Spatially dependent resonance cross sections in a fuel rod

The classical resonance absorption theory which treats a fuel pin as a single region, surrounded by moderator, is generalized to an arbitrary subregion of the fuel lump. Based on that generalization, a method is presented by which shielded resonance cross sections can be calculated for any number of annular regions in the fuel pin, using pretabulated resonance integrals, such as those appearing in the WIMS code. Numerical results obtained using that method are compared with those of ROLAIDS, a micro-group slowing down code in annular geometry, used here as reference.