Analysis of Categorical Subgroup Method for Resonance Self-Shielding Treatment

Abstract

To meet the requirements of one step lattice calculation on resonance effect, a self-developed design and construction of a resonance treatment code are composed based on subgroup method and HELIOS-1.11 library. Subgroup fixed source equations are solved by method of characteristics to get subgroup fluxes, which are subsequently used to deduce effective resonance cross sections combined with subgroup weights and subgroup levels. Bondarenko method is employed to handle resonance interference effect and a resonance category scheme and resonance geometry simplification method are introduced to improve efficiency. Benchmarks of single pin cells and assemblies of light water reactor are adopted for numerical validation and the calculating results indicate that this method can treat resonance effect both precisely and effectively.

Analysis of the fine-mesh subgroup method and its feasible improvement

“…Since the resonance self-shielding calculation provides the effective material cross-sections for all processes of the core simulation, handling the resonance effect accurately and effectively has been the research hotspot in recent years. There are three main resonance treatment methods applied in reactor physics, namely, the equivalence theory (Askew et al, 1966;Hebert et al, 1991), ultra-fine group method (Ishiguro et al, 1971;Sugimura et al, 2007;Kim et al, 2011;Zhang et al, 2020), and subgroup method (Nikolaev et al, 1971;Cullen, 1977;Hebert, 2009;Joo et al, 2009;Downar et al, 2016;Li et al, 2019). The equivalence method uses the neutron's first escape probability from absorption to develop the equivalence relation…”