Ollie felt he needed to clear his head and strolled through the famous Botanical Gardens in search of the renowned Goethe's palm tree that he hoped would give him inspiration as it had to Goethe when he wrote about plant metamorphosis. He had seen many palm trees growing naturally outdoors in Syria and Iraq where they were very common and served as an important source of food, so he was disappointed to see that the tree was situated in a greenhouse inside the Ortus Sphearicus and not out in the open as he had expected. Nevertheless he was thankful for the serenity the garden induced. He hoped that the combination of the racist Doctor Jay and the Catalan independence supporter Prof. Modena would not lead political altercations, but there was little he could do trying to re-educate these two grown men with huge egos.
The proprietor of the restaurant was glad to have three tourists dining on a quiet Thursday evening in mid-winter, especially as they ordered two bottles of his most expensive wine. Doctor Jay gave Ollie his shopping list and the three of them talked quietly about it. Ollie glanced at the list and expressed his opinion that there were only two items that would be difficult to purchase: the special explosives and the 32 detonators needed for simultaneously timing the implosion. He realized those would only be needed at the very final stage of the construction of the device but was very worried about their acquisition. Doctor Jay said that almost anything could be bought for the proper price on the nuclear black market or in China. Ollie noted that since the network of the Pakistani AQ Khan had been practically closed down and the Chinese were extremely careful about exporting items of this type, the best option was to discretely approach the North Koreans and offer them a large sum of hard currency with which they could buy food for the masses, or what was more likely, increase the foreign bank accounts of the country's elite leaders. The scientists had no idea how to contact the North Koreans so Ollie said that he would be responsible for obtaining these materials, while the lab's administrator could take care of acquiring all the other items, including those that were considered as "dual-use" and their sales were somewhat restricted. Jay and Ollie returned to their hotel and Modena to his small room above the laboratory. Arrangements were made for Dr. Jay to move to the dormitory above the laboratory as a long stay at the hotel would raise suspicion.
David arrived at Vienna airport on the evening flight and once again Orna met him at the airport and they exchanged a short hug and warm welcome kiss and immediately headed to the same café where Eugene and Vassilly were already waiting. Both had grim looks on their faces and appeared to be deep in thought so they barely acknowledged the presence of the two young Israelis. Eugene started speaking excitedly even before Orna and David were seated and summarized the insights he had gained during his discussions with the scientists from the national laboratories. He said that he had asked them if theoretically it was possible to produce U-233 through bombardment of thorium with gamma radiation. Their unanimous spontaneous reply was that it was not possible but after giving the matter some thought they said that in theory if the gamma radiation could somehow induce generation of neutrons they may be captured by thorium atoms and produce uranium-233. They were skeptical if this would be practical because of several physical considerations including the efficiency of neutron generation by this method, the energy of these neutrons and the uncertainty in the capture cross section of these neutrons by thorium. In conclusion, the scientists did not rule out the possibility that this could be done and also raised a question about the availability of suitable gamma radiation sources. Vassilly said that the Russian scientists with whom he consulted agreed with these observations and conclusions. He also stated that one of the experts he had talked to, took him aside during a tea break and in confidence told him that he had been one of the reviewers of the manuscript submitted to the journal (he did not know that it was written by Professor Modena) and was familiar with the idea. He said that at the time he thought the whole scheme was in contradiction of basic physical principles and ridiculed the idea, recommending rejection of the manuscript on those grounds, but he now had second thoughts that it may not be impossible to generate neutrons using gamma irradiation of thorium.
Eugene then said that he had obtained access to declassified files from the Manhattan project that described the efforts of the US Atomic Energy Commission to produce and test uranium-233 as the "fuel", or fissile material, in a fission atomic bomb. He said that the theoretical idea of producing U-233 from thorium in a nuclear pile (as a nuclear reactor was then called) was first proposed as early as May, 1943 but not seriously investigated until after the war. By 1950 about 300 g of U-233 were produced at the Hanford reactors in Washington State and separated from thorium at Oak Ridge, Tennessee by a chemical process that was called Thorex that he said was quite similar to the well-known Purex process used to separate plutonium from irradiated uranium fuel. After a long debate within the US-AEC, an actual test of a bomb core consisting of a mixture of plutonium and U-233 was carried out only in 1955 as part of the TEAPOT Operation and the explosion had a yield approximating the atomic bomb dropped on Nagasaki. However, by the late 1950s the US increased the production of plutonium and enriched uranium sharply curtailing the requirement for U-233, though a few more tests were carried out until completely abandoned in 1968. Vassilly smiled when he heard this detailed account and proudly stated that the Soviet Union had tested a primary core containing a blend of U-233 and U-235 even before the 1955 US test. When David asked them if configuration of a bomb based on U-233 was more complicated than using the more standard U-235 or plutonium both scientists agreed that there were some differences but on the whole the technical details were the same.
David was not really surprised by these reports as he had already discussed this again with Professor Kaufman and with experts from the Israeli Atomic Energy Commission. He felt that it was time for the three of them to jointly write a memo and to inform their respective governments about the potential of terrorist groups clandestinely producing fissile materials that could be used in an improvised nuclear device. He suggested that this should not be restricted to their three countries but that the information should also be passed on to the United Kingdom and France. He also proposed that they set up a task force to locate Professor Modena and his whereabouts as well as find out where all the radiation sources were shipped to and if there was a clandestine laboratory in which work for producing U-233 was being carried out. Eugene expressed his concern that if the IAEA got word of this it would disclose the plot and the source of information thus driving the perpetrators into deep cover. They deliberated whether Spain should be included in the loop as Professor Modena was officially a Spanish citizen but were afraid that he would be warned by some sympathizer of Catalonia in the Spanish establishment. Vassilly was not too happy about informing the UK and France but accepted the proposal to include them in the task force.
The participants knew that they could not really make these decisions without approval from their governments as they were not high enough on the totem pole. However, they were all aware of the historic precedent set by the letter sent by Albert Einstein and Leo Szilard to president Franklin Delano Roosevelt on August 2, 1939, which eventually set in motion the Manhattan Project that produced the first atomic bombs. They could only hope that their memo would produce similar results. In their memo they tried to explain the difference between an improvised nuclear device (IND) and a radiological dispersive device (RDD) in a simple language that would be understood even by politicians.