Organizational Unit:

Fusion Research Center

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https://hdl.handle.net/1853/70733

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Organizational Unit

George W. Woodruff School of Mechanical Engineering

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https://finding-aids.library.gatech.edu/agents/corporate_entities/1150

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Publication Search Results

Now showing 1 - 10 of 16

Tutorial: Principles and Rationale of the Fusion-Fission Hybrid Burner Reactor

(Georgia Institute of Technology, 2011-09-13) Stacey, Weston M.

The potential advantages of Fusion-Fission Hybrid (FFH) reactors (relative to critical fast reactors) for closing the back end of the nuclear fuel cycle are discussed. The choices of fission and fusion technologies for FFH burner reactors that would fission the transuranics remaining in spent fuel discharged from nuclear power reactors are summarized. The conceptual design and fuel cycle performance of the SABR FFH burner reactor are presented, and a fusion power development schedule with a symbiotic dual FFH path is outlined.
Investigation of the cause of the High-to-Low mode confinement transition following MARFE formation in DIII-D (DoE Grant ER54538)

(Georgia Institute of Technology, 2005-10) Stacey, Weston M. ; Friis, Zachary Ward ; Petrie, Thomas W. ; Leonard, Anthony W.

The common observation that the onset of a core MARFE (Multifaceted Asymmetric Radiation From Edge) is followed immediately by a H-L (High-to-Low) confinement mode transition in DIII-D [J. Luxon, Nucl. Fusion, 42, 614 (2002)] was investigated by comparing a theoretical prediction of the threshold non-radiative power across the separatrix needed to maintain H-mode with an experimental determination of the non-radiative power flowing across the separatrix. It was found that in three shots with continuous gas fueling the increased neutral influx associated with the MARFE formation caused a sharp increase in the predicted threshold non-radiative power crossing the separatrix that was required for the plasma to remain in H-mode to a value comparable to the experimental power crossing the separatrix.
Application of a particle, momentum and energy balance model to calculate the structure of the edge pedestal in DIII-D

(Georgia Institute of Technology, 2005-04) Stacey, Weston M. ; Groebner, Rich J.

A calculation of edge density and temperature profiles based on "classical" physics - particle, momentum and energy balance, heat conduction closure relations, neutral particle transport - yielded a pedestal structure that is qualitatively and quantitatively similar to that found experimentally in five DIII-D [J. Luxon, Nucl. Fusion,42, 614 (2002)] discharges, when experimental radial electric field and rotation profiles and experimentally inferred heat transport coefficients were used. The principal cause of the density pedestal was a peaking of the inward pinch velocity just inside the separatrix caused by the negative well in the experimental electric field, and the secondary cause was a peaking of the radial particle flux caused by the ionization of incoming neutrals. There is some evidence that this peaking of the radial particle flux just inside the separatrix may also be responsible in part for the negative electric field in that location.
Sub-critical Transmutation Reactors with Tokamak Fusion Neutron Sources

(Georgia Institute of Technology, 2005) Stacey, Weston M. ; Mandrekas, John ; Hoffman, E. A. (Elisha Albright)

The principal results of a series of design scoping studies of sub-critical fast transmutation reactors (based on the nuclear and processing technology being developed in the USDoE Generation IV, Advanced Fuel Cycle and Next Generation Nuclear Plant programs) coupled with a tokamak fusion neutron source (based on the ITER design basis physics and technology) are presented.
Edge Pedestal Structure

(Georgia Institute of Technology, 2004-12) Stacey, Weston M.

The hypothesis is advanced and investigated that, in between or in the absence of ELMs (edge-localized-modes), the structure of the edge pedestal is determined by the transport requirements of plasma particle, momentum and energy balance and recycling neutral atoms. "Pedestal equations" following from this hypothesis are presented and applied to calculate the edge density, temperature, rotation velocity and radial electric field profiles in a DIII-D H (high)-mode plasma. A distinct pedestal structure in the density and temperature profiles and sharp negative peaks in the radial electric field and poloidal velocity just inside the separatrix are predicted, in qualitative and quantitative agreement with measured values. Details of the calculation are discussed.
Structure of the edge density pedestal in tokamaks

(Georgia Institute of Technology, 2004-09) Stacey, Weston M.

A 'first-principles' model for the structure of the edge density pedestal in tokamaks between or in the absence of edge localized magnetohyrodynamic instabilities is derived from ion momentum and particle conservation and from the transport theory of recycling neutral atoms. A calculation for (high) H-mode tokamak discharge parameters indicates that the equations have a self-consistent solution which has an edge pedestal in the ion density profile and sharp negative spikes in the poloidal velocity and radial electric field profiles in the edge pedestal, features characteristic of H-mode edge profiles. These sharp negative spikes in radial electric field and poloidal rotation produce a peak in the inward ion pinch velocity in the sharp gradient (pedestal) region which produces an edge particle transport barrier. The calculated magnitude of the density at the top of the pedestal and the density gradient scale length and radial electric field in the pedestal region are comparable to measured values.
A neoclassical model for toroidal rotation and the radial electric field in the edge pedestal

(Georgia Institute of Technology, 2004-06) Stacey, Weston M.

A model for the calculation of toroidal rotation velocities and the radial electric field in the edge pedestal of tokamaks is described. The model is based on particle and momentum balance and the use of the neoclassical gyroviscous expression for the toroidal viscous force. Predicted toroidal rotation velocities in the edge pedestal are found to agree with measured values to within about a factor of 2 or less, for a range of DIII-D [Luxon, Nucl. Fusion, 42, 614, 2002] edge pedestal conditions.
Investigation of transport in the DIII-D edge pedestal

(Georgia Institute of Technology, 2004-04) Stacey, Weston M.

A comparison of various heat conduction theories with data from several DIII-D [Luxon, Nucl. Fusion, 42, 614, 2002] shots indicates: 1) that neoclassical theory is in somewhat better agreement with experiment than is ion temperature gradient mode theory for the ion thermal conductivity in the edge pedestal, although both are in reasonable agreement with experiment for most discharges; and 2) that electron temperature gradient theory (k┴cs ≤ ωpe) is in much better agreement with experiment than is electron drift wave theory (k┴cs ≤ Ωi) for the electron thermal conductivity. New theoretical expressions derived from momentum balance are presented for: 1) a ‘diffusive-pinch’ particle flux, 2) an experimental determination of the momentum transfer frequency, and 3) the density gradient scale length. Neither atomic physics nor convection can account for the measured momentum transfer frequencies, but neoclassical gyroviscosity predictions are of the correct magnitude.
Particle Transport and Density Gradient Scale Lengths in the Edge Pedestal

(Georgia Institute of Technology, 2004-04) Stacey, Weston M.

A new flux-gradient relation for the ion particle flux in the edge pedestal is derived from continuity and momentum balance, taking into account atomic physics, and cast in the form of a generalized ‘diffusion-pinch’ transport relation. This flux-gradient relation is used to derive a new expression for a first-principles calculation of the ion density gradient scale length.
Extensions of the TEP Neutral Transport Methodology

(Georgia Institute of Technology, 2004-04) Stacey, Weston M. ; Zhang, Dingkang ; Mandrekas, John

Recent extensions of the Transmission and Escape Probability methodology and its implementation in the 2-D neutral transport code GTNEUT are presented. These extensions address the issues of anisotropy of the neutral distribution function at the interfaces and the non-uniformity of the first collision source in short mean free path regions. Comparisons with Monte Carlo for a number of model problems are discussed.