Nikolaus Riehl (1901 in Saint Petersburg, Russia – 1990) was a German industrial nuclear chemist. 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. 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.
Riehl was born in Saint Petersburg, Russia in 1901. His mother was Russian and his father was a professional German engineer employed by Siemens and Halske. With this background, Riehl spoke fluent German and Russian. From 1920 to 1927, he was educated at the Saint Petersburg Polytechnical University and Humboldt University of Berlin. He received his doctorate in nuclear chemistry 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 rayspectroscopy.
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. 
In the Soviet Union
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 Lauriat 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 Elektrostal'. 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, Przybilla, Herbert Schmitz (PoW), Herbert Thieme, Tobein, Günter Wirths, and Karl Günter Zimmer. While Born, Catsch, and Zimmer collaborated with Riehl, they were actually not part of Auergesellschaft but with N. V. Timofeev-Resovskij’s Genetics Department at the Kaiser-Wilhelm Gesellschaft’sInstitut 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 Elektrostal’ 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. By 1950, Plant No. 12 was producing about one metric ton per day, and it was not the only metallic uranium production plant in operation.
After the detonation of the Russian uranium bomb, uranium production was going smoothly and Riehl’s oversight was no longer necessary at Plant No. 12. Riehl then went, in 1950, to head an institute in Sungul, where he stayed until 1952. The institute was known under a cover name as Объект 0211 (Ob'ekt 0211, Object 0211)  and was also called Laboratory B (Sungul/Snezhinsk); it was overseen by the 9th Chief Directorate of the NKVD, the same organization which oversaw the Russian Alsos operation. Essentially the remaining personnel in Riehl’s group in Elektrostal’ were assigned elsewhere, with the exception of Ortmann, Baroni, and Schmidtz, who went with Rielh. However, Riehl had already sent Born, Catsch, and Zimmer to the institute in Sungul, in December 1947, when it first opened, where they were able to continue the work they did in Germany. At its most active time, Laboratory B had nearly 300 personnel, only a small fraction of them Germans (15 in the early 1950s). Besides those already mentioned, other Germans at the institute were Rinatia von Ardenne (sister of Manfred von Ardenne, director of Institute A, in Sukhumi) Wilhelm Menke, Willi Lange (who married the widow of Karl-Heinrich Riewe, who had been at Heinz Pose’s Laboratory V, in Obninsk), Joachim Pani, and K. K. Rintelen. The Sungul institute was responsible for the handling, treatment, and use of radioactive products generated in reactors, as well as radiation biology, dosimetry, and radiochemistry; Riehl personally gravitated towards his interests in solid state physics and chemistry. The scientific staff at Sungul was both Soviet and German, the former being mostly political prisoners or exiles, although some of the service staff were criminals; this type of facility is known as a ShARAShKa. One of the political prisoners there was Riehl’s colleague from the KWIH, N. V. Timofeev-Resovskij, who had retained his Soviet citizenship when he worked in Germany and was arrested by the Soviet forces in Berlin at the conclusion of the war. The home in which Riehl lived had been designed by Max Volmer and had been previously occupied by Gustav Hertz, when he was director of Laboratory G. Until Riehl’s return to Germany in June 1955, which Riehl had to request and negotiate, he was quarantined in Agudseri. After Riehl left Sungul in 1952, the institute became known as Chelyabinsk-70 and one-third of the staff was sent to Arzamas-16.
For his contributions to the Soviet atomic bomb project, Riehl was awarded a Stalin Prize (first class), a Lenin Prize, and the Hero of Socialist Labor medal. As part of the awards, he was also given a dacha west of Moscow; he did not use the dacha. For work at Plant No. 12, Riehl’s colleagues Wirths and Thieme were awarded a Stalin Prize and the Order of the Red Banner of Soviet Labor, also known and the Order of the Red Flag.
Return to Germany
While Riehl’s work for the Soviet Union netted him significant prestige and wealth, his primary motivation for leaving Russia was freedom. Hence, while other German scientists who worked on the Soviet atomic bomb project chose to be repatriated to East Germany, Riehl went to West Germany. Once there, he joined Heinz Maier-Leibnitz on his nuclear reactor staff at Technische Hochschule München, where he made contributions, starting in 1957, to the nuclear facility Forschungsreaktor München (FRM). In 1961 he became an ordinarius professor of technical physics there and concentrated his research activities on solid state physics, especially the physics of ice and optical spectroscopy of solids.
