Nikolaus Riehl

Nikolaus Riehl (24 May 1901 – 2 August 1990) was a German nuclear physicist.

He was head of the scientific headquarters of Auergesellschaft.

When the Russians entered Berlin near the end of World War II, he was invited to the Soviet Union, where he stayed for 10 years.

For his work on the Soviet atomic bomb project, he was awarded a Stalin Prize, Lenin Prize, and Order of the Red Banner of Labor.

Riehl was born in Saint Petersburg, Russia in 1901.

His mother Elena Riehl (née Kagan) was Russian-Jewish and his father Wilhelm Gottfried Riehl was a professional German engineer employed by Siemens and Halske.

With this background, Riehl spoke fluent German and Russian.

From 1920 to 1927, he studied physics and physical chemistry at the Humboldt University of Berlin.

He received his doctorate in nuclear physics from the University of Berlin in 1927, under the guidance of the nuclear physicist Lise Meitner and the nuclear chemist Otto Hahn; his thesis topic was on Geiger-Müller counters for beta ray spectroscopy.

Riehl initially took a position in German industry with Auergesellschaft, where he became an authority on luminescence.

While he completed his Habilitation, he continued his industrial career at Auergesellschaft, as opposed to working in academia.

From 1927, he was a staff scientist in the radiology department.

From 1937, he was head of the optical engineering department.

From 1939 to 1945, he was the director of the scientific headquarters.

Auergesellschaft had a substantial amount of "waste" uranium from which it had extracted radium.

After reading a paper in 1939 by Siegfried Flügge, on the technical use of nuclear energy from uranium, Riehl recognized a business opportunity for the company, and, in July of that year, went to the Heereswaffenamt (HWA, Army Ordnance Office) to discuss the production of uranium.

The HWA was interested and Riehl committed corporate resources to the task.

The HWA eventually provided an order for the production of uranium oxide, which took place in the Auergesellschaft plant in Oranienburg, north of Berlin.

Near the close of World War II, as American, British, and Russian military forces were closing in on Berlin, Riehl and some of his staff moved to a village west of Berlin, to try and assure occupation by British or American forces.

However, in mid-May 1945, with the assistance of Riehl's colleague Karl Günter Zimmer, the Russian nuclear physicists Georgy Flerov and Lev Artsimovich showed up one day in NKVD colonel's uniforms.

The use of Russian nuclear physicists in the wake of Soviet troop advances to identify and "requisition" equipment, materiel, intellectual property, and personnel useful to the Russian atomic bomb project is similar to the American Operation Alsos.

The military head of Alsos was Lt. Col. Boris Pash, former head of security on the American atomic bomb effort, the Manhattan Project, and its chief scientist was the eminent physicist Samuel Goudsmit.

In early 1945, the Soviets initiated an effort similar to Alsos (Russian Alsos).

Forty out of less than 100 Russian scientists from the Soviet atomic bomb project's Laboratory 2 went to Germany, Austria, and Czechoslovakia in support of acquisitions for the project.

The two colonels requested that Riehl join them in Berlin for a few days, where he also met with nuclear physicist Yulii Borisovich Khariton, also in the uniform of an NKVD colonel.

This sojourn in Berlin turned into 10 years in the Soviet Union!

Riehl and his staff, including their families, were flown to Moscow on 9 July 1945.

Eventually, Riehl's entire laboratory was dismantled and transported to the Soviet Union.

Other prominent German scientists from Berlin who were taken to the Soviet Union at that time, and who would cross paths with Riehl, were Manfred von Ardenne, director of his private laboratory Forschungslaboratoriums für Elektronenphysik, Gustav Hertz, Nobel Laureate and director of Research Laboratory II at Siemens, Peter Adolf Thiessen, ordinarius professor at the Humboldt University of Berlin and director of the Kaiser-Wilhelm Institut für physikalische Chemi und Elektrochemie (KWIPC) in Berlin-Dahlem, and Max Volmer, ordinarius professor and director of the Physical Chemistry Institute at the Berlin Technische Hochschule.

Soon after being taken to the Soviet Union, Riehl, von Ardenne, Hertz, and Volmer were summoned for a meeting with Lavrentij Beria, head of the NKVD and the Soviet atomic bomb project.

When a Soviet search team arrived at the Auergesellschaft facility in Oranienburg, they found nearly 100 tons of fairly pure uranium oxide.

The Soviet Union took this uranium as reparations, which amounted to between 25% and 40% of the uranium taken from Germany and Czechoslovakia at the end of the war.

Khariton said the uranium found there saved the Soviet Union a year on its atomic bomb project.

From 1945 to 1950, Riehl was in charge of uranium production at Plant No. 12 in Ehlektrostal' (Электросталь ).

German scientists, who were mostly atomic scientists, sent by the Soviets, at the close of World War II, to work in the Riehl group at Plant No. 12 included A. Baroni (PoW), Hans-Joachim Born, Alexander Catsch (Katsch), Werner Kirst, H. E. Ortmann, Herbert Schmitz (PoW), Walter Sommerfeldt, Herbert Thieme, Günter Wirths, and Karl Günter Zimmer as well as Heinrich Tobien, formerly "Chemiemeister" at Auergesellschaft; Walter Przybilla, brother of Riehl's wife, and mentioned in this context, also spent 10 years in SU, but was not a scientist under Riehl.

While Born, Catsch, and Zimmer had collaborated with Riehl in Germany, they were actually not part of Auergesellschaft but with N. V. Timofeev-Resovskij's genetics department at the Kaiser-Wilhelm Gesellschaft's Institut für Hirnforschung (KWIH, Kaiser Wilhelm Institute for Brain Research) in Berlin-Buch.

Riehl had a hard time incorporating these three into his tasking at Plant No. 12 on his uranium production tasking, as Born was a radiochemist, Catsch was a physician and radiation biologist, and Zimmer was a physicist and radiation biologist.

The Ehlektrostal' Plant No. 12, by the last quarter of 1946, was delivering about three metric tons of metallic uranium per week to Laboratory No. 2., which was later known as the Kurchatov Institute of Atomic Energy.

When he was repatriated to Germany in 1955, he chose to go to West Germany, where he joined Heinz Maier-Leibnitz on his nuclear reactor staff at Technische Hochschule München (THM); Riehl made contributions to the nuclear facility Forschungsreaktor München (FRM).

In 1961 he became an ordinarius professor of technical physics at THM and concentrated his research activities on solid state physics, especially the physics of ice and the optical spectroscopy of solids.