The Leipzig L-IV experiment accident was the first nuclear accident in history. It occurred on 23 June 1942 in a laboratory at the Physical Institute of the

Leipzig University Leipzig University (), in Leipzig in Saxony, Germany, is one of the world's oldest universities and the second-oldest university (by consecutive years of existence) in Germany. The university was founded on 2 December 1409 by Frederick I, Electo ...

Leipzig Leipzig (, ; ; Upper Saxon: ; ) is the most populous city in the States of Germany, German state of Saxony. The city has a population of 628,718 inhabitants as of 2023. It is the List of cities in Germany by population, eighth-largest city in Ge ...

Germany Germany, officially the Federal Republic of Germany, is a country in Central Europe. It lies between the Baltic Sea and the North Sea to the north and the Alps to the south. Its sixteen States of Germany, constituent states have a total popu ...

. There was a steam explosion and a reactor fire in the "uranium machine", a primitive form of

research reactor Research reactors are nuclear fission-based nuclear reactors that serve primarily as a neutron source. They are also called non-power reactors, in contrast to power reactors that are used for electricity production, heat generation, or maritim ...

. Shortly after the Leipzig L-IV

atomic pile A nuclear reactor is a device used to initiate and control a fission nuclear chain reaction. They are used for commercial electricity, marine propulsion, weapons production and research. Fissile nuclei (primarily uranium-235 or plutonium-239 ...

—worked on by

Werner Heisenberg Werner Karl Heisenberg (; ; 5 December 1901 – 1 February 1976) was a German theoretical physicist, one of the main pioneers of the theory of quantum mechanics and a principal scientist in the German nuclear program during World War II. He pub ...

and

Robert Döpel Georg Robert Döpel (3 December 1895 – 2 December 1982), best known as Robert Döpel, was a German nuclear physicist and a professor of physics at the Technical University of Ilmenau in Germany. An early participant of the German program, the ...

—demonstrated Germany's first signs of neutron propagation, the device was checked for a possible

heavy water Heavy water (deuterium oxide, , ) is a form of water (molecule), water in which hydrogen atoms are all deuterium ( or D, also known as ''heavy hydrogen'') rather than the common hydrogen-1 isotope (, also called ''protium'') that makes up most o ...

leak. During the inspection, air leaked in, igniting the uranium powder inside. The burning uranium boiled the water jacket, generating enough steam pressure to blow the reactor apart. Burning uranium powder scattered throughout the lab causing a larger fire at the facility. This happened after 20 days of operation when Werner Paschen opened the machine at the request of Döpel after blisters formed at the gasket. As glowing uranium powder shot to the 6-meter-high ceiling and the apparatus heated up to 1000 degrees, Heisenberg was asked for help but could not provide it.

The experiment

Results from the L-IV trial, in the first half of 1942, indicated that the spherical geometry, with five tonnes of heavy water and 10 tonnes of metallic uranium, could sustain a fission reaction. They had achieved the first net neutron production of the German program, three years after the first such pile in history by

Hans von Halban Hans Heinrich von Halban (24 January 1908 – 28 November 1964) was a French physicist of Austrian-Jewish descent. Family He is a descendant of Polish Jews who left Kraków for Vienna in the 1850s on his father's side. His grandfather, Heinric ...

and colleagues in Paris. The results were set forth in an article by

Klara Döpel Klara (Minna) Renate Döpel (née Mannß; 1900 – 6 April 1945 in Leipzig) was a feminist and a German lawyer until 1933. Then she married the German nuclear physicist Robert Döpel, and they worked together as a team at Leipzig University stu ...

and W. Heisenberg. The article was published at first in the ''

Kernphysikalische Forschungsberichte ''Kernphysikalische Forschungsberichte'' (''Research Reports in Nuclear Physics'') was an internal publication of the German ''Uranverein'', which was initiated under the ''Heereswaffenamt'' (Army Ordnance Office) in 1939; in 1942, supervision of ...

'' (''Research Reports in Nuclear Physics''), a classified internal reporting vehicle of the

Uranverein Nazi Germany undertook several research programs relating to nuclear technology, including nuclear weapons and nuclear reactors, before and during World War II. These were variously called () or (). The first effort started in April 1939, ju ...

. The Leipzig research group was led by Heisenberg until 1942 who in winter 1939/1940 reported on the possibilities and feasibility of energy extraction from uranium for a uranium reactor and

nuclear bomb A nuclear weapon is an explosive device that derives its destructive force from nuclear reactions, either fission (fission or atomic bomb) or a combination of fission and fusion reactions (thermonuclear weapon), producing a nuclear exp ...

. After the report Heisenberg withdrew from practical experiments and left the execution of the experiments L-I, L-II, L-III and L-IV mostly up to his coworkers. The accident ended the Leipzig uranium projects. Bundesarchiv Bild183-R57262, Werner Heisenberg crop.jpg, Werner Heisenberg (1933) Döpel,Robert 1935 Stuttgart.jpg, Robert Döpel (1935) Physik. Inst. Leipzig 1909.jpg, Physical Institute Leipzig (1909) Leipziger Uranmaschine.jpg, Leipzig uranium machine (1942)

References

{{Leipzig University Nuclear accidents and incidents Nuclear program of Nazi Germany 1942 in Germany 1942 disasters in Germany Leipzig in World War II Leipzig University

The experiment

See also

References