Enrico Fermi and the Manhattan ProjectJune 26, 2021
Fermi arrived in New York City on January 2, 1939. He immediately received offers from five different universities and accepted one at Columbia University, where he taught in the summer of 1936.
In December 1938, he learned that German chemists Otto Hahn and Fritz Strassmann had found barium by neutron bombardment of uranium, and Lise Meitner and her nephew Otto Frisch identified it as the product of nuclear fusion. Frisch proved this experimentally on January 13, 1939. Frisch and Meitner’s review of Hahn and Strassmann’s discovery crossed the Atlantic Ocean with Niels Bohr. Bohr, who teaches at Princeton, told Isidor Isaac Rabi and Willis Lamb, and they took it to Columbia. Rabi claimed to have said this to Fermi, but Fermi later stated that Lamb said:
“I remember the month of January 1939 very well. I started working at Pupin Lab because everything was moving so fast. Niels Bohr was teaching at Princeton at the time, and one afternoon Willis Lamb came up to me excitedly and said that Bohr had given me good news. This news included a general idea of the invention and definition of fusion. That same month, there was a meeting in Washington where the importance of the newly found fusion and its potential to be a source of nuclear energy were discussed.”
Noddack was finally right. According to Fermi calculations, he ignored the possibility of fusion, but ignored the binding energy that occurs when a nuclide with a single neutron number receives an extra neutron. For Fermi, this news was embarrassing because the transuranic elements he thought he had discovered and for which he was awarded the Nobel Prize were not elements but fusion products. He added this to his Nobel acceptance speech. Scientists at Columbia decided to measure the energy uranium gives off in neutron bombardment. On January 25, 1939, in the basement of Pupin Hall in Columbia, Fermi and his experimental team conducted the United States’ first nuclear fusion experiment. Other members of the team were Herbert L. Anderson, Eugene T. Booth, John R. Dunning, G. Norris Glasoe and Francis G. Slack. The next day, the Fifth Washington Conference on Theoretical Physics began in Washington DC. At this joint conference of George Washington University and the Carnegie Institution, the news of fusion spread well and led to further experiments.
French scientists Hans von Halban, Lew Kowarski, and Frederic Joliot-Curie found that uranium gave off more neutrons than it received in neutron bombardment. Fermi and Anderson found it a few weeks later. To take Fermi and Anderson’s fusion experiments to a new level, Leo Szilard obtained 200 kilograms of uranium oxide from Canadian radium producer Eldorado Gold Mines Limited. Fermi and Szilard jointly developed a self-contained nuclear reaction (nuclear reactor). Because of the number and speed of neutrons that hydrogen absorbs in water, it was difficult to make a spontaneous nuclear reaction using natural uranium as a neutron moderator. Fermi suggested using uranium oxide blocks and graphite instead of water. Thus, the neutron capture rate would decrease and there would be a self-contained chain reaction. Szilard presented a design that worked: blocks of uranium oxide between graphite bricks. Szilard, Anderson, and Fermi wrote a paper called “Neutron Generation in Uranium.” However, he had a hard time working with Fermi Szilard because of their different personalities.
Fermi was the first to warn military leaders about the power of nuclear energy, and he did so in a lecture in the Navy on March 18, 1939. The Navy added $1,500 to the Columbia research, but their response was still not enough for Fermi. Later, Szilard, Eugene Wigner, and Edward Teller sent the famous letter signed by Einstein to President Roosevelt, writing that Nazi Germany could make an atomic bomb. Thus, Roosevelt created the S-1 Uranium Committee. The S-1 Committee funded Fermi to buy graphite, which he used to build a graphite brick pile at Pupil Hall Laboratory. In August 1941, he had six tons of uranium oxide and 30 tons of graffiti, and with that he set up a larger order at Columbia.
The S-1 Committee met again on December 18, 1941, and the work gained importance as the United States was now entering World War II. Most of the work was focused on producing enriched uranium, but committee member Arthur Compton said a more sensible alternative was plutonium, which could be mass-produced in reactors by the end of 1944. He started plutonium studies at the University of Chicago. Fermi reluctantly moved and took charge of the new Metallurgical Laboratory with his team. The results of a self-sustaining nuclear reaction were not conclusive, and so they decided not to do it in the middle of the city on the Chicago campus. Compton found a place in the Argonne Woods Forest, 20 miles from Chicago. Stone & Webster took business to develop the site but they stopped due to an industrial dispute. Fermi convinced Compton to build the reactor on the squash court below Chicago’s Stagg Field. This construction began on November 6, 1942, and Chicago Pile-1 went critical on December 2. The shape of the heap was spherical, but Fermi