So the Ames process gave the metal for the reactors?
Foote: Uh huh.
Groueff: Even for the first ones, for the first pile?
Foote: Yes. Well, the first pile was a miscellaneous loading, as I recall. It had some oxide in it because oxide was available. It had some metal that came from Ames. It had some Westinghouse metal. It had some Metal Hydrides metal. Indeed, you put in whatever you could lay hand to. Since the oxide was more available, you put in what you had. The physicists would have preferred metal because of the higher density and the higher concentration of it.
Foote: But if the stuff wasn’t available—
Groueff: So the very first pile used very mixed—
Groueff: material—oxide, metal.
Foote: Metal from various sources.
Groueff: That all created a pile, and the Hanford—
Schumar: Let’s take them in order. CP-2 [Chicago Pile-2] was metal and CP-3 [Chicago Pile-3] was—
Groueff: CP-3 is what the Hanford was?
Schumar: No. Metal, clad. This [Hanford’s B Reactor] is heavy water pooled. This metal [CP-3] was air-cooled. The reactor was air-cooled, and this was just the way it was. Then we went to Oak Ridge. It was called a Clinton Pile.
Groueff: Yes. Air-cooled.
Schumar: Right. Pile used metal, aluminum clad. But I think the key thing was the different directions that were being pursued simultaneously. For example, this existed.
Schumar: Yeah. They were making oxide. Metal Hydrides was reducing some of the oxide to metal. So they went this route. And then there was Westinghouse producing powder as metal powder and doing a little bit of melting and casting. This did not look like a very lucrative direction to go. And then they brought [Frank] Spedding in and, let’s take and make an alloy and reduce it with lime, calcium, or magnesium to get the metal. So you can get UF4 or UCl3 or 4 or 6.
Groueff: I see.
Schumar: While Ames was concentrating on reducing to metal—starting with the oxide and reducing to metal—
Foote: Well, converting it to halide first.
Schumar: Yeah, converting it to a halide. I’m sorry.
Foote: The oxide is extremely difficult when it’s time to reduce. Halides are much more easily reduced.
Schumar: So the trick was actually to get the oxide, which is fairly easily produced. Convert it to halide, which is much more easily reduced to metal. So you do it in two steps, which was better than any single step as Metal Hydrides and Westinghouse was trying.
Groueff: From what I see there, at the beginning—that’s the years 1941- 42—some different work was being done in different places.
Schumar: Most of this was 1942 on.
Groueff: When did you organize a metallurgical division here? And you concentrated on sort of more specialized—
Foote: That was the spring of ’43, before we had metallurgy within the metal—
Groueff: And Dr. Creutz was in charge of metallurgy?
Schumar: He was starting it, yes.
Foote: He started it, but he didn’t stay with it too long.
Groueff: And both of you work the—
Foote: [John] Chipman and [Alden B.] Greninger organized the metallurgy division here.
Groueff: I see.
Schumar: That was in about the later part of ’43. Wasn’t it, Frank?
Foote: No, early in ’43.
Schumar: Early ’43.
Groueff: Both of you used to work in this division?
Schumar: I wasn’t in the division per se. I was working in Detroit. With a company.
Groueff: And so you were working in—
Schumar: I was working with a private company in Detroit called the Wolverine Tubes. See, he still carries it. [Laughing] The Wolverine Tube Company, and I was in the copper and brass business.
Groueff: So nothing to do with uranium?
Schumar: Wait. I got involved in uranium in the fall of ’42 by Creutz.
Foote: [Laughing] I tell ya, things are real complicated.
Schumar: Oh, they sure are. Chicago and MIT were working on melting, casting, alloy, fabrication and properties of uranium metal. Also, the fabricating of what might be a fuel element for these reactors. This one, this one, and this one.
Groueff: CP-2 and Oak Ridge and Hanford.
Schumar: That’s what they were looking. They were looking way in advance for this.
Schumar: Now, in the meantime, they had a little bit of uranium that they would steal from here or here.
Groueff: From Ames?
Schumar: From Mallinckrodt. They were trying to make billets out of it to fabricate, you know, see and to measure properties. Then, when they were getting this started, it became quite apparent that they ought to have some metallurgists around. So, that’s when Frank is saying that Mr. Greninger and John Chipman from MIT started a metallurgy department within the Metallurgical Laboratory at the University of Chicago.
Groueff: And you joined later?
Schumar: I came here in ’46.
Groueff: I see. So during the war you always worked—
Schumar: In Detroit. But all my time was spent working on this fabrication of uranium and uranium alloy and the fuel elements.
Groueff: You worked for the Manhattan Project indirectly?
Schumar: Yeah, indirectly.
Groueff: Creutz and—
Schumar: Well, after Creutz got out, then Frank Foote, you see.
Groueff: So he would commission you to do this or that?
Groueff: Physically, you weren’t there? You were not a member of the team here in Chicago?
Groueff: I see. But you were?
Schumar: Frank was.
Groueff: Where was the metallurgical division located? In the University building?
Foote: It was located in a building which was owned by the university on South University Avenue, 6111 South University. The building, which had been built originally as an ice house, which, at the time we first saw it, was being used as a bottling works by a brewery. I forgot who it was.
