In 1946 the public first became informed of uranium-233 bred from thorium as "a third available source of nuclear energy and atom bombs" (in addition to uranium-235 and plutonium-239), following a United Nations report and a speech by Glenn T. Seaborg [REF].
The United States produced, over the course of the Cold War, approximately 2 metric tons of uranium-233, in varying levels of chemical and isotopic purity [REF].