Analytic basis function expansion method for neutron diffusion calculation in two-dimensional triangular geometry

A new nodal method for directly solving the two-group neutron diffusion equation in the triangular geometry was proposed. The neutron flux distributions within a node were expanded in a series of analytic basis functions for each group. Nodes were coupled each other with both the zero- and first-order partial neutron current moments simultaneously. With a new sweeping scheme developed for triangular geometry, the response matrix technique was used to solve the nodal diffusion equations iteratively. Based on the proposed model, the code ABFEM-T was developed. The numerical results for a series of benchmark problems show that the core multiplication factor and nodal powers are predicted accurately using this model for unstructured neutron diffusion problems.