Werner Heisenberg and the German Uranium Project 1939 - 1945. Myths and Facts

TL;DR

This paper analyzes Heisenberg's role in the German uranium project during 1939-1945, clarifying myths and facts about his involvement and intentions regarding nuclear weapons development.

Contribution

It provides a detailed historical analysis of Heisenberg's activities and decisions, correcting misconceptions about his participation in the Nazi nuclear program.

Findings

Heisenberg concluded the project was impractical during the war.

He avoided calculating the critical mass of U-235.

Heisenberg sought Niels Bohr's opinion on nuclear weapons.

Abstract

The results of a careful analysis of all the available information on the activities of Heisenberg and of his talks during the years 1939 to 1945 can be summarized in the following way. Like several other German physicists Heisenberg was drafted by German Army Ordnance when war began in Europe in September 1939 to investigate whether the energy from splitting Uranium nuclei by neutrons could be used for technical and military purposes. Heisenberg found that this is possible in principle but that military use would require such enormous industrial expenditures that it would take many years and would be impracticable while the war lasted. The project was therefore dropped by the Nazi government in 1942. Heisenberg even refrained from calculating a precise value for the critical mass of U 235. He was relieved that he was thus spared a moral decision between obeying an order to build the bomb or risking his life by refusing to be involved in the project or sabotaging it. He was happy to be confined to a project of building a small test reactor under civilian administration that the government had approved. In 1941 Heisenberg tried to get the opinion of Niels Bohr in Copenhagen on what the international community of nuclear physicist could possibly do or prevent regarding the long-range technical feasibility of making nuclear weapons. Bohr completely misunderstood the cautious approach of Heisenberg.