A Stable Condition and Adaptive Diffusion Coefficients for the Coarse-Mesh Finite Difference Method

Coarse-mesh finite difference (CMFD) method is a widely used numerical acceleration method. However, the stability of CMFD not good for problems with optically thick regions. In this paper, rule named “sign preservation rule” in field heat transfer extended to scheme CMFD. It required that disturbance neutron current positively correlated negative value flux gradient. A necessary condition derived, an adaptive diffusion coefficient equation proposed improve method, and corresponding revised called rCMFD With few modifications code, was implemented hexagonal-Z nodal S N (discrete-ordinates) solver NECP-SARAX code system. The other similar methods were tested by three fast reactor which obtained modifying hexagonal pitches benchmark problem. results indicated showed better than traditional artificially diffusive (adCMFD) convergence rate adCMFD optimally (odCMFD) these problems.