Processing Resonance Self-Shielding Effect of Gadolinia Based on Imptoved Supercell Scheme

Abstract

An improved supercell scheme has been proposed in this paper to efficiently and accurately process resonance self-shielding effect of gadolinia. Resonance effects are classified into global shadowing effect and local effects involving resonance interference, spatial self-shielding effects. Two categories of effects are decoupled and treated respectively based on different 1-D cylindrical pins. Hyperfine group method is applied to obtain multi-group cross sections for each 1-D pin. Afterwards, two categories of effects are coupled based on a correction formula. Because of the low efficiency for Carlvik method to compute collision probabilities in hyperfine group method, online tabulation and interpolation method is developed to accelerate gaining collision probabilities. The proposed scheme is verified against the problems of 3×3 pins with gadolinia rod, VERA 2O assembly with 12 gadolinia rods and VERA 2P with 24 gadolinia rods. The numerical results suggest promising consistence of multi-group cross sections and eigenvalues between the proposed scheme and reference solutions.