Schumar: I don't remember who it was either.
Foote: That’s the reason we called it Site B, for brewery. So we took over the building, tore out all the insulation that was part of the ice house construction, and rebuilt it as a laboratory. We worked in there for—about ’48 wasn’t it? About five, six years. Then we moved out there to the Quonset Huts on the east side. And finally, we built this building.
Groueff: What were the biggest difficulties? Dr. Hubert told me that it would be very interesting. You started telling me about the melting point. Can you give me all the other unknowns?
Foote: Well, the big difficulty was the so-called canning product.
Groueff: The canning of the slugs?
Foote: Yeah, the canning of the Hanford slugs in aluminum. This presented an extremely difficult problem, for a number of reasons. We had to have the uranium slug completely enclosed in uranium, because in water uranium reacts rather rapidly. We needed, therefore, to completely protect it from water—which was the coolant—which meant that the cans has to be completely tight and free of any defects.
This involved this aluminum welding problem. Obviously, in order to get the slug into the can, you have to have a hole to put it in. Then, sooner or later, you have to close this hole. Welding aluminum at that time wasn’t done too well. It wasn’t very well at all. So, it involved a great deal of work on simply how to weld aluminum in such a manner that it had no cracks or porosity in the weld. In addition, the contact between the slug, uranium slug, and the can had to be extremely good because this was our heat transfer surface. It was still thought that it was necessary to have a metallurgical body between the uranium and the can.
Groueff: No air between them.
Foote: Yes. No space. Well, as nearly a perfect bond as one could achieve. It was an awkward thing to do with any of the materials, and was particularly troublesome with aluminum and uranium because of the nature of the uranium-aluminum phase diagram, which also of course had to be developed as part of the job. No one knew anything about the uranium-aluminum phase system.
So it was an awkward brazing job to get these things bonded together. It was an awkward closure job, as no one knew much about how to weld aluminum. It turned out later that it was also a heat treating job, but we didn't realize it at the time. We discovered that later. Occasionally we did the right thing.
Groueff: —metallurgic divisions work on that problem?
Groueff: It wasn’t given to DuPont people?
Foote: DuPont was here working with us on this job. There were a large number of DuPont people assigned to the laboratory at that time.
Groueff: But that was one of the main problems, how to do the canning of the slugs?
Foote: But along with this, of course, there was a whole great deal of backup work that was necessary in order to understand what you were doing. We recognized that uranium by itself had rather poor physical, mechanical properties. So there was a great deal of work on alloy. This is the normal procedure for most metallurgical developments.
Most of the pure metals have not too good properties, from a mechanical standpoint. A great deal of metallurgy consists in trying to improve these properties by adding other elements to it. Well, as you know, most of our useful materials are alloys rather than pure metals—steels, iron, carbon alloys.
We rather quickly found that uranium wasn’t a very well behaved material. The obvious thing was to start adding alloy elements to it in an attempt to improve its properties. There was a fair amount of effort put into the development of uranium-based alloys. We’re still continuing that development. It goes on endlessly.
Groueff: You said uranium wasn’t behaving in an easy way—in what way? The physical properties?
Foote: One of the things that we worked on rather vigorously was trying to improve the oxidation or aqueous corrosion resistance. I remember at the time, we were trying to roll the material into a rod to then slice up into—
Foote: The material rolled in a very peculiar way. We heated up the furnace in air or some sort of— well, using nitrogen too, in an attempt to cut down on oxidation. But then when you start putting it through the rolling mill, it starts oxidizing.
Schumar: Just heat itself.
Foote: Yeah. It was sort of self-heating after you almost got it cut.
Schumar: The heat of oxidation would just keep heating the metal up—extra heat.
Groueff: And that changes the—
Foote: Well, yes. If it got too hot, then it would break up in the mill. So we were rolling this material in a mill, which was ordinarily done on weekends, or whenever we could get into the mill. A stainless mill. Well, in the rolling of stainless, the trick is that you get it out of the furnace and then you push it through the mill as fast as you can before it cools off to the point where it’s no longer fabricable. The rolling crew was very clever at jamming this stuff through.
With uranium, you can’t do this. You put it through the mill, through one pass of the mill. This cracks the oxide off and now a fresh surface is exposed. So it oxidizes more and it gets hotter. We usually put the bars through one or two passes and then we leave them to lie there on the steel floor until they cooled off enough to put them through the next pass. This, you see, was just the exact opposite of the stainless technology.
Schumar: You knew there were these transformations from one crystalline structure to another.
Groueff: How would you explain that to a complete layman?
Schumar: Well, the transformation means that in the solid, metals crystallize in definite geometric patterns.
Schumar: Now copper remains in—where the atoms are lined up in a cubic array. The atoms are lined up, so you get a cubic array. They call that the cubic structure. In uranium, the structure was not known, how the atoms lined up. Well, it was known. Yeah, the alpha was known. But we didn't know where the atoms rearranged themselves with an increase in temperature. So you call that an alpha phase, a beta phase, and then there was a second rearrangement called a gamma phase.
Groueff: And each phase changes the size and shape or what?
Schumar: It changes the properties.
Groueff: It changes with the heating?
Foote: The temperature.
