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Breaking ground on a new approach to construction
The drive to Kairos Power’s reactor demonstration site in Oak Ridge, Tenn., is not only scenic—it’s historic. Nearly 85 years ago, roughly 30,000 construction workers transformed orchards and farmland into a key Manhattan Project site. Depending on your route, you may pass by one of the three gatehouses that were once military checkpoints controlling access to Atomic Energy Commission production facilities.
Kirk A. Mathews
Nuclear Science and Engineering | Volume 132 | Number 2 | June 1999 | Pages 155-180
Technical Paper | doi.org/10.13182/NSE99-A2057
Articles are hosted by Taylor and Francis Online.
Discrete ordinates calculations are presumed to translate particles from cell to cell in the directions specified in the angular set. This should result in uncollided particles from a small source propagating through the spatial mesh in narrow beams in these directions. Accurate high-order angular quadratures presume accurately attenuated propagation in the intended directions. This work examines the ability of various spatial quadratures to propagate rays correctly. Some widely used methods are shown to fail at this fundamental task. Diamond-difference approximations introduce undamped lateral oscillations, resulting in severely unphysical flux representations. Nonlinear fixups can prevent negativity but do not correct the underlying failure to properly propagate rays. First-moment conserving schemes tend to be successful but can be degraded in performance by simplifying approximations that are often used. Characteristic schemes are shown to have significant advantages. New characteristic methods are developed here that are exact (in a certain sense) in propagating rays and that uncouple the calculation of adjacent spatial cells in the mesh sweep. This enables DO loops to be converted to DO INDEPENDENT loops, with obvious implications for vector and/or parallel implementations.