The Manhattan Project

Gerhart Friedlander's Interview

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German-American chemist Gerhart Friedlander fled Nazi persecution in 1936. He studied at the University of California with Glenn Seaborg, earning his Ph.D. in nuclear chemistry in 1942. The following year, he joined the Manhattan Project at Los Alamos and became group leader of the radioactive lanthanum group in the Chemistry Division. After World War II, Friedlander worked at Brookhaven National Laboratory for many years and chaired the Chemistry Department. In this interview, he describes how Seaborg secretly involved him in plutonium work and how his group investigated the implosion method for the plutonium bomb. He also recalls winning a bet with Enrico Fermi.
Manhattan Project Location(s): 
Date of Interview: 
April 27, 2002
Location of the Interview: 

Gerhart Friedlander: My name is Gerhart Friedlander.

Interviewer: What was your role in the Manhattan Project?

Friedlander: I got into the Manhattan Project very early; in fact, before there was an official Manhattan Project. I was a graduate student at Berkeley at the University of California. My thesis advisor was Glenn Seaborg, who later on got a Nobel Prize and became chairman of the Atomic Energy Commission, but at that time he was just a new instructor and I was his first graduate student. 

In the early stages of the war effort, before there was an official Manhattan Project, Seaborg started working on fission. One of my colleagues and another early graduate student, Arthur Wahl, who shared a lab with me, was the discoverer of plutonium. He worked alongside me, but since I had just recently come from Nazi Germany as a refugee, I was officially classified as an enemy alien. I was not supposed to know anything about this secret stuff that was going on. In actuality, of course, I was in day-to-day contact with what Art Wahl was doing. I was in on the very early stages of the discovery and early investigation of plutonium, although I myself was not supposed to work on that.  

As time went on and the pressures of the project became greater, Seaborg was so anxious to have me involved that he actually took a chance and had me work on what was to be secret projects that I wasn’t supposed to know anything about. I was involved in measuring the fast neutron cross-sections of uranium and plutonium. I actually had my name on a secret report, which was a very anomalous situation. Seaborg could have gone to jail for allowing this. It was really quite bizarre. 

But anyway, I got my Ph.D. on totally different aspects of nuclear chemistry in 1942. At that time, Seaborg tried very hard to get me officially involved on the project. He had by then gone to the Metallurgical Laboratory at Chicago and had a slot for me to work there, but he could not get permission for me to get clearance to work on the Manhattan Project. He tried very hard. He wrote letters to [James] Conant and [Vannevar] Bush, and simply could not get an okay. 

So I went sort of into exile for a year and taught at the University of Idaho. During that year, I got my citizenship papers. As soon as I had my citizenship papers, I was recruited to Los Alamos, and then spent the rest of the war years there as a nuclear chemist, and was involved in a number of projects there. 

Interviewer: How would you describe your general role in the Manhattan Project?

Friedlander: My first major assignment was in connection with the first homogeneous nuclear reactor. At that time, there already had been nuclear reactors: the first one at the University of Chicago, which Enrico Fermi built, and the prototype production reactor that had been built at Oak Ridge. These were both reactors in which uranium was embedded in a graphite lattice, and the later plutonium production reactors at Hanford were all of that type. 

What was needed to get vital information for building a bomb was a homogenous reactor in which the fissionable material was homogeneously distributed in the medium, because that’s the way a bomb functions. It’s a homogeneous medium of only uranium or plutonium. Los Alamos had the task to learn more about how to build a bomb to build a homogenous reactor. The way this was done was to use enriched uranium, enriched in U-235, in an aqueous solution.  

As a chemist, I and my colleagues had the task of producing this solution, purifying it, and analyzing it. We got the first samples of enriched U-235 from Oak Ridge. I remember how my boss came into my lab with this bottle of material and said, “Now, this is the very first sample of enriched uranium that anyone has ever handled. It’s worth several million dollars, so please be careful.” Indeed, we were very careful. We didn’t lose any, but it didn’t exactly make us feel very calm and comfortable. But we did it. We purified the stuff.  

One of the interesting stories about that is that there was some discussion about what uranium salts should be used. We had a meeting, and Enrico Fermi, who was really very respected for knowing everything about almost anything, said, “Well, of course, uranium nitrate. Everybody knows that’s the most soluble with uranium salt.”

And I said, “Excuse me, Enrico, but we’ve already done some experiments, and uranium sulfate is more soluble than uranium nitrate.”

He said, “You must be wrong. I bet you 25 cents.” 

So I won a 25-cent bet from Enrico Fermi, which is one of my proudest achievements because it was not easy to prove him wrong. But he was not a chemist, so I had the advantage over him. Uranium sulfate indeed was used in the device that was called a water boiler because it was a water solution, and while it didn’t exactly boil, it heated up from the nuclear reaction. We made this device; it became critical.

Another interesting thing was that we didn’t know exactly how much uranium it would take to make it a critical mass, but everybody guessed what the result would be. Of course, the theoretical physicists had the advantage because they had made calculations. The rest of us just made guesses, and I have an interesting graph that shows what everyone’s guess was. The one who was closest was Richard Feynman. 

The next project I was involved in, and spent most of the remainder of my time in Los Alamos on, was an experimental setup for investigating the so-called implosion method. Where you have massive uranium-235 or plutonium in a spherical arrangement, and around it a series of high-explosive lenses, which focus the explosive charge into the sphere so that the sphere then gets compressed and gets very dense to the point where it becomes critical. This was a new concept at the time, and what had to be investigated was whether these explosive lenses would make the implosion sufficiently symmetrical so it would really remain a sphere. 

