1 mei 1939: patent Joliot op uranium-kettingreactie

Three patents were thus registered in secret between May 1 and May 4 in the name of the Caisse Nationale de la Recherche Scientifique, the main financial backer of the Collège de France research. The four inventors intended to keep only 5% each of the benefits with the remaining 80% going to help scientific research. These patents were the first ever to be taken out on the chain reaction in uranium.

The first two patents concerned energy production and were entitled "Device for energy production" and "Method for stabilizing a device for energy production". They roughly defined the principles of the main components of our present power reactors: moderator in heterogeneous or homogeneous arrangements, cooling fluid, control rods, protection shield. The third patent called "Method for perfecting explosive charges" was less brilliant from a foresight point of view though it proposed valid solutions for the trigger, the tamper and the rapid obtainment of the critical assembly of a possible explosive device. Finally, nearly a year later, after Alfred Nier's experimental confirmation in March 1940 of Niels Bohr's theoretical prediction that uranium-235, the rare isotope of the mixture in natural uranium, was responsible for fission by slow neutrons, the French took out in April 1940 an additional patent on the advantage of using enriched uranium for the chain reaction.

http://www.cns-snc.ca/history/fifty_years/goldschmidt.html (20030612)