CHAPTER 12

“In the Interests of National Defense or Foreign Policy …”

IT IS CURIOUS that, after more than fifty-five years, despite the rules respecting automatic declassification of documents, much of the archive material relating to the cargo of the German submarine U-234 still has not been made public. In 1985 American journalist Robert K. Wilcox wrote: “Inquiries to government agencies have produced nothing. It is as if the incident never occurred, as if U-234, its important passengers and cargo, never arrived”.129 British rocket engineer Philip Henshall wrote in 1995: “Despite requests made to the US naval authorities, the reply has always been that matters relating to nuclear affairs are still subject to official secrecy”.130

Anybody who thinks this is legal should examine American law itself.131 In the United States, a request to a Government agency must be answered within ten days, and if denied a reason given. The courts have ruled that the Freedom of Information Act is to be broadly construed in favour of disclosure, and its exemptions are to be “narrowly construed”.

Where a matter is to be “kept secret in the interests of national defense or foreign policy” pursuant to an Executive Order, then the section relating to disclosure does not apply. If this exemption is being used secretly after 55 years, there must have been something extraordinary indeed about the heavy little cases of uranium on board the German submarine U-234. There is no blanket exemption by which nuclear matters generally are still subject to secrecy, and many formerly Top Secret documents in the matter have been declassified.

The Japanese Interest in Nuclear Materials

The interest of the Japanese Government in an atom bomb had waned in 1942 once it was realized that the separation of the U²³⁵ isotope for the purpose of making the bomb would require an enormous labour force, stupendous investment, one-tenth of Japan’s annual electricity requirement and half the nation’s copper output for a year. Professor Yoshio Nishina was the senior atomic scientist and headed the Army project. In 1943, when a link was established with Germany, Nishina asked for a cover story so that the Germans would not be suspicious of a request for uranium. The need for uranium as a catalyst was the excuse apparently adopted.132 It is firmly established that Japan did subsequently request uranium from Germany for experimental purposes in 1943133, and probably received a few tons. Japan had several hundred tons of uranium ore and had been prospecting successfully in Korea and Burma for more. Unless all this has a double meaning, one infers that Japanese physicists had worked unsuccessfully on an atom bomb project since 1941 and had not progressed beyond the early laboratory stage. The German naval historian Professor Jürgen Rohwer has confirmed from the first Magic decrypts for 1943 and 1944/45 that Japan requested from Germany a “quantity of uranium oxide” in connection with their atomic research into the fissile isotopes including plutonium.134

Accounting for the U-234 Cargo: the Primary Documents

The initial US Navy Unloading Manifest of U-234 was a translation carried out by the Office of Naval Intelligence and issued on 23 May 1945. The only item of uranium mentioned was ten cases of uranium oxide. Revised manifests, such as that of 16 June 1945, omit the uranium oxide. No mention was made of any uranium material in the long memorandum to C-in-C Atlantic Fleet of 6 June 1945 describing the U-234 voyage and cargo arrangements in close detail.

The first manifest showed “10 cases Uranium Oxide, 560 kilos” consigned to the Japanese Army. As the item is part of the overall weight of the cargo, 560 kilos means the combined weight of containers and contents.

The next primary document is the copy of a secret cable #262151 dated 27 May 1945 from Commander Naval Operations to Portsmouth Navy Yard on the subject of “Mine Tubes, Unloading Of”. Distribution of the memorandum was to the commandant and various duty and orderly officers. It reads:

“Interrogation Lt Pfaff second watch officer U-234 discloses he was in charge of cargo and personally supervised loading all mine tubes. Pfaff prepared manifest list and knows kind-documents and cargo in each tube. Pfaff stated long containers should be unpacked in horizontal position and short containers in vertical position. Uranium oxide loaded in gold lined cylinders and as long as cylinders not opened can be handled like crude TNT. These containers should not be opened as substance will become sensitive and dangerous. Pfaff is available and willing to aid unloading if RNEDT desires. Advise. CTM.”

