Category: Nuclear Scientist

Criticality, Nuclear ScientistBy E.Fermi

Fermi’s Pile

The Manhattan Project depended heavily on American industry through all of its activities, and the ability to build and operate Fermi’s reactor was no exception. Little or no uranium metal had been produced up to 1940. The open literature said that the melting point of the metal was “below 1850 degrees Centigrade.” Carbon was produced in the hundreds of tons, but its purity was unacceptable for a nuclear reactor. Westinghouse and the Metal Hydrides Company produced uranium pellets. Mallinckrodt Chemical provided a source that had reduced impurities. Harshaw Chemical and DuPont produced uranium tetrafluoride. The National Carbon Company and Speer Carbon Company were enlisted to produce the graphite that met high standards for purity. Fermi began to assemble the large […]

Nuclear Scientist, RadioactivityBy E.Fermi

Lise Meitner

Meitner’s escape from Germany is an interesting story. Niels Bohr led the efforts to arrange for her to take a train to the Dutch border. She had received notice she was forbidden to leave Germany, and she did not have a current visa. One account mentions that a Nazi officer examined her expired visa while she was on the train. He returned the visa to her without comment and moved on. We will never know whether his lack of action after looking at the expired document was because of incompetence or compassion. I choose to believe the officer looked at the small, frightened woman and allowed her to escape to Holland and then to Stockholm, Sweden, where Bohr had found […]

Nuclear Scientist, RadioactivityBy E.Fermi

History of Nuclear Physics

Perhaps a good place to begin the history of nuclear physics would be with the famous story of an accidental discovery by Henri Becquerel in the late 1800s. He had experimented with a photographic plate sprinkled with a layer of uranium salt and exposed to the sun. He had seen the silhouette of the phosphorescent substance in black on the negative. “When he tried to repeat his experiment…Paris was (overcast) gray. He put the covered photographic plate away in a dark drawer, uranium salt in place.” He decided to develop the plate despite the fact it hadn’t been exposed to the sun as planned and found that “the silhouettes appeared with great intensity.” He had discovered energetic, penetrating radiation, which, […]