Assessment of Computational Technicalities for 2D/1D Coupling Method and Its Comparison with 3D MOC

Abstract

The 2D/1D coupling method is recognized as one of the preferred high-fidelity calculation methods for reactors featured with well homogeneity in the axial direction. However, the choices of the technicalities, such as transverse leakage, axial solver, and transverse leakage splitting method, will lead to different calculational performance. This paper outlines the theory of the 2D/1D coupling method and describes the detailed implementations of the key technicalities. Based on numerical tests, the choices of the related calculational parameters are analyzed, such as the order of the quadrature set, ray spacing, and the axial mesh size. Then, the computational performance of six typical 2D/1D technicalities is compared and assessed. A comparison between 2D/1D coupling method and direct 3D MOC calculation is also made. For the transverse leakage, the Fourier expansion technique could significantly reduce the memory burden and computational cost, but with the similar accuracy as the anisotropic leakage term. It is recommended to use the axial DGFEM SN solver, which has better consistency and leads to higher computational efficiency. Additionally, the results also show that the 2D/1D coupling method can appropriately increase the axial mesh size, which only has slight effect on the accuracy. For nuclear reactors featured with nonstrong heterogeneity in axial direction, the 2D/1D coupling method has significant advantages than the direct 3D MOC calculation.