Haigerloch research reactor

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Haigerloch research reactor
Replica of the reactor in the Atomkeller Museum

Replica of the reactor in the Atomkeller Museum

location
Research reactor Haigerloch (Baden-Württemberg)
Haigerloch research reactor
Coordinates 48 ° 22 '2 "  N , 8 ° 48' 15"  E Coordinates: 48 ° 22 '2 "  N , 8 ° 48' 15"  E
country Germany
Data
start of building Late February 1945
Installation Early March 1945
Shutdown April 24, 1945
Reactor type Heavy water reactor

The Haigerloch research reactor was a German nuclear reactor test facility . It was built in a rock cellar in Haigerloch , Hohenzollern , during the final phase of the Second World War in early 1945 .

In this last large-scale experiment of the uranium project called B 8 , a nuclear chain reaction was brought about and observed by neutron bombardment of uranium in heavy water . The criticality of the chain reaction was not reached; The plant was also not designed for operation in a critical condition, and the term reactor often used today therefore only applies to a limited extent. Later calculations showed that the reactor would have to have been about one and a half times the size to become critical.

The US special unit Alsos found the facility on April 23, 1945 and dismantled it the following day. The scientists involved were captured and the materials used were flown to the United States. Today the atomic cellar museum is located at the former location of the reactor .

prehistory

Previous reactor tests

Werner Heisenberg , from 1942 head of the Kaiser Wilhelm Institute for Physics

The main goal of the German uranium project in World War II was to make the nuclear fission discovered in 1938 by Otto Hahn and Fritz Straßmann usable . In a series of reactor tests, known as “large-scale tests”, the aim was to test the theoretical considerations for generating energy from uranium in practice. For this purpose, natural uranium in heavy water was bombarded with neutrons as a moderator and the resulting increase in neutrons was observed. The researchers of the uranium project did not designate their development goal as a reactor, but as a “uranium machine” or “uranium burner”.

  • Under the direction of Nobel Prize winner Werner Heisenberg , a total of seven large-scale experiments named B 1 to B 7 were carried out at the Kaiser Wilhelm Institute for Physics in Berlin-Dahlem from 1941 to 1944 . The physicists examined plates made of uranium metal of various thicknesses for their reactivity with increasing success .
  • In a second research institute in Leipzig , Heisenberg and his colleagues carried out four further experiments L 1 to L 4 with uranium oxide dissolved in heavy water in 1941 and 1942 . After two minor accidents, this research direction was discontinued and since then only Gussuran has been used.
  • At the same time, another group was working on similar experiments at the Gottow experimental station near Berlin, under the direction of Kurt Diebner . In her three experiments G 1 to G 3 in 1942 and 1943, uranium cubes were used instead of plates with good results; In addition to heavy water, paraffin was also used as a moderator . The Heisenberg and Diebner groups competed for the scarce materials.

Relocation of research

Map of the Hohenzollern Lands

In 1943 all major German cities were threatened by Allied bombing raids. So it was decided to move the Kaiser Wilhelm Institute for Physics to a more rural area. The suggestion to use the Hohenzollerische Lande for this purpose probably came from the head of the physics department in the Reichsforschungsrat Walther Gerlach , who had studied at the University of Tübingen , had also been a professor there in the late 1920s and therefore knew the area. Another factor in favor of southern Germany was that it had been largely spared from air raids until then. In addition, the participating scientists favored southern Germany in order not to fall into Soviet captivity in the event of a defeat.

As a result, the Kaiser Wilhelm Institute for Physics was relocated to Hechingen, 15 kilometers away from Haigerloch, and housed there in the Grotz and Conzelmann textile companies and in the brewery building of the former Franciscan monastery of Sankt Luzen . The relocation took place in several steps; Around a third of the institute moved to Hechingen by the end of 1943, followed in 1944 by Carl Friedrich von Weizsäcker and Karl-Heinz Höcker from Strasbourg and finally Heisenberg himself. At the same time, the Kaiser Wilhelm Institute for Chemistry was established with Otto Hahn and Max from Laue to the nearby Tailfingen (today Albstadt -Tailfingen).

