Spatial self-shielding for heterogeneous cells

The subgroup method enables the calculation of the spatial self-shielding in resonance absorption for fast routine applications. It is well suited for use in highly heterogeneous cells such as those with cluster type fuels. The average pin concept is removed and the resonance absorption can be derived for each pin. As the transport equation is solved in the collision probability form, the method can be used in any geometry for which collision probabilities can be calculated. The accuracy of the method was explored for a number of cases and compared with Hellstrand's experiments. Two clusters (7 pins and 37 pins) were analyzed; the results were considered satisfactory. (author)