Schumar: Okay now, you go back and remember, he says if you roll the material too fast it will heat up. The nice place to roll it, so it wouldn’t oxidize too much and scale and throw the radioactive dust all over it, was black heat. So how do you measure anything that’s black? It’s not red. You can’t use an optical pyrometer on it. You look at it and you say, “Well, that’s about right. Let’s roll it some more.” By the feel—just literally by the art. Then, as long as it stayed in the black appearance, until the oxide got so damn thick. When it was black, it was red on the inside and you'd never see it.
Groueff: So it was an artisanal way, rather than scientific?
Schumar: Remember, we’re doing this with the eyes that we had in 1942 and ’43.
Groueff: Yeah. I’ve never seen anything similar.
Schumar: Usually, the rolling of metal is that you hurriedly hot work it so it doesn't lose its heat. Many times, you have to put it back into a furnace and heat it up. Here was a metal that you would let it cool down before you gave it the next reduction in area, you see.
Groueff: But do I understand it correctly that the different phases—each phase gives different characteristics? In other words, if you succeed completely, let’s say in some test or something in one phase, it doesn’t apply to the next two phases. It could be different.
Foote: Well, there are essentially two or three different materials that are on sets of properties. If you take the farthest, this is your teacher, there’s more transformation about 6/60.
Schumar: Yeah, but we didn’t know all this 6/60.
Foote: Well, we didn’t by that time.
Schumar: Well, you did by then.
Foote: There was no underground synthesis. This was known as gamma uranium. This is beta uranium. And this is copper. We were trying to work the material in this region in here. It’s not very ductile. You heat it up, it becomes fairly ductile and you can fabricate it into the right route without too much trouble. You get up in here, it’s brittle. Therefore, if you overheat it during rowing, this stuff just cracked up.
Groueff: Just cracked.
Foote: On the other hand, if you got it way up into this temperature range, the melting point of 1130, it’s extremely soft.
Foote: Ductile and more like trying to roll butter.
Schumar: Mushy. It wouldn’t even support its own weight.
Foote: It’s impossible to handle it in the mill because if you try to pick it up with a pair of tongs, you just pinch it off. You can’t pick up the rod. You get one end in the mill, the rest of it won’t come. It just pulls apart.
Groueff: I see. So all this you discovered as you went?
Foote: I think it was actually done in fabricating these rods for Hanford, to extrude this stuff in the gamma region. This wasn’t the best, it wasn’t a very good way, but it worked out pretty well. A lot of rough surfaces, a lot of shimming and stuff, but at least it got it done. So we found ourselves in, I guess to say, an absurd, peculiar situation in the very early days we were trying to roll uranium. All of the metal that went into the Hanford directors was extruded in the gamma. But now, practically all metal is rolled. So we were developing the process that is now used well ahead of time, what was not used during the early days.
Groueff: So it wasn’t just like working with another unknown metal, which has rather regular qualities. Everything was new. Now do you remember some particular cases of surprise or unexpected results or small accidents or something like this?
Schumar: How about the discovery of the dimensional instability by Andy.
Foote: Well the one thing, sort of unique behavior, is this so-called “thermal cycling growth.” We came upon this when we were working with the heat treatment of these alpha rolled rods. The usual metallurgical practice after rolling is to give the materials some sort of a stress relief or re-crystallization anneal in order to remove the effects of working. I had a man named Van Echo who now works for the AEC [Atomic Energy Commission] in Washington, who was carrying up heat treatment studies on rolled uranium rod. Well, he was a very careful investigator, so among other things, he was measuring the dimensions and the density as well as the changes in microstructure produced by his heat treatments. He discovered over the course of this work that there was a small dimensional change every time he heat treated one of these rods.
Groueff: The rods, the dimensions changed?
Groueff: Longer or shorter, yes?
Foote: They got a little longer, by a few mils or fraction of a percent. Well, this sort of interested him. So he took some of the rods that he’d heat treated and heat treated them again to see whether—well, the dimensional stabilization was often an important part of a heat treatment. And found that if he reheat treated them, they would roll a little more. And he did a few of them three times; they grew still more.
Groueff: But the rod physically was longer?
Foote: About that time, the war ended and Andy quit. We didn’t do anything more about it until what, about ‘47?
Schumar: ‘46, ’47, I think. We re-discovered it and it got us into a lot of trouble.
Foote: The fact that three successive heat treatments resulted in a small increase in length was a somewhat upsetting observation. So we started into simply thermal cycle. We just heat and cool, heat and cool, over and over and over again. And lo and behold the damn stuff just kept right on increasing in length. There was no way of stabilizing it, at least by the normal type of heat treatment. This intrigued us to no end. Finally, we just kept heating and cycling some of this material to see what would happen. This stuff kept on growing and we had some samples that were what, six times their original length.
Groueff: That much length? There wasn’t any more in millimeters—but they really got longer by inches?
Foote: Yes, by several times its—
Groueff: Several times, yeah?
Foote: We had what we called the museum sample. We just kept going on this thing just to see whether there was any end to it. We started with a piece two inches long, wasn’t it, Jim?
Schumar: Yeah, it went to about—
Foote: And it ended up about twelve inches long.
Groueff: From two inches to twelve.
Schumar: Just by heating and cooling.