In January 1945 only Karl Wirtz , Kurt Diebner and a few technicians from the Uranium Association remained in Berlin. Wirtz was in the process of setting up the largest reactor test to date in the still intact Dahlem institute bunker when the Red Army was able to advance up to 80 kilometers from Berlin. As a result, Gerlach decided on January 27, 1945 to break off the almost completed experimental setup. He immediately drove to Berlin to evacuate all scientists and materials to southern Germany.

Preparations

The rock cellar

Today's entrance to the rock cellar with the lime layer and castle church above

As early as July 29, 1944, the accidentally discovered potato and beer cellar of the Haigerloch Schwanenwirt was rented for 100 Reichsmarks a month as the new location for the Berlin research reactor . The rock cellar was laid out at the beginning of the 20th century for a tunnel for the Hohenzollern Railway . It was driven into the mountain of the local castle church in the narrow Eyach Valley and protected against bomb attacks by a 20 to 30 meter thick layer of shell limestone .

The tunnel section, about 20 meters long and about three meters high , had a trapezoidal cross-section, with the ceiling about four meters and the floor about five meters wide. The tunnel was supported along its entire length by wooden support beams that were placed at a distance of two meters. A small two-part porch hid the entrance to the rock cellar.

In the back of the rock cellar, a three-meter-deep cylindrical pit was dug for the reactor, a transport crane was installed on the cellar ceiling and a diesel generator was installed in the abandoned pub across the street . By the end of 1944, the renovation work in the rock cellar, which was disguised as a “cave research site”, had progressed so far that construction of the reactor could begin there.

Transportation of the materials

On January 31, 1945, Gerlach, Wirtz and Diebner left the capital at the head of a small convoy . They were followed by several trucks loaded with several tons of heavy water, uranium, graphite and technical equipment. After a night drive on an icy motorway , the convoy stopped about 240 kilometers south of Berlin in Stadtilm , Thuringia , where Diebner's work group had been relocated the previous summer. Gerlach believed that Diebner's laboratory was more advanced than Heisenberg's and decided without further ado to dump the materials there. Very upset about the change in the plan, Wirtz contacted Heisenberg in Hechingen, who immediately set off for Stadtilm with von Weizsäcker and arrived there three days later after an adventurous journey by bike, train and car.

On site, Heisenberg tried to convince Gerlach to bring the materials to Haigerloch after all. The two drove to Hohenzollern on February 12, 1945 to inspect the situation on site. Wirtz, however, stayed in Stadtilm to ensure that the materials were not used in Diebner's experiments. After Gerlach had ascertained in Haigerloch that the rock cellar was more suitable as the new location for the reactor, he agreed to move again. Trucks were procured again and on February 23, 1945, the physicist Erich Bagge set out with a new convoy from Haigerloch to collect the materials from their warehouse in Stadtilm.

Four weeks after leaving Berlin, 1.5 tons of uranium, 1.5 tons of heavy water, 10 tons of graphite and a small amount of cadmium finally arrived in Haigerloch at the end of February 1945 . The uranium was mined in Sankt Joachimsthal in the Sudetenland and came from the German Degussa . The heavy water was produced by Norsk Hydro in Norway . In addition, the physicist Fritz Bopp from Berlin flown in a 500 milligram radium - beryllium sample as a neutron source. At Diebner in Stadtilm, over ten tons of uranium oxide and small amounts of uranium metal and heavy water remained.

The research reactor

The attachment

Sketch of the research reactor
The spatial arrangement of the uranium cubes in a face-centered cubic lattice

As soon as the materials had arrived in Haigerloch, the reconstruction of the test facility began immediately. Von Weizsäcker and Wirtz worked in the lead on the construction and the experiments. Heisenberg himself managed the project from Hechingen, he often rode his bike between the two cities. In addition to Bagge and Bopp, other scientists involved in the project on site included Horst Korsching and Erich Fischer .

The outer shell of the reactor consisted of a concrete cylinder into which an aluminum boiler with a diameter of 210.8 centimeters and a height of 216 centimeters was inserted. The aluminum kettle rested on wooden support beams that lay on the floor, the space in between was filled with normal water . In the aluminum boiler another boiler was of a very light magnesium - alloy having a diameter of 124 centimeters and the same height. The magnesium boiler had already been used in large-scale test B 6 , and the aluminum boiler was used for the first time in large-scale test B 7 . Both boilers were manufactured by the Berlin company Bamag-Meguin .

