Fine Mesh Finite Difference acceleration method based on the Generalized Equivalence Theory for the 2-D MOC transport calculation

Abstract

Normally, the pin-cell-based Coarse Mesh Finite Difference (CMFD) method is directly used to accelerate the high-fidelity neutron transport calculations. However, the acceleration effect still has a bottleneck due to the fact that only the pin-cell homogenized flux can be used to update the fine-mesh flux, such as the flat-source-region flux for MOC calculation. In this paper, a Fine Mesh Finite Difference (FMFD) method based on the Flat Source Region (FSR) level is proposed and implemented in a two-dimensional transport code using Method Of Characteristics (MOC). FMFD could avoid the mapping error from pin-cell-wise mesh to fine FSR mesh. However, the solution of the FMFD system is time-consuming since the scale of the FMFD system is much larger than that of the pin-cell-based CMFD system. Therefore, Two-Level (TL) acceleration scheme is performed where the pin-cell-based CMFD is used to accelerate the solution of FMFD system. Both of these two acceleration methods are based on the Generalized Equivalence Theory (GET). Fourier analysis and numerical results show that FMFD with TL is more efficiency than conventional CMFD.