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. Wirths either flew out with Riehl or was later sent to join Riehl in Russia as a member of his group. Eventually, Riehl's entire laboratory was dismantled and transported to the Soviet Union. 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 Alexander Catsch (Katsch), H. J. Born, Ortmann, Przybilla, Herbert Schmitz, Sommerfeldt, Herbert Thieme, Tobein, Günter Wirths, and Karl Günter Zimmer. Three major technological upgrades were made at Plant No. 12 in the production metallic uranium, two of them involved Wirths as a principle driving force: Late in 1945, the United States released the book Atomic Energy for Military Purposes by Henry Smyth (the Smyth Report). The book was acquired by the Soviets, immediately translated, and distributed to the organizations involved in the Russian atomic bomb project. The translators noticed that the original printing contained a reference to Neutron poisoning in production reactors which was censored from subsequent versions. Riehl read the report in one night. From statements in the book, Wirths and Herbert Thieme worked out the ether process, the wet-chemistry extraction process of uranium production, which replaced the low-throughput fractional crystallization method. The ceramic components were obtained from the Hermsdorf ceramic factory in Thuringia, Germany. A small industrial plant was in operation by February 1946. Its success resulted in a much larger plant being built in 1947, which had a much larger production capacity. It was in operation by the end of 1947. Riehl was approached by a scientist from the Nauchno-Issledovatel'skij Institut-9 (NII-9, Scientific Research Institute No. 9). Riehl refers to this man as the Platinum Colonel. The Platinum Colonel expressed the opinion that uranium tetrafluoride could be used in metallic uranium production instead of uranium oxide. Riehl believed this information was derived through Russian espionage, while others more recently credit it to the State Institute for Rare Metals