Evaluation of Background Cross Section for Heterogeneous and Complicated Geometry by the Enhanced Neutron Current Method

Abstract

A new approach for evaluating the background cross section for heterogeneous and complicated geometry (the enhanced neutron current method) is presented. The present method utilizes the result of a onegroup fixed source transport calculation in heterogeneous geometry, which can be carried out in short computation time. The background cross section can be evaluated from the total reaction rate in a resonance region. Since the present method can be applied to complicated geometry, it will be useful not only for lattice physics calculation with production codes but also for general purpose neutronics code calculation for advanced reactors. The validity of the present method is confirmed by comparison with that of the conventional method by rational approximation for first-flight collision probability and the Dancoff factor. Calculation results indicate that the background cross sections obtained by both methods are identical.

KEYWORDS:

• background cross section
• resonance
• self-shielding
• equivalence theory
• escape cross section
• average chord length
• heterogeneous
• enhanced neutron current method