Kyoto Imperial University — F-Go Nuclear Research Project
京都帝国大学理学部（F号研究）
Site of the F-Go Project (F号研究), the Imperial Japanese Navy's secret nuclear weapons research program conducted at Kyoto Imperial University from 1943 to 1945. Led by physicist Bunsaku Arakatsu, the project pursued uranium-235 separation via ultracentrifuge technology. The team included future Nobel laureate Hideki Yukawa. The project never achieved a working weapon before Japan's surrender.
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History
The F-Go Project (F号研究, also known as "The F Project") was the Imperial Japanese Navy's nuclear weapons research program, conducted at Kyoto Imperial University (now Kyoto University) from 1943 to 1945. The project was separate from the Army's Ni-Go Project led by Yoshio Nishina at RIKEN in Tokyo.
The program was initiated when Commander Kitagawa, head of the Navy Research Institute's Chemical Section, commissioned Professor Bunsaku Arakatsu (荒勝文策, 1890–1973) to investigate uranium-235 separation. Arakatsu was Japan's second most prominent nuclear physicist after Nishina, having studied at the Cavendish Laboratory under Ernest Rutherford at Cambridge and at Berlin University under Albert Einstein. The "F" in the project name is generally explained as standing for "fission"; uranium hexafluoride (UF₆) was the compound the team planned to feed into its centrifuges.
Arakatsu's research team at the Kyoto Imperial University Faculty of Science included several distinguished physicists, most notably Hideki Yukawa, who would become the first Japanese Nobel Prize laureate in 1949 for his prediction of the meson. The team pursued uranium enrichment through ultracentrifuge technology rather than the thermal diffusion method used by RIKEN.
Progress was hampered by severe resource constraints. Navy funding was minuscule beside the Manhattan Project's roughly $2 billion budget, reflecting the low priority assigned to nuclear research. By war's end, Arakatsu had designed an ultracentrifuge capable of spinning at 60,000 rpm, but only the mechanical design was completed before Japan's surrender on August 15, 1945.
In spring 1944, as both Army and Navy nuclear programs stalled, the Army-Navy Technology Enforcement Committee was formed to coordinate efforts. The first and only joint meeting of the Kyoto scientists and the Navy took place on July 21, 1945 — just weeks before Hiroshima. After the war, American occupation forces confiscated research equipment and documents. Three notebooks kept by project member Sakae Shimizu, found at Kyoto University in 2015, provided new insights into how far the program had progressed.
Today, the Kyoto University Faculty of Science (Graduate School of Science) occupies the Kitashirakawa campus in Sakyo-ku, Kyoto, on the same grounds where F-Go research was conducted. No dedicated memorial marks the site, but the Yukawa Institute for Theoretical Physics (Yukawa Hall) on campus honors the legacy of Arakatsu's most famous team member.