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ANS Student Conference 2025
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General Kenneth Nichols and the Manhattan Project
Nichols
The Oak Ridger has published the latest in a series of articles about General Kenneth D. Nichols, the Manhattan Project, and the 1954 Atomic Energy Act. The series has been produced by Nichols’ grandniece Barbara Rogers Scollin and Oak Ridge (Tenn.) city historian David Ray Smith. Gen. Nichols (1907–2000) was the district engineer for the Manhattan Engineer District during the Manhattan Project.
As Smith and Scollin explain, Nichols “had supervision of the research and development connected with, and the design, construction, and operation of, all plants required to produce plutonium-239 and uranium-235, including the construction of the towns of Oak Ridge, Tennessee, and Richland, Washington. The responsibility of his position was massive as he oversaw a workforce of both military and civilian personnel of approximately 125,000; his Oak Ridge office became the center of the wartime atomic energy’s activities.”
M. Andersson, D. Blanchet, H. Nylén, R. Jacqmin
Nuclear Science and Engineering | Volume 181 | Number 2 | October 2015 | Pages 204-215
Technical Paper | doi.org/10.13182/NSE14-106
Articles are hosted by Taylor and Francis Online.
Advanced fast reactor concepts, such as the CFV core (French acronym of “Coeur à Faible effet de Vide Sodium,” meaning “low sodium void effect core”), are characterized by a heterogeneous axial core arrangement, with an inner fertile zone and a sodium plenum above the fuel. Such concepts represent a strong challenge for accurate predictions of the control-rod antireactivity effects, and the surrounding local fuel pin power. Classical equivalence procedures, which were developed for axially homogeneous cores, are put to the test when applied to such axially heterogeneous cores. In this work, we investigate the influence of variations in the local neutron spectra, for different control-rod environments, with the objective of understanding the impact of spectral variations in control-rod homogenization. This was conducted by considering a simple one-dimensional model of the equivalence procedure in which a transition zone between the fuel and control rod was introduced to represent different control-rod environments. Two types of situations were studied, one corresponding to softened neutron spectrum environments, for which the impact in the homogenized control-rod cross section was found to be smaller than 5%. The second situation was with wide elastic scattering resonances in the control-rod environment, which could locally lead to differences of up to 15% in the resulting equivalent cross sections. The reactivity effect of these changes was calculated to be less than 2%. In some cases, the numerical stability of the equivalence procedure was adversely affected, mainly in high-energy groups, due to the softening of the neutron spectra.