Uranium project

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The whole of the work in the German Reich during the Second World War in which the nuclear fission discovered in 1938 was to be made technically usable is referred to as the uranium project . The main aim was to assess the possibilities for building a nuclear weapon and to build a demonstration nuclear reactor . Despite some success, the scientists did not succeed in producing a self-sustaining nuclear chain reaction in such a reactor until the end of the war . There is no evidence that minor nuclear tests were undertaken towards the end of the war, as is occasionally claimed.

In the course of the war, the industrial production facilities were destroyed by the Allies. Towards the end of the war, eight scientists involved in the uranium project were caught by the Alsos mission and interned in Farm Hall ( England ). Others, like Manfred von Ardenne , were arrested by Soviet forces. The experimental set-ups of the uranium project were dismantled and the materials confiscated. The scientists were released after the war and returned to Germany , some of them after years of forced labor in the Soviet Union .

Involved

The main scientists involved in the uranium project were:

Other indirectly involved institutions were the Kaiser Wilhelm Institute for Chemistry ( Otto Hahn , Max von Laue and Horst Korsching ) in Berlin-Dahlem, the research laboratory for electron physics of Manfred von Ardenne in Berlin-Lichterfelde, and the universities of Heidelberg ( Walther Bothe and Wolfgang Gentner ) and Göttingen ( Wilhelm Hanle and Georg Joos ).

From the industrial side, the following were involved in the uranium project:

prehistory

Experimental set-up by Otto Hahn and Fritz Straßmann during the discovery of nuclear fission in the Deutsches Museum in Munich.

In 1934, the Italian physicist Enrico Fermi at the Sapienza University of Rome irradiated chemical elements, including uranium , with neutrons and thereby obtained artificial radioactive elements through a nuclear reaction . In the following years, the Austrian physicist Lise Meitner and the German chemist Otto Hahn checked Fermi's experiments at the Kaiser Wilhelm Institute for Chemistry in Berlin-Dahlem and believed to have detected some new elements, so-called transuranics , in the following years .

Lise Meitner had to leave Germany in July 1938 because of her Jewish descent and, thanks to Otto Hahn's help, was able to emigrate to Sweden via Holland . Hahn continued to experiment with his assistant Fritz Straßmann in Berlin. On December 17, 1938 they succeeded for the first time in the detection of a neutron-induced nuclear fission of uranium on the basis of barium isotopes , which were formed as fission products when uranium was bombarded with neutrons . In a letter to Lise Meitner, who wanted to celebrate Christmas with her nephew Otto Frisch near Gothenburg , Hahn described his decisive experiments two days later and spoke for the first time of the uranium nucleus bursting . He published his results in an essay that appeared in the journal Naturwissenschaften on January 6, 1939 . Another article by Hahn, in which he referred to the possibility of generating energy with the help of a chain reaction , followed on February 10, 1939.

In January 1939 Meitner and Frisch succeeded in interpreting the results for the first time in terms of nuclear physics. In fact, the uranium atoms had "burst" into smaller components, as Otto Hahn had initially formulated. You submitted a brief note to Nature on January 16, 1939 , which appeared on February 11, 1939. Frisch informed the Danish quantum physicist Niels Bohr , who made Hahn's discovery known on January 26, 1939 at the fifth conference for theoretical physics in Washington, DC . Several American physicists were able to repeat Hahn's results immediately afterwards. Various American daily newspapers then reported on their results.

The French physicist Frédéric Joliot-Curie was also able to repeat Hahn's experiments in March 1939 at the Collège de France in Paris. He found that every time uranium splits, two to three neutrons are released, creating the possibility of a chain reaction in which these new neutrons split other uranium nuclei. Since the fission of a uranium nucleus releases a relatively large amount of energy, the possibility of technical use of nuclear fission as an energy source or as a weapon was known to the physicists of the western world since the spring of 1939.

Foundation of the uranium association

Kurt Diebner
Werner Heisenberg , 1933

In April 1939, the Göttingen physicist Wilhelm Hanle gave a lecture on the peaceful use of nuclear fission in a "uranium machine", ie a nuclear reactor. His colleague Georg Joos heard this lecture and reported on April 22, 1939 in the Reich Ministry of Education together with Hanle on the technical, but also the military possibilities of nuclear fission. The ministry reacted quickly, and on April 29, 1939 , an expert conference was convened in the Reich Ministry of Education in Berlin under the leadership of Abraham Esau , then President of the Physikalisch-Technische Reichsanstalt . In addition to Hanle and Joos, the participants in the conference were the physicists Walther Bothe , Robert Döpel , Hans Geiger , Wolfgang Gentner and Gerhard Hoffmann . Hahn was absent from this meeting, he was even reprimanded in absentia for the publication of his decisive discovery. The assembled physicists made the following resolutions at this conference:

  • the production of a nuclear reactor (called "uranium burner"),
  • securing all uranium supplies in Germany and
  • the merging of the leading German nuclear physicists into one research group.

