Ants Solution to IAEA-Hex Kinetics Benchmark

A recently published two-dimensional two-group hexagonal geometry IAEA-Hex kinetics benchmark was solved using the nodal neutronics program Ants. Solutions to both ramp and step transients were obtained using either the hexagonal geometry model, or the triangular geometry model with different numbers of triangles per hexagon. For both transients and all geometry models, multiple solutions with different fixed time step lengths were calculated. The results were compared against the benchmark reference results. The Ants solutions to the ramp transient were found to be rather insensitive to the time step length. The triangular geometry model predicted the powers more accurately than the hexagonal model. Refining the radial mesh with the triangular geometry model did not affect the results of either transient. The Ants solutions to the step transients were more accurate with the triangular geometry model when using shorter time steps. Generally, Ants agreed very well with the reference solution when short enough time step was used, especially with the triangular model. This work provides nodal solutions to the benchmark using different time steps for comparison purposes for other nodal programs, as at the time of writing only the reference extrapolated FEM solutions have been published.