News Navigator: Did Japan also carry out research to create atomic weapons?

The Mainichi Shimbun answers some common questions readers may have about whether Japan has ever had a nuclear research program.

Question: I watched the film “Oppenheimer,” which won seven Academy Awards. Did Japan also research building atomic weapons?

Answer: While far from hitting the production stage, a renowned physicist did carry out research to create atomic weapons in total secrecy. In 1938, the splitting of the atom was announced by scientists in Germany. It became known that by impacting Uranium atoms with neutrons, the atomic nucleus is stripped away and a chain reaction produces enormous amounts of energy. The following year, Nazi Germany invaded Poland, sparking World War II. The United States and Britain began research on atomic weapons in the fear that the Nazis would develop a new form of weapon, and Japan also embarked on military-initiated research.

Q: Who was involved in the research?

A: The imperial army called upon Yoshio Nishina — referred to as the “father of modern physics in Japan” — at Riken, which is now Japan’s largest scientific research institution. The “Ni-go research” program was partly named after him. Meanwhile, the imperial navy asked professor Bunsaku Arakatsu at Kyoto Imperial University (now Kyoto University) and others for help, calling their program “F research,” with the “F” standing for “fission,” or the splitting of the atomic nucleus. Hideki Yukawa, Japan’s first Nobel Prize recipient, also worked on the research.

Q: Why did it fail?

A: The primary reason was a lack of sufficient uranium ore. Natural uranium contains only about 0.7% of the isotope for which fission is easily achievable, uranium-235. It seems the researchers were unable to develop the technology to enrich the substance as needed. Meanwhile, the U.S. used the technology to drop atomic bombs and devastate the cities of Hiroshima and Nagasaki. After the war, Yukawa committed himself to anti-nuclear weapon and pro-peace activism.

(Japanese original by Tomohiro Ikeda, Lifestyle, Science & Environment News Department)