Groueff: But it gets so much thinner, no?
Foote: Yeah. Got full of holes. It was a mess.
Groueff: But how could you then prepare this extremely precise slugs that every millimeter—
Schumar: [Laughing] That was the point.
Foote: Yeah, that was the whole—
Schumar: That’s the whole problem.
Foote: That was the problem. How do you stop this behavior? It turned out to be very easy to stop. It required a different kind of heat treatment.
Groueff: I can imagine the beginning, when you needed this precision and you see that it grew five times longer each time you—
Foote: This was a sort of cycling range, that if you cycled it say from 600 down to room temperature, it would show this very peculiar—
Schumar: Here’s a typical picture.
Groueff: Let me see that.
Schumar: Highly tested uranium rod, only this was under nuclear radiation.
Groueff: Uh huh.
Schumar: See how it’s grown?
Groueff: I see, because it gets thinner, but would get much longer.
Schumar: Now we found this before we found it under nuclear radiation. We found that it just happened because of thermal histories and thermals.
Groueff: Just simple heat?
Schumar: Just by simple heat.
Foote: Yeah. Just by heating and cooling.
Schumar: But we didn’t pursue it until after, much after the Manhattan Project.
Groueff: What do you call it—the cycling range?
Foote: Thermal cycling growth.
Groueff: The cycling—
Foote: I think we usually ran up around 600 centigrade. Now you can stop this thing here very easily by simply heating up into this temperature around 700 and then water quench it.
Groueff: Do you take the dimensions as they will be at 700 and you fix it there?
Foote: No. What you do is take your rod, heat it up to 700—
Foote: And quench it in water.
Foote: Then if you go through this thermal cycling down to say 600, the dimensions stay reasonably constant.
Foote: In other words, the so called beta heat treatment has wiped out whatever structure is giving rise to this growth.
Foote: Stabilizer. This is the stabilization heat treatment. It’s not perfect.
Groueff: But you discovered that later in the game, no?
Schumar: Let me tighten this in for you. Can I tighten this in for him because I think it’s interesting.
Foote: We’ve made observations on this as part of Van Echo’s study because he was also working—
Groueff: What was he there—Van?
Foote: Van Echo.
Groueff: How do you spell it?
Schumar: Capital V-A-N, Capital E-C-H-O.
Groueff: E-C-H-O. Yeah.
Foote: Because he was carrying out this annealing study on extruded material, along with the rolled material.
Foote: He observed that he got this growth only with the alpha rolled material.
Schumar: Yeah. Not the extruded.
Foote: He did not get it on the extruded material, which had been extruded at very high temperatures.
Groueff: So you went to the beta range and then cooled down to the alpha again?
Schumar: Remember Dr. Foote told you, just by a choice, not that we believed or Van Echo had established—well, he knew that the beta treated material or the material that had been alpha extruded did not grow.
Foote: No, no. Gamma extruded.
Schuumar: I mean, gamma extruded did not grow—the high stuff. But the Hanford reactors were loaded with gamma material, you see. So they did not see the effects of this instability. That was just sheer luck, right? That’s the point he’s trying to make here, you see. You gotta get the whole story.
Groueff: In other words, if you put, let’s say you needed ten inches precisely, slugs. You put them in the reactor.
Schumar: They would grow.
Groueff: And then they would grow to twenty or to twelve or to fifteen. Who knows?
Schumar: I mean, who knows?
Groueff: Eventually. The point is that all of this highly precision work will be completely compromised and you didn’t know it then.
Foote: The problem is, the cans break too.
Groueff: And the cans.
Schumar: It would break.
Groueff: But you didn’t know that then.
Schumar: I mean, this is the anecdote you want. But we had to build you into this, so you see how the hell it fits together.
Foote: All the metal that was used in the Hanford reactors had been extruded at around 1000, as I recall.
Groueff: Thousand? Yeah.
Schumar: High temperatures.
Foote: But you’re cooling the extrusion down, you go through this transformation, you go through the beta phase, you go through this transformation and the stuff has a heat treatment. That stuff is stable, reasonably stable. And that’s what we put into Hanford. But this is a sort of a messy fabrication process. The material comes out very, very rough. There’s a lot of machine losses and so we were working on the—
Foote: On a better fabrication process. But then it turns out that while you have a better fabrication process, you’ve got a new problem.
Groueff: I see. So you were [inaudible].
Schumar: Yes, it was a good thing we didn’t develop the rolling technique but developed the extrusion techniques first, or we would have been in a lot more trouble.
Groueff: The extrusion techniques are more primitive?
Schumar: The heat on the metal is very low.
Groueff: But it was just because you didn’t have the better method that you did it. Not by choice.
Schumar: Not by choice. Five, three, four years later, we find out that it was—yeah, at the end of the war, we really began to understand it.
Groueff: But didn’t you have similar problems with the slugs of the Oak Ridge, the Clinton pile?
Schumar: No, because they were extruded too. Both of these were extruded high.
Groueff: I see. High temperature.
Schumar: High temperaturem and it automatically got the thermal treatment, the heat treatment that you wanted.
Foote: They got the stabilization treatment automatically, without you’re knowing that this is what you were doing.