Between the two boilers was a 43 centimeter thick and 10 tonne graphite layer that served as a neutron reflector and shield. Graphite as a reflector was first used in the previous large-scale test B 7 ; it was not used in even earlier experiments because the neutron absorption in graphite was overestimated by Walther Bothe in 1941. The lid of the inner kettle consisted of two magnesium plates between which there was also a graphite layer.

A total of 664 cubes made of natural uranium with an edge length of five centimeters and each weighing 2.4 kilograms were attached to this lid on 78 aluminum wires. 40 wires each held nine cubes, the remaining 38 wires each held eight cubes. The uranium cubes with a total weight of 1.58 tons were inserted into the inner vessel with the aid of the crane, and the entire arrangement was closed by the lid. In the face -centered cubic lattice that resulted , the uranium cubes were each arranged in the corners and in the center points of an imaginary space cube. The uranium cubes were 14 centimeters apart.

The scheme with the staggered uranium cubes was first used by Diebner in 1943 in the large-scale G 3 test in the test facility of the Heereswaffenamt in Gottow. So far, uranium plates had been used in the Berlin experiments, but with poorer results. Originally, the physicists wanted to test a construction made of hanging uranium cylinders, comparable to today's fuel rods . However, there was no longer enough time to manufacture such cylinders and the researchers therefore decided to copy Diebner's design. Ideally, the cubes should have an edge length between six and seven centimeters, but the scientists had to use the smaller cubes from Diebner's last experiments and therefore cut the uranium plates to the same size.

The radium-beryllium neutron source could be introduced into the center of the reactor through a so-called chimney . During the following experiment, the heavy water, which was stored in three large tanks at the end of the tunnel, was also filled into the inner reactor vessel through the chimney. There were also channels in the lid through which neutron detectors were inserted. This enabled the spatial neutron distribution to be measured in the entire arrangement using the cylindrical symmetry. Construction work on the reactor was completed in the first week of March 1945.

Objectives of the experiment

Scheme of a nuclear fission chain reaction , here with a multiplication factor of 2

In the large-scale experiment B 8 , a nuclear fission chain reaction was to be brought about and observed by neutron bombardment of uranium . The Haigerloch experiments were basic research. Its purpose was to use the measurements to determine the associated core physical parameters, such as cross sections , as far as possible. These findings were necessary for peaceful uses of nuclear fission, but also at least helpful for military uses. At least some of those involved also hoped to achieve criticality of the system and thus - supposedly for the first time - to prove a self-sustaining fission chain reaction. Little did they know that in December 1942, Enrico Fermi and his co-workers at the Chicago Pile 1 nuclear reactor in the United States had succeeded.

However, the system had no facilities to regulate a critical condition and switch it off again. There were no control rods and there was no way to quickly drain the heavy water once it had been filled. If the measured neutron flux density and thus the nuclear reaction rate had increased too much, it was planned to abort the experiment before reaching criticality by quickly pulling out the neutron source and stopping the heavy water supply. To limit the performance in the case of criticality, one relied on the Doppler coefficient , which would have automatically reduced the neutron multiplication with increasing temperature. If, contrary to all expectations, the plant had got out of control, the piece of cadmium, which acts as a neutron absorber , would have been thrown through the chimney into the reactor, thus interrupting the chain reaction. However, even with a very high neutron multiplication of the subcritical arrangement, the physicists would have exposed themselves to a high radiation dose because the system did not have sufficient radiation shielding at the top .

Those involved were aware of the possibility of military use of their work, because Heisenberg had already informed the Army Weapons Office at the end of 1939 that uranium-235 must be a strong nuclear explosive . Von Weizsäcker also pointed out early on that it could be used as a weapon, as well as the fact that a new fissile element - later known as plutonium - would have to be created in uranium reactors . The Haigerloch experiments could have basically confirmed these assumptions, but it was also clear to the scientists that many years of extensive research would have been necessary to develop ready-to-use weapons.

