Posts Tagged ‘Nuclear power’


Szilard’s chain reaction: visionary or crank?

Friday, May 16th, 2014

Leo Szilard is one of the most fascinating characters of the nuclear age. He was colorful, principled, clever, and often genuinely ahead of his time. And he always shows up early in the story.

Leo Szilard at the University of Chicago in 1954. Source.

Leo Szilard at the University of Chicago in 1954. Source.

Richard Rhodes starts off his The Making of the Atomic Bomb with Szilard’s famous 1933 epiphany:

In London, where Southampton Row passes Russell Square, across from the British Museum in Bloomsbury, Leo Szilard waited irritably one gray Depression morning for the stoplight to change. A trace of rain had fallen during the night; Tuesday, September 12, 1933, dawned cool, humid and dull. Drizzling rain would begin again in early afternoon. When Szilard told the story later he never mentioned his destination that morning. He may have had none; he often walked to think. In any case another destination intervened. The stoplight changed to green. Szilard stepped off the curb. As he crossed the street time cracked open before him and he saw a way to the future, death into the world and all our woe, the shape of things to come. [...]

“As the light changed to green and I crossed the street,” Szilard recalls, “it … suddenly occurred to me that if we could find an element which is split by neutrons and which would emit two neutrons when it absorbs one neutron, such an element, if assembled in sufficiently large mass, could sustain a nuclear chain reaction. “I didn’t see at the moment just how one would go about finding such an element, or what experiments would be needed, but the idea never left me. In certain circumstances it might be possible to set up a nuclear chain reaction, liberate energy on an industrial scale, and construct atomic bombs.” Leo Szilard stepped up onto the sidewalk. Behind him the light changed to red.1

It makes for a good read, though there are disputes about the exact timing of this apparent epiphany. But the basic fact seems to remain: Leo Szilard thought up the nuclear chain reaction over five years before fission was discovered. But he wasn’t taken seriously.

But what did he really propose at the time, though, and not just in retrospect? And should he have been taken more seriously? This is what I want to discuss at some length here, because it is a point of common confusion in a lot of writing on nuclear history.

Szilard had a really interesting idea in the fall of 1933. He took out a patent on it in the United Kingdom, which he required to be made secret. Was Szilard’s idea really an atomic bomb? Was it even a nuclear reactor?  The reason to suspect it was not, on the face of it, is that nuclear fission hadn’t been discovered in 1933. That didn’t happen until late 1938, and it wasn’t announced until early 1939. So what, really, was Szilard’s idea? And why did he file a (secret) patent on it? Was Szilard ahead of his time, or just a crank?

Szilard patent GB630726

Szilard’s 1934 patent is easily available these days, and is worth looking at carefully with an eye to what it both says and doesn’t says. The patent in question is GB630,726: “Improvements in or relating to the Transmutation of Chemical Elements.”2 He filed the application first in late June 1934, updated it in early July, and finalized it by April 1935. The UK Patent Office accepted it as valid in late March 1936, but it was “withheld from publication” at Szilard’s request under Section 30 of the Patent and Designs Act. It was eventually published in late September 1949, 15 years after it had been originally applied for.

The basic summary of the patent is straightforward:

This invention has for its object the production of radio active bodies[,] the storage of energy through the production of such bodies, and the liberation of nuclear energy for power production and other purposes through nuclear transmutation.

In accordance with the present invention nuclear transmutation leading to the liberation of neutrons and of energy may be brought about by maintaining a chain reaction in which particles which carry no positive charge and the mass of which is approximately equal to the proton mass or a multiple thereof form the links of the chain.

This sounds awfully promising, especially when you know what you are looking for. It looks like he’s got the right idea, for a reactor at least: it is patent for creating a neutron-based chain reaction. The reason that neutrons matter is because they lack an electrical charge, and so are not repelled by either the protons or the electrons in atoms. This allows them to penetrate into the nucleus. If they can be linked up so that one reaction produces more reaction, they become a chain reaction. Sounds good, especially if we assume that he means an exponential chain reaction (i.e. each reaction produces more than one subsequent reaction).

But once you get beyond the heading, the details of the patent are, frankly, kind of a confused mess.

Szilard doesn’t actually even state that the chain reaction is going to be produced by neutrons. He hedges his bets there — he describes a neutron, essentially, but generalizes the claim for anything that might behave like a neutron. He calls these “efficient particles” (terrible name), and they have to basically be proton-like in mass but lacking a positive charge. OK, fine. The neutron had just been discovered in 1932, so Szilard is probably thinking that there might be other possible particles out there that acted the same way.

The really weird stuff comes in when he tries to explain how this really works. He defines a chain reaction as when “two efficient particles of different mass number alternate a ‘doublet chain.’” Wait, what? He gives an example:

C(12) + n(2) = C(13) + n(1)
Be(9) + n(1) = “Be(8)” + n(2)

Let’s unpack this. C-12 is Carbon-12, C-13 is Carbon-13, Be-9 is Beryllium-9, “Be(8)” is Beryllium-8, put in quotes here because Szilard know it is pretty unstable (it has an extremely short half-life before it alpha decays). The weird parts are the neutrons — n(1) is just a regular neutron. n(2) seems to be a dineutron, a particle which does exist but was only discovered in 2012, and is certainly not something you can count on. (Szilard never says it is a dineutron, but he implies that you might be able separate n(2) into n(1)+n(1) with another reaction, so it seems to be just that.)

