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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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The Standards Committee is responsible for the development and maintenance of voluntary consensus standards that address the design, analysis, and operation of components, systems, and facilities related to the application of nuclear science and technology. Find out What’s New, check out the Standards Store, or Get Involved today!
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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.”
Quan Zhou, Rizwan-uddin
Nuclear Science and Engineering | Volume 151 | Number 1 | September 2005 | Pages 95-113
Technical Paper | doi.org/10.13182/NSE05-A2532
Articles are hosted by Taylor and Francis Online.
Stability and bifurcation analyses of boiling water reactors have been carried out using a reduced-order two-channel model developed earlier by Karve et al. To parameterize azimuthal asymmetry in core loading, an amplification factor F is introduced into the model to vary azimuthal mode feedback coefficients. Bifurcation analysis code BIFDD and numerical integration are used to analyze the reduced-order model composed of 22 modified ordinary differential equations. Results are presented for effects of azimuthal asymmetry (as parameterized by the amplification parameter F) on characteristics of oscillations. Analysis of eigenvectors corresponding to the two pairs of complex conjugate eigenvalues with the largest and second largest real parts suggests that one of these pairs is responsible for in-phase oscillations and the other for the out-of-phase oscillations.For a uniform core without azimuthal asymmetry (F = 1), as a bifurcation parameter (total pressure drop) is varied, the pair of eigenvalues corresponding to the fundamental mode first cross the imaginary axis, thus making the system unstable and leading to in-phase oscillations. However, for azimuthally asymmetric cores (corresponding to large values of F) and small inlet subcooling, the pair of eigenvalues corresponding to the first azimuthal mode, whose real part is the second largest for F = 1 case, approach the vertical axis faster (as a bifurcation parameter is varied) than those corresponding to the fundamental mode, thus becoming the dominant pair of eigenvalues. This leads to out-of-phase oscillations. Results of bifurcation analyses show that both sub- and supercritical bifurcation can occur for large as well as small azimuthal asymmetry, depending on values of other operating parameters. Changes in characteristics of oscillations (in-phase or out-of-phase; super- or subcritical bifurcation), therefore, result along the stability boundary. Numerical integrations confirm the results of stability and bifurcation analyses.