The large-scale test B 8

Reactor interior and uranium cube (replica)
The heavy water tanks (replica)

During the decisive attempt at the beginning of March 1945, Heisenberg was also present in the cellar, who “sat there and calculated all the time”. After the reactor was closed and the neutron source admitted, the heavy water was carefully poured into the inner reactor vessel. The water supply was interrupted at regular intervals and the proliferation of neutrons at the probes was monitored. By applying the reciprocal of the measured neutron intensity versus the amount of heavy water filled in - an idea by Heisenberg - the scientists were able to predict the water level at which the reactor would become critical.

However, no criticality occurred even after all available heavy water had been added. The neutron density in the filled arrangement had increased 6.7 times compared to the empty measurement. Although this value was twice as high as in the previous experiment, it was still not enough to achieve a self-sustaining nuclear chain reaction . The neutron multiplication factor was k = 0.85; the criticality would have corresponded to k = 1. Later calculations showed that the system would have had to be about one and a half times the size to become critical.

An enlargement of the arrangement was not possible under the given circumstances, because neither time nor enough more uranium and heavy water was available. Norsk Hydro's heavy water factory in Rjukan had already been destroyed by British bombers in November 1943, and in September 1944 the Degussa works in Frankfurt am Main were also badly hit by a bomber squad.

In a final attempt to let the reactor become critical after all, Heisenberg wanted to move the remains of heavy water and uranium that had remained in Stadtilm to Haigerloch. In addition, he wanted to ignore all theory and introduce uranium oxide into the graphite shield. During the last measurements, Wirtz found that graphite would make a better moderator than previously assumed. However, in the meanwhile collapsing German communications network, they were no longer able to establish contact with Stadtilm.

More precise details about the facility and the course of the experiment can no longer be determined today, as the original report is no longer available among the group's documents that were later brought to the USA. However, there is a thorough overview of all eight large-scale experiments written by Heisenberg and Wirtz afterwards, probably around 1950. A later analysis of two uranium cube fragments from Haigerloch by the Institute for Transuranium Elements at the Karlsruhe Research Center showed that the uranium had only been irradiated with relatively few neutrons; Plutonium could not be detected.

This indicates that the researchers were not on the verge of a nuclear chain reaction. They were still a long way from being able to manufacture a nuclear weapon.

Persecution and destruction

The Alsos Mission

Boris Pash (right) during the Alsos III mission in Hechingen
Samuel Goudsmit (pictured right) during the Alsos III mission in Stadtilm

The Allies had long suspected that the German researchers were working on an atomic bomb. The aim of the US special unit Alsos , founded in 1943 as part of the Manhattan project under General Leslie R. Groves , was to expose and secure the German nuclear research facilities and to arrest the leading scientists. In this way, not only should the own nuclear weapons program be promoted, but the use of knowledge by the Soviet Union and the other later occupation powers should also be prevented. The military head of the mission was Lieutenant Colonel Boris Pash , and the scientific team was led by physicist Samuel Goudsmit of Dutch origin .

Until the end of 1944, the Americans did not know exactly how far German research had progressed. The Alsos I mission in Italy in the winter of 1943/44 was largely unsuccessful. It was not until the end of November 1944 that letters from other members of the Uranium Association were found in Weizsäcker's office at the University of Strasbourg during the Alsos II mission in France , from which it could be concluded that Germany did not have an atom bomb and would not be producing one in the foreseeable future. However, documents were also discovered that indicated a suspicious research laboratory in the future French occupation zone in Hechingen. To forestall the French troops, Groves and Pash considered attacking the facility with paratroopers from the air or bombing it. However, the physicist Goudsmit was able to convince the two that the uranium project was not worth the effort, and so it was decided to undertake a land operation.

The first special forces of the Alsos III mission crossed the Rhine together with the 7th US Army on March 26, 1945 . On March 30, 1945, they were able to pick up physicists Walther Bothe and Wolfgang Gentner in Heidelberg , who were working there on their cyclotron . There Goudsmit learned that the nuclear research facilities of the uranium project had been relocated to Haigerloch near Hechingen and to Stadtilm in the future Soviet occupation zone . Pash decided to first visit Stadtilm to forestall the Soviet army. They managed to get there about three weeks before the Soviet armed forces, but Diebner had already fled with his staff and materials in the direction of Munich in the future American occupation zone . All they had to do now was to prevent the Haigerloch reactor from falling into French hands.

