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Latest News
Mike Kramer: Navigating power deals in the new data economy
Mike Kramer has a background in finance, not engineering, but a combined 20 years at Exelon and Constellation and a key role in the deals that have Meta and Microsoft buying power from Constellation’s Clinton and Crane sites have made him something of a nuclear expert.
Kramer spoke with Nuclear News staff writer Susan Gallier in late August, just after a visit to Clinton in central Illinois to celebrate a power purchase agreement (PPA) with Meta that closed in June. As Constellation’s vice president for data economy strategy, Kramer was part of the deal-making—not just the celebration.
Yaqi Wang, Jean C. Ragusa
Nuclear Science and Engineering | Volume 166 | Number 2 | October 2010 | Pages 145-166
Technical Paper | doi.org/10.13182/NSE09-46
Articles are hosted by Taylor and Francis Online.
Diffusion synthetic acceleration (DSA) schemes compatible with adaptive mesh refinement (AMR) grids are derived for the SN transport equations discretized using high-order discontinuous finite elements. These schemes are directly obtained from the discretized transport equations by assuming a linear dependence in angle of the angular flux along with an exact Fick's law and, therefore, are categorized as partially consistent. These schemes are akin to the symmetric interior penalty technique applied to elliptic problems and are all based on a second-order discontinuous finite element discretization of a diffusion equation (as opposed to a mixed or P1 formulation). Therefore, they only have the scalar flux as unknowns. A Fourier analysis has been carried out to determine the convergence properties of the three proposed DSA schemes for various cell optical thicknesses and aspect ratios. Out of the three DSA schemes derived, the modified interior penalty (MIP) scheme is stable and effective for realistic problems, even with distorted elements, but loses effectiveness for some highly heterogeneous configurations. The MIP scheme is also symmetric positive definite and can be solved efficiently with a preconditioned conjugate gradient method. Its implementation in an AMR SN transport code has been performed for both source iteration and GMRes-based transport solves, with polynomial orders up to 4. Numerical results are provided and show good agreement with the Fourier analysis results. Results on AMR grids demonstrate that the cost of DSA can be kept low on locally refined meshes.