MOCUM solutions to the 2-D hexagonal HTTR benchmark problems

The 2-D hexagonal HTTR benchmark problems were calculated by MOCUM code, whose fundamental methodologies are method of characteristics and unstructured meshing. MOCUM multiplication factors, fuel block and fuel pin fission rates, burnable poison and control rod absorption rates of three control rod configurations were compared with MCNP5 reference solutions. Excellent agreements were achieved. Maximum keff and reaction rate different among three cases are 0.01% and 0.26%, respectively. Sensitivity studies on parameter impacts are also presented. These benchmark problems are insensitive to the number of azimuthal angles. Small zone size is required for modeling the strong absorbers. Leonard type polar angles perform better than the Gauss–Legendre polar angles.

► Method of characteristic solutions of prismatic heterogeneous HTTR benchmarks are presented.
► Excellent agreements between MOCUM and MCNP5 results were achieved.
► HTTR benchmark problems are insensitive to azimuthal angle number.
► Leonard polar angle performs better than the Gauss–Legendre polar angles.
► Small zone size is required for accurate modeling of the strong flux gradient.