Utilization of Regionwise Even-Parity Discontinuity Factor to Reduce Discretization Error of MOC

Abstract

To reduce angular and spatial discretization error of the method of characteristics with a coarse calculation condition, the regionwise even-parity discontinuity factor (EPDF) for transport calculations is evaluated through an iterative procedure using only the regionwise scalar flux, i.e., without the odd-parity angular flux, the partial current, or the net current at the region boundary. The regionwise EPDF is evaluated in a single-assembly geometry with the reflective boundary condition. The evaluated EPDF is applied to a 2 × 2 colorset assembly and core configurations, and the performance is compared to that of the conventional superhomogenization (SPH) method. The calculation results indicate that (1) no convergence issue is observed during the iteration process to estimate the EPDF, (2) the performance of the regionwise EPDF is better than that of the conventional SPH method, and (3) the normalization of the EPDF is necessary to incorporate different surface scalar flux levels among different types of fuel assemblies.

Keywords:

• method of characteristics
• GENESIS
• even-parity discontinuity factor
• superhomogenization method

Acknowledgments

This work was supported in part by Japan Society for the Promotion of Science KAKENHI, Grant-in-Aid for Scientific Research (C) (16K06956). The authors sincerely thank Masato Tabuchi of Nuclear Engineering, Ltd., for his invaluable comments on the SPH factor and the DF.