Fears of a German dirty bomb

by Alex Wellerstein, published September 6th, 2013

For good reason, much has been made of the initial fear of a German atomic bomb. But there was another, lesser-known atomic fear as well. If the Germans could make nuclear reactors — which the Americans thought they were probably doing — could they not take the dangerously-radioactive spent-fuel out of them and use them to make dirty bombs? 

Hanford spent fuel rods — the sort of thing that could have been weaponized during World War II as a radiological weapon.

Hanford spent fuel rods — the sort of thing that could have been weaponized during World War II as a radiological weapon.

In the summer of 1942, Arthur Compton, head of the University of Chicago’s Metallurgical Laboratory, wrote a memo to Harvard President and atomic-bomb big-wig James B. Conant expressing the need for “protection against ionizing bombs”:

We have become convinced there is real danger of bombardment by the Germans within the next few months using bombs designed to spread radio-active materials in lethal quantities. … Since protection against the danger from such bombs will be primarily a matter of detection of radiation and instruction with regards to the dangers, it is essential that the matter be brought at once to the attention of the appropriate military officers.1

Compton and his scientists were, at the time, working under the assumption that the Germans were ahead of the Americans, and had already gotten a nuclear reactor running. They estimated that with a 100 kilowatt reactor, 100,000 Curies of radioactivity could be produced daily for bomb usage.

A radiation survey device of the sort produced during World War II by the Victoreen Instrument Company in Cleveland, in collaboration with the University of Chicago scientists.

A radiation survey device of the sort produced during World War II by the Victoreen Instrument Company in Cleveland, in collaboration with the University of Chicago scientists.

A result of this was that in the fall of 1942, the first steps were taken to, at a minimum, detect whether the Germans used any kind of radiological attack against the Allies. Survey meters were developed that would trigger alarms if they detected high levels of radioactivity. These were secretly dispersed to Manhattan District offices in Boston, Chicago, New York, San Francisco, and Washington, DC. At each location, a small number of officers were trained in their use. Further instruments were held in reserve in case they needed to be deployed further. If the alarms went off,  or if there were other suspicious signs (like reports of a large-scale blackening of photographic film), scientists at the University of Chicago were kept on the ready to be brought in to assess the situation.2

This was a fairly small program, as far as they go. Those involved were acutely aware that the secrecy of the atomic bomb made it impossible to adequately prepare for this possibility. They were stuck in a bind that was very common during the wartime period. The atomic bomb was, at that time, what I like to call an “absolute secret”: the fact that there was a “secret” at all was itself a secret. They could not draw attention to matters relating to atomic energy without drawing attention to the fact that they were engaged in a secret research program with regards to atomic energy. This is a very peculiar situation, one primarily specific to the war, when the secrecy of the project could not be acknowledged (they could not simply say, “oh, the details are secret,” as they could in the Cold War).

What did they think the Germans would do with such a radiological weapon? They considered four possibilities. First, it could be used as an “area-denial” weapon, by making areas uninhabitable. Second, it could be used to contaminate critical war infrastructure (e.g. airports). Third, it could be used as a “radioactive poison gas” to attack troops. Fourth, it could be used “against large cities, to promote panic, and create casualties among civilian populations.”3 Their assessment of the effects, by 1943, was grim:

Areas so contaminated by radioactive material would be dangerous until decay of the material took place, perhaps for weeks or months. … As a gas warfare instrument the material would be ground into particles of microscopic size to form dust and smoke and distributed by a ground-fired projectile, land vehicles, or aerial bombs.  In this form it would be inhaled by personnel.  The amount necessary to cause death to a person inhaling the material is extremely small.  It has been estimated that one millionth at a gram accumulating in a person’s body would be fatal.  There are no known methods of treatment for such a casualty.4

In the time-honored method of worrying about threats, they also then immediately realized that maybe the United States should be weaponizing fission products: “It is the recommendation of this Subcommittee that if military authorities feel that the United States should be ready to use radioactive weapons in case the enemy started it first, studies on the subject should be started immediately.” Note that this isn’t really a deterrent capability, it is a response capability. Deterrence requires your enemy knowing that you have the capability to respond, and secrecy precluded true deterrence.