This group was formally called the “Working Group for Nuclear Physics”, informally it was known as the first “Uranium Association”. The research was to be advanced primarily at the Physikalisch-Technische Reichsanstalt in Berlin and at the University of Göttingen .

At the same time, however, the Army High Command was preparing a corresponding research project. The Hamburg physical chemist Paul Harteck and his assistant Wilhelm Groth wrote to the Reichswehr Ministry on April 24, 1939 that the latest developments in nuclear physics could make an explosive possible that would far exceed the effectiveness of conventional explosives. This letter ultimately landed with Kurt Diebner , the Army specialist in explosives and nuclear physics. He immediately requested funds from the army in order to be able to set up a test laboratory in Kummersdorf, south of Berlin. Diebner was then appointed head of a newly established nuclear research department in the Heereswaffenamt . At the same time, the Army Command ordered the Physikalisch-Technische Reichsanstalt to stop its uranium research attempts immediately. From then on, all statements about uranium reactors and uranium weapons were considered secret.

In September 1939, immediately after the start of the war, Germany's leading nuclear physicists were summoned to the Kaiser Wilhelm Institute for Physics in Berlin . Together with nuclear physicist Erich Bagge, Diebner drafted a program on September 20, 1939 with the title “Preparatory work plan for starting experiments for the utilization of nuclear fission”, which was supposed to coordinate the research work. The aim of the program was to achieve a controlled chain reaction in a uranium burner. Only a few physicists followed the call to Berlin, but all of them agreed to work on the project. Among those who moved to Berlin were Carl Friedrich von Weizsäcker and Karl Wirtz . In addition to her curiosity, she said that the exemption from military service was the reason for the move.

The then director of the Kaiser Wilhelm Institute, the Dutch physicist Peter Debye , was advised to accept or abdicate German citizenship. Debye refused, however, and did not return to Germany after a stay in the United States in January 1940. The Heereswaffenamt suggested Diebner as his successor, but this was rejected by the Kaiser Wilhelm Society . Diebner was then installed as acting head for the duration of Debye's absence. In addition, the theoretical physicist and Nobel Prize winner Werner Heisenberg was brought into the institute as a consultant. Some time later, on October 1, 1942, Heisenberg was appointed the new head of the institute.

The results of the research were published in the nuclear physics research reports , an internal publication series that was classified as top secret. The research reports had a very limited distribution, not even the authors themselves were allowed to keep copies.

Selection of moderator substance

In a report to the Heereswaffenamt dated December 6, 1939, Heisenberg described the possibility of technical energy generation with the help of uranium fission in more detail. He showed that one could use natural uranium if one slows down the fast neutrons released during the fission with another substance (the moderator , then called braking substance ) , but only absorbs them slightly. Either heavy water or particularly pure carbon can be used for this purpose . At several research institutes, various substances have been investigated as braking substances for a possible uranium reactor. Walter Bothe tested graphite in Heidelberg , while Heisenberg himself calculated the values ​​for heavy water.

Bothe came to the conclusion that graphite was not well suited because of its high neutron absorption, but could only just be used if necessary. His measurement results were later recognized as incorrect; he had used graphite, which was contaminated with the strong neutron absorbers boron and cadmium . In contrast, Heisenberg found out that heavy water had an even better effect than originally assumed. So the decision was made in favor of heavy water.

In the Manhattan Project of the USA, which started three years later, graphite was used in reactor development from the start because it was easier to obtain (see Chicago Pile ).

Material procurement

Several tons of both high-purity uranium and very pure heavy water were required to operate a uranium reactor. At the time, both materials were difficult to obtain in large quantities.

uranium

Uranium factory in Katanga , Belgian Congo, 1917

The Heereswaffenamt initially demanded the delivery of all uranium supplies to the Physikalisch-Technische Reichsanstalt. Esau was reluctant to comply with this request after the research area had already been taken from him. In addition, the Berliner Auergesellschaft was commissioned to deliver several tons of uranium oxide . The uranium came from the uranium mines in Sankt Joachimsthal , which were exploited by the Auergesellschaft after the German annexation of the Sudetenland in 1938. Within a few weeks, the company set up a plant in Oranienburg with a monthly production capacity of around one ton of uranium oxide. The first delivery to the Heereswaffenamt took place at the beginning of 1940.

At the end of May, during the occupation of Belgium, a large part of the uranium supplies of the Belgian company Union Minière du Haut Katanga , which imported uranium ore from the Belgian Congo , was secured.

