COMBINE/PC: A portable ENDF/B Version 5 neutron spectrum and cross-section generation program

Abstract

COMBINE/PC is a FORTRAN 77 code that calculates neutron spectra and ENDF/B Version 5-based neutron cross sections. The program is capable of handling a wide variety of practical fission and fusion-related applications, while remaining machine-independent. The energy range treated extends from 0.001 eV to 16.905 MeV. The calculations in the fast and epithermal energy range are based on extensive modification and reprogramming of the GAM code. COMBINE/PC incorporates superior methods of performing both the resolved and unresolved resonance calculations. This code includes a routine to calculate a Dancoff-Ginsburg correction factor in conjunction with the resonance calculation for either a rectangular or hexagonal arrangement of cylindrical fuel rods. In the thermal energy range, COMBINE/PC solves for the neutron spectrum using an iterative solution to the integral formulation of the neutron thermalization problem. The fast and thermal energy ranges are coupled using slowing down theory to generate scatter sources into the thermal energy range. An option to self-shield cross sections in the thermal energy range using the Amouyal/Benoist/Horowitz method is available. COMBINE/PC generates output multigroup macroscopic and microscopic cross sections for all materials in the calculation using standard flux-weighting techniques. The multigroup cross sections may be output in any of several standardmore » formats including ANISNB 14{asterisk}{asterisk} free format, CCCC ISOTXS format, and AMPX working library format. 46 refs.« less