Leo Szilard

So the idea here is that the Carbon-12 absorbs a dineutron, emits a neutron, which is then absorbed by the Beryllium-9, which emits another dineutron. It’s essentially a linear chain reaction, which is not nearly as impressive or fast as an exponential chain reaction. But it would generate some significant energy: calculating the mass deficit of these equations shows that together the net energy release would be around 3.3 MeV, about 100X less than a fission reaction, but is some 330,000X more powerful than the combustion of a single molecule of TNT (~10 eV).3 You’d also maybe get some alpha particles (from the Be(8) decay), but it isn’t going to generate a lot of neutrons or dineutrons (they are going to be eaten up by the reaction itself).

Szilard then notes that maybe there are exponential ways to do this. He suggests that maybe some elements will create multiple neutrons when irradiated with neutrons, e.g.

 Be(9) n(1) = “Be(8)” + n(1) + n(1)

This is a much more exciting possibility, because if every reaction creates the possibility of two more reactions, now we are talking about a reaction that can grow really dramatically. The only problem here is that this reaction seems to be endothermic; if you use E=mc2 to calculate the mass deficit, it comes out as -1.67 MeV. Which ought to be a hint that it isn’t going to work.

The final specification of Szilard’s reactor chamber, which is much more simple in operation than it at first appears.

Szilard then continues by saying that he could make this work well if only he knew what elements might behave this wayWhich is really the crux of it, of course. Szilard has no evidence that any element behaves this way. He has no a priori reason to think any of them do. It’s just a pie-in-the-sky idea: what if there were elements that, when they absorbed one neutron, released two? But Szilard doesn’t dwell on this lack of knowledge. He immediately moves on to how he would design a simple reactor if an element was found. It is nothing terribly interesting: he describes a way to create neutrons and aims them at the reacting substance, then siphons off heat with a heat exchanger and uses it to run a turbine.

In July 1934, Szilard filed an “additional specification” — another patent claim attached to his original patent application. It is an elaboration on the reactor idea. Since he still doesn’t know what fuel would make it run, it’s still not very interesting, other than the fact that he’s put a lot of evident work into figuring out some of the basic properties of the reactor despite not having any clue how its core would actually work. Interestingly he does discuss uranium, but not as a fuel (he thinks it would maybe emit X-rays if he shot high energy electrons at it).

Finally, in April 1935 he filed the last, “Complete” specification. This is more or less identical to a combination of the previous two, except he further makes explicit that he thinks there are going to be “explicit particles” other than neutrons that might work. Basically he asserts that there are probably “heavier isotopes of the neutron”4 and that “It is essential that two isotopes of the neutron should take part in the reaction in order to obtain a chain” (my emphasis). The latter instance shows that he is still not thinking of this quite right — it is not essential that there are multiple isotopes of neutrons.

In his examples, he believes that a “tetraneutron” (i.e. n(4)) exists and can play a role in the reactions. (I know nothing of tetraneutrons, but Wikipedia says that they were claimed to be discovered in 2002 but that the experiments could not be replicated.) Szilard seems to be basing his patent claims here on experiments, but it’s not clear whether he did them or someone else did them, but it seems likely he’s misinterpreting the data. It’s a very odd argument, and he rests quite a lot on it — he seems to think it is far more likely that a nuclear reaction will release bunches of bound neutrons (dineutrons, tetraneutrons) instead of multiples of free neutrons (i.e. as fission does). And then the whole thing was kept secret until 1949 — an awful long time for something that actually reveals nothing of any practical utility, much less military applications.

According to The Collected Works of Leo Szilard, there was an additional claim in his patent application of March 1934 that Szilard had removed from the final specification:

(a) Pure neutron chains, in which the links of the chain are formed by neutrons of the mass number 1, alone. Such chains are only possible in the presence of a metastable element. A metastable element is an element the mass of which (packing fraction) is sufficiently high to allow its disintegration into its parts under liberation of energy. Elements like uranium and thorium are examples of such metastable elements; these two elements reveal their metastable nature by emitting alpha particles. Other elements may be metastable without revealing their nature in this way.5

This is much, much closer to the truth, although it is still somewhat unclear what Szilard really thinks about this. It’s not clear whether he’s describing radioactive decay in the traditional sense, nuclear metastability (which is something different altogether), or something different. Uranium and thorium are radioactive and undergo alpha decay — that, by itself, doesn’t actually indicate that they are good candidates for the kinds of reactions Szilard is thinking about. Szilard doesn’t think they are going to split, he thinks they are going to become artificially radioactive. Not the same thing at all. Still, this is a lot closer to the correct formulation, but we have to read it in the context of everything else he put in the patent.

Anyway, so what’s the verdict? Does the patent describe a bomb? Does it even describe a reactor? Definitely not a bomb, and not really a reactor. Most of Szilard’s energies on the patent are describing something that would, at best, take an input amount of energy and magnify it a bit: you’d use a cathode ray to generate high energy electrons, which would generate high energy neutrons, which would stimulate linear chain reactions that would create radioactive byproducts and release a little energy. Maybe you could keep it self-sustaining but it seems like kind of a long-shot to me.6

An animated version of the above "reactor" operating in a pulsed fashion.

A crudely animated version of the 1934 “reactor” operating in a pulsed fashion, just in case you are having trouble visualizing it.

