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Thermal Hydraulics
The division provides a forum for focused technical dialogue on thermal hydraulic technology in the nuclear industry. Specifically, this will include heat transfer and fluid mechanics involved in the utilization of nuclear energy. It is intended to attract the highest quality of theoretical and experimental work to ANS, including research on basic phenomena and application to nuclear system design.
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ANS Student Conference 2025
April 3–5, 2025
Albuquerque, NM|The University of New Mexico
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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.”
R. R. Lee, P. B. Daitch
Nuclear Science and Engineering | Volume 28 | Number 2 | May 1967 | Pages 247-258
Technical Paper | doi.org/10.13182/NSE67-A17475
Articles are hosted by Taylor and Francis Online.
An eigenvalue-eigenfunction analysis of beryllium assemblies over a large buckling range has been performed in a discrete energy representation. Transverse harmonics and the treatment of the energy dependence of the transverse buckling are shown not to change the conclusions. The decay in small assemblies that do not have an asymptotic (discrete) eigenvalue is seen to be dominated by a highly excited region of the continuous eigenvalue spectrum. This is characterized as a pseudo-fundamental eigenvalue-eigenfunction and is seen to be responsible for the observation of experimental decay constants that are greater than the minimum interaction rate. The pseudo-fundamental eigenfunction is peaked at the Bragg energies and describes a trapping of neutrons at these energies for the intermediate times accessible to experiment. It is doubtful that the theoretical long-time buildup of near-zero-energy neutrons, seen as a peak at the lowest energy mesh point for the lowest “continuum” eigenfunction can be observed by experiment. Spatial effects are examined by comparing Marshak and zero-flux boundary-condition results. The Marshak boundary condition gives, for example, a 3% increase in the decay constant and a higher peak in the spectrum at the major Bragg energy for B2 = 0.0753 cm−2. A surface spectrum predicted by diffusion theory is seen to be in qualitative agreement with experiment. The P3 pseudofundamental eigenvalue is nearly identical to the diffusion theory result, lending support to the assumption that transport effects are not dominant for the times, energies, and assembly sizes considered here. Spectra at energies below the Bragg cutoff are very sensitive to the transport approximation used, but these energies are outside the experimental range and have a negligible effect on integral parameters, such as the decay constant. The major features of the theory are checked against experiment.