Selected Citation

John Ray Dunning 1907-1975

Authors(s):Herbert L. Anderson Publication:Biographical Memoirs Publication Date:1989 Publisher: National. Academy of Sciences Citation:Anderson, Herbert L., John Ray Dunning 1907-1975, Biographical Memoirs, National Science Foundation, 1989 Link:PDF

JOHN RAY DUNNING, professor of physics at Columbia University, was a pioneer in the development of nuclear energy. From 1932, when he was twenty-five, he worked almost exclusively on the study of the then newly discovered neutron. His work led naturally to the demonstration—the first in the United States—of the large release of energy in the fission of uranium by slow neutron bombardment. Dunning realized that by enriching uranium in the light isotope, he could make a nuclear chain reaction a practicality. His work to adapt the gaseous diffusion process for this purpose made possible the nuclear power industry as we know it today. This achievement, pursued with unique vigor and single-mindedness, places him in the ranks of outstanding scientists of this century. After leaving active research, Dunning served with great distinction as dean of the School of Engineering at Columbia, obtaining financial support for many scientific projects.

From Dunning's letter to Nier:

[W]hile the chain reaction may be made to go eventually with ordinary U, clearly if U235 is the one, we open a whole new realm of possibilities with a really concentrated energy source. Reasonably pure U235 probably will be explosive under some conditions, which may make a great military weapon of enormous power. 

We are pushing up the cyclotron neutron output steadily. If you could effectively separate even tiny amounts of the two main isotopes, there is a good chance we could use very tiny samples to demonstrate which isotope is responsible, and study the whole phenomena. There is no other way to settle this business except to work with separated isotopes. Dr. Booth and I have the cyclotron and all the other necessary equipment and techniques. If we could all cooperate, and you aid by separating some samples, then we could by combining forces settle the whole matter.