Symposium on Advanced Sensors and Modeling Techniques for Nuclear Reactor Safety

Multi-Grid Acceleration Scheme for Neutron Transport Calculations using Optimally Diffusive CMFD Method

Method of characteristics (MOC) is one of the most efficient deterministic techniques for high fidelity neutronic analysis of complex and heterogeneous reactor problems. However, the conventional MOC inner-outer iteration scheme suffers from poor convergence speeds for problems with large scattering to transport cross-section ratio and/or large dominance ratio. This creates a serious hindrance for its effective application to realistic reactor problems. A High Order – Low Order (HO-LO) multi-grid scheme using optimally diffusive coarse mesh finite difference (odCMFD) method has been introduced for improving the performance of code DIAMOND, an assembly level neutronic analysis code based on MOC and unstructured meshing for 2D rectangular assemblies in arbitrary energy group structures. The odCMFD scheme is unconditionally stable like the partial current-based CMFD (pCMFD) method, and as efficient as the standard CMFD scheme and can be easily implemented with minimum overhead. The odCMFD method has been validated for different benchmark problems to establish its efficacy. Implementation of this scheme in the code DIAMOND and benchmarking results have been presented in this work.