The destruction of the plant

The dismantling of the reactor by members of the Alsos III mission

The French army came to Haigerloch on April 22, 1945, but they did not notice the underground nuclear laboratory. As part of Operation Harborage, the Alsos mission arrived in the French occupation zone one day later, found the equipment and dismantled it the following day. Only now did the Americans realize that German research was more than two years behind their own. It was now becoming apparent to them that the entire German uranium project was on a very small scale compared to the Manhattan project:

"Here was the central group of laboratories, and all it to was a little underground cave, a wing of a small textile factory, a few rooms in an old brewery."

"Here was the main part of the laboratories, and it consisted only of a small underground cave, a wing of a small textile factory, a few rooms in an old brewery."

- Samuel Goudsmit , April 24, 1945
The discovery of the buried uranium cubes

The German scientists, on the other hand, believed that their work was more advanced than that of the Americans and were initially uncooperative. The uranium cubes and the heavy water had been removed from the facility and well hidden. After hours of interrogation, Wirtz and von Weizsäcker were able to elicit the names of the hiding places with the false promise that they would be allowed to resume their attempts after the war under the protection of the Allies. 659 of the 664 uranium cubes were found buried in a field next to the castle church, the heavy water had been carried into the cellar of an old mill. Von Weizsäcker had hidden the scientific documents, including the top-secret nuclear physics research reports , in a cesspool behind his house in Hechingen.

The materials and scientific reports were seized by the Americans and flown to the United States via Paris . The parts of the reactor plant that could not be removed were destroyed by several small explosions. A larger blast in the rock cellar would probably have seriously damaged the baroque castle church above. The pastor at the time was able to prevent this by showing the Americans the church and thus persuading Pash to carry out only smaller explosions.

A French task force led by the physicist Yves Rocard , who came to Hechingen shortly after the US troops in search of the facility, found only a piece of uranium from a laboratory the size of a sugar cube. Nevertheless, parts from the Haigerloch research reactor, such as the high-purity graphite bricks, are said to have been reused in the first French nuclear reactor ZOÉ .

consequences

Further developments

The Farm Hall country estate

The scientists from the two Kaiser Wilhelm Institutes were arrested by the Americans in their offices and apartments in Hechingen and Tailfingen. Heisenberg himself was picked up a few days later in Urfeld am Walchensee , where he owned a house and spent the last days of the war with his family. Gerlach and Diebner were found in and near Munich . The ten leading figures of the uranium project (Bagge, Diebner, Gerlach, Hahn, Heisenberg, Korsching, von Laue, von Weizsäcker and Wirtz, plus the physicist Paul Harteck ) were interned in Operation Epsilon from July 1945 to January 1946 in the British Farm Hall . It was there in August 1945 that they learned of the atomic bombs being dropped on Hiroshima and Nagasaki and thus also of the progress made by the Americans in nuclear technology and its consequences. The German scientists were deeply shocked, but at the same time also relieved:

"I would say I was absolutely convinced that we could make a uranium machine, but I never thought we would make a bomb, and at the bottom of my heart I was really glad that it was supposed to be a machine and not a bomb. "

- Werner Heisenberg , August 6, 1945
The two original uranium cubes

The ten researchers returned to their homeland after internment, where they - with the exception of Diebner - were able to take up prestigious positions in the scientific community. In the post-war years, the Control Council Act No. 25 forbade Germany to advance further developments in a nuclear reactor, but Heisenberg was already thinking about a German reactor again in 1950. It would take until 1957 for the first nuclear reactor on German soil, the Munich Research Reactor , to go into operation. In the same year, most members of the uranium project, together with other leading German nuclear physicists, spoke out in the Göttingen Manifesto against the military use of nuclear energy in Germany.

Today, the Atomkeller Museum , which opened in 1980, is located in the Felsenkeller.There is a replica of the reactor and two of the five remaining uranium cubes are on display. Heisenberg took one of the two cubes with him and found it again in the early 1960s by children playing on the Loisach river near his home.

