Native MOOSE meshing capability for light water reactor analysis

This paper presents a new strategy for creating quadrilateral, two-dimensional (2D) fuel pin meshes for finite element light water reactor (LWR) analysis, implemented within the Multiphysics Object Oriented Simulation Environment (MOOSE). The presented automated and rapid mesh scheme overcomes bottlenecks that often occur in LWR analyses and reduces the computational and human effort of the meshing generation process. Our algorithms mesh the innermost circle by introducing a uniform square mesh in its center portion. Meshing the innermost circle is completed by connecting nodes on the perimeter of uniform square mesh with nodes uniformly distributed on the circular arc of the innermost circle. Annular rings are meshed by extending the azimuthally uniform mesh outward. The moderator region is meshed last using a custom algorithm that seeks to reduce element size non-uniformity. Laplace smoothing is used to obtain a smooth and high-quality mesh in the innermost circle by removing the non-smooth transition from square mesh to the mesh around the circle’s circumference. In addition, a volume preservation option is added for ensuring the conservation of volume of all material regions. The BEAVRS benchmark unit cell was meshed with CUBIT and the presented MOOSE algorithms. This resulted in high shape qualities (between 0.88 and 1) for the moderator mesh. The proposed algorithms’ mesh quality did not deteriorate under mesh refinement. The neutron transport k-eigenvalue problem using the 2D C5G7 MOOSE mesh was solved by Rattlesnake, and physical fast and thermal fluxes were determined consistent with the benchmark results.