A simplified method based on an extension of the rigorous pole representation of cross sections has been developed to facilitate the utilization of the newly released Reich-Moore parameters in reactor applications. By using the analytical properties of each pole term with energy-independent parameters, it is possible to cast the original representation into the Humblet-Rosenfeld form in which the “background” term can be explicitly identified with pole terms attributed to outlying poles and poles with wide “width.” The computational efficiency and its amenability to existing reactor codes can be enhanced significantly when the background term is replaced by a low-order rational function via nonlinear least-squares fitting. Codes have been developed to compute all pertinent parameters from any given set of Reich-Moore parameters. The method, which preserves both the rigor of the Reich-Moore cross section and the desirable features of the traditional formalisms, is readily amenable to all ENDF/B format based codes. Extensive calculations have been carried out to demonstrate the viability of the proposed method for treating the R matrix data for major nuclides given in the ENDF/B- VI files, and the results are presented.