During the following five years, the German troops transported 3,500 tons of uranium compounds from Belgium to the Friedrichshall potash plant near Leopoldshall . The Auergesellschaft met its further uranium requirements from these reserves until the end of the war.

Heavy water

Chemical and hydropower plant Vemork by Norsk Hydro near Rjukan with heavy water production plant in the front building, 1935

At the beginning of the war, only the Norwegian Hydroelectric Company (Norsk Hydro) produced significant quantities of heavy water at a plant in Vemork near Rjukan . The plant was mainly used for the production of artificial fertilizers and only supplied heavy water as a by-product . In the years 1934 to 1938, the plant had only produced 40 kilograms of water, at the end of 1939 the monthly production was a maximum of ten kilograms.

Since setting up our own heavy water production in Germany seemed too complex, a delegation from IG Farben contacted Norsk Hydro with the aim of purchasing the entire supply of 185 kilograms of heavy water. The French secret service , however, got ahead of the German negotiators and agreed with the company management to bring all the heavy water to Paris to Frédéric Joliot-Curie , who carried out his own experiments there to split uranium.

In April 1940 the German army occupied Norway and marched into Rjukan on May 3, 1940. The only heavy water factory in the world fell undamaged into German hands , but it was found that the entire supply of heavy water had already been given up. This was not only disappointing for the army command , but above all a warning that the Allies were also interested in the use of nuclear fission. As a result, heavy water production in Vemork was increased to 1,500 kilograms per year. As a result, the Allies, together with resistance fighters, undertook a series of military operations to stop production.

First try

Paul Harteck , 1948

In early 1940, in addition to Werner Heisenberg at the Kaiser Wilhelm Institute in Berlin and Kurt Diebner in Kummersdorf , Paul Harteck at the University of Hamburg also worked on a uranium pile. At that time, the uranium and heavy water supplies in Germany were still very limited and a fight for resources began between the institutions. When Heisenberg asked the Heereswaffenamt for 500 to 1000 kilograms of uranium oxide in April 1940, Diebner wrote back to him that he should come to an agreement with Harteck, who had just asked for 100 to 300 kilograms himself. Harteck wanted to embed uranium oxide in solid carbon dioxide ( dry ice ) in a test reactor in his institute cellar, which he was to receive from the Leuna works of IG Farben in Merseburg . Harteck was in a hurry because the carbon dioxide block only lasted a week, and he asked Heisenberg to let him have the uranium oxide until he had finished his experiment. At the end of May, 50 kilograms of uranium oxide finally arrived in Hamburg, considerably less than Harteck had hoped for. Together with an additional delivery from Auergesellschaft, he had a total of only 185 kilograms of uranium oxide available - far too little to cause a nuclear chain reaction.

Paris fell in mid-June 1940 and shortly afterwards the head of the research department of the Army Weapons Office, Erich Schumann and Kurt Diebner, arrived there to visit Joliot-Curie in his laboratory at the Collège de France. The French physicist had not fled to London like his colleagues, and Diebner was able to persuade him to continue working on non-military projects. He promised him that his semi-finished cyclotron could then be completed. A Paris working group led by Wolfgang Gentner began work in July .

At the same time, in July 1940, a laboratory was set up on the premises of the Kaiser Wilhelm Institute for Biology in Berlin-Dahlem, in which Germany's first uranium reactor was to be located. In order to keep unwanted visitors away, the building was given the chilling alias "Virus House". Construction was completed in the autumn of 1940 and shortly afterwards the Berlin researchers began building the nuclear reactor.

There is a retrospective, probably around 1950, written by Heisenberg and Wirtz summarizing all reactor tests of the uranium project.

Paths to the atomic bomb

Manfred von Ardenne , 1933

In principle, it was clear to the German physicists that nuclear fission would also make it possible to build an atomic bomb, called the “uranium bomb” by scientists, but not with natural uranium.

Uranium-235

One possibility would have been to increase the proportion of the fissile uranium isotope 235 U, which is only 0.7% in natural uranium, correspondingly strong. Work on this was carried out by Wilhelm Walcher in Kiel and the Josef Mattauch group at the Kaiser Wilhelm Institute for Chemistry. Physicist Heinz Ewald from the Kaiser Wilhelm Institute for Chemistry made a proposal for efficient uranium enrichment in 1942. He proposed an "atomic conversion system", a type of mass spectrometer in which ionized uranium atoms are accelerated in an electric field and then separated in a ring-shaped magnetic field based on the differences in atomic mass (see Fig. 97 in), i.e. in the same way as in the American calutrons .