Riehl and his wife Ilse, had two daughters, Ingeborg (oldest) and Irene. Riehl had a son who had died of natural causes and was buried in Germany.
Selected Literature and Patents
The majority of these literature citations have been garnered by searching on variations of the author’s name on Google, Google Scholar, the Energy Citations Database.
P. M. Wolf and N. Riehl Über die Zerstörung von Zinksulfidphosphoren durch - Strahlung, Annalen der Physik, Volume 403, Issue 1, 103-112 (1931)
P. M. Wolf and N. Riehl Über die Zerstörung von Zinksulfidphosphoren durch - Strahlen. 2. Mitteilung, Annalen der Physik, Volume 409, Issue 5, 581-586 (1933)
Nikolaus Riehl Transparent Coating, Patent number: CA 350884, Patent owner: Degea Aktiengesellschft (Auergesellschaft), Issue date: June 11, 1935, Canadian Class (CPC): 117/238.
Nikolaus Riehl Light-Modifying Article and Method of Producing the Same, Patent number: 2088438, Filing date: Jun 2, 1934, Issue date: Jul 27, 1937, Assignee: Degea.
N. Riehl and H. Ortmann Über die Druckzerstörung von Phosphoren, Annalen der Physik, Volume 421, Issue 6, 556-568 (1937)
N. Riehl New results with luminescent zinc sulphide and other luminous substances, Trans. Faraday Soc. Volume 35, 135 - 140 (1939)
N. Riehl Die „Energiewanderung“ in Kristallen und Molekülkomplexen, Naturwissenschaften Volume 28, Number 38, Pages 601-607 (1940). The author was identified as being at the wissenschaftlichen Laboratorium der Auergesellschaft, Berlin.
N. Riehl, N. V. Timofeev-Resovskij, and K. G. Zimmer Mechanismus der Wirkung ionisierender Strahlen auf biologische Elementareinheiten, Die Naturwissenschaften Volume 29, Numbers 42-43, 625-639 (1941). Riehl was identified as being in Berlin, and the other two were identified as being in Berlin-Buch.
N. Riehl Zum Mechanismus der Energiewanderung bei Oxydationsfermenten, Naturwissenschaften Volume 31, Numbers 49-50, 590-591 (1943)
N. Riehl, R. Rompe, N. W. Timoféeff-Ressovsky und K. G. Zimmer Über Energiewanderungsvorgänge und Ihre Bedeutung Für Einige Biologische Prozesse, Protoplasma Volume 38, Number 1, 105-126 (1943). The article was received on 19 April 1943.
G. I. Born (H. J. Born), N. Riehl, K. G. Zimmer, Title translated from the Russian: Efficiency of Luminescence Production by Beta Rays in Zinc Sulfide, Doklady Akademii Nauk SSSR Volume 59, March, 1269-1272 (1948)
N. Riehl and H. Ortmann Über die Struktur von Leuchtzentren in aktivatorhaltigen Zinksulfidphosphoren, Annalen der Physik, Volume 459, Issue 1, 3-14 (1959). Institutional affiliations: Technische Hochschule und Liebenwalde, Munich; Deutschen Akademie der Wissenschaften, Munich.
N. Riehl and R. Sizmann Production of Extremely High Lattice Defect Concentration in the Irradiation of Solid Bodies in Reactors [In German], Zeitschrift für Angewandte Physik Volume 11, 202-207 (1959). Institutional affiliation: Technische Physik der Technische Hochschule, Munich.
N. Riehl, R. Sizmann, and O. J. Stadler Effects of Alpha-Irradiation on Zinc Sulfide Phosphors [In German], Zeitschrift für Naturforschung A Volume 16, 13-20 (1961). Institutional affiliation: Technische Hochschule, Munich.
K. Fink, N. Riehl, and O. Selig Contribution to the Question of the Cobalt Content in Reactor Construction Steel [In German], Nukleonik Volume 3, 41-49 (1961). Institutional Affiliations: Phoenix-Rheinrohr A.G., Dusseldorf; and Technische Hochschule, Munich.
N. Riehl and R. Sizmann Effects of High Energy Irradiation on Phosphors [In German], Physica Status Solidi Volume 1, 97-119 (1961). Institutional affiliation: Technische Hochschule, Munich.
