Diary shows Nobel Winner Yukawa attended 1945 A-Bomb meetings

December 22, 2017

Kyoto- A newly disclosed diary of the late Japanese Nobel prize-winning physicist Hideki Yukawa has shown that he attended in 1945 meetings of an atomic bomb development project commissioned by the now-defunct Imperial Japanese Navy.

This is the first time that Yukawa's own writing about his participation in the project, referred to as "the F project" in the diary, has been confirmed, said Keio University professor emeritus Michiji Konuma, who analyzed the diary.

In the diary, written between January and December 1945 and made public by Kyoto University on Thursday, Yukawa also wrote about how he listened to the radio broadcast on Aug. 15 that year, in which then Emperor Hirohito announced Japan's surrender in World War II.

Yukawa, who was born in 1907 and died in 1981, was a professor at Kyoto University. In 1949, he became the first Japanese Nobel laureate, winning the prize in physics for his contribution to the meson theory of nuclear forces.

Yukawa is also known for having put energy into peace movements, including one for the abolition of nuclear arms.

The newly released record represents part of the diary donated by Yukawa's bereaved family to the university.

In the June 23 entry, he wrote, "Afternoon, wartime research, the F project, the first meeting," showing that he was mobilized for the project, commissioned to the university, then called Kyoto Imperial University.

The July 21 entry reads, "Left home just after seven in the morning and traveled to Biwako Hotel on a Keishin train. Walked in the rain," indicating that he attended the F project's final meeting, held in Otsu, Shiga Prefecture, near Kyoto.

On Aug. 7, the day after the U.S. atomic bombing of Hiroshima, Yukawa wrote that he turned down requests from newspaper publishers for explanations about atomic bombs in connection with "the new type of bomb in Hiroshima."

The Aug. 13 entry shows he received a report from a colleague who observed the situation in Hiroshima firsthand.

On Aug. 15, Yukawa wrote that he listened to the Emperor's announcement about Japan's acceptance of the Potsdam Declaration defining terms for Japan's surrender, broadcast at noon, after a haircut and tidying himself up in the morning.

"The Great East Asia War is finally over," he wrote.

Yukawa also described how he made the rounds of his neighborhood during his watch for air strikes to let people know that an air-raid warning had been issued. He also wrote about the damage done by air raids and interrogations by the Allied forces.

Konuma, 86, who was a friend of Yukawa, said he believes Yukawa neither hid nor promoted the F project. Yukawa wrote about the topic in a detached manner, he said.

Yukawa is believed to have reported to the navy on the state of atomic research around the world, Konuma said.

The Nobel laureate started participating in peace movements after a U.S. nuclear test at Bikini Atoll in 1954, Konuma also said. Jiji Press