If you read the patent today with the benefit of hindsight, it’s easy to see where Szilard was right and where he was wrong. There is a germ of rightness in the patent, but it is clouded by a fog of wrongness, or at least confusion. I’m not blaming Szilard for this, of course. Like almost everyone else, he didn’t predict fission. He was ahead of his time, in the sense of anticipating that neutrons in particular were going to be important particles for creating nuclear chain reactions. But he didn’t really understand how it would work. As a result, most of the patent involves describing a device that wouldn’t work. To guess even something right about the future is a large task, even if one gets a few things wrong.

So was Szilard a visionary or a crank? To someone in 1934 or 1935, it would have been completely reasonable to dismiss Szilard’s patent as being too speculative and potentially too wrong (dineutrons, tetraneutrons, etc.) to be worth spending time worrying about. It also isn’t clear it has any real military implications — it isn’t even clear it would work as a power source, much less a weapon. To dismiss Szilard as something of a crank prior to the discovery of fission wouldn’t have been wrong. Szilard’s point of reference here isn’t fission, it’s artificial (induced) radioactivity, which had been discovered by the Joliot-Curies just prior to Szilard’s patent filing. But you can’t make artificial radioactivity work the way Szilard wants it to. I don’t fault anyone for not taking him very seriously at the time — because Szilard’s scheme was missing an absolutely essential component, and in its place there were a lot of incorrect assumptions.

After the discovery of fission in late 1938/early 1939, suddenly it is easy to pick out the visionary aspects of Szilard’s work. It suddenly becomes clear that Szilard was, in fact, a little ahead of the game. That if instead of his plans for beryllium-carbon reactions with neutrons and dineutrons, that a simple, neutron-based, exponential chain reaction would be possible with nuclear fission, and that furthermore it would release a lot more energy a lot quicker than what Szilard had dreamed up in the early 1930s.

Which is a conclusion that complicates the simple visionary/crank dichotomy. Szilard wasn’t really either in my mind. He had a germ of a good idea, but not the whole picture. But when the missing element came along, he was uniquely ready to see how it would complete his original idea. That’s the real story here, the real accomplishment: Szilard didn’t have to play catch-up when fission was announced, because he’d already thought a lot of this through. But that shouldn’t lead us to over-estimate the importance of the original patent work — it wasn’t a bomb, it wasn’t really even a reactor. But it did become a useful framework for thinking about fission, when fission came along.

  1. Richard Rhodes, The Making of the Atomic Bomb (Simon and Schuster, 1986), 13 and 28. []
  2. It should not be confused with another patent he filed for at the same time with an identical name (GB440,023) which has nothing to do with chain reactions at all.  GB440,023 is basically a patent for producing artificially radioactive elements. The device it describes involves using a cathode tube to generate X-rays, then using the X-rays to stimulate neutron emission in beryllium, and using those neutrons to make artificially radioactive elements through induced radioactivity. It’s not a bad idea — it is now known as the Szilard-Chalmers method and it works. But it’s not a chain reaction at all . Szilard filed a patent for the same idea in the US as well. That Szilard considered it something quite different is also evidenced by the fact that he doesn’t seem to have tried to keep it secret. He references the basic method in GB630,726 as the driver of the reactions in question. []
  3. The beryllium reaction is endothermic but the carbon one is not. []
  4. “I have reason to believe that apart from neutrons which carry no charge and have a mass approximately equal to the proton mass heavier isotopes of the neutron exist which particles carry no charge and has a mass number approximately equal to a multiple of the proton mass.” []
  5. Quoted in Julius Tabin, Introduction, Part V: Patents, Patent Applications, and Disclosures (1923-1959), The Collected Works of Leo Szilard: Scientific Papers (MIT Press, 1972), on 529. []
  6. The neutron multiplication factor, to use modern reactor terminology, seems to me like it is going to be 1 at best, and probably less than that given inefficiencies, losses, etc. One question unasked and unanswered in the patent is how many neutrons he thinks he is going to produce per blast. I think it is easy to overestimate how effective this would be from that point of view. The neutron initiator used in the Fat Man bomb, as an aside, produced only around 100 neutrons on average. This isn’t the same process at all, but in terms of orders of magnitude this is probably not inaccurate when it comes to imagining how many neutrons can be easily stimulated. It is nothing like what a fission chain reaction can generate with its exponential growth. []

Death dust, 1941

Friday, March 7th, 2014

One of the biggest misconceptions that people have about the Manhattan Project is that prior to Hiroshima, all knowledge of atomic energy and nuclear fission was secret — that the very idea of nuclear weapons was unthought except inside classified circles. This is a side-effect of the narratives we tell about Manhattan Project secrecy, which emphasize how extreme and successful these restrictions on information were. The reality is, as always, more complicated, and more interesting. Fission had been discovered in 1939, chain reactions were talked about publicly a few months later, and by the early 1940s the subject of atomic power and atomic bombs had become a staple of science journalists and science fiction authors.

Campbell's magazine, Cartmill's story. Image source.

Leaks or speculation? Campbell’s magazine, Cartmill’s story. Image source.

John W. Campbell, Jr., was a prolific editor and publisher of science fiction throughout the mid-20th century. In the annals of nuclear weapons history, he is best known for publishing Cleve Cartmill’s story “Deadline” in March 1944, which talks about forming an atomic bomb from U-235. This got Cartmill and Campbell visitors from the FBI, trying to figure out whether they had access to classified information. They found nothing compromising (and, indeed, if you read Cartmill’s story, you can see that while it gets — as did many — that you can make atomic bombs from separated U-235, it doesn’t really have much truth in the specifics), but told Campbell to stop talking about atomic bombs.