Manfred von Ardenne , who headed the research laboratory for electron physics in Berlin-Lichterfelde , took up the idea and built a prototype. He was supported in this project by the head of the Reich Ministry of Post, Wilhelm Ohnesorge . This separation system is similar to the cyclotron, which was finally completed in 1943 near Miersdorf with funds from the Reichspost . A ring bunker was found on the site of an air force base near Bad Saarow , which corresponds to the cyclotron hall in Miersdorf. It can only be guessed whether this plant contained a large-scale version of the isotope separator. In Germany, however, there never was a large-scale isotope separation of uranium, as in the USA with the hundreds of calutrons as part of the Manhattan project .

Plutonium-239

Also from the Research Institute of Ardenne came by physicist Fritz Houtermans the proposal in a uranium reactor from the much more common uranium isotope 238 U is also easily fissionable plutonium isotope 239 to Pu erbrüten . He summarized his theories in a secret research report "On the question of the initiation of nuclear chain reactions". Although this report was accessible to government agencies and some physicists organized in the Uranium Association, it was ignored. Carl Friedrich von Weizsäcker reported to the Heereswaffenamt about the possibility that 239 Pu could be used “to build very small machines”, “as explosives” and “to convert other elements”. Weizsäcker's draft patent is known from the spring of 1941. In addition to claims on nuclear reactors, it includes a “method for the explosive generation of energy and neutrons” that “is brought to a place in such quantities, e.g. B. in a bomb ". However, this draft did not exist and was revised and expanded within the Uranium Association working group at the Kaiser Wilhelm Institute . The expanded list of patent claims for a “uranium machine” from August 1941 no longer gives any indication of a bomb.

Crisis of conscience

Werner Heisenberg (left) in conversation with Niels Bohr

The discussion about the proposals for the development of a uranium bomb was slow. Some leading German researchers have now shown scruples about the extent to which they should get involved in the uranium project at all. In the week from September 15 to 21, 1941, Werner Heisenberg visited his former mentor Niels Bohr in Copenhagen at the suggestion and mediation of Carl Friedrich von Weizsäcker . There are different statements about the intention of the trip and the course of the conversation. In any case, the conversation turned out to be unpleasant for both sides. According to a version published by Spiegel in 1967 , Heisenberg Bohr asked whether a physicist had the moral right to work on an atomic bomb in times of war. Bohr responded with the counter-question as to whether a military use of nuclear fission was at all possible in Heisenberg's view. Heisenberg replied that he recognized the possibility. He suggested that all scientists in the world could agree to refrain from working on an atomic bomb. To Heisenberg's dismay, Bohr replied that military research by physicists was inevitable and correct. Apparently Bohr feared that Germany was on the threshold of building an atomic bomb and suspected that Heisenberg's proposal was only intended to slow down America's lead in nuclear physics. Heisenberg, on the other hand, felt abandoned by Bohr and had to return to Germany without having achieved anything.

Michael Frayn's play Copenhagen is about this meeting.

Further reactor tests

At the end of 1941, the German war economy came under pressure after the now very stressful Russian campaign . The uranium project made no promise of any application in the foreseeable future. Therefore, the Heereswaffenamt decided to release the project from the control of the army and leave it to the Reich Research Council under the supervision of the Reich Ministry of Education. The Reich Research Council passed the research project on to its physics department, and so the uranium project ended up again at Abraham Esau at the turn of 1941/42 , from whom it had been withdrawn at the beginning of the war. A year later, Esau was even appointed “Agent for Nuclear Physics” and from then on he was able to control all physical research groups. Until then, however, German research into building a nuclear reactor had made little progress. The bottleneck of the project continued to be the lack of heavy water and of highly enriched uranium, of which only a small amount could be extracted.

Since the materials produced so far were not sufficient and the plants abroad were vulnerable to attacks, attempts were made to boost their production in Germany as well. The construction of a heavy water system in Merseburg was agreed with the Leunawerke . In return, Leuna should be informed about the current state of research on energy generation from uranium. The Degussa in Frankfurt was henceforth procure uranium metal. The first deliveries of uranium went to the physical university institutes in Leipzig so that the world's first uranium burner could finally be set in motion. It was designed by Werner Heisenberg, the theorist, and realized together with the experimental physicist Robert Döpel.

In the summer of 1942 Robert Döpel succeeded in demonstrating a neutron multiplication in a spherical layer arrangement of uranium powder and heavy water (experiment L IV), even before Enrico Fermi's team in Chicago. The demonstration of neutron multiplication in the USA was achieved in late July 1942 by Enrico Fermi, who and his nuclear reactor team soon overtook the Germans. Fermi, who had a “ unique dual talent for theoretical and experimental work ”, had been working on the problem since the spring of 1939. He spoke to Heisenberg on his last visit to the USA before the approaching war about the dangers that both were aware of.

