A Method of Generating Multigroup Transfer Matrices Using an Analytic Angular Integration Free of Truncation Error,

摘要

The evaluation of generalized multigroup transfer matrices for transport calculations required a double integration extending over the primary and secondary energy groups where,for a given initial energy,the integration over the secondary energy group may be replaced by an integral over the possible scattering angles. The XLACS cross-section processing code presently used in the AMPX system treats this angular integral in an approximate manner. The more recent MINX cross-section processing code treats this angular integral analytically but can admit some small truncation error. These treatments are reviewed along with their weaknesses. In the present work,analytic expressions for these angular integrals are derived which are free of truncation error. Straightforward extensions to include inelastic and/or anisotropic scattering are included. Fortran routines are provided for nuclides having isotropic elastic scattering in the center-of-mass system.