But Campbell’s flirtation with the subject goes a bit deeper than that. Gene Dannen, who runs the wonderful Leo Szilard Online website, recently sent me a rare article from his personal collection. In July 1941, Campbell authored an article in PIC magazine with the provocative title, Is Death Dust America’s Secret Weapon?” It’s a story about radiological warfare in what appears to be rather middle-brow publication about entertainment. Click here to download the PDF. I don’t know anything about PIC, and haven’t been able to find much on it, but from the cover one wouldn’t necessarily expect it to be a source for people looking for hard-hitting science reporting — though the juxtaposition of DEATH DUST, “world’s strangest child,” and the “DAY DREAM” woman is a wonderfully American tableau.

PIC magazine 1941 - Campbell - Death Dust - cover

The story itself starts off with what has even by then become a clichéd way of talking about atomic energy (“A lump of U-235 the size of an ordinary pack of cigarettes would supply power enough to run the greatest bomb in the world three continuous years of unceasing flight“), other than the fact that it is one of the many publications that points out that after an exciting few years of talk about fission, by 1941 the scientists of the United States had clamped themselves up on the topic. The article itself admits none of this is really a secret, though — that all nations were interested in atomic energy to some degree. It vacillates between talking about using U-235 as a power source and using it to convert innocuous chemicals into radioactive ones.

Which is itself interesting — it doesn’t seem to be talking about fission products here, but “synthetic radium powders.” It’s a dirty bomb, but probably not that potent of one. Still, pretty exciting copy for 1941. (Campbell would much later write a book about the history of atomic energy, The Atomic Story, where he also spent a lot of time talking about “death dust.”)

The article contains a really wonderful, lurid illustration of what a city that had been sprayed with “horrible ‘death dust’” would look like:

"Even rats wouldn't survive the blue, luminescent radioactive dust. Vultures would be poisoned by their own appetites."

“Even rats wouldn’t survive the blue, luminescent radioactive dust. Vultures would be poisoned by their own appetites.”

The most interesting parts of the article are when it veers into speculation about what the United States might be doing:

With all the world seeking frantically for the secret of that irresistible weapon, what are America’s chances in the race?

It is a question of men and brains and equipment. Thanks to Hitler’s belief that those who don’t agree with him must be wrong, America now has nearly all the first-rank theoretical physicists of the world. Mussolini’s helped us somewhat, too, by exiling his best scientists. Niels Bohr, father of modern atomic theory, is at Princeton, along with Albert Einstein and others of Europe’s greatest.

The National Defense Research Committee is actively and vigorously supporting the research in atomic physics that seeks the final secrets of atomic power. Actively, because the world situation means that they must, yet reluctantly because they know better than anyone else can the full and frightful consequences of success. Dr. Vannevar Bush, Chairman of the Committee, has said: “I hope they never succeed in tapping atomic power. It will be a hell of a thing for civilization.”

Bohr was in fact still in occupied Denmark in July 1941 — he had his famous meeting with Heisenberg in September 1941 and wouldn’t be spirited out of the country until 1943. The photographs identify Harold Urey and Ernest Lawrence as American scientists who were trying to harness the power of atomic energy. Since Urey and Lawrence were, in fact, trying to do that, and since Vannevar Bush was, in fact, ostensibly in charge of the Uranium Committee work at this point, this superficially looks rather suggestive.

PIC magazine 1941 - death dust - scientists

But I think it’s just a good guess. Urey had worked on isotope separation years before fission was discovered (he got his Nobel Prize in 1934 for learning how to separate deuterium from regular hydrogen), so if you know that isotope separation is an issue, he’s your man. Lawrence was by that point known worldwide for his “atom smashing” particle accelerators, and had snagged the 1939 Nobel Prize for the work done at his Radiation Laboratory. If you were going to pick two scientists to be involved with nuclear weapons, those are the two you’d pick. As for Bush — he coordinated all of the nation’s scientific defense programs. So of course, if the US was working on atomic energy as part of their defense research, Bush would have to be in charge of it.

The other illustrations seem to be just generically chosen. They are particle accelerators of various sorts; one cyclotron and many electrostatic (e.g. Van De Graff) accelerators. Cyclotrons did have relevance to isotope separation — they were used to develop the Calutrons used at Y-12 — but the captions don’t indicate that this is why these machines are featured.

I’ve never seen any evidence that Campbell’s story in PIC came to any kind of official attention. Why not? In the summer of 1941, there was a lot of talk about U-235 and atomic energy — and Campbell’s article really isn’t the most provocative of the bunch. There wasn’t any official press secrecy of any form on the topic yet. “Voluntary censorship” of atomic energy issues, which is what would get Cartmill and Campbell in trouble later, didn’t start up until early 1943. Mid-1941 was still a time when a journalist could speculate wildly on these topics and not get visits from the FBI.

The irony is, there were official fears of a German dirty bomb, but they didn’t really crop up until 1942. But the American bomb effort was starting to get rolling in the late summer of 1941. By the end of 1941, Bush would be a convert to the idea of making the bomb and would start trying to accelerate the program greatly. It wasn’t the Manhattan Project, yet, but it was on its way. Campbell’s article was, in this sense, a bit ahead of its time.

A Campbell publication from 1947 — where he apparently has a better understanding of atomic power. Here he seems to have just scaled down a Hanford-style "pile" and added a turbine to it. It took a little more effort than that in reality...