Further processing of the events

In the two-part German television film End of Innocence from 1991, the development of the uranium project from the discovery of nuclear fission in 1938 to the experiments in Haigerloch and the subsequent internment of the scientists in 1945 is documented. Some of the film scenes were shot on the original location in the Haigerloch rock cellar. In 1991 , screenwriter Wolfgang Menge and director Frank Beyer received the German Television Film Award for writing and directing .

The play Copenhagen by Michael Frayn from 1998 is about a fictitious meeting between Heisenberg with Niels Bohr and his wife Margaret at an unspecified time after the war. At the end of the first act, Heisenberg reflects on the work on the Haigerloch research reactor, the lack of safety measures and the effort to achieve criticality for the first time. The three-person play received the Tony Award for best play in 2000 .

The 1999 novel The Klingsor Paradox by the Mexican author Jorge Volpi is about the search for two scientists for the alleged closest scientific advisor to Hitler , alias Klingsor . A flashback shows one of the two protagonists as he uncovered the German nuclear program as a fictional part of the Alsos mission together with Goudsmit and Pash in Heidelberg, Hechingen and Haigerloch. Ultimately, Klingsor - evil personified - turns out to be intangible. The bestseller received several awards, including the 1999 Spanish literary prize Premio Biblioteca Breve .

In the computer game Undercover: Operation Winter Sun by dtp entertainment from 2006, the player takes on the role of a British physicist who has the task of infiltrating the German atomic bomb program in a secret operation. In the course of the point-and-click adventure , the player gets to a fictional underground research laboratory in Haigerloch, but the facility is abandoned and the “bomb prototype” is stolen.

literature

Web links

Commons : Research reactor Haigerloch  - collection of images, videos and audio files

