PUBLICATIONS

Based on the observation that the ignorance of the angle dependency of multigroup resonance cross sections within a fuel pellet would result in nontrivial underestimation of the spatial self-shielding of flux, namely the overestimation of flux itself inside the pellet, a parametrized spectral super homogenization (SPH) factor library method is developed as a practical means of resolving the problem. Region-wise spectral SPH factors are calculated by the normal and transport corrected SPH iterations after performing ultra-fine group slowing down calculation over various light water reactor pin-cell configurations. The parametrization is done with fuel temperature, U238 number density, fuel radius, moderator source represented by ΣmodVmod, and the number density ratio of resonance nuclides to that of U238 in a form of resonance interference correction factors. The parametrization turns out to be successful in that the root mean square errors of the interpolated SPH factors over the fuel regions of various pincells are within 0.1% RMS. The improvement in reactivity error of the proposed method is shown to be superior to that by the old SPH method in that the reactivity bias of about -200 to -300 caused by the overestimation of the resonance group flux vanishes almost completely for most cases. It is demonstrated that the proposed method is effective in the assembly problems as well despite that the SPH factors are generated from pin cell calculations. In this regard, it is conformed that considering only the local effect is sufficient because the surrounding effect takes only about 4% in the reactivity improvement.