On June 4, 1942, Heisenberg and the leading scientists of the uranium project were summoned to a secret meeting in Berlin to report to Albert Speer , the new Reich Minister for Armaments and Ammunition, and to provide him with a basis for decision-making for the future of German uranium research. When asked how big a uranium bomb would be, the effect of which would be sufficient to destroy a large city, Heisenberg replied: “As big as a pineapple”, probably referring only to the actual explosive charge. The army command was impressed, but also had doubts. Heisenberg emphasized that such a bomb could not be developed within a few months and that it was currently economically impossible to manufacture. The construction of a nuclear reactor, on the other hand, would be of great economic and military importance, especially for the period after the war. As a result, the uranium project was not discontinued, but it was also not given any further support. At least Speer approved the construction of a bunker on the grounds of the Kaiser Wilhelm Institute for Physics in Berlin, in which the first large German uranium pile was to be built.

Three weeks later, a serious accident occurred in the Leipzig research reactor. For the “uranium machine”, 750 kilograms of uranium powder and 140 kilograms of water were filled into two aluminum hemispheres that were firmly screwed together and sunk into a water tank. The experiment seemed to be successful, because more neutrons were generated than used, which was finally confirmed by previous experiments. The ball hung like this in the water container for months until hydrogen bubbles suddenly escaped from it on June 23, 1942 . As a result, the ball warmed up, it was removed from the container, but after an unsuccessful attempt to open it it was quickly sunk back into the water container. The ball continued to heat up until the water began to boil towards evening. A little later the bullet exploded and set the room on fire with burning uranium without harming the people present (including Heisenberg and the Döpel couple). Döpel's first attempts to extinguish the fire were largely unsuccessful. The fire brigade was ultimately able to put out the fire under his guidance, but only a lot of uranium oxide sludge was left of the fissile material. No nuclear chain reaction had taken place; instead, water had seeped into the uranium layer and hydrogen and, together with atmospheric oxygen, oxyhydrogen gas had formed, which exploded with the uranium . - This accident was the first in a long series of incidents in nuclear facilities, in which explosive gases (oxyhydrogen or water gas ) were formed and ignited with air from water vapor and superheated metal (here uranium powder) or graphite (as in Chernobyl ) .

In order to rule out similar incidents in the uranium project, it was decided to only use uranium in the solid form of cast uranium in future experiments. Heisenberg calculated that around ten tons of cast uranium and around five tons of heavy water would be needed to make the first critical chain reaction possible. While Heisenberg experimented with uranium plates in Berlin-Dahlem, Diebner in Kummersdorf relied on uranium cubes. The two working groups did not cooperate, however, but worked against each other. When Diebner achieved unexpectedly good results with uranium cubes in frozen heavy water, Heisenberg refused him recognition and continued to insist on the use of uranium plates in liquid heavy water, which is more favorable for calculations.

Allied attacks on supplies

The “Hydro” ferry, 1925

In the meantime, the Allies had suspected that the German researchers were working intensively on a uranium bomb. On the night of February 27-28, 1943, as part of the Norwegian heavy water sabotage during Operation Gunnerside, eight Norwegian resistance fighters succeeded in breaking into the heavy water works of Norsk Hydro and 18 electrolysis cells with which the heavy water was separated . to be destroyed by explosive devices. In addition, half a ton of heavy water that had already been produced was destroyed. By April 1943, the damage caused by the Germans had been repaired to some extent, but the uranium project was dealt a heavy blow.

On November 16, 1943, the Norsk Hydro heavy water factory was finally destroyed by British bomber forces. The heavy water concentration system in the basement remained intact, but the power station had been hit, which meant that the entire factory could no longer work. The Germans therefore tried to transport the remaining, partially concentrated heavy water by train for further processing in the meanwhile almost completed facility of the Leunawerke in Germany. To exit Rjukan, the transport had with the railway ferry lake "Hydro" Tinnsjå cross. The Allies learned of the Germans' plans and the ferry was sunk by Norwegian resistance fighters on February 20, 1944. Some of the only partially filled heavy water barrels were rescued by the Germans, but the majority sank to the bottom of the lake.

A little later, a British air raid on Frankfurt am Main destroyed the Degussa works and their uranium production facilities. In August 1944 the Leunawerke were also hit and IG Farben subsequently showed no further interest in the production of heavy water. This brought the entire German uranium and heavy water production to a standstill in the summer of 1944. Overall, towards the end of the war, the German physicists had no more than 2.5 tons of water at their disposal, and it was questionable whether this amount would be sufficient to operate a uranium reactor.

Relocation of research to southern Germany

On October 23, 1943, Walther Gerlach was appointed head of the physics department in the Reich Research Council and thus head of the uranium project. At the turn of the year Gerlach also took over the position of authorized representative for nuclear physics from Esau, who had made himself unpopular with the management of the Kaiser Wilhelm Society and with Albert Speer. In the period that followed, Gerlach refused the funds available to him for research projects with military application areas, such as the uranium project or the particle accelerators that were now available, and instead used them primarily for basic research projects. On the other hand, he prevented the German physicists from being drafted into military service.