N. Riehl Effects of High Energy Radiation on the Surface of Solid Bodies [In German], Kerntechnik Volume 3, 518-521 (1961). Institutional affiliation: Technische Hochschule, Munich.
H. Blicks, N. Riehl, and R. Sizmann Reversible Light Center Transformations in ZnS Phosphors [In German], Z. Physik Volume 163, 594-603 (1961). Institutional affiliation: Technische Hochschule, Munich.
N. Riehl, W. Schilling, and H. Meissner Design and Installation of a Low Temperature Irradiation Facility at the Munich Research Reactor FRM, Res. Reactor J. Volume 3, Number 1, 9-13 (1962). Institutional affiliation: Technische Hochschule, Munich.
S. Hoffmann, N. Riehl, W. Rupp, and R. Sizmann Radiolysis of Water Vapor by Alpha-Radiation [In German], Radiochimica Acta Volume 1, 203-207 (1963). Institutional affiliation: Technische Hochschule, Munich.
O. Degel and N. Riehl Diffusion of Protons (Tritons) in Ice Crystals [In German], Physik Kondensierten Materie Volume 1, 191-196 (1963). Institutional affiliation: Technische Hochschule, Munich.
R. Doll, H. Meissner, N. Riehl, W. Schiling, and F. Schemissner Construction of a Low-Temperature Irradiation Apparatus at the Munich Research Reactor [In German] Zeitschrift für Angewandte Physik Volume 17, 321-329 (1964). Institutional affiliation: Bayerische Akademie der Wissenschaften, Munich.
N. Riehl and R. Sizmann The Abnormal Volatility of Alpha-Irradiated Materials [In German], Radiochimica Acta Volume 3, 44-47 (1964). Institutional affiliation: Technische Hochschule, Munich.
H. Blicks, O. Dengel, and N. Riehl Diffusion of Protons (Tritons) in Pure and Doped Ice Monocrystals [In German], Physik der Kondensierten Materie Volume 4, 375-381 (1966). Institutional affiliation: Technische Hochschule, Munich.
O. Dengel, E. Jacobs, and N. Riehl Diffusion of Tritons in NH4-Doped Ice Single Crystals [In German], Physik der Kondensierten Materie Volume 5, 58-59 (1966). Institutional affiliation: Technische Hochschule, Munich.
H. Engelhardt, H. Müller-Krumbhaar, B. Bullemer, and N. Riehl Detection of Single Collisions of Fast Neutrons by Nucleation of Tyndall Flowers in Ice, J. Appl. Phys. Volume 40: 5308-5311(Dec 1969). Institutional affiliation: Technische Hochschule, Munich.
N. Riehl, A. Muller, and R. Wengert Release of trapped charge carriers by phonons generated by alpha-particles [In German], Z. Naturforsch., Volume 28, Number 6, 1040-1041 (1973). Institutional affiliation: Technische Universität, Munich.
N. Riehl and R. Wengert Charge carrier release in He-cooled crystals by phonon fluxes generated by impinging hot gas atoms, by heat pulses, or by alpha-particles, Journal: Phys. Status Solidi (a), Volume 28, Number 2, 503-509 (1975). Institutional affiliation: Technische Universität, Munich.
Nikolaus Riehl and Henry Ortmann Über den Aufbau der Zinksulfid-Luminophore (Verl. Chemie, 1957)
Riehl, Nikolaus, Bernhard Bullemer, and Hermann Engelhardt (editors). Physics of Ice. Proceedings of the International Symposium, Munich, 1968 (Plenum, 1969)
Fred Fischer and Nikolaus Riehl Einführung in die Lumineszenz (Thiemig,1971)
Nikolaus Riehl and Frederick Seitz Stalin’s Captive: Nikolaus Riehl and the Soviet Race for the Bomb (American Chemical Society and the Chemical Heritage Foundations, 1996) ISBN 0-8412-3310-1. This book is a translation of Nikolaus Riehl’s book Zehn Jahre im goldenen Käfig (Ten Years in a Golden Cage) (Riederer-Verlag, 1988); Seitz has written a lengthy introduction to the book. This book is a treasure trove with its 58 photographs.
