Chebyshev acceleration for lambda mode calculations

Coordenadoria para Projetos Especals (COPESP) has been making an effort to develop a power distribution mapping system utilizing self-powered neutron detectors. The scheme adopted to estimate the power distribution is based on an expansion of lambda modes for a given reactor state. Two-dimensional lambda modes were obtained previously with a modified version of the CITATION code. The method was based on the orthogonality properties of the lambda modes. Several modes could be obtained, but the convergence was slow because of the lack of an appropriate accelerating scheme in the CITATION code for calculating lambda modes. This work presents the acceleration scheme implemented into the CITATION code to obtain lambda modes.