A Comparison Between the Embedded Self-Shielding Method and the Enhanced Neutron Current Method Based on the Equivalent Pin Cell Model on the Irregular Fuel Lattice Problem

The Embedded Self-Shielding Method (ESSM) coupled with the heterogeneous Resonance Integral tables and the Enhanced Neutron Current Method (ENCM) with equivalent Dancoff factor are reviewed and reformulated to a unified framework by incorporating the ultra-fine-group slowing-down calculation on two-dimensional square pin cell problems. The comparison between the two approaches on the resonance self-shielding calculation of irregular fuel lattices shows that the reformulated ESSM approach will bring errors to the cross-section prediction of fuel pins in the irregular lattice, especially when the moderator density is low. Also, the reformulated ENCM approach is more stable for different configurations. Further numerical tests show that the scalar flux calculated by the ESSM approach is affected by the global neutron balance across the fuel lattice and ESSM is more sensitive to the error brought by the enforced equivalence.