1943 - Oppenheimer to Fermi

In this context, there is an interesting letter in the J. Robert Oppenheimer papers at the Library of Congress, where Oppenheimer is writing to Enrico Fermi in May 1943 on “the question of radioactively poisoned foods.” From the context, it is clear that both Edward Teller and Fermi had devoted time to this project. The full document is available here. Two parts stand out. One is that one of the acute problems in looking into the issue was, as Oppenheimer put it, difficult to study the subject “without telling anyone about it.” That is, it would be hard to investigate some of the substances in question “without letting a number of people into of the secret of why we want” the substances. The “absolute secret” bind again.

The other is Oppenheimer’s criteria for the project being worth looking into:

…I think that we should not attempt a plan unless we can poison food sufficient to kill a half a million men, since there is no doubt that the actual number affected will, because of non-uniform distribution, be much smaller than this.5

Frank Oppenheimer later called this a very “bloodthirsty” statement by his brother; the historian Barton Bernstein instead argued that this was just scientists trying to help the war effort.6 Either way, it makes Oppenheimer look like a very cold fish indeed. And not much of a “dove.” Even if one isn’t clear how much of a “non-uniform distribution” he was assuming.

1943 - Oppenheimer to Fermi - quote

The offensive angle was basically dropped — they didn’t think they’d need it, and they were focused intently on making the actual atomic bomb, a much more devastating weapon. But defensive measures did proceed. By late 1943, it was thought that the use of radioactive poisons against the UK by the Germans was of low probability, but an unpleasant possibility.7 To avoid being completely taken by surprise in such an event, General Groves (with the concurrence of General Marshall) had four officers from the European Theater of Operations staff briefed on the subject “under most complete secrecy,” and a Manual on Use of Radioactive Materials in Warfare was drawn up for these four officers. Signals officers were instructed to report any “peculiar or unexplained effects” on photographic films or personnel, and the officers in question were given radiation detection instruments to use in the case of suspected cases.

In March 1944, General Groves had the matter brought to the attention of General Dwight D. Eisenhower, commanding general of the Supreme Headquarters Allied Expeditionary Force, fearing that the Nazis might use such weapons to prevent an Allied invasion of Europe. Eisenhower concluded that since the Combined Chiefs of Staff had not brought up the issue, that they must consider that “the enemy will not implement this project.” To keep secrecy, in order to “to avoid a possible scare,” Eisenhower informed only a handful of people, which he acknowledged was not really enough to counter “enemy action of this nature”: “No US or British Commander participating in OVERLORD [the landing at Normandy] has been briefed.” However, radiation detectors were being kept in the UK for deployment on short notice, and a “cover” letter was sent out with symptoms of radiation poisoning listed as a “mild disease of unknown etiology” that was going around, requesting any medical officers to report further cases.8

Dry-run of using radiation detection equipment during a beach landing, as part of "Operation Peppermint." Source.

Team performing a dry-run of a beach landing with radiation detection equipment, as part of “Operation Peppermint.” Source.

The plan to deploy radiation monitoring during the D-Day invasions was dubbed “Operation Peppermint,” one of the more amusing code-names of the war. Dry runs of the detection apparatus were taken before D-Day, and German bomb craters were surveyed for radioactive residues, but since no evidence of German radiological weapons preparations or use were uncovered, the “Peppermint” preparations were never put into effect. 

We now know that the Germans never got anywhere near this kind of plan. They didn’t even get a reactor running by the end of the war, the necessary prerequisite for this kind of operation. It wasn’t a totally crazy fear, though. There are aspects of radiological warfare which would make it preferable to, say, chemical warfare from the German point of view. Still, there’s an aspect to this of the old saying, “when the only tool you have is a hammer, every problem looks like a nail.” When you’re studying radioactive hazards intently, every threat looks like a radioactive hazard.

The secrecy angle is what intrigues me the most about this story: the secrecy of the bomb made it difficult to enact serious preparation from this related, but separate threat. The secrecy of one fear made addressing another fear difficult, because the relevant information of both fears were too deeply entangled. 