Schumar: Because after the war, this phenomenon here, I would say several millions of dollars had been spent trying to understand this, not only by the Americans, but by the Germans, by the French, by the British, and even by the Russians.
Foote: Oh well the Russians are intrigued by this thing. They’re doing a lot of work on that.
Schumar: But we did not have the problem of this roll in this reactor or this one because by sheer luck, we went the extruded metal and not the rolled metal.
Groueff: And you did it only because it was a matter of time? They ask you to do it as fast as possible, and you were not ready with the other metal?
Foote: Right. See, the extrusion process was developed very early.
Schumar: Yeah. ‘42 I’d say.
Foote: Just why I don’t quite know. It has some advantages in that you can extrude almost anything if you get it hot enough, as people knew very little about the fabricability of uranium. The approach was simply to heat it up as hot as you could and push it through a hole in a die.
Groueff: What is actually the extrusion, is to push something through a small hole?
Schumar: Yeah. You see, you take a container that looks like this. That’s the toothpaste tube.
Schumar: And then you have down at the bottom, a die like that.
Groueff: And then you squeeze it?
Schumar: You put the metal in here. Then you put pressure on it in this direction. And when you squeeze it, it just flows through this die and makes a rod.
Groueff: It’s like the toothpaste.
Foote: That’s right. You go from a big to a small—
Groueff: I see.
Schumar: That’s all extrusion does. But the choice was very good because first approximation is, if you know nothing about the material, you are much more assured of success of getting a rod from a large mass of metal by extruding it then you are by rolling it. That would be your first approximation, assuming you knew nothing about the metal.
Groueff: But rolling will be better?
Schumar: Rolling gave you a higher yield of metal. And you did have a lot of waste. Here you have a lot of waste. You’ve got an attack between the uranium and the die material and the surfaces came out very rough and jagged. You had to machine them, and you had to set up a lot of machines to do that. You have the toxicity problem. You have the problem of how you handle your waste because the uranium chips and powder are far apart. They’ll react with water and moisture.
Groueff: And for the extrusion, you need very high temperature?
Schumar: We thought, yeah.
Groueff: That will save you by accident, actually in this case.
Schumar: It saved the measurements.
Groueff: So if you could do extrusion at 700 degrees or 600, you would still have this phenomenon?
Schumar: Yes, exactly.
Schumar: Get right back in trouble.
Foote: Get right back in trouble.
Groueff: Weren’t you scared a little bit when you began to doubt that probably what you did was wrong? Or you found out after the bomb?
Schumar: Oh, way after. I would say after the bomb.
Foote: Yes, this was what? Around ‘46?
Schumar: ’46, ’47.
Foote: ’46, ‘47 that we began to really get a hold of this problem.
Groueff: Who was the person or the group taking decisions on this process, whether to do it by extrusion or rolling or what temperature? Or was it centralized here in Chicago?
Schumar: Yeah. I would say so. The expediency, you see, was to get some uranium into a pile.
Groueff: I see.
Schumar: The emphasis here was not to study the metallurgy. The emphasis was to get the uranium into a reactor, and here were two reactors.
Groueff: Who was in charge of that?
Schumar: It would be Chipman, wouldn’t it?
Foote: Chipman and Greninger.
Groueff: Chipman. Greninger. Under the supervision of—
Schumar: The lab director.
Groueff: The lab director would be Compton, no? Or [Sam] Allison?
Schumar: Yeah. Those people.
Groueff: But people like Fermi or [Eugene] Wigner, they didn’t know anything about those problems?
Schumar: Well, they made this canning—
Foote: They knew about it.
Schumar: They knew the canning problem.
Schumar: They were quite cognizant of the canning problem. Both of them were.
Groueff: But they wouldn’t know about the cycling?
Foote: Well no, this wasn’t discovered actually until the—
Schumar: What did Andy write there?
Foote: ’45, he wrote it.
Schumar: Let’s see, he left here at the latter part of ‘45 and it was one of the last things that he wrote up. I think we looked it up, to establish that. And then based on that recent information, when we start—
Foote: By that time, you see, all these reactors were running through.
Groueff: But he didn’t himself, this Van Echo, while he was working, wasn’t he a little bit scared that in the meantime, he knew that the slugs were already in the reactor?
Schumar: Yeah, but nothing was happening in the reactor.
Groueff: Because everything worked well?
Schumar: Well, yeah.
Foote: You see this?
Groueff: Otherwise the aluminum thing would’ve exploded, no?
Foote: This thing now, you have actually two phenomena we were concerned with here. Initially we were concerned only with the thermal effects.
Foote: But it turned out that you could produce exactly the same effect by reactor radiation.
Foote: Here in Chicago, of course, we started studying this thermal cycling effect because this is something we could do. It was later that it showed up, that the same material which will undergo growth by cooling thermal cycling will also undergo growth by simple radiation.
Groueff: Uh huh.
Foote: The two phenomena are not the same. But in a general sort of way, the overall effect, the overall result—
Groueff: The practical and the result is the same?
Foote: They arise from two entirely different phenomena, but the overall effect is the same. As a matter of fact, work still continues on this interrelationship between thermal cycling and growth under radiation.
Groueff: That’s quite an interesting aspect. Yes.
Foote: You see, the same heat treatment that will minimize the thermal cycling growth also minimizes the radiation growth.