Individual evidence

  1. ↑ a b c 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 , Vol. 14 Part II (Eds. W. Bothe and S. Flügge), Wiesbaden: Dieterich. Also printed in: Stadt Haigerloch (ed.): Atommuseum Haigerloch , Eigenverlag, 1982, pp. 43–65.
  2. ↑ Research Center Berlin. In: Secret documents on the German nuclear program 1938–1945. Deutsches Museum , accessed on October 19, 2016 .
  3. ^ Research Center Leipzig. In: Secret documents on the German nuclear program 1938–1945. Deutsches Museum , accessed on October 19, 2016 .
  4. ↑ Gottow Research Center. In: Secret documents on the German nuclear program 1938–1945. Deutsches Museum , accessed on October 19, 2016 .
  5. ^ A b c Dahl: Heavy Water and the Wartime Race for Nuclear Energy , p. 254.
  6. ↑ Atomic Museum in the rock basement. In: Die Zeit No. 25, 14 June 1985, p. 52 , accessed on 19 October 2016 .
  7. ↑ Historical city tour in Haigerloch. City of Haigerloch, accessed on October 19, 2016 .
  8. ^ A b Dahl: Heavy Water and the Wartime Race for Nuclear Energy , p. 255.
  9. ↑ Ground plan of the atomic cellar. City of Haigerloch, accessed on October 19, 2016 .
  10. ^ A b c Dahl: Heavy Water and the Wartime Race for Nuclear Energy , p. 256.
  11. ↑ Klaus Mayer et al: Uranium from German nuclear projects of the 1940s - a nuclear forensic investigation . In: Angewandte Chemie . tape 127 , 2015, doi : 10.1002 / anie.201504874 .
  12. ↑ a b Name of the original report: F. Bopp, E. Fischer, W. Heisenberg, K. Wirtz, W. Bothe, P. Jensen and O. Ritter. Report on experiment B 8 in Haigerloch.
  13. ^ A b c Dahl: Heavy Water and the Wartime Race for Nuclear Energy , p. 257.
  14. ↑ W. Bothe and P. Jensen: The absorption of thermal neutrons in electrographite. Research report 1941. Zeitschrift für Physik Vol. 122 (1944) p. 749.
  15. ↑ a b Klaus Hentschel, Ann. M. Hentschel: Physics and national socialism: an anthology of primary sources . Birkhäuser, 1996, ISBN 3-7643-5312-0 , p. 377 (English).
  16. ↑ Experiment B-VIII. In: Secret documents on the German nuclear program 1938–1945. Deutsches Museum, accessed on October 19, 2016 .
  17. ↑ Mark Walker : An Armory? Nuclear weapons and reactor research at the Kaiser Wilhelm Institute for Physics . In: History of the Kaiser Wilhelm Society in National Socialism . Results 26, 2005, p. 32-33 .
  18. ^ A b c d Dahl: Heavy Water and the Wartime Race for Nuclear Energy , p. 258.
  19. ↑ Wirtz: In the vicinity of physics , p. 61: "If the experiment were successful, d. H. the arrangement would become critical, it would ... "
  20. ^ Dahl: Heavy Water and the Wartime Race for Nuclear Energy , p. 138.
  21. ↑ Joseph J. Ermenc: Interview with Werner Heisenberg about the nuclear energy developments in World War II. City of Haigerloch, August 29, 1967, accessed on October 19, 2016 .
  22. ↑ Wirtz: In the vicinity of physics , p. 62.
  23. ^ Dahl: Heavy Water and the Wartime Race for Nuclear Energy , pp. 214-217.
  24. ^ Dahl: Heavy Water and the Wartime Race for Nuclear Energy , p. 260.
  25. ↑ Wirtz: In the vicinity of physics , p. 63.
  26. ↑ a b Markus Becker: “Heisenberg Cube” reveals details about Hitler's nuclear program. In: Spiegel Online. March 19, 2009, accessed January 1, 2019 .
  27. ^ Dahl: Heavy Water and the Wartime Race for Nuclear Energy , pp. 247-249.
  28. ^ Dahl: Heavy Water and the Wartime Race for Nuclear Energy , pp. 250-251.
  29. ^ Dahl: Heavy Water and the Wartime Race for Nuclear Energy , pp. 252-253.
  30. ^ Dahl: Heavy Water and the Wartime Race for Nuclear Energy , p. 259.
  31. ^ Dahl: Heavy Water and the Wartime Race for Nuclear Energy , p. 261.
  32. ↑ Samuel Goudsmit : Alsos . History of modern physics and astronomy, volume 1 . Springer, 1996, ISBN 1-56396-415-5 , pp. 106 (English).
  33. ^ A b Klaus Hoffmann: Guilt and responsibility: Otto Hahn, conflicts of a scientist . Springer, 1993, ISBN 3-540-56766-6 , pp. 193 .
  34. ^ A b Dahl: Heavy Water and the Wartime Race for Nuclear Energy , p. 262.
  35. ^ Otto G. Folberth, Michael Thorwart and Egidius Fechter: Haigerloch cave survived the war . In: Physics Today . tape 54 (4) , 2001, pp. 93-94 (English).
  36. ↑ Roland Kollert: The policy of latent proliferation: military use of "peaceful" nuclear technology in Western Europe . Deutscher Universitäts-Verlag, 1994, ISBN 3-8244-4156-X , p. 181 .
  37. ^ Dahl: Heavy Water and the Wartime Race for Nuclear Energy , p. 263.
  38. ^ Hoffmann: Operation Epsilon. The Farm Hall Protocols or The Allies' Fear of the German Atomic Bomb , p. 78.
  39. ^ Hoffmann: Operation Epsilon. The Farm Hall Protocols or The Allies' Fear of the German Atomic Bomb , p. 153.
  40. ^ Dieter Hoffmann , Ulrich Schmidt-Rohr: Wolfgang Gentner: Festschrift for the 100th birthday . Springer, 2006, ISBN 3-540-33699-0 , pp. 78 .
  41. ↑ Wolfgang Quantity : End of Innocence. The Germans and their atomic bombs . Volk und Welt, 1991, ISBN 3-353-00841-1 .
  42. ↑ Michael Frayn , Matthias Dörries, Inge Greiffenhagen: Copenhagen: piece in two acts . Wallstein, 2003, ISBN 3-89244-635-0 , p. 47-51 .
  43. ↑ Jorge Volpi : The Klingsor Paradox . Klett-Cotta, 2001, ISBN 3-608-93066-3 .
This article was added to the list of excellent articles on October 9, 2009 in this version .