Enhancing CMFD acceleration in MOC-based direct transport code

Abstract

The implementation of CMFD acceleration and recent enhancements in STREAM deterministic transport code are presented in this study. A comprehensive description of the two-level CMFD approach in STREAM is provided, including its parallelization strategies and iteration algorithms. The main performance improvement comes from adopting an improved odCMFD method, complemented with code optimization at the programming level. Numerical evaluations against various realistic core problems demonstrate that the adopted odCMFD significantly improve the efficiency and robustness of CMFD acceleration in STREAM, enabling stable and accurate simulations with coarser meshes and reduced computational time.