  1. Arthur H. Compton to James B. Conant (15 July 1942), Bush-Conant file, Roll 7, Target 10, Folder 75, “Espionage.” []
  2. Manhattan District History, Book 1, Volume 14, Foreign Intelligence Supplement No. 2 (Peppermint), 31 July 1952. []
  3. Use of Radioactive Material as a Military Weapon” (n.d., c.a. early 1943). []
  4. Ibid. []
  5. J. Robert Oppenheimer to Enrico Fermi (25 May 1943), J. Robert Oppenheimer Papers, Library of Congress. []
  6. Barton J. Bernstein, “Oppenheimer and the Radioactive Poison Plan,” Technology Review, 88 (May-June 1985), 14-17. There is also some follow-up in Barton J. Bernstein, “Four physicists and the bomb: The early years, 1945-1950,” Historical Studies in the Physical and Biological Sciences, 18, No. 2 (1988), pp. 231-263, on 252-253. []
  7. Leslie Groves to George C. Marshall (30 November 1944), Manhattan Engineer District (MED) records, Records of the Army Corps of Engineers, RG 77, National Archives and Records Administration, Box 64, “Security.” []
  8. Dwight D. Eisenhower to George Marshall (11 May 1944), Correspondence (“Top Secret”) of the Manhattan Engineer District, 1942-1946, microfilm publication M1109 (Washington, D.C.: National Archives and Records Administration, 1980), Roll 5, Target 8, Folder 18, “Radiological Defense.” []

9 Responses to “Fears of a German dirty bomb”

  1. Paul Guinnessy says:

    If I remember correctly, one of Churchill’s science advisors, R. V. Jones, looked at radioactive weapons back in 1940-41, as there was concern they might use it during the blitz. His book is worth reading if you have the chance.

  2. Bill Higgins says:

    More worries about possible German dirty bombs:

    On 20 April 1944, Capt. Deak Parsons, an ordnance expert, reported to General Groves about reconnaissance photos of “rocket installations” in France that showed “additional unknown construction” nearby. He had discussed radioactive poison weapons with the UK’s Joseph Rotblat, and speculates that the mysterious structures might be nuclear reactors supplying

    “radioactive disintegration products which the Germans considered so ‘hot’ that they could not transport them from manufacturing points in Germany by any available transportation. These might be placed in bombs with ordinary explosives to be functioning over the ground to gain maximum distribution of the radioactive products.”

    He goes on to suggest some characteristics of such an operation, I presume to tell intelligence folks what to look for.

    (V-2s weren’t in operation until September of 1944, so I’d guess he was looking at V-1 launch sites.)

    I obtained the PDF of this memo, “Possible Use of Radioactive Poison in Rocket Propelled, Unmanned Aircraft,” in April 2008. I think it was on a Los Alamos National Laboratory history site. Sorry, I can’t find a link to it just now.

  3. To invoke the danger of a German radiological w. in order to justify an American one is typical of a general principle : the dirty ideas you attribute someone else may, or may not, be in his mind, but they certainly are in yours. Ernest Lawrence c ertainly did not need any such input to think of these w. after Seaborg discovered Pu in L’s lab and it was realized that a nuclear pile would produce vast amounts of Pu. Lawrence was still advocating radiological w. circa 1950. See e.g. Herken, Brotherhood of the bomb.

    Roger Godement. Paris

    • In May 1941, a National Academy of Science committee (Arthur Compton, Ernest Lawrence, John Van Vleck and William Coolidge) came to the conclusion that the militarily most important applications of the U business were (in order or decreasing importance) (1) “radioactive fission products which could be dropped over enemy territory” , (2) a submarine engine, (3) a bomb. The importance of these developments was based on the estimated length of time they would take, the most urgent task being of course to attain a chain reaction.
      Richard G. Hewlett and Oscar E.Anderson, Jr, The New World, 1939/1946 (Pennsylvania Stat UP, 1962), p. 36-39. This is volume I of a well known official history of the AEC. My first (and rather heavy…) introduction to the subject some 40 years ago.
      Roger Godement, Paris.

  4. Cthippo says:

    This is a prime, and possibly the prime, example of what Richard Rhodes described as “the dark mirror”. Assessing an enemy’s capabilities and intentions without any real data is like looking into a dark mirror, all you see is your own worst fears reflected. It starts with the fairly logical thought of “If we don’t know what they’re up to then we have to assume they’re ahead of us”.

    In this case, they came up with an idea that might be possible, and since we didn’t know what the Germans were up to we had to assume that they had though of it too and might even be building such weapons. This same thought process brought us the bomber gap, the missile gap, and countless other expensive and dangerous programs that proved to have no basis in fact.

    This is what happens when a nation lives in fear, especially when that fear is encouraged and perpetuated by it’s leaders.

    • Peter Solem says:

      The astonishing thing about this story of the U.S. military fears of radiological weapons – (and this is a great historical find, more proof of the value of this blog!) – is that this is not where the German military ‘superweapon’ effort was actually focused. My general understanding of the German nuclear effort is that they had abandoned the goal of a nuclear bomb in favor of a nuclear-powered engine, perhaps due to erroneous calculations of the amount of fissionable nuclear material (U-235) required to sustain a runaway chain reaction – they estimated tons, instead of kilograms.