The third item is US Navy Secret Telephone Transcript 292045 between Commander Naval Operations, Brooklyn Navy Yard, Major Francis J. Smith, and Major Traynor at Portsmouth, NH Naval Yard. This recorded that on 30 May 1945, Lt-Cdr Karl B. Reese, Lt (j.g.) Edward P. McDermott (USNR) and Major John E. Vance, Corps of Engineers, US Army, arrived at Portsmouth Navy Yard in connection with the cargo of U-234. Large quantities were unloaded and taken by ship to Brooklyn. The following telephone conversation ensued on 14 June 1945 between Major Smith and Major Traynor:

Smith: “I have just got a shipment in of captured material and there were 39 drums and 70 wooden barrels, and all of that is liquid. What I need is a test to see what the concentration is and a set of recommendations as to disposal. I have just talked to Vance and they are taking it [i.e. the cargo] off the ship and putting it in the 73rd Street Warehouse. In addition to that I have about 80 cases of U powder in cases. Vance is handling all of that now. Can you do the testing and how quickly can it be done? All we know is that it ranges from 10% to 85% and we want to know which and what.”

Traynor: “Can you give me what was in those cases?”

Smith: “U powder. Vance will take care of the testing of that.”

Traynor: “The other stuff is something else?”

Smith: “The other is water.”

The use of the letter “U” as an abbreviation for uranium was widespread throughout the Manhattan Project. The Corps of Engineers to which Major Vance was attached was the parent organization of the Manhattan Project and Major Vance was part of the latter project.

The fourth document originates from the Manhattan Project Foreign Intelligence files and confirms that the remaining cargo was unloaded on 24 July 1945. This included the ten cases of uranium oxide assayed as 77% pure Yellow Cake. The document confirms that the bulk of the U-234 cargo was held in the custody of Major Francis Smith at the Brooklyn Navy Yard.135

Interpreting the Primary Documents

In the first manifest are listed ten bales of drums containing “confidential material” and fifty bales of barrels containing benzyl cellulose, which latter can be used for biological shielding purposes or as a coolant in a liquid reactor. The thirty-nine drums are said by Major Smith to contain “water” for which he needs a test done “to see what the concentration is”: he knows that it ranges from 10% to 85%. If this is heavy water, the percentage describes the degree to which a consignment of water had been depleted of its hydrogen molecules.

It will be observed from the primary documents that uranium oxide was unloaded from U-234 on 24 July 1945, while eighty cases of uranium powder had already been unloaded and shipped to Brooklyn by 14 June 1945. Therefore aboard U-234 were two different uranium consignments and one of them never appeared at any time in the manifests translated by the Americans.

We now observe that what seem to be discrepancies in the secondary, eyewitness evidence of Wolfgang Hirschfeld actually confirm the existence of two distinct shipments aboard U-234. The Unloading Manifest states “10 cases Uranium Oxide” but on the quayside at Kiel Hirschfeld said he saw “at least fifty of the little cases.”136 Obviously, what he saw the Japanese loading at Kiel was not the ten cases of uranium oxide, but the eighty little cases of uranium powder. The little cases he saw were cubic in shape about nine inches along the sides, whereas the uranium oxide described by Pfaff, and unloaded by him on 24 July 1945, was stowed in gold-lined cylinders, the dimensions of which are not known. Hirschfeld did not witness the actual unloading by Pfaff.

As to the eighty little cases of uranium powder, besides the fact that it was shipped in what seemed to be lead radioisotope shipping containers and that Major Vance of the Manhattan Project was going to test it, the American authorities have not been forthcoming.

The Ten Cases of Uranium Oxide

It will be recalled that the Magic decrypts for 1943 and 1944/45 show Japan requesting from Germany “a quantity of uranium oxide” in connection with their atomic research into the fissile isotopes including plutonium.

What is “uranium oxide”? Generally speaking, after the ore is mined, the crude concentrate know as Yellow Cake is recovered by leaching followed by solvent extraction and roasting. The material assays at between 60%-90% uranium oxide. It is poisonous, but not radioactive.

