Recent advances in utilization of the R-matrix parameters for reactor applications

A simplified version of the rigorous pole representation of cross sections has been developed to facilitate utilization of the newly released ENDF/B VI resonance data based on the Reich-Moore parameters for reactor applications. The procedure is equivalent to the extraction of the Humblet-Rosenfeld-type parameters and the associated 'background' term explicitly from the rigorous pole and residue parameters which, in turn, are converted from a given set of the Reich-Moore parameters. The computational efficiency and its amenability to the existing reactor codes are significantly enhanced by the introduction of the pertinent analytic continuation in place of the smooth 'background' term via the non-linear least square fitting. The method has been successfully applied to all major nuclides examined and the results are presented. (orig.)