Application of the multiband method to square cell calculations in light water reactors

The effect caused by the cylindrical approximation of the geometry for cell calculations was investigated using a continuous energy Monte-Carlo Code MVP. It was found that the K∞ values were underestimated with the approximation of the geometry, especially in the case of MOX fuel. In order to avoid the error in deterministic cell calculations, a cell calculation code KRAM-B was developed where the multiband method was combined with the characteristics method to performed cell calculations including the resonance calculations in the explicit square geometries. It was found that K∞ values and the effective microscopic cross sections by KRAM-B agreed well with the reference MVP results. (author)