• Nuclear Engineering and Technology
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• v.52 no.10
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• pp.2162-2172
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• 2020

Due to its computational efficiency and geometrical flexibility, the Method of Characteristics (MOC) has been widely used for light water reactor lattice physics analysis. Usually acceleration methods are necessary for MOC to achieve acceptable convergence on practical reactor physics problems. Among them, Coarse Mesh Finite Difference (CMFD) is very popular and can drastically reduce the number of transport iterations. In OpenMOC, CMFD acceleration was implemented but had the limitation of supporting only a uniform CMFD mesh, which would often lead to splitting MOC source regions, thus creating an unnecessary increase in computation and memory use. In this study, CMFD acceleration with a non-uniform Cartesian mesh is implemented into OpenMOC. We also propose a quadratic fit based CMFD prolongation method in the axial direction to further improve the acceleration when multiple MOC source regions are contained in one CMFD coarse mesh. Numerical results are presented to demonstrate the improvement of the CMFD acceleration capability in OpenMOC in terms of both efficiency and stability.

• Journal of Electrical Engineering and Technology
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• v.6 no.1
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• pp.128-132
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• 2011

In this paper, two automatic mesh generation algorithms are presented. The methods seek to optimize mesh density with regard to geometries exhibiting both fine and coarse physical structures. When generating meshes, the algorithms attempt to satisfy the conditions on the maximum mesh spacing and the maximum grading ratio simultaneously. Both algorithms successfully produce non-uniform meshes that satisfy the requirements for finite-difference time-domain simulations of microwave components. Additionally, an algorithm successfully generates a minimum number of grid points while maintaining the simulation accuracy.