Accurate resonance calculation method coupling simplified embedded self-shielding method and ultra-fine group method

Highlights: • A simpler ESSM iteration process is developed to improve the computation efficiency. • The impact of heterogeneous resonance integral tables on the final results is assessed. • A method is proposed to calculate exact spatially dependent self-shielded cross sections in a fuel rod. - Abstract: An accurate resonance calculation method coupling embedded self-shielding method (ESSM) and ultra-fine group method is proposed in this paper. Based on the analysis on the ESSM theory, a simpler ESSM iteration is developed. Comparing with the original ESSM method, the simplified ESSM just performs the iteration between solving the fixed source transport equation and interpolating the resonance integral (RI) table for one representative resonant nuclide and energy group, which is helpful to increase the computation efficiency. The impact of heterogeneous RI table on the results is analyzed, because the accuracy of ESSM deeply relies on the heterogeneous RI table. The numerical results show that the heterogeneous RI tables generated by different manners will produce different results. A method coupling the simplified ESSM and ultra-fine group method is proposed, which is capable of treating the temperature distribution, spatial self-shielding effect and interference effect in the fuel rod, and providing exact spatially dependent self-shielded cross sections.