If it was not symmetrical, the material would squirt out in one direction and it would make a much less powerful device, so this was the preferred method for investigating the mechanics of the implosion. In the center of the sphere, there would be a very strong radioactive source, which emits high-energy gamma rays. All around were counters, like Geiger counters, measuring the gamma rays during the implosion, and measuring the time-dependence of the gamma ray intensity at many points around the sphere to make sure they all recorded the same decrease in intensity as the sphere became denser. If it wasn’t symmetrical, they had to take measures to improve the design. Throughout the project, there were dozens of such experiments done, each one with a very powerful gamma ray source. This went on long after I left Los Alamos. It was really the method of investigating implosion devices.  

My task as leader of the chemistry group involved was to prepare these intense gamma ray sources, concentrate them into a very small volume of a few millimeters in diameter, and put them in the middle of the sphere. This was a very tricky task. It was done with extremely primitive means. Today, what we did would never be allowed to be done, because we worked with long-handled tools with a mirror. No remote controlled equipment, really. Nevertheless, none of us got overdosed. We were allowed to get ten times the dose that other people on the project were allowed because it was such an important project. Well, I’m here at age 85 and I didn’t die from radiation. I guess that proves something.

We dealt with extremely intense sources. Up to two kilograms of radium, which is an enormous amount of gamma ray activity. There were all kinds of problems in preparing this. I won’t go in any detail about it, but as I said, that was the major project.

I think one of the lessons to be learned about all this – what was important at Los Alamos and what was the key to success – was the cooperation between the different disciplines. Chemists, physics, mathematicians, metallurgists, explosive experts all working together in close corroboration, and constantly in touch with each other and each other’s progress or lack of progress. I think the interdisciplinary nature of the work was absolutely essential. 

The other thing, of course, was that it was wartime. We were given the highest priority in procuring everything and there were, by present standards, minimal considerations for environmental damage. We didn’t have to write environmental impact statements and all this stuff. 

Something like the Manhattan Project, I think, would nowadays be totally impossible. If you think of what was achieved from the short time from initiation of the project in 1942 to dropping the bomb in 1945, it’s absolutely miraculous considering that there were thousands of people involved, an enormous diversity of effort that was done with great dispatch and success, 

Interviewer: You were not even thirty when you became a leader. Could you tell us if that was common there?

Friedlander: It was a very young group. Almost everyone was in their twenties. I became a group leader when I was 27. The head of the entire chemistry effort, which involved hundreds of people, was Joe Kennedy, who was I think a year younger then I was or about the same age. The few older people – like Oppenheimer, who was in his 40s – were the old men. It was very much an effort of young people.  

Of course, the whole life at Los Alamos – this is a separate story – was extremely interesting and stimulating. We were confined to this community. We had very little contact with the outside world. We were not allowed to travel. We could go down to Santa Fe, but Santa Fe was just teeming with military police in civilian clothes watching everybody, and making sure that we didn’t talk to unauthorized strangers. They also deliberately spread false rumors about what was going on in the place up on The Hill to divert attention from what was really going on. It was a very close-knit community of lots of interesting and brilliant people. Even though we were working very hard around the clock, there was also a considerable amount of social and cultural life there. We had a theater group and a choral group, and all sorts of interesting discussion groups and lectures, movies, and dances. It was a very interesting life.  

Interviewer: Were you married at the time? 

Friedlander: I was married. My wife really had no idea what was going on. The secrecy was remarkable, and as I said, we were not allowed to have contact with the outside world. One time, a cousin of mine from New York wrote to me saying she had the address. Our address was all a post office box – I forget the number now – at a post office in Santa Fe. She knew I was there, and she said, “I am coming to Santa Fe for a short vacation. Can we get together?”

Everything incoming and outgoing went through the censor’s office. I showed the letter to the censor’s office. I went there and I said, “How do I respond to this?”  

They said, “All you can say is, ‘I’m sorry I can’t see you.’ Period.”  

No reason. My cousin was very miffed until she found out after the war what the reason was. So there were all kinds of interesting events going on.

Interviewer: Did you know that the bomb was designed already to be actually dropped on your own homeland?

Friedlander: Of course. That was very obvious. What I think drove most of those who came from Europe and many from Nazi Germany as refugees, and what I think was our main impetus, was to make sure that Hitler didn’t get an atomic bomb first. What we didn’t know until after the war is that the Germans in fact didn’t get very far and didn’t have a serious bomb project. They were working on nuclear reactor development.

That was indeed the motivation certainly for us of European origin, but also I think for the American scientists. It would have been disastrous if the Nazis had developed the bomb before us, but then of course Germany surrendered, and we went on to develop the bomb for use on Japan. I really only know of one person who at that point left the project because the Germans were out of it, and there was now no justification to continue. [That] was Joseph Rotblat, who in recent years got the Nobel Peace Prize, as a matter of fact, because he continued to work on measures to stop the use of atomic weapons. 

Most of us I think quite gladly continued to work on it until the bomb was dropped on Hiroshima. But many of us couldn’t understand why we dropped the second bomb on Nagasaki, because it seemed that one atomic bomb was sufficient really to persuade the Japanese to give up. I’ve never heard a really convincing explanation of why we dropped the second bomb.  

Interviewer: What do you think is important for future generations to know? What lessons, do you think, have we learned?

Friedlander: That’s a hard question. Some of the lessons I think we learned is that secrecy doesn’t work in science. I think science has to be open. If you want progress in science, you need a lot of freedom of action, and controlling science from the government is not fruitful.  

Of course, that I think we should do everything possible to avoid use of atomic weapons is clearly a lesson that I think everybody should have learned. The arms buildup that we had when we were in the Cold War with the Soviet Union is absurd. We still have way too many atomic weapons.