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NRC updating GEIS rule for new nuclear technology
The Nuclear Regulatory Agency is issuing a proposed generic environmental impact statement (GEIS) for use in reviewing applications for new nuclear reactors.
In an April 17 memo, NRC secretary Carrie Safford wrote that the commission approved NRC staff’s recommendation to publish in the Federal Register a proposed rule amending 10 CFR Part 51, “Environmental Protection Regulations for Domestic Licensing and Related Regulatory Functions.”
Teresa S. Bailey, Jim E. Morel, Jae H. Chang
Nuclear Science and Engineering | Volume 165 | Number 2 | June 2010 | Pages 149-169
Technical Paper | doi.org/10.13182/NSE08-66
Articles are hosted by Taylor and Francis Online.
In a previous paper, Morel and Montry used a Galerkin-based diffusion analysis to define a particular weighted diamond angular discretization for Sn calculations in curvilinear geometries. The weighting factors were chosen to ensure that the Galerkin diffusion approximation was preserved, which eliminated the discrete ordinates flux dip. It was also shown that the step and diamond angular differencing schemes, which both suffer from the flux dip, do not preserve the diffusion approximation in the Galerkin sense. In this paper we re-derive the Morel and Montry weighted diamond scheme using a formal asymptotic diffusion-limit analysis. The asymptotic analysis yields more information than the Galerkin analysis and demonstrates that the step and diamond schemes do in fact formally preserve the diffusion limit to leading order, while the Morel and Montry weighted diamond scheme preserves it to first order, which is required for full consistency in this limit. Nonetheless, the fact that the step and diamond differencing schemes preserve the diffusion limit to leading order suggests that the flux dip should disappear as the diffusion limit is approached for these schemes. Computational results are presented that confirm this conjecture. We further conjecture that preserving the Galerkin diffusion approximation is equivalent to preserving the asymptotic diffusion limit to first order.