Groueff: Uh huh.
Foote: At first sight, the two phenomena appear to be identical, but actually they’re not. They’re two entirely different things.
Groueff: Is that proper only to uranium and transuranium metals? Or some common metals have different phases too?
Foote: Other metals have different phases. But you see, the thermal cycling you get without a phase change, this is entirely within the alpha phase.
Foote: It arises from a very peculiar property of uranium. Uranium has three crystallographic directions. The particular property that we’re concerned with here is the thermal expansion coefficient. This thermal cycling effect arises through the fact that thermal expansion in one of the crystallographic directions is negative.
Groueff: Uh huh.
Foote: It’s about minus three, approximately. Whereas the other two are positive and fairly large. I can’t remember what they are, but twenty, I guess. Yeah. Well, it’s this high degree of thermal expansion and isocopy that gives rise to this thermal cycling growth. What happens is that I had two grains jarring one another. This is the B direction of this crystal. Then on heating, this crystal tends to shrink.
Groueff: Uh huh.
Foote: Whereas if this is the A direction of the giant crystal, then on heating this one tends to expand.
Groueff: To expand.
Foote: Well, it sets up a high stress along the boundary.
Groueff: I see.
Foote: You either tear the boundary or one of the grains deforms.
Groueff: That doesn’t happen normally in metals?
Groueff: You didn’t know this phenomenon in 1942?
Groueff: In practice? I mean, the other metals, like when you work with steel or with other metals, you don’t have anything similar?
Foote: See, most of the technical materials are cubic and crystal structure, and their properties are pretty much the same no matter what direction you measure in.
Groueff: Then when you heat the metal, it—
Foote: Expands uniformly.
Groueff: Expands. But then when it cools, it goes down?
Foote: It’s uniform expansion.
Groueff: Yeah, but uranium expands and remains expanded?
Foote: Well, in one direction.
Groueff: In one direction, yeah. And then you heat again and again, it expands. I see. So that was one of the spectacular difficulties. Not knowing about the growth and not knowing the melting point and not knowing—what else? Was it dangerous to work with? Radioactive? To handle it?
Foote: Not really. It’s somewhat radioactive, but not too much so.
Groueff: Not too much.
Schumar: There’s a side issue here that was very interesting. The health people did not know the later effects that one could get by—
Groueff: That they didn’t know then.
Schumar: No. So what they did is made very stringent rules as to how you handled the metal. For example, at one time a machinist or a scientist was only allowed to work with uranium eight hours a week.
Groueff: I see. Because nobody knew—
Schumar: Nobody knew the tolerances. No one knew the limits. That’s been changed. I mean, we know more about how to measure radioactivity and know more about the effects of radioactivity on cells and tissue and everything else. But I’m looking at this in 1942 eyes, you see.
Groueff: Yeah, but it could have worked in the other direction?
Schumar: No, I doubt it. I doubt it, because the activity is not hard.
Foote: It’s not very radioactive, but in order to play it safe, we handle it under very well-controlled conditions. Actually people have been mining uranium and handling it for many years without the sort of precautions that we now use. I don’t know whether there’s any incidents of uranium poisoning—
Schumar: I don’t know of any.
Foote: —that have come from these earlier operations or not. But see uranium had been mined for many years as a source of radium. What the refineries did was to simply throw away the uranium, or they stockpiled it in the hopes it might be useful for some. This turned out to be sort of a handy thing too when the war started, because we had a large amount of this material aboveground and partially processed as a result of the radium operations. But prior to the project work, uranium was just handled as just another ore. No one took any particular precautions with it.
Groueff: Did you have some difficulties by the fact that it’s such a heavy metal?
Foote: I guess the only difficulties we had were after the war, when the damn stuff kept showing up in the lead refineries. Yeah. It seems to me for a while about every couple weeks, the FBI was in here with a slug that they’d recovered from some of the lead refineries. This stuff was heavy, you see, and occasionally a piece gets lost and it would show up eventually in a lead refinery. Plop. The damn stuff wouldn’t melt. It didn’t dissolve with lead very well. We kept fishing these out.
Groueff: I asked about what was the attitude of the people who didn’t know the secret. For instance, you worked in Detroit. Probably you had some simple workmen around you or a laboratory assistant that had never seen anything like that, behaving in a strange way or heavy?
Schumar: Well, the thing that intrigued the common worker in our plant was that the uranium metal sparked so beautifully.
Groueff: It did spark?
Schumar: It did spark, very beautifully. So one day I was walking through the machine shop, and one of the machinists had a piece of uranium metal and he was machining it. I said, “What the hell are you going to do with that?”
He says, “I am making some flints for my cigarette lighter.” [Laughter]
“Give me that damn uranium back.” He did not know it was uranium. We called it “Tube Alloy.” It had a code name, Tube Alloy.
Groueff: Only two people—
Schumar: Only two people knew it.
Groueff: But the other people thought it was just—
Schumar: Another alloy, a special metal. It sparked so beautifully, see, you could go make lighter flints out of it, and I said, “You give me that back.” I never told him why he had to give it back to me, because they had no idea what they were working with. This is in an outlying place like Wolverine in Detroit. The workmen here knew, didn’t they, Frank?