A Campbell publication from 1947 — where he apparently has a better understanding of atomic power. Here he seems to have just scaled down a Hanford-style “pile” and added a turbine to it. It took a little more effort than that in reality…

What I find most interesting about Campbell’s article is that it reveals what the informed, amateur view of atomic energy was like in this early period. Some aspects of it are completely dead-on — that U-235 is the important isotope, that isotope separation is going to matter, that places with particle accelerators are going to play a role, that the acquisition of uranium ore was about to get important, that fears of German use of atomic energy existed. But parts of it are completely wrong — not only would dirty bombs not play a role, he doesn’t seem to understand that fission products, not irradiated substances, would play the strongest role. He doesn’t really seem to understand how nuclear power would be harnessed in a reactor. He doesn’t really seem to get fission bombs at all.

This mixture of accuracy and confusion, of guess and folly, tells us a lot about the state of public knowledge at the time. Atomic energy was a topic, it was an idea — but it wasn’t yet something tangible, a reality. So when people found out, in 1945, that the United States had made and detonated atomic fission bombs, they were primed to understand this as the beginning of a “new era,” as the realization of something they had been talking about for a long time — even if the details had been secret.

News and Notes

Webcast: “What’s become of our nuclear golden age?”

Monday, September 9th, 2013

A 1959 advertisement for Union Carbide in the Saturday Evening Post.

We no longer live in the nuclear age, or, at least, we don’t think we do — so I concluded awhile back. But that won’t stop me from talking about it! This Wednesday, September 11th, 2013, I will be participating in a live webcast at the Chemical Heritage Foundation in Philadelphia:

On Sept. 11, 2013 the Chemical Heritage Foundation will present a live online video discussion, “Power and Promise: What’s become of our nuclear golden age?” Guests Alex Wellerstein and Linda Richards will take stock of our turbulent nuclear past and look at how it has shaped our current attitudes, for better and for worse.

Some say we are on the verge of a bright nuclear future in which nuclear power will play a major role in responding to climate change. Others say that we should expect more Fukushimas. Whichever way our nuclear future goes, there will be energy and environmental tradeoffs. On CHF’s blog you can decide on the tradeoffs you are willing to make. Tweet to vote your choices. Viewers can also tweet questions to the guests before or during the show by using the hashtag #HistChem.

“Power and Promise: What’s Become of Our Nuclear Golden Age?” will air at 6 p.m. EST.  Watch the livecast episode at

Guest Bios:

Alex Wellerstein is an associate historian at the Center for History of Physics at the American Institute of Physics. He holds a Ph.D. in the history of science from Harvard University and his research interests include the history of Cold War technology, including nuclear technology. He blogs at

Linda M. Richards is a former CHF fellow and will be returning in 2014 as a Doan Fellow. She is working on a Ph.D. on nuclear history at Oregon State University. Her dissertation is titled “Rocks and Reactors: The Origins of Radiation Exposure Disparity, 1941-1979.” In 2012 she received a National Science Foundation grant that took her to the International Atomic Energy Agency (IAEA) in Vienna, UN agencies and archives in Geneva, and to North American indigenous uranium mining sites.

About the Show:

#HistChem is a monthly interactive livestreamed show produced by the Chemical Heritage Foundation. It features topically compelling issues that intersect science, history and culture. Hosts are Michal Meyer, editor of Chemical Heritage Magazine, and Bob Kenworthy, a CHF staff member and chemist. The first episode, “How We Learned to Stop Worrying and Love the Zombie Apocalypse,” debuted in August, 2013. Follow the show and related news at

About the Chemical Heritage Foundation:

The Chemical Heritage Foundation is a collections-based nonprofit organization that preserves the history and heritage of chemistry, chemical engineering, and related sciences and technologies. The collections are used to create a body of original scholarship that illuminates chemistry’s role in shaping society. In bridging science with the humanities, arts, and social sciences, CHF is committed to building a vibrant, international community of scholars; creating a rich source of traditional and emerging media; expanding the reach of our museum; and engaging the broader society through inventive public events.

This should be a fun thing, as Linda and I take somewhat different approaches (both interesting) to many nuclear issues, and the CHF team asks great questions. You can Tweet in questions for the show with the right hashtag (#HistChem) and it may somehow magically get to us while we’re talking. And hey, I’ll be wearing a suit!

Update: The video has been posted online, enjoy!


Enough Fallout for Everyone

Friday, August 3rd, 2012

Nuclear fallout is an incredible thing. As if the initial, prompt effects of a nuclear bomb weren’t bad enough — take that and then spread out a plume of radioactive contamination. The Castle BRAVO accident was the event that really brought this to the public forefront. I mean, the initial effects of 15 megaton explosion are pretty stunning in and of themselves:

But the fallout plume extended for hundreds of miles:

Why yes, you can get this on a coffee mug!

Superimposed on an unfamiliar atoll, it’s hard to get a sense of how long that plume is. Put it on the American Northeast, though, and it’s pretty, well, awesome, in the original sense of the word:

Of course, it’s all about which direction the wind blows, in the end.

And remember… that’s just a single bomb!

Of course, if you’re interested in the more diffuse amounts of radioactivity — more than just the stuff that you know is probably bad for you — the fallout maps get even more interesting. Here’s what the BRAVO fallout did over the next month or so after the detonation:1

Now, you can’t see the numbers there, but they aren’t high — it’s not the same as being immediately downwind of these things. They’re low numbers… but they’re non-zero. But one of the “special” things about nuclear contaminants is that you can track them for a very long time, and see exactly how one test — or accident — in a remote area is intimately connected to the entire rest of the planet. 