When the British Air Force began its attacks on Berlin in late autumn 1943, parts of the Kaiser Wilhelm Institute for Physics were relocated to Hechingen in southwest Germany. A little later, the Kaiser Wilhelm Institute for Chemistry under Otto Hahn moved to nearby Tailfingen . The other working groups of the uranium project also moved to other parts of Germany. Diebner relocated his test laboratory to Stadtilm in Thuringia, Harteck and Groth moved their new ultracentrifuge first to Freiburg , then to Celle .

Last attempts

Dismantling of the Haigerloch research reactor in 1945

However, some physicists, including Heisenberg, Bothe and Wirtz, initially stayed in Berlin and prepared the construction of the large uranium reactor in the almost completed bunker. Towards the end of 1944, Wirtz was able to equip the uranium pile with 1.25 tons of uranium and 1.5 tons of heavy water. This experiment showed a significant increase in the neutrons supplied from a radioactive neutron source. Wirtz was preparing a larger experiment. After the Red Army had crossed the Oder near Kienitz on January 30, 1945 , immediately afterwards built a bridgehead and their advance on Berlin was foreseeable, Gerlach gave the order to leave Berlin. The uranium and the heavy water were shipped to Diebner in Stadtilm, and the physicists fled to Hechingen.

The last of a long series of experiments was to be carried out in a rock cellar in Haigerloch near Hechingen (Hohenzollern). The materials were then transported from Stadtilm to Haigerloch by truck. At the end of February 1945, the Haigerloch research reactor with 1.5 tons of uranium and the same amount of heavy water was put into operation. However, the materials were not sufficient to make the reactor critical. Heisenberg tried to get the last supplies of uranium and heavy water from Stadtilm, but the delivery no longer arrived.

The US had long feared that the Germans were working on a uranium bomb, and in 1943 it had set up the military Alsos mission . Their goal was to explore the status of the German uranium project, to stop the research and to get hold of the physicist. On April 23, 1945, the Alsos mission finally reached Haigerloch. The reactor was destroyed and all materials and research reports were confiscated and taken to the United States for analysis. The German scientists involved in the uranium project were arrested. Bagge, von Weizsäcker and Wirtz were caught in Hechingen, Heisenberg in his native Urfeld, Gerlach and Diebner in Munich and Harteck in Hamburg. In addition, Otto Hahn, Horst Korsching and Max von Laue were picked up in Tailfingen.

Internment in Farm Hall

The country estate Farm Hall in England

The elite of German atomic research were brought to the British country estate Farm Hall near Cambridge as part of Operation Epsilon . They spent the time in the idyllic brick building and the surrounding gardens with fistball, billiards, bridge and discussions. The scientists' conversations were bugged and recorded by the British military.

On August 6, 1945, the officer on duty at the internment camp, Major TH Rittner, received an order from London that his prisoners should listen to the radio at 6 p.m. Rittner was supposed to follow the men's reactions to the reports. Hahn, Heisenberg and Wirtz heard the news from the BBC in Rittner's office that evening that American scientists had made an atomic bomb and had already dropped it on a Japanese city .

The reactions of the three Germans were different. Wirtz said he was glad they didn't have the bomb themselves. Heisenberg thought the report was a "bluff" and initially doubted that a physical effect was involved. Otto Hahn was deeply shaken and felt responsible for the deaths of hundreds of thousands of Japanese. The 9 p.m. news revealed that a uranium atomic bomb with an explosive force of 20,000 tons of TNT equivalent had exploded over Hiroshima . In the discussion that followed, von Weizsäcker said it was terrible that the Americans did it and that he thought the action was madness. Heisenberg replied that this was probably the fastest way to end the war. Hahn saw himself confirmed in all of his fears which had tormented him since his discovery in December 1938. In the end, he was just happy that the Germans hadn't made it.

On November 18, 1945, during his internment, Hahn learned that he had been awarded the 1944 Nobel Prize in Chemistry for his 1938 discovery . On January 3, 1946, the ten scientists involved in the uranium project were finally released and returned to Germany.