      What the Germans were more focused on was their secret chemical warfare program:

      “Dyhernfurth was one of the Third Reich’s largest and most secret factories. It covered an area over a mile and a half long and half a mile wide… It had a monthly capacity for producing 3,000 tons of nerve gas – 500 tons from each of
      its six separate units. The factory was completely self-contained. It made the intermediate products needed in the manufacture of tabun; it made the tabun itself; and it had a cavernous underground shell-filling plant, where the liquid nerve gas was loaded into aircraft bombs and shells.” – Harris & Paxman, 1982, “A Higher Form of Killing”

      Yet, as with the Allied fears of radiological weapons based on their own secret military research, the Germans feared that the U.S. and Britain had also been secretly developing organophospate pesticide-based nerve gas agents, and would retalitate in kind against German cities if they deployed their own nerve agents against invading troops, or against British cities.

      As with the Manhattan Project, the German nerve agent program was a massive and secret industrial effort that the U.S. and Britain were completely unaware of until the war’s end – when they discovered the stockpiles. The story of the secret German effort to develop their nerve agent arsenal has many parallels to the problems encountered in the UF6 gaseous diffusion plants, since UF6 is about as nasty a gas as anyone can imagine – similar problems involving corrosion and worker exposure existed in both cases (and indeed, UF6 and related gases might have been candidates for radiological warfare). Prior to the Manhattan Project, the most complex U.S. military industrial-chemical effort took place at Edgewood Arsenal – for production of chemical agents like mustard or phosgene – and it seems that the UF6 program, critical to the production of U-235, must have borrowed heavily from prior experience with toxic gases at Edgewood Arsenal.

      The bottom line, historically, is that while the U.S. had this fear of radiological warfare based on their own research and development program, what they really should have feared is being soaked with nerve agents on D-Day – but they knew nothing of that threat – thus the statement, “all you see is your own worst fears reflected” – rings true. Now, it is possible that the use of nerve agents might have temporarily blocked the D-Day landings in 1944 – but then, it would have been not just Japan, but Germany, who would have been subject to nuclear bombardment in 1945 – for the Germans did not understand the nuclear threat, just as the Allies did not understand the chemical threat. After the war, however, more became clear:

      “April 1945 was Porton’s moment of truth. A German ammunition dump was captured and a mysterious shell shipped back to the United Kingdom. Gingerly dismantled with the help of a nearby American field laboratory, the scientists discovered Hitler’s secret weapon. It was a terrible shock. Thirty-five years later it is still a source of embarrassment. ‘The one time we were really caught with our trousers down,’ says one senior Porton man today.” – Harris & Paxman, 1982, “A Higher Form of Killing”

      So, why did the Nazis believe that their secret was known? According to Harris and Paxman:

      “Nazi scientists, for example, read great significance into the fact that references to compounds related to nerve gases suddenly ceased to be mentioned in American scientific journals at the beginning of the war. They correctly deduced this was a result of censorship by the US authorities. What they did not know was that this was to protect the secrecy of the insecticide DDT then under development, not the secrecy of any new war gas.”

  5. Alex,

    I recently filed a FOIA request with the National Nuclear Security Administration. Their response arrived today, and there was a bit of surprised enclosed. Here’s why I filed it….

    About ten years ago, the physicist Philip Morrison gave an interview in which he discussed his activities with the Manhattan Project. While he skirted around the issues and he mentioned two young scientists he worked with and his main project without details, I filed a FOIA request hoping to fill in some of the blanks. They were.

    Morrison’s project was the detection of radiation near a German facility that might suggest the Germans were developing a weapon. Some of the documents were as I thought: ways to detect radiation, ways to know if the Germans were operating an atomic pile, etc. But one of the documents surprised me. It was a memo from a Captain in the U.S. Navy to General Groves.

    It discussed the possibility that the Germans might want to build a “dirty bomb” to be flown by un-manned aircraft at civilian targets. The letter is very lengthy: It discusses the hazards in producing and handling of the material, how an atomic pile is required to produce the nuclear material, what raw materials are needed to build such a bomb (such as heavy water or graphite), and what to look out for to detect if the Germans had actually done it.

    Since I intend to publish the contents of the memo, I can’t post it here. But I would be more than happy to send you a copy (so that you can quote from it)… that is, if you haven’t already seen it.

    — Bill Streifer: The Flight of the Hog Wild