Improved leakage splitting method for the 2D/1D transport calculation

The 2D/1D transport method is widely implemented for direct whole-core calculations because of its good balance between efficiency and accuracy. In the 2D/1D transport method, negative total source may occur for MOC calculation in iteration process, which will lead to iteration divergence. The negative total source in the MOC equation is studied and an improved leakage splitting method is proposed to improve stability for 2D/1D transport method in this paper. With the new method, the accuracy is preserved while the memory cost only increases slightly. Finally, high leakage cases, the C5G7 and VERA benchmark are tested to show the accuracy and performance of the proposed method.