Albrecht, Ulrich, Andreas Heinemann-Grüder, and Arend Wellmann Die Spezialisten: Deutsche Naturwissenschaftler und Techniker in der Sowjetunion nach 1945 (Dietz, 1992, 2001) ISBN 3320017888
Barwich, Heinz and Elfi Barwich Das rote Atom (Fischer-TB.-Vlg., 1984)
Heinemann-Grüder, Andreas Die sowjetische Atombombe (Westfaelisches Dampfboot, 1992)
Heinemann-Grüder, Andreas Keinerlei Untergang: German Armaments Engineers during the Second World War and in the Service of the Victorious Powers in Monika Renneberg and Mark Walker (editors) Science, Technology and National Socialism 30-50 (Cambridge, 2002 paperback edition) ISBN 0-521-528607
Hentschel, Klaus (editor) and Ann M. Hentschel (editorial assistant and translator) Physics and National Socialism: An Anthology of Primary Sources (Birkhäuser, 1996) ISBN 0-8176-5312-0
Holloway, David Stalin and the Bomb: The Soviet Union and Atomic Energy 1939–1956 (Yale, 1994) ISBN 0-300-06056-4
Maddrell, Paul "Spying on Science: Western Intelligence in Divided Germany 1945–1961" (Oxford, 2006) ISBN 0-19-926750-2
Naimark, Norman M. The Russians in Germany: A History of the Soviet Zone of Occupation, 1945-1949 (Belknap, 1995)
Oleynikov, Pavel V. German Scientists in the Soviet Atomic Project, The Nonproliferation Review Volume 7, Number 2, 1 – 30 (2000). The author has been a group leader at the Institute of Technical Physics of the Russian Federal Nuclear Center in Snezhinsk (Chelyabinsk-70).
Riehl, Nikolaus and Frederick Seitz Stalin’s Captive: Nikolaus Riehl and the Soviet Race for the Bomb (American Chemical Society and the Chemical Heritage Foundations, 1996) ISBN 0-8412-3310-1.
Walker, Mark German National Socialism and the Quest for Nuclear Power 1939–1949 (Cambridge, 1993) ISBN 0-521-43804-7
^ Hentschel and Hentschel, 1996, Appendix F; see the entry for Riehl.
^ Siegfried Flügge Kann der Energieinhalt der Atomkerne technisch nutzbar gemacht warden?, Die Naturwissenschaften Volume 27, 402 (1939).
^ Also see the article by Siegfried Flügge Document 74. Siegfried Flügge: Exploiting Atomic Energy. From the Laboratory Experiment to the Uranium Machine – Research Results in Dahlem [August 15, 1939] reprinted in English in Hentschel and Hentschel, 1996, 197-206.
^ Hentschel and Hentschel, 1996, 369, Appendix F, see the entry for Riehl, and Appendix D, see the entry for Auergesellschaft.
^ H. J. Born, N. W. Timoféeff-Ressovsky and K. G. Zimmer Biologische Anwendungen des Zählrohres, Naturwissenschaften Volume 30, Number 40, 600-603 (1942). The authors were identified as being in the Genetics Department of the Kaiser Wilhelm Institute in Berlin-Buch.
^ Riehl and Seitz, 1996, 2, 31, 71, 83, 121-128, and 202.
^ Albrecht, Heinemann-Grüder, and Wellmann, 1992, Reference #22 on p. 57.
^ Holloway, 1994, 180 and Reference #56 on p. 410.
^ Ratner, V. A. Session in Memory of N. V. Timofeev-Resovskij in the Institute of Cytology and Genetics of the Siberian Department of the Russian Academy of Sciences [In Russian], Vestnik VOGis Article 4, No. 15 (2000).
^ Vogt, Annette Ein russisches Forscherehepaar in Berlin-Buch, Edition Luisenstadt (1998).
^ The Russians used various types of cover names for facilities to obfuscate both the location and function of a facility; in fact, the same facility could have multiple designations. The nuclear design bureau and assembly plant Arzamas-16, for example, had more than one designation – see Yuli Khariton and Yuri Smirnov The Khariton Version, Bulletin of the Atomic Scientist, 20-31 (May 1993). Some facilities were know as post office box numbers, such as Post Box 1037 (P), which apparently included Riehl’s Plant No. 12 in Elektrostal’, Laboratory G of Gustav Hertz, and Laboratory A of Manfred von Ardenne – see Maddrell, 2006, 182-183.
^ Riehl and Seitz, 1996, 2, 31, 52-55, 71, 83, 121-128, and 202.
^ Oleynikov, 2000, 11-12, 16-17, Reference #151 on p. 29, and Reference #154 on p. 29.