Soviet atomic bomb project

As in the USA, around 300 German nuclear specialists and their families were brought to the Soviet Union after the Second World War . Systems of the German uranium project at the Kaiser Wilhelm Institutes for Physics and Chemistry, in the electrical laboratories of Siemens and at the Physics Institute of the Reich Ministry of Post were dismantled and transported to the USSR. These included three of the four German cyclotrons, strong magnets, electron microscopes, oscilloscopes, transformers and precision measuring instruments. The contribution made by German scientists to the development of nuclear technology for the Soviet atomic bomb project was essentially limited to uranium production and isotope separation. You continued to participate in the first Soviet atomic bomb test.

reception

See also

literature

  • Vera Keizer (Ed.): Radiochemistry, Diligence and Intuition. New research on Otto Hahn. Berlin 2018, ISBN 978-3-86225-113-1 .
  • Christian Kleint, Gerald Wiemers (ed.): Werner Heisenberg in Leipzig 1927–1942 (= treatises of the Saxon Academy of Sciences in Leipzig, mathematical and natural science class. Volume 58, no. 2). Akademie, Berlin 1993, ISBN 3-05-501585-1 , Part I: “Contributions to the development of nuclear reactors under W. Heisenberg and R. Döpel in the physical institute of the University of Leipzig (1939–1942) - On the 50th anniversary of the first evidence of the Neutron multiplication in a uranium machine ”, pp. 11–84.
  • Günter Nagel: The secret German uranium project - spoils of the allies. Jung, Zella-Mehlis 2016, ISBN 978-3-943552-10-2 .
  • Günter Nagel: Science for War. Franz Steiner, Stuttgart 2012, ISBN 978-3-515-10173-8 .
  • Michael Schaaf: Heisenberg, Hitler and the bomb. Conversations with contemporary witnesses. GNT-Verlag, Diepholz 2018, ISBN 978-3-86225-115-5 .
  • Mark Walker : An armory? Nuclear weapons and reactor research at the Kaiser Wilhelm Institute for Physics. Preprints from the research program “History of the Kaiser Wilhelm Society under National Socialism”. No. 26. Max Planck Institute for the History of Science, Berlin 2005 (PDF; 402 kB) .
  • Mark Walker: The uranium machine. Myth and reality of the German atomic bomb. Siedler, Berlin 1992, ISBN 3-442-12835-8 .
    • Original edition: German National Socialsm and the Quest for Nuclear Power 1939–1945 , Cambridge University Press 1989
  • Mark Walker: Nazi Science - myth, truth and the German atomic bomb , Plenum Press 1995, Perseus 2001
  • David C. Cassidy : Farm Hall and the German atomic bomb project of world war II. A dramatic history , Springer 2017

