Accuracy and analysis of the iteratively coupling 2D/3D method for the three-dimensional transport calculations

The characteristics based coupling method is almost becoming a standard transport solver for the whole-core calculations, which includes the 2D/1D fusion method and the 2D/1D method. Different with the 2D/1D method that utilizes 1D calculation to get the axial leakage, here introduces a 2D/3D coupling method employing the 3D S_N method to get the axial leakage. Compared with the 2D/1D method, because of the better axial leakage from the 3D S_N method, the 2D/3D could decrease the number of MOC layers while keeping the accuracy. In another word, it could improve the accuracy with the same axial mesh size. In the paper, the theory and leakage analysis of this 2D/3D coupling method is introduced. And a small test problem is given to show the leakage comparison of axial leakage between the 2D/1D method and 2D/3D method. Finally the results of the 3D C5G7 problems are given to demonstrate the accuracy and performance of the 2D/3D method.