The German Army seized over 1000 tonnes of uranium oxide at Oolen in Belgium in May 1940. It was stored in wooden barrels each containing about 500 kilos. Where a barrel was damaged, the uranium oxide was repacked in a stout paper bag secured at the neck by a knotted wire. To consign this sort of material in gold-lined cylinders makes no sense unless it is radioactive in some way and handlers need biological shielding from the effects.

Experiments can be performed on uranium oxide in sub-critical reactors, and it had been Professor Harteck’s idea in 1940 to use about 30 tonnes of uranium oxide to build a rudimentary low temperature nuclear reactor, and in either case some level of biological shielding would be required if the spent material was being shipped.

Gold-lined containers would be used where it was necessary to absorb fission fragments, emissions of gamma radiation or neutron radiation, or a combination of all three. Alpha and beta radiation is easily stopped by a 7mm thickness of aluminium or perspex.

What sense can be made of the fact that the ten cases of uranium oxide were stowed in a secure steel tube upright through the hull casing of the submarine and yet still leaked so much radioactivity that the forward part of the boat gave uniform Geiger counter readings over its entire surface? Men lived for months in close proximity to this radioactive contamination, yet none complained of radiation sickness. How was this to be explained?

Lt Colonel Richard Thurston, a former member of the Manhattan Project radiological team, supplied the answer137: the radiation could not have been gamma radiation. What occurred to him was that all the reported conditions could only be met if the substance detected was radon gas, which is notoriously difficult to contain. It would seep through the containers and steel tubes and adhere to exposed surfaces but not be particularly dangerous to humans.

Radon gas would imply the presence within the containers of radium in some form. A radium-beryllium source within a small sphere of heavy water at the centre of uranium oxide in a gold-lined cylinder would amount to a sub-reactor in miniature and meet the request of the Japanese for “a quantity of uranium oxide” in connection with their atomic research into the fissile isotopes including plutonium.

Pfaff’s warning that the material must be handled like crude TNT indicates that the same precautions apply to the material as for the most unstable explosive. This is because the substance within the small cylinders becomes sensitive and dangerous on exposure to air. If these gold-lined cylinders were miniature sub-reactors, then the following dangers would present themselves when the cylinders were opened:

(1) Plutonium particles from the irradiated uranium oxide would rise into the atmosphere. The inhalation or ingestion of 1mg of plutonium will result in the lingering death of the victim within weeks and even a microgram results in a later high susceptibility to pulmonary cancer.

(2) Dangerous neutron radiation would be emitted from the reaction of the radium-beryllium source as would gamma and corpuscular radiation from the products of fission decay in the uranium powder.

This was why it was so dangerous to open the cylinders. The use of a gold lining in addition to the lead shielding is the clearest possible indication that a reaction process was continuing in the cylinders, and Professor Nishina of the Imperial Japanese Army nuclear project would have received, on the arrival of U-234 in Tokyo, ten cases of uranium oxide containing precisely what had been requested in the Magic signals.

The cylinders though dangerous were basically nothing more than an elementary research material for the laboratory and would not have led the Americans to panic and suspect that Japan was on the verge of developing an atom bomb.

The Eighty Small Heavy Cases

To the exclusion of everything else aboard U-234, these eighty small containers in the custody of Major Vance, the tests performed on them by the Manhattan Project, and their ultimate disposal, are the obvious basis for further research.

They were removed from their loading tube at the end of May. Aboard the submarine there was no mystery as to where they had been stowed for probably half the crew had worked on the loading that day in February and the contents excited interest by their unusual weight. Portentous omens have been read into the meaning of the symbol “U-235” painted by Tomonaga on the wrapping of each of the small containers, but probably it served merely to identify the consignment as being uranium. I have no idea what the correct chemical formula is for natural uranium enriched with plutonium isotopes, and I doubt if Tomonaga would have known either: if on the other hand the cases actually had contained the isotope, it is unlikely in the extreme that the fact would have been advertised to all and sundry on the quayside: the Japanese, past masters of deception, even disguised their initial interest in uranium as being a sort of “catalyst”.