Foote: I would assume so.
Schumar: Yeah, the workmen—
Groueff: They knew? And it is unusually heavy, no? It is heavier than lead?
Schumar: Nineteen times heavier than water.
Foote: Yeah, it is about the same density as gold or tungsten.
Groueff: And is it difficult, hard to cut? For instance, if you had to—
Schumar: Machine it? No.
Groueff: No problem, then?
Schumar: Well, it was a little bit of a problem, yeah. It depends on the quality of the material. If it has much carbon in it, it gets to be a little bit difficult to machine.
Groueff: It is hard?
Schumar: In particular, it dulls the tools very rapidly and is also very difficult to drill and tap. I think this was a major machining operation. Difficulty was in the drilling.
Groueff: But mostly you had to roll it into tubes, though? They extruded in bars?
Schumar: Rods, yeah.
Groueff: Rods. You did not have to cut it to different shapes?
Foote: For the most part, it was used simply as a round rod. The machining was essentially cutting off to length and removing the contaminated or roughened surface. So it was mostly lathe operations.
Schumar: A lot of grinding, Frank.
Foote: Well yes, there was some work done. Yeah, there was a fair amount of grinding to finish dimensions. It turns out to be unnecessary. As a matter of fact, I was [inaudible].
Schumar: You want an interesting anecdote?
Schumar: The Joslyn Steel Company in Fort Wayne, Indiana—
Schumar: Joslyn Steel was doing the rolling of the uranium bars, and they also were doing some of the, what we call, centerless grinding. They would grind the surface of the bars to clean them up. Now with this grinding, one used an oil emulsion as a lubricant and a coolant on the grinding wheels and on the metal. Now as you are grinding, you remove uranium in very, very fine chips of powder. This sinks and goes down to a sump, a retainer. It is flushed down with the coolant and the lubricant.
Sometime during the night on one of these machines, uranium was oxidizing to uranium oxide, and it was taking the oxygen from the water and liberating hydrogen and it blew up. All right? The sump just blew up. There was enough hydrogen in there that the sump blew up. Well, then you learned how to handle this, you see? One could speculate that this would happen, but no one paid any attention that it was going to happen.
Now, when you remove the ground material out of the sump, you have to collect that uranium. The point was to ship it back from Fort Wayne, Indiana to Chicago. They put it in containers and it was shipped by railway express usually and handled like money.
Foote: A money waybill.
Schumar: It was shipped like money on a money waybill. Usually in the shipping, it was identified as chemicals, not otherwise identified by name. Well, one day, one of these cans during this oxidation of the uranium powder inside of this can. Because there was still moisture in it, got hot and burned the platform at the railroad station. Then the agent there got mad. “No more!” We could not ship chemicals from there anymore. [Laughter]
So we put them on the truck and go down to the next station about ten miles down the railroad track, and they would ship it from there. You cannot tell them why and you do not start any argument, so you go down to the next railroad station and you would ship from there, all right?
Foote: Start a fire down there, they’d throw you out of there too. [Laughter]
Schumar: This is the kind of thing you had to do.
Groueff: Finally this canning with aluminum was all only on the site at Hanford, what I understand, and those people—
Schumar: Yes, we had to find a very clever way of doing the operations.
Groueff: I saw one of the men at DuPont. Dr. Grills, I think was connected.
Schumar: Who? Grills?
Groueff: Grills, Raymond Grills.
Schumar: Might have been a production worker.
Groueff: He was in the group which solved the problem by—
Groueff: Immersion in liquid. But so in other words, all the slugs for Oak Ridge and for Hanford, where uranium was made by a mixture, and not by—
Schumar: Yeah. Now, the Oak Ridge slugs were not bonded. No, they were just canned.
Groueff: They did not have the water on—
Schumar: Yeah, they were just encased.
Groueff: You developed the process, though, of—
Schumar: At Site B.
Groueff: Who did the extra? Who prepared physically the—
Schumar: Two people. Chase Brass.
Foote: Yeah, who was doing the—
Schumar: Chase Brass – no, I mean Revere [Copper &] Brass did the productions. Yeah. Revere and B&T Metals down in Columbus, Ohio.
Schumar: Remember, they were doing—
Foote: Yeah, yeah.
Schumar: Yeah, B&T Metals and Revere.
Groueff: DuPont were not involved?
Schumar: Oh, yeah. No, no, that is when DuPont got involved.
Groueff: I see.
Schumar: But previous to that—
Groueff: But mass production was done at Wilmington and Hanford?
Schumar: No, it was done at Hanford, the mass production. They set the extrusion.
Groueff: You did not—
Schumar: We did the development of the extract.
Groueff: Only development, but not fabrication, not production?
Schumar: No, the development was done with me at Wolverine Tube on extrusion. See, that is where the first extrusion development was done. Then the production extrusion was done at Revere Copper and Brass.
Foote: Also Detroit.
Schumar: That was also in Detroit. Then they bought an extrusion press and set an extrusion press at Hanford for their production for the Hanford slugs. That was where DuPont came in. They procured the equipment to set up the mass production.
Groueff: You were telling this story about Creutz.
Schumar: The first one?
Groueff: The first one. When did he come down? I don’t recall it.