Web links

Notes and individual references

  1. ↑ No trace of "Hitler's bomb" in soil samples. Physikalisch-Technische Bundesanstalt , February 15, 2006, archived from the original on December 21, 2015 ; Retrieved December 8, 2015 . The claim was made by Rainer Karlsch in his book Hitler's Bomb , which was published in 2005, and this has permanently damaged his reputation.
  2. ↑ a b c d e f g h i j k l m n o p q r s t David Irving : As big as a pineapple ... In: Der Spiegel . No. 23 , 1967, p. 65 ( online ).
  3. ^ Michael Schaaf: The physical chemist Paul Harteck (1902–1985) , Stuttgart 1999.
  4. ↑ Reprint of the letter in: Michael Schaaf: Heisenberg, Hitler and the bomb. Conversations with contemporary witnesses. Gütersloh 2018, ISBN 978-3-86225-115-5 .
  5. ↑ W. Bothe, P. Jensen: The absorption of thermal neutrons in electrographite. Research report 1941. In: Zeitschrift für Physik. Volume 122 (1944) p. 749.
  6. ^ Per F. Dahl: Heavy Water and the Wartime Race for Nuclear Energy , IOP Publishing Ltd 1999, ISBN 0-7503-0633-5 , pp. 139-140
  7. ↑ Michael Schaaf: Nuclear fission in the heart of darkness. Africa and the origins of the nuclear age in: Vera Keizer (Ed.): Radiochemie, Diligence and Intuition. New research on Otto Hahn Berlin 2018. ISBN 978-3-86225-113-1 .
  8. ↑ cf. Michael Schaaf: Nuclear fission in the heart of darkness. Africa and the origins of the nuclear age
  9. ↑ 70 years ago: Americans liberate Staßfurt. In: volksstimme.de. Retrieved April 19, 2020 .
  10. ↑ a b c d e f g h i j k David Irving: As big as a pineapple ... In: Der Spiegel . No. 24 , 1967, p. 80 ( online - 1st continuation).
  11. ↑ W. Heisenberg, K. Wirtz: Large tests to prepare the construction of a uranium burner. In: Nature research and medicine in Germany 1939–1946. Edition of the FIAT Review of German Science intended for Germany . Volume 14, Part II (Eds. W. Bothe and S. Flügge): Dieterich, Wiesbaden. Also printed in: Stadt Haigerloch (Ed.): Atommuseum Haigerloch. Eigenverlag, 1982, pp. 43-65.
  12. ↑ Heinz Ewald: A new method for magnetic isotope separation. In: Reports on the work of the Kaiser Wilhelm Institute for Chemistry. G-139, May 3, 1942.
  13. ↑ H. Ewald, H. Hintenberger: Methods and applications of mass spectrometry. Verlag Chemie, Weinheim / Bergstrasse 1953.
  14. ↑ M. Walker: German National Socialism and the Quest for Nuclear Power: 1939-1949. Cambridge University Press, 1989.
  15. ^ Heiko Petermann: Manfred Baron von Ardenne and the Reichspost. ( Memento from September 8, 2012 in the web archive archive.today ) www.petermann-heiko.de. Retrieved July 9, 2011.
  16. ^ Carl Friedrich von Weizsäcker: A possibility of generating energy from uranium 238. July 17, 1940; Online archive of the Deutsches Museum, accessed on June 8, 2012.
  17. ↑ a b C. F. v. Weizsäcker, draft patent, spring 1941; partly reprinted and analyzed in Reinhard Brandt, Rainer Karlsch: Kurt Starke and Element 93: Was the search for the transuranium elements delayed? In: Rainer Karlsch, Heiko Petermann (Hrsg.): Pros and cons of Hitler's bomb - studies on nuclear research in Germany. (= Cottbus studies on the history of technology, work and the environment. Volume 29). Waxmann, Münster 2007, pp. 293–326.
  18. ↑ a b Helmut Rechenberg: Copenhagen 1941 and the nature of the German uranium project. In: Christian Kleint, Helmut Rechenberg, Gerald Wiemers (eds.): Werner Heisenberg 1901–1976. Festschrift for his 100th birthday. (= Treatises of the Saxon Akad. Der Wiss. Zu Leipzig, Math.-Naturw. Class. Volume 62). 2005, pp. 160-191.
  19. ↑ a b In R. Döpel's original test protocols, under “Test L4”, 30 measurement series between April 21 and June 18, 1942 are recorded; reproduced by Dietmar Lehmann and Christian Kleint: Reconstruction of the then secret Leipzig uranium machine work from the test protocols. In: Christian Kleint, Gerald Wiemers (ed.): Werner Heisenberg in Leipzig 1927–1942 . (= Treatises of the Saxon Akad. Der Wiss. Zu Leipzig, Math.-Naturw. Class. Volume 58). H. 2, 1993, pp. 53-61.
  20. ^ Wilhelm Hanle, Helmut Rechenberg: 1982: Jubilee year of nuclear fission research. In: Physical sheets. 38, No. 12, 1982, pp. 365-367.
  21. ↑ Robert Döpel, report on two accidents when handling uranium metal. (II. Ignition of uranium when opening a uranium container.) In: Christian Kleint, Gerald Wiemers (Ed.): Werner Heisenberg in Leipzig 1927–1942. Treatises d. Saxon. Akad. D. Sciences zu Leipzig 58 (1993, no. 2) and Wiley-VCH Weinheim 1993, pp. 62-67. Online: Accident report 1942 from facsimile document 2 of 10.
  22. ↑ Mark Walker, Die Uranmaschine, Goldmann 1992, p. 106
  23. ↑ Reinhard Steffler: The first fire service on a uranium machine. Elbe-Dnjepr-Verlag, Leipzig-Mockrehna 2010.
  24. ↑ Reinhard Steffler: Reactor accidents and the actions of the fire brigade: Leipzig, Chernobyl and Fukushima - an initial analysis. Elbe-Dnjepr-Verlag, Leipzig-Mockrehna 2011.
  25. ↑ Christian Kleint: From the history of the Leipzig uranium tests - On the 90th birthday of Robert Döpel. In: nuclear energy. Volume 29, H. 7, 1986, pp. 245-251. - In today's nuclear power plants , the reactor pressure vessel is enclosed by the containment due to the risk of radioactive environmental contamination , within which the hydrogen formation can and must be prevented or reversed by appropriate safety precautions , such as the so-called potter's candle .
  26. ↑ David Irving: As big as a pineapple ... In: Der Spiegel . No. 25 , 1967, p. 70 ( online - 2nd continuation).
  27. ↑ a b c David Irving: As big as a pineapple ... In: Der Spiegel . No. 26 , 1967, p. 87 ( online - 3rd continuation).
  28. ^ Michael Schaaf: Atomic research in Celle. in: Celle. The city book. Edited by Reinhard WLE Möller, Bernd Polster, Bonn 2003.
  29. ↑ a b c d David Irving: As big as a pineapple ... In: Der Spiegel . No. 27 , 1967, p. 80 ( online - 4th continuation).
  30. ↑ Secret reports from 1939 to 1945 on German nuclear research in the Haigerloch city archive . Directory ( Memento of May 13, 2009 in the Internet Archive )