is the anniversary of the first artificial sustained atomic chain reaction. The Chicago Pile 1 atomic pile was constructed as part of the secret Manhattan Project to test the possibility of achieving an atomic chain reaction that could be controlled and sustained. The pile was a massive construction using 771,000 pounds of graphite, 80,590 pounds of uranium
oxide and 12,400 pounds of uranium metal. Three sets of cadmium
control rods were used to regulate the flow of neutrons. One set was an automatic set that could be controlled from the control room. Another set acted as a safety that was heavily weighted to fall back into the pile when a supporting rope was cut by a man stationed with an axe. The third set of rods was hand controlled and was the actual set used to initiate the experiment.
The men spent the morning initiating tests of the system to lead up to the actual chain reaction. The final test achieved the critical self-sustaining chain reaction they were trying for. They allowed their reactor to operate for 28 minutes before shutting it down. It was the first time atomic energy was used and controlled and one of the most important events leading into the Atomic Age. Find out what else occurred on this day in science history