And, in fact, nearly everyone born during the era of atmospheric nuclear testing had some tiny bits of fallout in their bones — you can even use it to determine how old a set of teeth are, to a very high degree of accuracy, by measuring their fallout content. (And before you think atmospheric testing is a matter of ancient history, remember that France and China both tested atmospheric nuclear weapons long after the Limited Test Ban Treaty! The last atmospheric test, by China, was in 1980!)

The same sorts of maps are used to show the dispersion of radioactive byproducts of nuclear reactors when accidents occur. I find these things sort of hypnotizing. Here are four “frames” from a simulation run by Lawrence Livermore National Laboratory on their ARAC computer showing the dispersion of radioactivity after the Chernobyl accident in 1986:2

Chernobyl ARAC simulation, day 2

Chernobyl ARAC simulation, day 4

Chernobyl ARAC simulation, day 6

Chernobyl ARAC simulation, day 10

Pretty incredible, no? Now, the odds are that there are lots of other contaminants that, could we track them, would show similar world-wide effects. Nuclear may not be unique in the fact that it has global reach — though the concentrations of radioactivity are far higher than you’d find anywhere else — but it may be unique that you can always measure it. 

Yesterday I saw a new set of plots predicting the dispersion of Caesium-137 after the Fukushima accident from 2011. These are just models, not based on measurements; and all models have their issues, as the modelers at the Centre d’Enseignement et de Recherche en Environnement Atmosphérique (CEREA) who produced these plots acknowledge.

Here is their map for Cs-137 deposition after Fukushima. I’m not sure what the numbers really mean, health-wise, but the long reach of the accident is dramatic:

Map of ground deposition of caesium-137 for the Fukushima-Daichii accident

Map of ground deposition of caesium-137 for the Fukushima-Daichii accident by Victor Winiarek, Marc Bocquet, Yelva Roustan, Camille Birman, and Pierre Tran at CEREA. (Source)

Compare with Chernobyl. (Warning: the scales of these two images are different, so the colors don’t map onto the same values. This is kind of annoying and makes it hard to compare them, though it illustrates well the local effects of Chernobyl as compared to Fukushima.)

Map of ground deposition of caesium-137 for the Chernobyl accident

Map of ground deposition of caesium-137 for the Chernobyl accident, by Victor Winiarek, Marc Bocquet, Yelva Roustan, Camille Birman, and Pierre Tran at CEREA. (Source)

Lastly, they have an amazing animated map showing the plume as it expands across the Pacific. It’s about 5MB in size, and a Flash SWF, so I’m just going to link to it here. But you must check it out — it’s hypnotic, strangely beautiful, and disturbing. Here is a very stop-motion GIF version derived from their map, just to give you an incentive to see the real thing, which is much more impressive:

Fukushima-Daichii activity in the air (caesium-137, ground level) (animated)

There’s plenty of fallout for everyone — well enough to go around. No need to be stingy. And nearly seven decades into the nuclear age, there’s a little bit of fallout in everyone, too.

Update: The CEREA site seems to be struggling a bit. Here’s a locally-hosted version of the full animation. I’ll remove this when CEREA gets up and running again…

  1. Image from “Nature of Radioactive Fall-Out and Its Effects on Man, Part 1,” Hearings of the Joint Committee on Atomic Energy, Special Joint Subcommittee on Radiation (May 27-29 and June 3, 1957), on 169. []
  2. These images are courtesy of the DOE Digital Archive. []

Rare Photos of the Soviet Bomb Project

Friday, July 27th, 2012

I was recently perusing some Russian-language books on the Soviet atomic bomb project at the Library of Congress, and I stumbled across one that was really pretty amazing. The book itself is a catalog of a big exhibit on the Soviet bomb project (“Atomic project USSR: The 60th Anniversary of the Russian nuclear shield”1 which was held in Moscow in the fall of 2009. Much of the text is a rote repetition of what has been known for years — with some historical weirdness, like repeat using of “we” to mean the USSR, which is not the most encouraging thing for Russians to do — but the images are fantastic, and many of them are quite new.

Calling this “new” is a bit of a stretch, since the book was published three years ago. But it’s new to me, and if it’s new to me, it’s probably new to you! It’s definitely newer than most of the Soviet nuclear program photos that are out there, most of which showed up in the early 1990s when the Russian archives (temporarily) became easier to use.

Before I start, I would like to just point out how crazy it is that this book is so well-produced. It’s on glossy paper. The design is well done. The pictures are in color! None of this would be remarkable if the book was from the United States or a country in Western Europe, but most Russian-language books that I’ve seen in this country look like they were mimeographed on recycled newsprint by old Marxists. Somebody spent a comparative fortune on getting this book published. It’s a slick book; I wish there were an easy place to buy it online.

The whole thing kicks off with this amazing photograph of Vladimir Putin and a number of Russian Orthodox big-wigs at Sarov, the city that was once known as Arzamas-16, the Soviet equivalent of Los Alamos. Apparently the Soviet bomb scientists liked to call the place “Los Arzamas.” Sarov has been the site of a big Russian Orthodox monastery for centuries.

There are some great, rare photographs of key Soviet weapons scientists in the book. From left to right here, we have young, beardless Igor Kurchatov; Kurchatov after he grew his famous beard; a dashing portrait of Georgii Flerov, and finally, Yuli Khariton. Kurchatov agreed not to shave his beard until the enemy was defeated, during World War II, but being “the Beard” somewhat became him so I don’t think he ever shaved it off. He looks like such a goofy kid on the photograph to the left, which I think was taken when he was in his early twenties. The beard photo is from the early 1940s.

