Herbert G. MacPherson

Herbert G. MacPherson (2 November 1911 – 6 January 1993) was an American nuclear engineer and deputy director of Oak Ridge National Laboratory (ORNL). He contributed to the design and development of nuclear reactors and in the opinion of Alvin Weinberg he was "the country's foremost expert on graphite"...

After receiving his Ph.D. in Physics from the University of California at Berkeley in 1936, MacPherson went to work at the National Weather Service in Washington DC. The following year he was hired by the National Carbon Division of the Union Carbide and Carbon Corporation in Cleveland Ohio, where he investigated the spectra of carbon arcs that were often used in the movie industry. In 1956 he moved to Oak Ridge TN to become a research scientist at the Oak Ridge National Laboratory. MacPherson became deputy director of Oak Ridge National Laboratory in 1965, a position he held until 1970. From 1970 to 1976 he held the position of Professor of Nuclear Engineering at the University of Tennessee. In 1973 he served as acting director of the Institute for Energy Analysis, an organization founded by Alvin Weinberg for the study of management and future sources of energy. In 1978 he was elected to membership in the National Academy of Engineering.

The possibility of creating a chain reaction in uranium became apparent in 1939 following the nuclear fission experiments of Otto Hahn and Fritz Strassman, and the interpretation of these results by Lise Meitner and Otto Frisch. The exciting possibilities that this presented rapidly spread throughout the world physics community. In order for the fission process to chain react, the neutrons created by uranium fission must be slowed down by interacting with a neutron moderator (an element with a low atomic weight, that will "bounce", when hit by a neutron) before they will be captured by other uranium atoms. It was well known in 1939 that the two most promising moderators were heavy water and graphite (a semi-crystalline form of pure carbon).

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