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Can hydrogen be the transportation fuel in an otherwise nuclear economy?
Let’s face it: The global economy should be powered primarily by nuclear power. And it probably will by the end of this century, with a still-significant assist from renewables and hydro. Once nuclear systems are dominant, the costs come down to where gas is now; and when carbon emissions are reduced to a small portion of their present state, it will become obvious that most other sources are only good in niche settings. I mean, why use small modular reactors to load-follow when they can just produce that power instead of buffering it?
Hans R. Hammer, Jim E. Morel, Yaqi Wang
Nuclear Science and Engineering | Volume 193 | Number 5 | May 2019 | Pages 453-480
Technical Paper | doi.org/10.1080/00295639.2018.1542865
Articles are hosted by Taylor and Francis Online.
In this paper we show the extension of nonlinear diffusion acceleration (NDA) to geometries containing small voids using a weighted-least-squares (WLS) high-order equation. Even though the WLS equation is well defined in voids, the low-order drift-diffusion equation was not defined in materials with a zero cross section. This paper derives the necessary modifications to the NDA algorithm. We show that a small change to the NDA closure term and a nonlocal definition of the diffusion coefficient solve the problems for void regions. These changes do not affect the algorithm for optically thick material regions while making the algorithm well defined in optically thin ones. We use a Fourier analysis to perform an iterative analysis to confirm that the modifications result in a stable and efficient algorithm. Later in the paper, numerical results of our method are presented. We test this formulation with a small, one-dimensional test problem. Additionally, we present results for a modified version of the C5G7 benchmark containing voids as a more complex, reactor-like problem. We compared our results to Texas A&M’s transport code PDT, utilizing a first-order discontinuous formulation as reference and the self-adjoint angular flux equation with void treatment (SAAF), a different second-order form. The results indicate that the NDA WLS performed comparably or slightly worse then the asymmetric SAAF while maintaining a symmetric discretization matrix.