Herbert G. MacPherson

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Herbert G. MacPherson (2 November 1911 – 6 January 1993) was an American nuclear engineer and deputy director of

Alvin Weinberg he was "the country's foremost expert on graphite"...[1]

Career

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

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
.

Nuclear graphite and the Manhattan Project

The possibility of creating a

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[5]
(a semi-crystalline form of pure carbon).

In February 1940, using funds that were allocated partly as a result of the

Einstein-Szilard letter to President Roosevelt, Leo Szilard purchased 4 tons of graphite from National Carbon for use in Enrico Fermi's experimental reactor, the so-called exponential pile.[6]: 190  Fermi writes that "The results of this experiment was [sic] somewhat discouraging"[7] presumably due to the absorption of neutrons by some unknown impurity.[8]: 40  So, in December 1940 Fermi and Szilard met with H. G. MacPherson and V. C. Hamister at National Carbon to discuss the possible existence of impurities in graphite, without specifically describing the reasons for their visit.[9]: 143  Having previously (September 1939) read the article[10] of R. B. Roberts and J. B. H. Kuper (which described the necessity of a moderator in a chain reaction), MacPherson was able to deduce the purpose of the visit.[11] Because of his experience with the spectra of carbon arcs he realized that even high quality graphite contains minute quantities of boron impurities that could make it potentially unusable as a neutron moderator in a uranium reactor,[11] confirming a suspicion of Szilard.[5]

As a result of this meeting, over the next two years, MacPherson (together with L. M. Currie and V. C. Hamister) developed thermal purification techniques for the production of low boron content graphite,

X-10 graphite reactor in Oak Ridge TN and the reactors at the Hanford Site in Washington, which produced plutonium during and after World War II.[11][13] This process and its later refinements became standard techniques in the manufacture of nuclear graphite.[14]

This crucial information concerning boron impurities was not known to the German scientists who attempted to create a chain reaction in uranium during the second world war. The cross section for neutron absorption in graphite was investigated in Germany by

Walter Bothe, P. Jensen, and Werner Heisenberg who found it to be too high, thereby eliminating graphite as a possible moderator.[5][15][16] Consequently, the German effort to create a chain reaction involved attempts to use heavy water, an expensive and scarce alternative. Writing as late as 1947, Heisenberg still did not understand that the only problem with graphite was the boron impurities.[15]

Molten Salt Reactor

In 1956 MacPherson was appointed by ORNL director

Clinch River Breeder Reactor.[4]: 200 [22]
)

In 1958, concurrently with the publication of the first textbook on nuclear reactors,[23] MacPherson (together with James Lane and Frank Maslan) edited and published their engineering treatise on fluid fuel reactors[24]

Mayan Archaeology

After he retired, MacPherson developed an interest in Mayan culture and writings, especially those pertaining to the Dresden Codex. This ancient Mayan manuscript contains a table, commonly referred to as the "Eclipse Warning Table" of dates, the intervals between which approximately correspond to the intervals between solar eclipses that occur worldwide. Hundreds of articles have been written in attempts to understand this table (see[25][26]). MacPherson studied the baffling problem of how an ancient civilization may have succeeded in generating such a table when it did not possess the astronomical models that would be needed to predict eclipses worldwide[27][28] and when only several solar eclipses would have been visible to the Maya throughout the whole period of their civilization.[29][30] In what some experts consider to be "the most interesting of the recent studies of the eclipse table",[25]: 275 MacPherson described[31] a simple procedure by which such a table may have been assembled by Mayan astronomers in the process of determining the "lunar season".

References

  1. ^
    ISBN 978-1563963582
    .
  2. ^ MacPherson, H. G. (1941), "The Carbon Arc as a Radiation Standard", Temperature, Its Measure and Control in Science and Industry, Scranton PA: Reinhold Publishers, pp. 1141–1149
  3. ^ Alison Perruso, ed. (1980), Who's Who in America, vol. 2, Marquis Who's Who, p. 2112
  4. ^
    ISBN 978-1563963582
    .
  5. ^
    doi:10.1063/1.1292473
  6. ^
    ISBN 3540221417
    .
  7. ^ Fermi, Enrico (1946), "Development of the First chain reacting pile", Proceedings of the American Philosophical Society, 90 (1): 2024
  8. ^ Fermi, Enrico (1965). Collected Papers. Vol. 2. University of Chicago Press.
  9. ISBN 0262191687
    .
  10. doi:10.1063/1.1707351
  11. ^
    ISBN 978-0-309-05146-0
  12. ^ Currie, L. M.; Hamister, V. C.; MacPherson, H. G. (1955). The Production and Properties of Graphite for Reactors. National Carbon Company.
  13. ^
    doi:10.1016/0022-3115(81)90519-5
  14. ^ R. E. Nightingale, ed. (1962). Nuclear Graphite. Division of Technical Information, United States Atomic Energy Commission. New York: Academic Press.
  15. ^
    S2CID 4077785
  16. ISBN 978-3-0348-0202-4 {{citation}}: |first1= has generic name (help
    )
  17. ^ a b Johnson, Leland; Schaffer, Daniel (1994). Oak Ridge National Laboratory, the first fifty years. Knoxville TN: University of Tennessee Press.
  18. ^ a b "Olympian Feats", ONRL Review, 25 (3, 4), U.S. Department of Energy, Martin Marietta Energy Systems, 1992, archived from the original on 2014-01-09, retrieved 2015-03-21
  19. ^ a b Molten Salt Reactor Program Quarterly Progress Report for the period ending Jan 31, 1958 (PDF), vol. ORNL-2474, Oak Ridge National Laboratory
  20. ISBN 978-1573565219
    .
  21. doi:10.13182/NT8-2-118
    .
  22. ^
    doi:10.13182/NSE90-374
  23. ISBN 0226885178
    .
  24. ^ Lane, James A.; MacPherson, H. G.; Maslan, Frank (1958). Fluid Fuel Reactors. Reading MA: Addison-Wesley Publishing Co.
  25. ^
    ISBN 9780871692658
    .
  26. ISBN 9781441976239
    .
  27. ^ Lounsbury, Floyd G. (1978), "Maya numeration, computation, and calendrical astronomy", in Charles Gilispie (ed.), Dictionary of Scientific Biography, vol. 15, Supplement I, New York, N.Y.: Charles Scribner's Sons, pp. 759–818
  28. ISBN 9780521247313
  29. S2CID 163330918
  30. ^ Malmström, Vincent H. (2008), Beyond the "Dresden Codex": New Insights into the Evolution of Maya Eclipse Prediction (PDF), Dartmouth College
  31. S2CID 164115214

External links
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