Flerov is the guy who really got the Soviet project off the ground initially. His story is pretty fascinating. In 1942, he had hoped to get the Stalin Prize for his work on the spontaneous fission of U-238, which would have kept him from the murderous Eastern Front of World War II, but was rejected because his paper wasn’t cited by anyone, and thus was judged as unimportant. Flerov did a literature search and realized that nobody was publishing on fission anymore — and indeed, all of those who had been publishing on it had dropped off the map completely. He immediately started writing letters — including to Stalin himself — pointing out that this could only indicate that the United States was working on an atomic bomb. Anyway, this is the most dashing photograph I’ve seen of him. It dates from 1940.

Khariton was the head Soviet theorist — something of an equivalent to their Oppenheimer. The photo dates from the 1940s. Khariton, oddly enough, has some links to Freud’s inner circle. I don’t find that changes my understanding of the bomb much, but it’s still unexpected. (Hat-tip to Michael Dennis for forwarding that to me.)

Perspective view of a mine at Taboshar, Tajikistan, from 1944.2 Taboshar was one of the few early sources of Soviet uranium, known since the 1920s and mined extensively for uranium since 1945. The acquisition of raw uranium was the key setter of the timetable of the Soviet bomb program. They had very few known sources of the ore at the end of World War II, and the United States and the United Kingdom had worked behind the scenes to attempt secure a monopoly on all other known world supplies. General Groves thought their access to uranium was so bad that it would take the Soviets 20 years to get a bomb — but it turned out that uranium is more plentiful than he realized, and concentrations that wouldn’t be economic to mine for the United States turned out to be just fine for Soviet slave labor.

Here we have two diagrams of the Nagasaki atomic bomb (Fat Man) based on information passed on to the Soviets from Klaus Fuchs and other spies. These aren’t particularly sensitive today, but would have been Top Secret–Restricted Data when they were acquired. On the right is the basic dimensions of the body of the bomb, and on the left is a more detailed arrangement showing the electrical systems inside the bomb. As anyone reading this blog no doubt knows, the Soviet Union had a number of spies in high places in both the US and UK sides of the Manhattan Project, which they dubbed “ENORMOZ” in their code language.

What I like about these drawings, aside from their novelty, is that the labels are first in English, and then translated into Russian again — betraying their obvious roots in espionage.

There are also some cool documents reproduced in here. This one is from a report written for Lavrenty Beria, dated February 28, 1945, on the “Progress of the atomic bomb abroad.” It says that it is expected that the United States will produce a bomb by July of that year, and then explains in very basic terms how it works. I also love the punctuation of the technical terms with handwritten English (“High explosive,” “Composition C,” “commercial radium tube.”) Even without much Russian beyond transliteration, you can recognize a bunch of what’s being discussed: the fact that only about 5 kg of plutonium was used in the implosion bomb (actual value was close to 6kg, but who’s counting), the discussion of the different explosives involve in implosion, and, amusingly, the term “tube alloy” as a codename for uranium.

The last line, underlined, says “The explosion is expected approximately July 10.” As Solzhenitsyn wrote in The Gulag Archipelago, “the Organs always earned their pay.”

A nice spread labeled as “the territory of Laboratory No. 2, 1943.” Pretty desolate. Laboratory No. 2 is located just outside of Moscow and was run by Kurchatov, and was the site of the first Soviet nuclear reactor and now the Kurchatov Institute.

This is an outside view of a tent at Laboratory No. 2, also from 1943. Apparently “experiments with uranium” were performed.3

And here is an interior view of the same tent. The stack at the right looks like graphite blocks, which the first Soviet reactor was made out of. (As was the first American reactor, of course.)

Here are three views of the assembly of F-1, the first Soviet reactor. On the left, they are laying the graphite blocks; in the middle, you can see it more completely assembled; on the far right, the diagram of the design. One can easily compare these with the first American reactor design, Chicago Pile-1.

The F-1 reactor in 2009. Fun fact of the day: Reactor F-1 is still a functional, operating nuclear reactor. It achieved criticality on December 25, 1946, and is still using its original fuel load. (It is very low power, so that’s not quite as impressive as it sounds.) It’s the oldest functioning nuclear reactor in the world.

This is listed a the central hall of Reactor “A” after it received an upgrade, from the late 1950s.4 Reactor A was a military production reactor in Chelyabinsk, running on natural uranium fuel, with graphite as the moderator. It was up and running by June 1948, and provided plutonium for the first Soviet atomic bomb.

In other words, this is something like the Soviet equivalent of the B-Reactor at Hanford, though after the aforementioned upgrade, Reactor A was able to run at 500 MW, about twice what B-Reactor could do.

And lastly… the bomb itself. Well, a model of it, anyway. The caption says this is model of the first Soviet bomb at “the Polygon,” which was the code name for the Semipalatinsk test site.5 Somehow it manages to look very futuristic (the big circles, the large poles) and yet quite rustic (the trees, the way in which everything looks like it has been fashioned by hand by some ancient Kazakh craftsman).

(If anyone has any insight into what function the poles and  the big circle have, I’d love to know.)

This is one of the more intimate photographs of the Soviet bomb I’ve ever seen. Photographs of the Trinity gadget in arrangements like this have been common for a few decades, now, but Soviet equivalents are quite rare.

