Convergence analysis for the CMFD accelerated 2D/1D neutron transport calculation method based on Fourier analysis

Abstract

The two-dimension/one-dimension (2D/1D) transport method and the coarse mesh finite difference (CMFD) method are widely used for high-fidelity transport calculation. The CMFD method could dramatically reduce the calculating time while preserving accuracy. But the CMFD method accelerating the 2D/1D transport calculations may lead to divergence problems in some high scattering rate problems. The results of Fourier analysis indicate that the convergence is improved by increasing transport inner iterations. But more inner iterations lead to time burden in the method of characteristic (MOC) calculation. Fourier analysis is performed on the MOC based 2D/1D method to analyze the convergence feature, including increasing 1D transport inner iterations, iteration sequence of the 2D and 1D calculations, and so on. The results show that the effect of the 1D transport inner iteration on the convergence is related to the coarse-mesh height, and more 1D iteration could improve the convergence rate without introducing much more computation burden. Compared to the 1D2D computation sequence, the 2D1D sequence calculation has better convergence performance.