R. Scott Kemp, a friend of mine at Princeton's Science and Global Security program, has just informed me that the latest issue of Technology and Culture has come out with his new article: "The End of Manhattan: How the Gas Centrifuge Changed the Quest for Nuclear Weapons."1
It's a good read and I highly recommend tracking down a copy if you are interested in nuclear history, but especially if you're interested in the history of proliferation. Scott's article is the best account I've read about how the gas centrifuge went from being a more-or-less abandoned approach to uranium enrichment during World War II to being the proliferation concern of the late-20th and early-21st centuries.
Gas centrifuges had been one of the many types of enrichment technology pursued during the Manhattan Project. Early on, they were heavily favored over the more technically daunting electromagnetic and the totally-untried gaseous diffusion method. Jesse W. Beams at the University of Virginia was the country's centrifuge expert and he had been looking into using them for isotopic separation as early as 1940. As a result, all of the Manhattan Project centrifuge work was concentrated with him at his laboratory, and in 1941, nearly four times more was allocated to the centrifuge project as was the more speculative gaseous diffusion method.
This is an interesting point to note — we give the Manhattan Project management a lot of credit for trying everything. They spent far more money than a more "optimized" project might have, because they investigated a lot of things that didn't work out. But despite this approach, they still centralized the work being done on any specific method, usually within a single laboratory, often under the direction of a single scientific luminiary. So Ernest Lawrence was the don of the electromagnetic method; Arthur Compton oversaw reactor research; Harold Urey ran diffusion; and so on. Which seems like a great idea on the face of it. But what if the person you chose just didn't take the research in the right directions? What if, within that short timescale, they just didn't hit upon the right answer?
Such was the case with Beams, in Kemp's assessment: Beams just didn't figure out how to get centrifuges to work sufficiently well enough. As a result, the Manhattan Project folks proclaimed centrifuges a dead end and dropped the approach in 1944. After the war, there was little US interest in centrifuges — it didn't seem like they were very workable, certainly not compared to gaseous diffusion. And since gaseous diffusion worked fine for them, they didn't look too far afield. The lesson of the war, as the US saw it, was that centrifuges weren't worth the effort.
But in Europe and the USSR, though, work on centrifuges continued. Scott's account goes into this in some wonderfully wonky technical detail. The end result is that Gernot Zippe, an Austrian physicist, who in the early 1950s figured out (with others) how to fix the problems that Beams had with his centrifuges. Amazingly, he did this while being a prisoner of war in the Soviet Union.
The Zippe centrifuges weren't anything magical. There was no "secret," per se, and they didn't involved any special materials. They just involved working out a few engineering details that made the devices reliable and stable. The major new features introduced by another Austrian POW, Max Steenbeck, and implemented by Zippe were:
- "a 'point' bearing that allowed the centrifuge rotor to spin on the tip of a needle (like a toy top) with almost no friction."
- "the application of loose bearings and weak damping, which allowed the centrifuge to adjust itself so that it spun quietly on its center-of-mass axis without vibration instead of trying to force the axis of rotation"
- "to drive the rotation using electromagnetic fields, just as the armature of an electric motor drives its internal rotating shaft"
That's it. In engineering terms, these are clever, but hardly revolutionary. These three relatively simply engineering changes "solved essentially all the mechanical problems that had plagued Manhattan Project centrifuges," Scott writes. In fact, he argues:
It wasn't that the centrifuge wasn't possible in the World War II period — it's just that Beams never figured it out. Scott notes:
The flawed centrifuge was made viable by the application of engineering solutions that were mostly invented around the turn of the twentieth century and all of which predated the Manhattan Project—evidence that the latter’s centrifuge program was frustrated not by the limitations of manufacturing or the technology of the day, but rather by a preliminary design that was never developed to its fullest possible extent.
So the gas centrifuge was really completely viable as early as World War II, but the Manhattan Project scientists just couldn't get it to work. I thought that was a pretty bold conclusion, one that goes in the face of the standard "superiority myth" that pervades the Manhattan Project work.
Things get really interesting, though, after Zippe et al. figure out how to make it work. Zippe and his colleagues actually convinced the Soviets to let him out early (and to pay him!) if he helped them commercialize centrifuges in Europe. (I think we can file this under "cool things that can happen once Stalin buys the farm.") Zippe and his colleagues were released from the USSR in 1956, and he went to East Germany. From there, though, he made his way west, and became a centrifuge evangelical — he wanted to commercialize them.
He went around Europe and the United States showing folks how to make efficient gas centrifuges. In 1958 and 1959 he spent time at the University of Virginia (Beams' home turf) showing them how it was done. Amazingly, this work seems to have been unclassified — you can find the progress reports, featuring the diagrams and photographs I've used in his article, on the Department of Energy's Information Bridge.2
In 1960, the US realized that the centrifuge was actually going to be a proliferation issue, and started trying to classify the technology again. The problem was, of course, that all of the key developments were produced by non-Americans not in the United States. So in effect the US was saying that nobody in the United States was going to be allowed to work on this without a security clearance, while scientists in Europe could pursue it with a freer hand.
The result of all of this Atoms-for-Peace (Atoms-for-Cash?) enthusiasm with regards to gas centrifuges is that the technology is pretty well dispersed. Scott concludes that:
Today, at least twenty countries have built or acquired centrifuge technology, and the history lesson drawn here suggests that it is within the capability of nearly any state to do so.
As Scott (and Alex Glaser and Houston Wood) have argued elsewhere in another great article,3 all of this should put to rest any idea that technical solutions alone can limit future nuclear proliferation — we live in a definitely post-Manhattan Project world, and this stuff just isn't rocket science anymore.
- R. Scott Kemp, "The End of Manhattan: How the Gas Centrifuge Changed the Quest for Nuclear Weapons," Technology and Culture 53, no. 2 (June 2012), 272-305. [↩]
- The photograph of the centrifuge is from Gernot Zippe, "A Progress Report: The Development of Short Bowl Ultracentrifuges," UVA/ORL-2400-59 (1 July 1959); the diagram is from Gernot Zippe, J.W. Beams, and A.R. Kuhlthau, "The Development of Short Bowl Ultracentrifuges," UVA/ORL-2400-58. Scott's article brought both of these reports to my awareness. [↩]
- Houston G. Wood, Alexander Glaser, and R. Scott Kemp, "The gas centrifuge and nuclear weapons proliferation," Physics Today 61, no. 9 (September 2008), 40-45. [↩]