December 14, 1940 – Dr. Glenn T. Seaborg, Joseph W. Kennedy, Edwin M. McMillan, and Arthur C. Wahl Produce and Isolate Plutonium
1940s – Uranium is First Enriched in the United States as Part of The Manhattan Project
1940 – Soviet physicists Georgy Flyorov and Konstantin Petrzhak Demonstrate Spontaneous Fission
