A one-dimensional model for multi-group equivalence parameters in subgroup method

In the previous study, a non-iterative equivalence method is proposed, which guarantees that the reaction rates calculated by subgroup method in self-shielding calculation are preserved in subgroup-collapsed one-group calculation. This method shows advantage in efficiency over the Super-Homogenization (SPH) method. However, one-group fixed-source calculations are still needed for obtaining multi-group (MG) equivalence parameters. In this paper, a one-dimensional model is employed for obtaining the MG equivalence parameters in subgroup method. Based on the one-dimensional model, the one-group fixed-source calculation is simplified to one-angle tracking sweeping, which is time-saving. The numerical results show that the reaction rates can be preserved with the MG equivalence parameters obtained based on the one-dimensional model for pin cell problems. For fuel assembly problems, the k_inf is improved by 140 pcm ∼ 187 pcm with negligible increase in computational time.