This may be my favorite photo of the whole set: the most profoundly indicative of the Soviet situation and the most graphically arresting. A bedraggled Russian worker, straight out of Gogol, posing next to a riveted, crude, and terrible atomic bomb. It’s a dystopic juxtaposition: the desperate old paired with the horrible new.

The “bomb” appears to be an early bomb casing model used for aerodynamic testing.6 I suspect they used these proto-casing the same way the US did: dropping them endlessly from planes, to make sure they wouldn’t spin or pinwheel in unpleasant ways that would rattle the sensitive internal components.

This is from a report on the first atomic bomb test co-written by Beria and Kurchatov for the pleasure of Comrade Stalin. It shows what happened to a Lavochkin La-9 which was 500 meters from the test blast. It’s dramatic, all right.

Igor Kurchatov, father of the Soviet bomb, and Sergei Korolev, father of the Soviet ICBM, hanging out in the 1950s. I can’t quite tell what Korolev has in his hands — it sort of looks like a giant (Lysenko-enhanced) cabbage, but it also looks somewhat reflective, which most cabbages aren’t. Hard to tell, but Kurchatov and Korolev seem rather amused by it. [My father suggests it looks an awful lot like Jiffy-Pop, no doubt acquired through special intelligence sources. Hey, who knows?]

And with a job well done came… an appreciative letter to Stalin. In the Soviet Union, Stalin doesn’t thank you when you accomplish something difficult… you thank Stalin!7 OK, in truth, it was them thanking Stalin for giving them awards (and not, you know, executing them) after the successful test. But it’s still amusing.

It reads something like this (pardon my likely spotty translation):

Comrade Stalin
Dear Josef Vissarionovich!

We heartily thank you for the high appreciation of our work, which the Party, government and you personally awarded us.

Only the daily attention, care and support that you gave us for those four-plus years of hard work have enabled use to successfully solve the task of organizing the production of nuclear energy and the creation of atomic weapons.

We promise you, dear Comrade Stalin, that we will be working with even more energy and dedication on the further development of the business entrusted to us, and we shall give all our strength and knowledge to justify your confidence in us.8

It’s signed by Beria, Kurchatov, Khariton, and a boat load of other Soviet scientists. Was Stalin pleased? Well, no. The note at the upper left is in Stalin’s handwriting, and it says, Why not Riehl (the German)?”9 As in, where is Nikolaus Riehl’s signature? Riehl was one of the German scientists who had gone to work on the Soviet bomb after World War II. Ah, that Stalin… never could just take a compliment!

(Riehl’s story is an interesting one — he was half guest, half captive. He got many nice things for his work, but was also in a legally ambiguous status. He was not present at the first Soviet test; he learned of it later from listening to British radio. Riehl’s lack of signature on the letter probably had less to do with trying to offend Stalin — he wasn’t suicidal — but because he had been compartmentalized out of that part of the project.)

Finally, it ends with a picture of “veterans of the first Soviet atomic bomb test,” gathered in 1999. I’ve seen a number of photos of folks with the Soviet bomb, but this one really brought out the fact that it’s actually a very large bomb indeed.

  1. “Атомный проект СССР. К 60-летию создания ядерного щита России.” All translations are mine with help from Google Translate and an old Soviet technical dictionary. Original Russian will be in the footnotes. I am happy for clarifications and corrections; I acknowledge my Russian is far from perfect. Citation for the book: Atomnii proekt SSSR: katalog vystavki (Moscow: Rosatom, 2009). []
  2. “Axonometric projection of the mines of the eastern section of the field ‘Taboshar.’ 1944.” / “Аксонометрическая проекция горных выработок восточного участка месторождения ‘Табошар.’ 1944 .” []
  3. “Laboratory No. 2 tent — location of experiments with uranium. External and internal views.” [1943] / Палатка Лаборатории No. 2 — место проведения экспериментов с ураном. Внешний и внутренний виды. [1943] []
  4. “Central hall of the reactor “A” after the upgrade. The end of the 1950s.” / Центральный зал реактора “А” после модернизации. Конец 1950-х. []
  5. “Model of the bomb at the Polygon. Not earlier than 1948.” / Макет установки взрывного устройства на полигоне. Не ранее 1948. []
  6. “Bomb casing before aviation testing.” / Корпус авиабомби перед авиационними испытаниями. []
  7. “Letter of appreciation awarded with orders and ranks of academics, specialists, and scientists to Stalin in appreciation for the work in the field of nuclear energy and the creation of atomic weapons. November 18, 1949.” / Благодарственное письмо награжденных орденами и званиями академиков и ученых специалистов Сталину И.В. за высокую оценку работы в области производства атомной энергии и создания атомного оружия. 18 ноября 1949. []
  8. Товаришу Сталину И.В

    Дорогой Иосиф Виссарионович!

    Горячо благодарим Вас за высокую оценку нашей работы, которой Партия, Правительство и лично Вы удостоили нас.

    Только повседневное внимание, забота и помощь, которые Вы оказывали нам но протяжении этих 4-х с лишним лет кропотливой работы, позволили успешно решить поставленную Вами задачу организации производства атомной энергии и создания атомного оружия.

    Обещаем Вам, дорогой товарищ Сталин, что мы с еще дольшей энергией и самоотверженностью будем работать над дальнейшим развитием порученного нам дела и отдадим все свои силы и знания на то, чтобы с честью оправдать Ваше доверие. []

  9. Почему нет Рилля (немец)?” []