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Fusion Research Center Annual Report Series

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Now showing 1 - 5 of 5
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    A sub-critical, He-cooled, fast reactor for the transmutation of spent nuclear fuel (DOE Grant ER54350)
    (Georgia Institute of Technology, 2005-10) Stacey, Weston M.
    A design concept and supporting analysis are presented for a He-cooled, fast reactor for the transmutation of spent nuclear fuel. Coated TRU fuel particles in a SiC matrix are used. The reactor operates sub-critical (k ≤ 0.95), with a tokamak D-T fusion neutron source, to achieve > 90% TRU burnup in repeated 5-batch fuel cycles, fissions 1.1 MT/FPY, and produces 700 MWe net electrical power. The reactor design is based on nuclear, fuels, materials and separations technologies being developed in the GEN-IV, NGNP and AFCI Programs and similar international programs, and the fusion neutron source is based on the physics and technology supporting the ITER design.
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    Calculation of toroidal rotation profiles in DIII-D using neoclassical viscosity (DoE Grant ER54538)
    (Georgia Institute of Technology, 2005-10) Stacey, Weston M. ; Johnson, R. W. ; Mandrekas, John
    Momentum and particle balance and neoclassical viscosity were applied to calculate the radial profile of toroidal rotation in several DIII-D [J. Luxon, Nucl. Fusion, 42, 614 (2002)] discharges in a variety of energy confinement regimes (Low-mode, Low-mode with Internal Transport Barrier, Highmode, and High-mode with Quiescent Double Barrier). Calculated toroidal rotation velocities were found to over-predict measured values most in the center—by factors of 1.5 to 3--with the over-prediction generally decreasing with increasing radius, for the L, H and ITB mode shots, but the single impurity species approximation could not properly model the multiple Ni and Cu charge states in the QDB shots.
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    Rotation velocities and radial electric field in the plasma edge
    (Georgia Institute of Technology, 2005-10) Stacey, Weston M.
    The toroidal and poloidal rotation and related radial electric field observed in the edge (and core) of tokamak plasmas are of interest for several reasons, not least of which is what they reveal about radial momentum transport, but also because of their apparent role in the L-H transition and the edge pedestal. It was recently shown that if the heat transport coefficients and rotation velocities are taken from experiment, then the particle, momentum and energy balance equations and the conductive heat conduction relation are sufficient to determine the observed edge pedestal profile structure in the density and temperature profiles in several DIII-D discharges. Thus, it would seem that understanding the edge pedestal structure is a matter of understanding the edge rotation profiles. We present a practical computational model for the rotation and the radial electric field profiles in the plasma edge that is based on momentum and particle balance, includes both convective (including anomalous) and neoclassical gyroviscous momentum transport, and incorporates atomic physics effects associated with recycling neutrals.
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    Investigation of edge pedestal structure in DIII-D (DoE Grant ER54538)
    (Georgia Institute of Technology, 2005-10) Stacey, Weston M. ; Groebner, Rich J.
    A calculation based on the requirements of particle, momentum and energy conservation, conductive heat transport and atomic physics resulting from a recycling and fueling neutral influx was employed to investigate the experimental density, temperature, rotation velocities and radial electric field profiles in the edge of three DIII-D [J. Luxon, Nucl. Fusion, 42, 614 (2002)] high-mode plasmas. The calculation indicated that the cause of the pedestal structure in the density was a momentum balance requirement for a steep negative pressure gradient to balance the forces associated with an edge peaking in the inward pinch velocity (caused by the observed edge peaking in the radial electric field and rotation velocity profiles) and, to a lesser extent, in the outward radial particle flux (caused by the ionization of recycling neutrals). Thermal and angular momentum transport coefficients were inferred from experiment and compared with theoretical predictions, indicating that thermal transport coefficients were of the magnitude predicted by neoclassical and ion-temperature-gradient theories (ions) and electrontemperature- gradient theory (electrons), but that neoclassical gyroviscous theory plus atomic physics effects combined were not sufficient to explain the inferred angular momentum transfer rate throughout the edge region.
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    Improvements in the 2D TEP Neutral Particle Transport Calculation in Edge Plasmas (DoE Grant ER54538)
    (Georgia Institute of Technology, 2005-10) Zhang, Dingkang ; Mandrekas, John ; Stacey, Weston M.
    Extensions of the 2D Transmission and Escape Probability neutral particle transport method in treating the spatial non-uniformity of collision sources and neutral energy effects are presented. These extensions have been tested by benchmarks against Monte Carlo calculations for specially designed models and for realistic DIII-D discharges. The comparisons indicate these extensions improve accuracy of the TEP method.