Schumar: Creutz came to Wolverine, and he and [David H.] Gurinski one morning, Frank, with one billet – a billet. We put it in the furnace and heated it up, and we had no idea what temperature we ought to extrude it. We certainly wanted to stay in the red heat and not in the alpha or the beta. I mean, they knew enough that there was a beta phase.
So we heated the billet up, and before we put it in the container, the operator said, “Should I give it the 500 pounds of pressure, or should I give it the full 750 tons of pressure?” Because he did not want it to hang up in the container.
So I told Creutz, “Go down in the pit,” because this was a vertical extrusion press. To observe that, what was happening there, I would stand with the operator, and Gurinski was going to try to tempil stick to see how hot the damn thing was or cite it with an optical pyrometer.
Well, we dropped the billet in the container, and the operator gave it 500 pounds and nothing happened. So he gave it the 750 tons, and the damn thing came out in a million pieces. There were sparks all over just like a Fourth of July. Well, running up out of the pit was Creutz and a helper all on fire. [Laugh] Their coveralls got burned from the hot sparks. We never found the uranium oxide, believe me.
Creutz almost started to cry because that was the only billet he had. He waited three weeks for the damn thing. So I said, “What do you want to do?”
He said, “Well, they will have to cast another billet and come back next week.” It was tough getting metal. But that was the early pioneering of the extrusion.
Foote: Well, the thing that you did not realize is that these high temperatures, this stuff is just mushy soft.
Schumar: Yeah, the operator did not know better. Because here is another example where when you normally work metals and you take the metal out of the hot furnace and you put it into your mechanical working apparatus, you work it rapidly so it does not lose heat. The operator felt the same way as the rollers did, that you have got to hurry it through. Well, he hurried it through. It is soft and mushy, it poured out on the guy. It came out as a liquid.
Foote: Well, not really. Almost. It felt like soft butter.
Schumar: Then this took a little time to train people to understand that you just do not do it this way.
Foote: Yeah, or you do not heat it quite so hot.
Schumar: Or you do not heat it quite so hot.
Groueff: Did you work also in plutonium?
Schumar: No, no.
Foote: No, that was—
Schumar: That was Los Alamos.
Groueff: Uranium. Yeah, Los Alamos, they had to work with plutonium and—
Groueff: 235, yeah. They had a lot of problems.
Schumar: Their problems were fabricating the bomb.
Groueff: The bomb, right.
Schumar: Yeah, ours was fabricating the metal to use in the production of plutonium, for reactors to make plutonium.
Groueff: That had also some terrific metallurgical problems?
Schumar: Oh, they sure did. Yes, sir.
Foote: Well, see, uranium has these two transformations. Plutonium has five.
Schumar: Yeah, five.
Groueff: And it had to be with pedantic precision in everything and how you make a sphere—
Foote: They had more difficult shapes to make, took greater precision, [inaudible].
Schumar: They could not handle large quantities at any one time because of the critical mass.
Schumar: It is fully enriched uranium. Where with natural uranium you can make an ingot a thousand pounds if you wanted, but you could never make an ingot of a thousand pounds of plutonium or uranium-235. They had the added problem of the critical mass where with the natural uranium, we did not. They had stuff worth several thousand dollars a kilogram, too – or gram, not per kilogram.
Groueff: Yeah, they had also—
Schumar: Natural uranium. So any alloy or any bonding material or any canning material had to be material that was not parasitic to neutrons, or the chain reaction would not go on. We did not have the information as to how many of the materials or the elements absorbed neutrons. The cross sections had not been measured because there were no piles. There were no reactors anywhere else. So the cross sections were calculated, or the cross sections were measured by other techniques. That is why the aluminum can was selected, because it has a low absorption through thermal neutrons. Now, if you wanted to find a bonding material or another canning material, you could not use iron because it has a high cross section. So you had to stick with a very narrow family of materials.
Now, it was the same problem with the development of alloys. You see, normally, iron will rust in air and water, right? So what do we do? We can chrome plate the iron or steel, we can put a chrome plating on it. Or we put a nickel plate and then put a chrome plate. Or you can do the other thing. You can add the nickel and the chromium to the steel to make stainless steel. See what I am driving at? But you could not add aluminum to uranium to make it corrosion resistant. So you had to put the can around the doggone thing or a plating or a coating of some kind.
Now, the corrosion-resistant uranium alloys that looked like they might be corrosion resistant were alloys of zirconium and uranium, and niobium and uranium, and molybdenum and uranium. But they take five to ten atom percent. The Hanford reactors never would have operated because of the parasitic nature of molybdenum and columbium.
Groueff: They would absorb the—
Schumar: They will absorb the neutrons and you would have no chain reaction. Today, where we have enriched uranium—
Groueff: It does not matter so much.
Schumar: It does not matter so much. So in those early days where all you had was natural uranium, it was very, very important that you kept the impurities down to a minimum. You wanted to work with high purity material, high purity uranium. Now, that was also the problem with the graphite. I am sure [Norman] Hilberry pointed this out to you.
Now the stories are a hell of a lot different today. So there you see in the Oak Ridge reactor, the Hanford reactors for the production of plutonium, you had natural uranium, and to keep the mass critical, you had to have high purity uranium.