The New Hampshire evening paper Portsmouth Herald announced in the week following the capture of U-234 that the submarine had been “headed for Japan for the purpose of aiding Japan’s air war with rocket and jet planes and other German V-type bombs”. This is the first reference from a source well-connected to the US Navy to a “V-type bomb” and a “jet plane”, neither of which feature on the Unloading Manifest. And in June the same newspaper claimed that there had been sufficient uranium aboard U-234 to produce an explosion to eradicate all of Portsmouth and its surrounding suburbs from the face of the earth. Newspaper reports must, of course, not be awarded too much credence as historical documents, but they are nevertheless useful pointers. The Portsmouth Herald knew about a “jet plane” aboard U-234 which is claimed by the German crew to have been shipped, but as to which the official record on the American side is silent. And to what extent before the first Trinity test in July 1945 was the effect of fantastic explosives openly discussed, and where did the idea come from that such a substance was aboard the German submarine?

Lt-Col John Lansdale, chief of atomic security and intelligence for the Manhattan Project, admitted that he handled the disposal of the small cases aboard U-234.138 He recalled that the American military authorities reacted with panic when they discovered the cargo aboard the U-boat. Lansdale went on to say that the German material was sent to Oak Ridge where the isotopes were separated and put into the pot of material used to make America’s first atom bombs.

Obviously Lansdale did not mean U²³⁵ isotopes here since they are the final result of the separation process. The only fissile isotopes which can be separated from irradiated uranium are the range of plutonium isotopes from fissioned material bred in a working reactor or sub-reactor assembly. This would have made them panic, particularly if they knew how a small-scale German atom bomb was constructed. All that was needed for detonation would be an effective implosion fuse.

Natural uranium powder in its natural state is highly pyrophorous and ignites spontaneously on contact with air, but this would not require it to be packed in eighty small radioisotope containers. It is, however, the manner in which plutonium-enriched uranium powder would need to be transported.

The thickness of lead required to reduce the initial intensity of gamma radiation by a factor of ten is 1.8 inches. The thickness of the walls, lid and base of the lead containers described by Hirschfeld would have provided an interior volume for each container sufficient for about 19 kilos of uranium metal powder, multiply by eighty = 1520 kilos: divide by 750 kilos = enough for two small-scale atom bombs.

The Implosion Fuses

A final twist to the U-234 story has been suggested.139 The German small-yield device could not have been properly detonated without an effective implosion fuse. For eighteen months the scientists at Los Alamos had failed to develop such a fuse. In October 1944 Robert Oppenheimer created a three-man committee to look into the problem. Luis Alvarez was on this team and became one of the heroes of the American A-bomb story when he solved it in the final days before the Trinity test at Alamogordo in July 1945.

The need was for a fusing system that could fire multiple detonators simultaneously. Harlow Russ, who worked on the plutonium bomb team, stated in his book Project Alberta that improvements were made to the detonator at the last moment. A new type of implosion fuse suddenly becoming available to the Manhattan Project gave a result four times better than expected at the Trinity A-test.

But did the real impetus for this success come from Luis Alvarez or German technology? Germany could not have detonated small-scale atom bombs without the most superior implosion fuse. According to the CI0S-BI0S/FIAT 20 report published by the US authorities in October 1946, by May 1945 Germany already had every kind of fuse known to the Americans –; “and then some”. Professor Heinz Schlicke, one of the passengers aboard U-234, was an expert in fuse technology. Infra-red proximity fuses were discovered to be aboard U-234 on 24 May 1945, apparently as a result of the interrogation of Dr Schlicke in which he mentioned that he had fuses which worked on the principles that govern light. A memorandum by Jack H. Alberti dated 24 May 1945 states:

“Dr Schlicke knows about the infra-red proximity fuses which are contained in some of these packages. Dr Schlicke knows how to handle them and is willing to do so.”

Schlicke and two others were then flown to Portsmouth NH to retrieve the fuses. It is not suggested that these were the fuses used to explode the American plutonium bomb, but rather confirms that Schlicke knew more about fuses than the Manhattan Project did. From a transcript of a lecture given by Dr Schlicke to the Navy Department in July 1945, there seems to have been a close cooperation for some reason between Dr Schlicke and Luis Alvarez. And it is in the fact that the technological side of the Manhattan Project failed them that the real weakness of the American project is exposed.